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10/11/93 (RCR2102 AV 0004 SI) PAGE: 1

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LYCOMIAIG

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IBDEXIhe articles contained herein are not intended to supersede manufacturers service

publications, instructions or manuals or any other qtFcial publications, bur are proridedin order to augment or erplain in pilot5 or mechanic’s language these publications, as

well as provide other supplemental helpfitl information for our customers and operators.

GENERAL

Title Page No.

Facts About The Flyer and Key Reprints...............................-´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•--´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 3

Some Definitions of Terms.........................................´•.´•´•´•´•´•´•´•--´•´•´•´•´•´•-´•-´•´•-´•´•´•´•´•-´•´•-´•´•´•´•´•-´•´•´•--´•´•-´•´•´•-´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 5

How To Get Textron Lycoming Engine and Accessory Maintenance Publications.......................-´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 5

Determining Engine Condition of High Time Piston Powerplants..................................´•´•-´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•-´•´•´•´•´•´•´• 5

Questions Most Often-Asked by Pilots and Mechanics

About Textron Lycoming Geared and Supercharged Engines............................-....-´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´• 7

Time Between Overhaul (TBO).................................´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 8

Spectrometric Oil Analysis.....................................´•.´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•-´•´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 10

Engine Overhaul--What Does It Mean...................................-´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•---´•´•´•´•´•--´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´• 11

SomeDefinitions Applicable to Textron Lycoming Williamsport Engines.................................´•-´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 12

What Is An Aerobatic Engine?........,......................´•.´•.´•-´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•---´•-´•´•´•´•´•--´•´•´•-´•-´•´•´•´•´•´•´•-´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 14

The Use of Higher Octane Aviation Fuel. 100 LL Blue

or 1M) Green, for Engines Rated for 80187 Octane Fuel.....................................´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 15

What is Avgas?.......................................´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•-´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´• 16

80 Octane Engine Grade 100 Aviation Fuel..................................´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 17

Minimizing The Spark Plug Fouling Problem............................´•.-´•´•´•´•´•´•´•´•´•´•´•´•-´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 18

Fuel Contamination..........................................´•´•´•´•´•´•´•´•´•´•-´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•---´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 19

Do Not Use Automotive Gasoline In Textron Lycoming Aircraft Engines..............................´•´•´•´•-´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´• 19

Understanding The AD............................................´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•-´•´•--´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 20

Let’s Talk Turbocharging...........................-´•´•´•´•´•´•´•´•´•-´•´•´•´•-´•´•--´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´• 20

The Dual Maeneto.,..................................´•-´•´•´•´•´•-´•´•-´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´• 21

Information About Textron Lycoming Approved Full-Flow Oil Filters.........................-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 73

Detonation And Pre-Ignition................................-´•´•´•´•´•´•´•´•´•´•-´•-´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•-´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 22

Nitridinp: What Is It?...........................................-.--´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•--´•--´•´•´•´•´•´•´•´•--´•´•´•-´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´• 73

Compression Ratio An Explanation As It Relates To Textron Lycoming Enpines............................´•´•´•.´•´•´•´•´•´•´•´•´•´• 73

How to Keep Engine Costs Down Through Do-It-Yourself

Preventive Maintenance And Sound Operation..........................´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•-´•´•´•-´•-´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• ZJ

"Watts" Horsepower...............................´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•--´•´•´•-´•´•´•´•´•´•-´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 25

Cut-Away Of A Four Cylinder Powerplant...........................´•´•´•-´•´•´•´•-´•´•´•---´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´• 35

Your Engine And The Fixed Pitch Propeller............................´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•-´•´•--´•´•´•´•-´•´•´•´•-´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 96

Induced Engine Damage..................................´•´•.´•´•´•´•´•´•´•´•´•´•´•-´•-´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•-´•-´•-´•´•´•´•--´•--´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•-´•´•-´•´•´•´•´•´•´•´•´•´•´•´• 27

The Whistle Slot..........................................-.´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•--´•-´•-´•´•-´•´•-´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 29

Welding Is Wastefui................................´•.-...--´•´•´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 29

Look What They Are Doing To Our Engines....................................´•-.´•-´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 30

Questions To Ask The Engine Modifier...................................-.´•´•´•´•-´•´•´•´•´•´•´•´•´•-´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•´•--´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 32

Engine Balance 33

Low Time Engine May Not Mean Quality and Value.....................................´•.--´•´•´•´•´•´•´•´•´•´•´•-´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 33

OPERATION

Hard Facts About Engine Break-In...................................´•..´•´•´•´•-´•´•´•-´•´•´•´•´•´•´•-´•´•´•´•´•´•-´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•

Leaning Tcxtron Lycoming Engines......................................´•.----´•´•´•´•´•--´•´•-´•-´•´•´•´•´•-´•´•´•-´•-´•´•´•´•´•´•´•´•´•-´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•Proper Leaning at Cruise Aids Safe Flight--And Saves S Dollars........................................´•´•´•-´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´• 39

Operating The Direct Drive Fixed Pitch Lycoming Engine..............................´•-.-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• 39

Operating Your Lycoming Engines At Takeoff And Climb............................................´•´•´•´•´•´•´•-´•´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•- :90Landings And Takeoffs From High Elevation Airports..................................-.´•.´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•The Need For Good Fuel Manaeement........................´•´•.´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• ~1

The Exhaust Gas Temperature (EGT) And Fuel Management.................................´•...-´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•-´•´•´•´• JI

An Explanation Of Power Settings..................................´•´•.-´•´•´•´•´•´•´•´•-´•´•-´•´•-´•´•-´•´•-´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•Basic Power Sequence (Governed Engines)......................´•´•-´•´•´•-´•´•´•´•´•´•--´•´•-´•´•´•´•´•´•´•´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´• ~3

Considerations For Low Power Low RPM Cruise................................--´•´•´•--´•´•´•´•´•´•-´•´•´•´•´•´•´•-´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• -13

Engine Operational Tip..............................´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•´•´•´•-´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´• ~-5

A Special On Fuel Management...........................´•´•´•´•´•´•-´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´• ‘tS

Full Starvation Accidents..................................´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•--´•´•-´•´•´•-´•´•´•´•´•´•-´•-´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• ~5

More About Fuels....................´•´•.-´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•--´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•-´•´•´•´•´•´•´•´•´• ~b

Induction Icinf........................´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•-´•-´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´• -th

Cold Weatherj8

Cold Weather

Protecting TheEngine During Simulated Emergency Procedure Operation. 51National Transportation Safety Board Warning On Simulated Engine-Out s~Importance Of The Cylinder Head Temperature............... 52More On Cylinder Head Temperature. 5~Interpreting Your Engine Instruments. 53Engine Starting Suggestions.´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•´•´•-´•-´•´•´•´•´•´•-´•´•´•´•´•´•-´•´•´•---´•´•´•´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•-´•´•´•´•´•´•´•´•´•.............................53More Suggestions On Engine Starts.... 53Use Of Fuel Boost Pumps With Textron Lycoming gjHow To Avoid Broken Piston Rings And Cracked gjAvoid Sudden Cooling Of Your Engine. 5$Operational And Maintenance Procedures To Avoid Sticking 55Sticking Valves Do Not Neglect The Warning Signs. 57Tips From The

57The Pilot And 58Turbocharging A Brief Refresher. 61Thieves Of Airc~raft Engine 63Wet Air Effect On Engine Power. 65Frequency Of Flight And Its Effect On The Engine. 66Throttle Jockeying Bad Technique. 66A Daily Engine Preflight Checklist............ 66

-Spark Plug 67Test Your Knowledge On 67Lest We Forget The Engine Will Not Run Without Air. 69

MAINTENANCE

Mechanic’s Creed. 72The Basics Of Maintenanceln General Aviation. 72Ask About Reference Publications Before Your Engine Is Taken 73The Oil And Your Engine. 73More About Oil And Your Aircraft Engine. 74Safety Tip--Sealant Use......................................... 75Maintaining Oil Levels of Wet Sump Engines.............. 76Multi-Viscosity Oils. 76Tips For Changing Your Spin-On Oil Filter. 76Understanding Engine Color 77Test Procedure For The 77Engine Test After 77The Compression Check As A Maintenance 78Oil and Filter Change Recommendations...................... 80Spark Plugs Key To Smooth Engine Operation, I. 80Spark Flues Key To Smooth Engine Operation, n. 81Is Your Spark Plug Connector Overtorqued?................. 82Why Rotate Spark 8~Engine 83Air Filter Maintenance. 83Checking And Adjusting Dry Tappet Clearance On Textron Lycoming 83Importance Of The Correct Cylinder Base Nut Tightening 8jFuel Injector Nozzles Have Been 8jUnauthorized Additions To Your Engine Can Cause 85A Simple Check Of Internal Engine Timing.............. 85Installation of Counterveight Rollers............ 86Maintenance Suggestions From The Lycoming Service Hanger, 86Maintenance Suggestions From The Lycoming Service Hanger, 87Safety Notes.......................... 88Engine Suggestions For 88Top 89Recommendation Regarding Use Of Incorrect Fuel. 89Recommendations For Aircraft Or Engine Struck By 89Keep Your Direct Drive Engine Starter Clean To Avoid 90Propeller Ground Strike or Sudden Stoppage Can Be 90Some Tips On The Lycoming 0-235 g0Notes on Replacing Connecting Rods or Pistons. 91Maintenance Tip--Fuel Injector Nozzies. 91Lycoming Model Code For Reciprocating 9´•

Facts About The Flyer and Key Reprints

Textron Lycoming has been pleased and impressed by the number of requests for copies

of the "Key Reprints" pleased by your many favorable comments concemmg it, and im-

pressed by the thirst for knowledge of General Aviation aircraft engines by operators.

Some of our readers may wonder how authentic is the Flyer and Key Repnnrs or

are these two publications an official word from Textron Lycoming?

In answer to the above question, yes, the information in the Flyer and Key Reprints is

official and supplements our other official service publications.

Some of the articles published are based on information contained in Service Bulletins.

Service Instructions, and Service Letters. In addition, other articles are taken from actual field

test data carried on by Textron Lycoming personnel. Furthermore, the Texuon Lycomin_g factor´•

is a central collecting agency on its aircraft engines out in the field with a return flow of ailkinds of experiences and information from all over the world, which is recorded and ana-

lyzed, We share this information with our readers in the Flyer and Key Reprints.

During the preparation process of each article, updating of service information is pan of

the procedure, After articles are written, each one is carefully screened and checked by mana´•e-

ment, engineering, and service personnel to insure accuracy before being released fd~r publi~a-tion. Once in awhile isolated cases may arise whereby arficles dealing with service informa-

tion may be published in advance of distribution through normal publication channels. The

data contained therein is correlated with the responsible departments to insure that all infor-

mation is accurate and factual.

The Flyer does not have an established publishing date for each issue. Whenever enoughitems of mutual interest have accumulated we publish the next Flyer: as a result. we have aver-

aged an issue about once or twice per year.

The original concept of the Flyer has not changed since the first issue was published in

1963~ Approximately 85 of the prepared text deals with technical information related to Tex-

tron Lvcoming engines, and the remaining 15rr covers general newsworthy items. Distribu-

tion oi the Flyer is made to owners and operators of Textron Lycomin_g powered aircraft,

authorized distributors, and others who write us and request that we place them on our mail-

ing list, with all costs of printing and mailing absorbed by Textron Lycomin_e.

It is the intention of Textron Lycomin_g to continue to make available service maintenance

and operational data in the Flyer and Key Reprints, which will assist the owner and operatorto improve engine performance and reliabilitr.

PERhlIssION TO REPRIhT

Permission to reprint material from

the Textron Lvcoming "Kee Repnnts"is eranred. so long as the context of

information remains tnract and appropnatecredit Is given.

GENERAL

Some Definitions Of Terms How To Get Textron Lycoming Engine

If you are not sure of the meaning of such terms asAccessory Maintenance Publications

normally aspirated, turbocharged, supercharged or direct All publications may be ordered through authorized T~uondrive engines, then perhaps you’ll want to read our simplified Lycoming distributors or direct from Textron Lycoming,definition of them. Williamsport Plant. If ordered direct from Textron Lycominf

Williamsport Plant, payment must be submitted with the requestThe Normally Aspirated Engine is one that is not as outlined in the latest revision of Textron Lycoming Service

turbocharged or supercharged. If the airplane has a manifold Letter No. 114.

pressure gauge, at full takeoff power at sea level on a standard The available maintenance publications for Textronday it would indicate a MP reading of approximately 29" of Lycoming engines and accessories consist of the followmg:Hg. Takeoff power at 5,000 ft. density altitude airport would

read about 24" MP. The normally aspirated engine uses OPERATOR’S MANUAL

atmospheric pressure and is thereby altitude limited. The Operator’s Manual contains information of use to pilotsand maintenance personnel. It contains engine specifications,Direct Drive Engines are those piston powered engines inspection procedures, operational information and is used in

where the propeller is bolted-on the end of the crankshaft andconjunction with the Pilots Operating Handbook for the aircraft.

the prop turns at the same speed as the crankshaft.

OVERHAUL MANUALSGeared Engines are usually the higher powered, more

complex engines using a reduction gear on the nose of the The Overhaul Manual is a guide for major repair of the

aircraft, and_with the prop attached to it. As a result, the propengine. It contains complete disassembly, inspection, repair,reassembly and test procedures for the various Textron

will turn somewhat slower than the crankshafU, resulting in aLycoming engines. When used in conjunction with applicable

lower prop noise level. When the engine is geared, we precede parts -catalog, this manual provides an authoritative text forthe engine designation with a "G". Thus a geared, opposed complete overhaul of the engine.(Or normally aspirated Lycoming engine with a 480 cubic inch

displacement of the cylinders would be designated a GO-480 PARTS CATALOGS

model. Textron Lycoming Parts Catalogs are illustrated to permitidentification of parts; they are kept up-to-date by revision and

Turbocharged Engines as manufactured by Lycoming supplemental listings. A referenced numerical list is alsosimply consist ofa turbocharger unit with a small turbine wheel included.attached by a common shaft to a compressor wheel, and utilizes

the engine exhaust gas by directing it over the turbine wheel SERVICE BULLETINS, INSTRUCTIONS, LETTERS

to drive the compressor. The horsepower loss in operating the These publications are issued as required. Service Bulletins

turbocharger is negligible. Turbocharging can provide greater are generally of a mandatory nature and require some

utility to the piston engine by providing sea level horsepower, modification to be accomplished on the engine within a specifiedin some models. as high as 20,000 feet; or it can be used to time. Service Instructions are not of a mandatory nature and

add horsepower to die engine particularly for takeoff. The faster cover a variety of subjects; such as repair processes,

the engine runs, the more air the turbocharger can pack into modification procedures, inspection procedures and overhaul

the cylinder to compensate for the thin air of altittde, or tomethods. Service Letters are of an informative nature usuallypertaining to service policy or vendor products.

increase the horsepower, Although this definition is somewhat

over-simplified, it is a basic definition of turbocharging of SPECIAL SERVICE PUBLICATIONS.

General Aviation power-plants. These publications are concerned with topics of generalWhere turbocharging is used with a fuel injected, opposed interest or subjects that are too lengthy for inclusion in

Textron Lycoming engine with a 540 cubic inch displacement, maintenance manuals.

we designate it as a TIG-540 model. "T" represents the

turt~o-charging.

Supercharged Engines as manufactured by Textron Determining Engine Condition Of

Lycoming use a compressor wheel to pack air into the cylinders; High Time Piston Powerplantsbut the compressor is driven by the crankshaft through an

intricate gearing system, which takes considerable horsepower As an engine gets considerable time on it and approachesfrom the engine to operate. In comparison with a turbocharged the manufacturer’s recommended total overhaul hours, the

engine, it is a medium altitude powerplant. question arises concerning the decision to either continue dying,or top overhaul, major overhaul, or exchange engines. Here

The trend in manufactnring is away from supercharging andbelow is a quick reference checklist to help make such a

decision, followed by a brief explanation of the ten paints.definitely to turbocharging because of the several advantagesof the latter, i. Oil Consumption-any unusual increase?

A supercharged. geared, opposed, fuel injected Textron 9. Fuel consumption--any drift lean at higher than cruise

engine with cylinders of 540 cubic inch displacement power?

is designated an 1GSO-540 model. "S" represents 3. General engine history.supercharging.

4. Pilot and maintenance opinions of the engine. checklist. He will have an opinion based on whether it has been5. How has the engine been operated? a dependable powerplant, and whether or not he has confidence

6. Maintenance--wh~at kind has the engine received? in it. If the pilot lacks confidence in an engine as it approaches7.

the expected overhaul time, this could be a weighty factor inWhat does the oil filter tell; if no filter, have there been

frequent oil changes?the decision to continue flying or overhaul it. He should consull

8. What has been the trend in compression checks?with his maintenance personnel concerning their evaluation ofthe condition of his powerplant.

9. What do the spark plugs show?V. OPERATION

10. Refer to the engine manufacturer’s service letter forengine life and recommended overhaul periods. The basic question here would be how the engine has been

Along with the above quick reference checklist, as an engine operated the majority of its life. Some engines operatingmanufacturer we would like to share our experience with the continuously at high power, or in dusty conditions, could have

interested operators by means of the following discussion of a reduced life. Likewise, if the pilot hasn’t followed the

the basic ten points: manufacturer’s recommendations on operation it may cause

I. OIL CONSUMPTIONengine problems and reduce the expected life. This becomesa more critical influence on a decision in single engine aircraft.

The operator and maintenance people should know what has and also for single or twin engine planes flown frequently atbeen the general history of oil consumption during the life of night or IFR.an engine.

VI. MAINTENANCEA possible danger signal concerning engine health is a

definite~-incrcase in oil consumption during the recent 25 to 50 Good maintenance should aid in achieving maximum enginehours of flight time. The oil screens and filler should be carefully life; alternately, poor maintenance tends to reduce the expectedobserved for signs of metal. Maintenance should also take a

life. We notice among those powerplants coming back to the

good differential compression check at this time. They should factory for remanufacture or other reasons, that the smalleralso look in the cylinders with a gooseneck light or a borescope engines in general have had less care and attention, and in a

to detect any unusual conditions infhe combustion chamber. number of instances have been run until something goes wrong.If you haven’t looked at your air filter lately, it would be

The higher powered engines have generally had better

a good idea to carefully inspect it for wear and proper fit. Thismaintenance and show evidence that the operators do not wait

is all the more important when operating in dusty areas, and until something goes wrong, but tend to observe the

definitely could be a cause of increased oil consumption. manufacturer’s recommended overhaul time for change. The

engine logbook should properly reflect the kind of maintenanceII. FUEL CONSUMPTION

provided the engine or engines.If there has been radical change in fuel consumption

VII. IS ENGINE on, FILTERED ORon the lean side of the manufacturer’s predicted consumption,particularly at takeoff and climb, then damage from detonation FREQUENTLY CHANGED

may have been done to the engine which is not easily detected Clean oil has consistently been an important factor in aidingin some cases. A higher time engine which has been in and extending engine life. A good full flow oil filter has beendetonation might necessitate an engine change or overhaul. a most desirable application here. When the filter is exchangedIII. GENERAL ENGINE HISTORY ask the mechanic to open it and carefully examine for any foreign

If a powerplant has been basically healthy throughout itselements, just as is accomplished at oil change when the engineoil screen is also examined for the same purpose. Since the sparklife, this would be a favorable factor in continuing to operate

it as the engine approached high time. Alternately, if it has plugs also tell a story about what is going on in the engine, so

required frequent repairs. the engine may not achieve itsthe engine oil screen and the external oil filter tell a story about

expected normal life. The engine logbook should contain thisthe health of an engine. If the engine has no oil filter, oil changes

accumulative record, should have been accomplished in accordance with the

Another important aspect of an engine’s history would bemanufacturer’s recommendations. These oil changes should

its calendar age. Although our discussion is primarily concernedhave been recorded in the engine logbook.

with engine flight time, the calendar age could be equally vm. COMPRESSION CHECKSimportant to the operator. We have observed that engines What has been the trend in compression in at least the lastinfrequently flown do tend to age or deteriorate more quickly two differential compression checks. The differentialthan those flown on a regular basis. Therefore. an operator whohas ten years on a 2000 hour overhaul life engine may have

compression check is the more reliable type and should be takenon a warm engine. If the differential check reveals 95~ lossflown it only 600 hours, yet finds it necessary to top or major

overhaul it because of the calendar age deterioration.or more, then trouble may be developing.

IV. PILOT AND MAINTENANCE OPINIONS OFOperators are still confused by the compression check and

its application. A compression test can be made any time faultyTHE ENGINE

compression is suspected. and should be made if the pilotThe pilot’s opinion of the powerplant based on his observes a loss of power in flight, experiences high oil

experience operating it is another important point in our consumption, or notices sofi spots when hand pulling the prop.

It is also considered part of the 100 hour engine inspection and there is a problem requiring a top overhaul, this is a needless

the annual inspection. Most experienced maintenance men feel cost; likewise, if the engine is healthy and running satisfactorily,that the differential compression check is best used to chart a then leave it alone!

trend over a period of flight hours. A gradual deterioration ofOne other point deserves attention here; there is no

charted compression taken during maintenance checks wouldsubstitute or cheap route to safety in the proper maintenance

he a sound basis for further investigation.or correct overhaul of an engine.

IX. SPARKPLUGS CONCLUSION:

The spark plugs when removed and carefully observed, tell Apply all of these basic ten points concerning your enginethe skilled mechanic what has been happening~in the cylinders or engines and then make a decision whether to top overhaul,

during flight, and can be a helpful factor in deciding what to major overhaul, exchange engines, or continue flying.do with a high time engine:

i. Copper runout andlor lead fouling means excessive heat.

2. Black carbon and lead bromide indicate low temperatures Questions Most Often Asked By Theand possibly excessive richness of fuel metering at idle.

Pilots And/Or Mechanics About3. Oil fouled plugs may indicate that piston rings are failing

to seat, or excessive wear is taking place. Textron Lycoming Geared And

4. The normal color of a spark plug deposit is generally Mechanically Supercharged Enginesbrownish gray.

5. In high compression and supercharged engines, a cracked QUESTION--In a couple of sentences, why gear an engine’.’

spark plug porcelain will cause or has been caused by ANSWER--The easiest and cheapest way to get more

preignition. horsepower out of an engine is to turn it faster. However, a

rather severe restriction is placed on propeller RPM becauseX. ENGINE MANUFACTURER’S

as propeller RPM increases beyond a certain point, propellerRECOMMENDED OVERHAUL LIFE

efficiency decreases. So--the increased horsepower we get from

The engine manufacturers publish a recommended overhaul increased RPM is not coverted into thrust. The answer is-

time period for each specific engine model. The amount of total place a reduction gear device between the engine and the

time on an engine will be a basic factor in any decision to either propeller so that the propeller turns at less RPM than the engine.

continue flying, change, top, or major overhaul the powerplant. QUESTION--in two parts:Operators should be reminded, however, that the hours of

PART I. I hear so much about engine de-tuning--whatservice life shown in the chart are recommendations for engines

is de-tuning?as manufactured and delivered from the factory. These hours

can be normally expected provided recommended operation, ANSWER--Floating weights are placed on the engine

periodic inspections, frequent flights, and engine maintenancecrankshaft to eliminate, or move out of the engine operating

have been exercised in accordance with respective engine range, harmful or undersirable vibration characteristics. Should

operator’s manuals,the counterweight bearing surface, or the surface of the rollers

on which they ride become deformed ("detuned") the purposeIf an operator desires to operate an engine beyond the for which the weights were installed is defeated. Engine structure

recommended time and he is concerned with cost of overhaul, failure may occur.

there is the possibility that the overhaul cost will be higher withPART II. Is there much chance of the average pilot de-

increased time, or an engine failure is a potential to consider.tuning an engine?

Operators have topped their engine in some cases at some ANSWER--Not really. With one exception a guy has to

point in the engine life. Invariably they want to know if this be an "odd-ball" to de-tune an engine. The exception--duringextends the life of the engine. As engine manufacturers increase engine out training, should the throttle be abruptly closed at take-

the overhaul life of their powerplants, the latter becomes an off or climb powers, there is a good chance of de-tuning. For

important question. The chances are that if the operator applies this kind of training the pilot should study our Service Bulletin

the checklist we have been discussing and comes up with No. 245.

favorable answers to these questions about his engine, he can QUESTION--Do all your GO and GSO engines have the

probably get the hours desired--with some exceptions. But asame starting techniques?

top overhaul does not increase the official life or TBO of theANSWER--Definitely not. Here is an excellent opportumty

engine.to stress the importance of using the airplane pilot operator’s

We are surprised from time to time to have owners tell us manuals. It’s very important for pilots and mechanics who have

they top overhauled their engine at some point less than the to operate various engines. However, there are four different

major overhaul life for no reason other than somebody said it fuel metering systems and several different ignition systems used

was a good idea. Unless the manufacturer recommends it, or on various aircraft. So, when in doubt, check the manual.

QUESTION--I hear the term "Shower of Sparks’’ relative to

ignition systems. What does this term mean to us pilots? \iP

121 1‘)ANSWER--It means that while the engine is cranking during =I

a start, that a prolonged series of sparks is jumping the spark plug ~4 ,33

gap as compared to one single spark. This results in improved cold 6

STiLweather starting. 1 I-

2_3

2 Su c)llnder Models (QEluave 2

QUESTION--During starts with the shower of sparks ignition 3 of Intc~nl Acrruon Dme ModeLi 34 4system, I get some pretty severe kickbacks. How come?

-L-s

ANSWER--The common cause here is the retard breaker 6

doesn’t close, resulting in a start attempt on the advance points.A simple check is to run the engine at about 700 RPM and for a 3 17 7fmction of a second hold the staner switch to the stan position.The tachometer will indicate an immediate drop in RPM if the retard

Integnl Accnsory Dnve Models Fwr cylinder Models Etght CIIIIIJcr hlnlellpoints are operating. There will be no drop in RPM with a

malfunctioning retard breaker. C~lindcr Nwrbcr Ss~emr

CAUTION--This check not recommended on our direct drive lYiewcdfrom Topl

engines using automotive type starters.

QUESTION--At what RPM should I check my mags? TBO What Is It-

ANSWER--Where the airplane manual says. For example, HOW It Affects Youchecking at a lower than indicated RPM may give a higher than

normal mag drop. How It Affects Your PocketbookQUESTION--Is the actual mag drop in RPM very important?ANSWER--No. We are more concerned that the mag drop is

Textron Lycoming publishes the latest edition of Service

less than 50 RPM between the two mags and smooth, rather thanLetter No. 201 which sets forth factory recommendiations for

whether it’s 50-75 or 150. Again, it should be within the limits astime between overhaul (TBO).

indicated in the manual. There have always been many questions concerning this

QUESTION-- I noticed some ofyour engines show practically subject. Questions such as: Does this document mean I must

no mag drop. Is this normal? overhaul my engine at the recommended time interval althoughANSWER--Yes--but give it a litle more time and I think you’ll it is operating satisfactorily? What is the penalty, if any, if I

note some mag drop. However, if in doubt about any mag drop, do not comply with the factory recommended overhaul interval?be suspicious of a hot mag. Reduce engine RPM to idle and turn How does Texuon Lycoming arrive at the recommended hoursswitch to offand see if engine dies out. If it keeps running, beware for the various engine models? The questions are many andof hot mag. It’s sad but true that we will still have people gening varied and far too often the answers are as variable as thehurt due to hot mags.

questions and do not come from a reliable and/or official source.QUESTION--Can I save the engine any by using less than take-

off power?It is our objective here to set forth our policy and responsibilityconcerning this subject.

ANSWER--Indeed not. In fact, harm to the engine can be

caused by using less than take-off power.SERVICE LETTER NO. 201

First, let us consider the matter of how the factory arnvls

at the recommended overhaul time published in Service Letter

No. 201. The old timers in flying will remember when TBO’s

of 300 to 500 hours were considered exceptionally good. As

a matter of fact, when Lindberg flew the Atlantic and his engineperformed for over 33 consecutive hours it was considered on

extraordinary mechanical achievement. After World War Il.

IW-hour TBO’s rvere considered not only exceptional but the

maximum we could ever hope to receive from a reciprocatingengine. All of this not withstanding, our service and engineenngdepartments continued to seek new methods for extending the

TBO on Lycoming reciprocating engines. The methods used

would have to be capable of producing conclusive data that

would warrant extending overhaul hours. At the same time. the

engineerin~ fraternity was looking for improved metals, designs.etc., that would put more reliability in the engine.

~enThe best source for observince the wear chancrsrlsrlcs ot

THE FOUR STROKE CYCLE the various model engines was n_eht in our own plant where

approximately 2,500 engines a year are torn down to go into these engines could be operated satisfactorily to 2000 hoursour remanufactured engine program. These are run-out engines TBO. Other model engines were similarly programmed andreturned as exchange on either factory new or remanufactured TBO’s established in accordance with the inspection findings.zero time engines. It was a matter of setting up a system for

compiling this data and assigning reliable personnel to the pro-We must next consider the significance of the overhaul

ject to observe and examine each engine part to determine itshours set forth is SL201. First, we must understand that the

condition and further serviceability. Under condition of part,factory does not extablish firm hours for TBO. This can only

we were interested in whether or not it was in or out of specifica-be done by those maintenance personnel responsible for each

tion, whether it was an obsolete or current production part,particular engine. Our TBO hours are only guidelines used so

whether the part was damaged, burned, rusty, worn out, scoredan operator can have some idea of the hours he can expect from

or any of the other various conditions which could affect itshis engine, providing the criteria are met as set forth later in

serviceability. To make these determinations, it was necessarythis article. He must also consider any federal regulations he

to make dimensional measurements, magnaflux inspections,is operating under as well as any restrictions set forth by his

zyglo inspections, and all of the other inspections and tests thatinsurance company. We mentioned previously that certain

are required to make a decision on the condition of the part.criteria must be met ifan operator wishes to reach factory recom-

With a complete report on every engine torn down in our plant,mended TBO hours.

certain patterns began to take shape, and those areas that weren’t

"cutting the mustard" began to stand out.GOOD OPERATION AND MAINTENANCE

SERVICE INFORMATION RECORDThe two general categories which establish the standards

to be met are: (1) good operation in which pilots follow air-The next step was to inaugurate a system farcompiling data frame and engine manufacturer’s recommendations, and (2)

on field complaints from all over the world. Thus the SIR (Ser- good maintenance practices as set forth by the airframe andvice Information Record) system was born. Every Textron engine manufacturer. Indeed it is conceivable for an operator~ycdining employee receiving a complaint on any ofour engines to run an engine to destruction by 100 hours or less if hewas assigned the responsibility ofcompleting one of these forms disregards standards established by the manufacturer. We agreefor our factory. All of these complaints were then put into com- this would be an unusual and extreme case, but we are tryingputers and tabulated monthly, quarterly and yearly, thereby giv- to point out that the overhaul time for each particular engineing us another excellent source of data to tell us where our can vary all the way from the low extreme, to the factory recom-

weakness existed in each engine model, mended TBO, depending on operating conditions and

When the data from factory teardown engines was putmaintenance practices. For example, if pilots climb at steep

together with our field complaint data, our engineers were able angles, make abrupt throttle changes, improperly lean the

to go back to the drawing boa~s and apply the advances made engines in climb, exceed maximum allowable specified manifold

in metallurgy and technologies known to the present "state of pressure and/or RPM, chop the throttles abruptly and let down

the an", and improve or eliminate the trouble areas, thereby rapidly thereby causing rapid contraction of metals that have

increasing the TBO to as much as 2400 hours on some enginebeen up to operating temperatures, the TBO will be shortened

models, accord-ingly. On the other hand, maintenance personnel who

do not follow factory recommended inspection procedures andIt now became apparent to us, ifwe were to increase TBO intervals also contribute to premature engine replacement. Those

hours: beyond those already established, additional data would operators who use unqualified personnel for maintenance, orbe required. We needed a progressive maintenance program stretch inspection periods and oil changes under the illusion thevsimilar to that used by the airlines if we were to gather the in- are saving money, are operating under a false economy. Im-formation we required. Thus another system was inaugurated, provements in lubricants such as ashless dispersant oils, sparkwherein engineering personnel were assigned to literally live plugs, improvements in use of oil filters, etc., have also beenwith certain operators where there was a heavy concentration vital to our predicting longer periods between engine overhaul:c,f Textron Lycoming engines. Certain third level air carriers, however, if they are not properly utilized, the benefits achiev-air charter and air taxi operators and flying schools agreed to ed by the engineering fraternity cannot be realized. Ifpilots use

cooperate with us and allow our engineering personnel access proper techniques and judgment, and maintenance personnelto their operation and operational records. They also agreed to follow recommended procedures, the factory recommendedall inspection procedures set forth by our factory; and in addi- overhaul hours can be reasonably expected. This is not intend-tion to the normal inspections, they agreed to differential com- ed to mean all systems incorporated on the engine will go to

pression checks at recommended intervals, spectrometric oil the TBO hours. Indeed it may be necessary to replace certainanalysis as a safety monitor, and other inspections and innova- components such as magnetos, harness. governors, and othertions that would allow us to compile the records we needed to engine driven accessories. It may also be necessary to do a topaccomplish our goal. Engines in this program were inspected overhaul, depending upon oil consumption, compression leaks.at 100-hour intervals in order to establish a longer but safe TBO. etc. All of this notwithstanding, by increasing the TBO. theFor example, engines with a 1500-hour TBO were run to 1600 operator can reap economic rewards not possible heretofore.hours, completely disassembled and inspected. When it had been Economic benefits are gained in two ways. By increasing thedetermined that 168() hours was a safe operating time, engines overhaul rime. the cost of operation per hour is greatly nduc-were allowed to operate to 1700 hours and the procedure ed and longer engine life expectation increases the resale valuerepeated. After two years with improvements, it was determined of the aircraft.

Too much emphasis cannot be placed on the relationship especially good practice in those areas where lead foulln~of calendar time of engine life. The aircraft being flown every is a problem. Use of worn out plugs is false economy and

day, properly operated~with good maintenance should have no will shorten engine life immeasureably.problem in reaching recommended TBO’s. 7. When reaching mid-point of the published overhaul time

and at every 100-hour inspection thereafter, a differentialEFFECT OF FREQUENCY OF FLIGHT compression check and boroscope inspection should be

made.On the other hand, the aircraft which is only flown occa-

sionally becomes subject to factors which can and will shorten8. Remember, it will not be uncommon to be required to

TBO’s. Why will only occasional flights shorten TBO? Thereoverhaul accessories prior to engine overhaul. We are refrr-

am many reasons. Among them are the extended time between ring to such items as propellers, governors, magnetos,

oil changes which allow acids in the oil to build up and anackharness replacement, turbochargers, etc.

internal metallic parts of the engine, moisture can enter the If the above rules are followed, the engine should reach

engine via the breather and exhaust system causing rusting of our published TBO hours. Better filtration products, better

cylinders and other steel parts, rings may take a set and stick lubricants, improved metals, improved technology, etc., havein the groove, condensation in the magnetos will cause shor- all contributed to longer engine life. You are the only one who

ting of the breaker points, etc. Ifyour aircraft is i_n this category, can control these matters. Ifyou do not follow the recommended

you should fly it as often as possible, and a ground-run only rules, let the engine lay around and become rusty from lack ofis not considered satisfactory-temperatures must reach flight use, you will be overhauling your engine long before the fac-conditions to evaporate the condensation caused by starting the tory recommended hours.

engine. In_addition, engine oil should be changed more frequent- THE NUMBER OF HOURS YOUR ENGINE ISly to help prevent die acid build-up which attacks the internal OPERATED BEFORE A MAJOR OVERHAUL IS RE-parts of the engine. QUIRED IS STRICTLY DEPENDENT UPON YOU.

What is the magic number of hours per month an aircraftmust be flown to be classified in the category that will reachrecommended TBO’s? Again there are many variables to be con- Spectrometric Oil Analysissidcred, such as geographic location, temperatures, etc.;however, as close as we can calculate at this time, an aircraftnown a minimum of 15 hours per month, with proper opera-

Much is heard these days about spectrometric oil analysis;tion and maintenance, an owner can reasonably expect to reach

however, little is understood about the subject by the vast ma-

the hours set forth in S,L. No. 201.jority of the general aviation public. We will attempt here to

set forth our position on the subject and to point out the advan-

tages and disadvantages of the service.SUMMATION

Oil analysis is not new to military and commercial airlineO.K., let’s sum it all up and see where the operator stands operation, but it came to general aviation later. The object is

in relation to the latest edition of S.L. No. 201 and TBO. to examine oil samples from an engine, and break down the

He can expect longer TBO on his engines if the followin_gsample in parts per million in order to determine the internal

criteria are met:health of the engine. This is based on the fact that all lubricated

engine parts wear and deposit a certain amount of metallic prir-i. Proper pilot techniques. tides in the oil. The number of particles per million of each

2. Have maintenance personnel follow factory engine inspec- metal determines the wear pattern for the particular engine be-

tion procedures using good aircraft maintenance practices ing analyzed. It is of the utmost importance to understand that

at all times, the results of the analysis is only pertinent to THE ENGINE

3. Change oil and oil filter at recommended intervals. Use theBEING ANALYZED, although accumulation of data on anyspecific engine series is a basis for establishing standards for

ashless dispersant oils after engine has been broken inonstraightmineral oil.that series of engine. The fact that is important is a sharp nsr

of the amount of a particular metal in the oil. It is imperative4, Keep the air filter clean and do not operate with carburetor then to build a case history of each engine, wherein a sharp nse

heat on the ground except for brief check. With carburetor in any one metal will indicate abnormal engine wear. Theheat on, the intake air by-passes the filter and unfrltered analysis can also tell you whether the oil contains other liquidair is taken into engine. Remember, in sandy or dusty opera- contaminants such as gasoline or water. Gasoline contarmna-

tions it may be necessary to clean the air filter daily. tion of the oil can result from blow-by from the combustion

5. Do not attempt to drive any accessory or "hang" anythingchamber caused by poor combustion, bad timing, improper fuel

on the engine that is not approved by the factory. This will mixture, worn rings, and the like. Water contamination is usuril-

not only void the warranty, but often shorten overall engine ly restricted to condensed vapor, but this vapor combines with

life, the fuel combustion products to form harmful metal-attackingacids. Water also helps to form sludge, which is death to a t~lter.

h, Use only approved spark plugs. clean them at regular inter- Based on this contamination in the oil, the analysis will be ablevals, and above all, do not try to stretch the life of spark to pinpoint improper mixture, poor maintenance, etc.plugs. Some maintenance personnel rotate plugs, bottomto top and vice versa. between plug cleaning;. This is

There are five basic types of solid contamination In airplaneengines--carbon. gums, tars. sand (dirt). and metal.

Carbon contamination is a product of incomplete combus- of silicon) increased rapidly beyond its normal level of 10.

tian, high-speed operation, high load, or high temperature. Gum resulting in increased wear to the piston rings and cylinders.in the crankcase is usually a direct result of raw fuel washing This is clearly shown by the sharp rise in the chrome and iron

the cylinder walls and getting into the oil, caused by infrequent content. Corrective action by the operator (filter change and

and sporadic operation of the engine, improper mixture, and better fit) quickly resulted in normal iron levels with resultant

bad rings. Tar is created when the oil itself starts to decom- good health to the engine. If long TBO’s are to be achieved,

pare, and high engine temperature is the prime cause. Sand or it is MOST IMPORTANT that clean air be provided to the

din is perhaps the most common contaminant in aircraft engines engines.and can get into the engine much easier than might be expected. Basically, that is the oil analysis story. It is a good tool

The oil is analyzed on an emission-type direct-reading spec- IF PROPERLY USED. Like any other tool. it is only one of

trometer. When the machine operator pushes a button, an elec- many things that must be used to determine engine health.

trical spark passes through the specimen to be analyzed. This

spark vaporizes a sample ofall the elements present and causes

their atoms and ions in the spark column to emit light of Engine Overhaul-- What Does It Mean?

wavelengths characteristic to iron. If the specimen also contains Overhaul is a term which certainly means different thingsnickel, chromium, or other elements, the emitted light will then

to different people. When the aircraft owner has run a factoryinclude these wavelengths also. All this information is instant-

new engine to TBO, and then paid for an overhaul, that owner

ly recorded. The machine, or instrument measures 16 key usually has expectations of running the engine until the manufac-elements present in normal aviation lubricating oil, thus im- turer’s recommended TBO has again been achieved. These ex-

mediately indicating excessive traces ofany one element or com- pectations may or may not be realistic depending on what thebination of elements, overhauler puts into the overhaul.

Textron Lycoming Service Letter No. L171, entitled Perhaps it would be interesting to look at what an overhaul"General Aspects of Spectrometric Oil Analysis", provides a is in the legal terms of the Code of Fede~al Regulations for

guide for the use of oil analysis in measuring engine health. Aeronautics and Space usually referred to as FARs. WithThe information is in general terms since the health of each regard to overhaul, FAR Part 43.2 says that an aircraft, engine,engine must be determined on its own merits. or other component may not be described as overhauled unless

Differences in manufacturing processes may cause a varia- "(1) Using methods, techniques, and practices acceptabletion in analysis results for different engine models. The amount to the Administrator, it has been disassembled, cleaned,

of tin plating, copper plating, nitriding, etc., performed dur- inspected, repaired as necessary, and reassembled; and (2)

ing manufacture has a definite relationship to the oil analysis It has been tested in accordance with approved standard and

repons. It is not uncommon, for example, to see what seems technical data, or in accordance with current standards and

to be high copper content early in the life of an engine, only technical data acceptable to the Administrator, which have

to have this content continually decrease as the engine ac- been developed and documented by the holder of the type

cumulates time and then disappear altogether. Poor air filter certificate, supplemental type certificate.

maintenance, running the aircraft on the ground with car- This brief quote from FAR Part 43.2 should tell us that

buretorlalternate air on and holes in the air intake system are overhaul is a term open to broad interpretation. The re-

all factors which will allow an engine to ingest dirt and foreign quirements stated in part (1) say nothing about replacement of

matter. The result of this will show up as high iron (cylinder wo~ out or damaged components although there are enginebarrels) and chrome (piston rings) content at the next oil components which are not repairable. Part (2) requires that an

analysis. Neither time nor space permits us here to list all of engine be tested to designated standards. Certainly this re-

the variables involved (indeed we do not profess to know them quirements is meant to assure that an engine is airworthy at the

all) but it should be obvious to everyone that a history of each conclusion of an overhaul.

engine is the only criteria by which its health can be determin- Let us assume for a moment that the overhauler has follow-ed. Remember that several samples must be taken to determine ed the FAR to the letter in overhauling. All parts of thethe characteristics of an engine, and also remember that the first disassembled engine have been cleaned and inspected. Thosefew samples on factory fresh engines will read high as new parts parts which are worn beyond service limits are replaced whileare: wearing in and conforming to each other. those which meet service limits are reused. Then the engine is

These traces show up in parts per million on the spec- installed in the airframe for the test of performance. After a

trograph long before detrimental flaking or scoring takes place thorough inspection of the installation to insure it is airworthy,and almost always before any outward indication of trouble. the engine is run up and static RPM falls within the limits

Such an example is illustrated by a curve showing a plot of specified for this engine and propeller. This engine now meets

pans/million of siiicone, copper. aluminum, iron, etc., as ob- the FAR overhaul standard and is judged to be ainvorthy. Is

tlined on a Lycoming IO-540-D4A5 installation in a Piper Com- the engine actually producing at the certiticated power level and

;(nche airplane operating at a flying school. At 270 and 300 how long will it be until the service limit parts wear beyondhours, the dirt ingested by the engine las shown by parts/million those limits? These are questions we cannot answer.

There are some things we can do to help make sure that NEW ENGINE"engine overhaul" has the meaning we expect. First, refer to

the latest revision of Tutron Lycoming Service Bulletin No.A new engine is a product manufactured by Textron

240. The subject of this bulletin is replacement of parts at nor-Lycoming-Williamspon containing all new parts and ac-

mal overhaul, The list has about 25 items (times the numbercessories, and meeting all production test specifications, quali-

ofeach in the engine) which Lycoming recommends be replac-ty control tests, and regulations necessary to hold and maintain

ed at each overhaul regardless of their apparent condition. Thea production certificate issued by the FAA. When this finally

use of this list to establish the ’’must replace" items at overhaulaccepted engine is shipped to an airframe manufacturer, it will

will help to insure the quality of the overhaul.be subject to further testing during flight test of the aircraft forits certification acceptance. When the ultimate purchaser

To meet your expectations when your Lycoming piston receives the aircraft, it may have also been subjected to ferryengine is overhauled, there is one last consideration. No one time. However, all flight testing and ferry time will be logged.knows an engine better than its manufacturer, and therefore if The user then receives the engine with the full Textronyou choose to overhaul, Textron Lycoming would be a logical Lycoming-Williamspor new engine warranty, accompanied bychoice, In addition to new and remanufactured engines direct an Engine Logbook.from the factory, Lycoming also overhauls engines at the fac-

tory. To produce a first-class, quality overhaul, all parts listedREMANUFACTURE

in Service Bulletin 240 are replaced with genuineLycoming To the aircraft engine purchaser, the "remanufactured"pans, The Lycoming overhaul does not stop with the S.B. 240 engine, as provided by Textron Lycoming-Williamspon, offerslist. New engine limits on cylinders are assured by installing the opportunity to obtain some of the benefits of a new engine,all factory new cylinder heads, cylinder barrels, valve guides, but at a price savings.valve seats and exhaust valves. The overhaul includes updating The general term "remanuEdcture" has no specific defini-to comply with all ADs, all Textron Lycoming bulletins and tion in FAA Regulations. We have observad it to be consideredinstructions, and all product improvements. generally the same in the industry as a major overhaul. However,

To summarize, all engine overhauls are not the same. The the Textron Lycoming Factory Remanufactured Engine is in a

Textron Lycoming overhauled engine is a QUALITY product somewhat different category. The specifications for the factorywhich assures long-term reliability to meet your expectations. remanufacture ofour engines are carefUlly written and made an

It carries a one year parts and labor warranty and can be ordered integral part of our Repair Station Manual, which specifiesfrom all Textron Lycoming distributors. precisely what must be done to an engine. The factory rcmanufac-

And f~nally, remember that the term "engine overhaul"ture specifications get their authority from FAR, Part 43.

can have more than one meaning. Be sure you and the overhauler A Textron Lycoming Factory Remanufactured Engine is

agree completely on the exact meaning before placing yourdefined as an aircraft engine originally designed and manufac-

order, tured by Textron Lycoming that has been disassembled, repairedor altered, and inspected in accordance with Lycoming ServiceBulletins and/or Instructions, incorporating applicable mandatoryengineering changes, and any Airworthiness Directives, at the

Some Definitions Applicable To Lycoming factory. Tolerances and limits established and publish-

Textron Lycoming-Williamsport Enginesed by Lycoming, and those approved applicable rework applica-tions, are used during the remanufacturing of the engine and the

In the manufacture, sale, operation and maintenance ofair- engine is brought back to zero time. Such engines retain theircraft engines, terms such as new, rebuilt, remanufactured, original serial number, but will add the letter "R" preceding the

overhaul. major overhaul, top overhaul, etc., are used letter "L" on the data plate which designates remanufactured

throughout the aviation industry. by Lycoming.

While we all have a general understanding of most or all Thus, a factory remanufactured engine, by Lycoming’sof these terms, there is no industry dictionary to which we can

definition, has all the foregoing, plus the fact that it is done byrefer for a commonly accepted definition of all of them. The Lycoming at its factory, by factory personnel with manufactur-

Federal Air Regulations, which would have to be the starting ing and engineering expertise. This factory remanufactured enginepoint for definitions. refers only to new, rebuilt and alterations must also meet the same production test specifications used for

when referencing engines; but the term "rebuilt" is not useda new engine. With each Textron Lycoming factory remanuf8c-

~pecifically by Textron Lycoming-Williamsport. tured engine an Engine Logbook is fUrnished with Form No. 776

The purpose of this article is to define the terms new,

attached on the inside of the fiist page. Additionally, each engineas released through the remanufacturing system is accompaniedremanufactured and overhaul, as used by Textron Lycoming- by a maintenance release that refers to the factory order to which

Williamspon, Pennsylvania with its engines, and to offer com- all work was performed, and showing that it was inspected byment on some of the other related terms. We do add this point-- FAA authorized personnel.these definitions and explanations have been reviewed byManagement, Engineering, and Service personnel at our fac- WARRANTY ON TEXTRON LYCOMING FACTORY

tory and they are accurate as far as Textron Lycoming- REMANUFACTURED ENGINES

Williamspan Plant is concerned. However, they are nor offered "En~ines are remanufactured under Textron Lycoming’~in contradiction to any authorized manual or publication regar- Repair Station Certificate No. 1108 and afford the same Tex-ding our engines. or to any FAR or FAA authorized publication. tron Lycoming Standard Warranty as new engines."

Our factory remanufactured specification lists engine parts OVERHAULwhich must be 100% replaced. The major reuse parts of the

Although there is no specific defmition of the term overhaulused engine. such as crankcase, crankshafts, housing, gears, in the FAR’s, Pan 43, Section 43.13 of the Federal Aviationgearshafts, are thoroughly reconditioned, generally in the same

Regulations apply--and it states the following:manufacturing areas in which they were formerly made. These

time-tested parts, upon completion of their re-conditioning pro- MAINTENANCE, PREVENTIVEcesscs, are then inspected the same as new pans and returned

MAINTENANCE, REBUILDING AND ALTERATIONto holding areas for re-assembly into an engine, now designatedas remanufactured. These factory reconditioned parts, for all (a) Each person maintaining or altering, or performingpractical purposes have become zero time parts from which preventive maintenance, shall use methods, techniques, and

evolved the general phrase--’’zero time since remanufacture". practices acceptable to the Administrator. He shall use the tools,

Wherever new pans are used, they may be described as new equipment, and test apparatus necessary to assure completionand unused except for normal testing. of the work in accordance with accepted industry practices. If

Any discussion of parts reused in the factory remanufac- special equipment or test apparatus is recommended 4v the

tured engine should include an explanation of the reuse limita-manufacturer involved, he must use that equipment acceptable

tions of parts. Our engine paRs have specific limits and are iden-to the Administrator.

tified as recommended replacement parts by an enti’iely different (b) Each person maintaining or altering, or performingbut effective method. For example, when a part becomes worn preventive maintenance, shall do that work in such a manner

to a certain size, it is no longer usable in our engines in accor- and use materials of such quality, that the condition of the airdance with our publications and our practices. Therefore, it has craft, airframe, aircraft engine, propeller, or appliance work-

a life equarto its wear dimensions, or otherphysical proper- ed on will be at least equal to its original or properly altered

ties, which are spelled out in our manuals,service bulletins, conditions (with regard to aerodnamic function, structuralservice letters and service instructions. strength, resistance to vibration and deterioration, and other

The term "zero time" might very well be misunderstood, qualities affecting airworthiness).

but the fact is that the historical time on the parts has no real The Textron Lycoming overhaul manuals clearly stipulatemeaning since the parts have been completely inspected and the work to be done to accomplish an overhaul. We, at Tex-found to meet Lycoming’s specifications. This allows the engine tron Lycoming, do not distinguish between major overhaul andthe same amount of time between overhauls as a new engine, overhaul. We prefer to use the one word-overhaul-becauseand the factory remanufactured powerplant is considered capable we want it to be as broad as possible. Overhaul means the en-of being overhauled by another agency and attaining at least tire engine must be considered part by part as per the applicableone additional time between overhaul run. overhaul manuals. To accomplish this, there must be complete

While we are on the subject, time between overhauls in the teardown so that all parts can be examined. In overhaul, there

United States is nothing more or less than a recommended are certain parts that must be replaced, regardless of condition

number of use hours by the engine manufacturer. There are as per the overhaul manuals, and Textron Lycoming Service

some operators who never get to the recommended time of Bulletin No. 240. The remaining parts must then be examined

overhaul because of improper operation and poor maintenance. as required by one or more of the following: (1) visual examina-

There are many more who go beyond it with no problems. It tion for discrepancy, (2) non-destructive testing or other

is strictly a function of how the engine is operated and main- mechanical examination, and (3) dimensional checking. At this

tained. Furthermore, since time between overhauls is not a re- point, parts must conform to the fits and limits specificationsquirement of law in the United States, it is the responsibility listed as part of the Textron Lycoming Overhaul Manual. and

of the pilot and his qualified mechanic concerning the condi- the Table of Limits.

tion of the engine and whether or not to continue it in service.By means of overhaul manuals for the various enginePlease note that to certain special FAA certified aircraft opera- models, Textron Lycoming makes available all maintenance data

tions, the above may not apply, i. e., air taxi, commuter airlines, and information necessary to maintain, repair, or overhauletc,

engines which are in service. In addition, Service Bulletin 230

lists the parts that are recommended for replacement at overhaul.REMANUFACTURE A SUMMARY

Service Letter No. L201 lists the recommended overhaul periodsThe Textron Lycoming-Williamsport factory remanufac- for the various engine models. However, the FAA has no

tured engine is an aircraft engine originally designed and specific requirements that the repair agency must comply withmanufactured by Lycoming, and later remanufactured under the the Lycoming manual, or with the applicable service bulletins

authority of the Federal Air Regulations by factory personnel and instructions. The final decision on the type of maintenancewith manufacturing and engineering expertise. It is a zero time or repair accomplished is left to the mechanic doing the work.

powerplant with the same warranty as a new engine. The key When the mechanic signs for the overhaul of an aircraft eneine.benefit for the owner is price he saves money by purchasing he certifies that he has performed the work using metl;ods.a factory remanufactured engine instead of a new one. In addi- techniques, and practices acceptable to the FAA Administrator.tion, the factory remanufactured engine greatly reduces aircraft The previous time on an overhauled engine is carried forwarddown time in comparison with an overhaul. The factory engine in the en_ei?e logbook: whereas, a factory remanufactured enginealso benefits from the latest improvements and engineering goes back to zero time.

changes.

In addition to manufacturing and remanufacturing aircraft limited aerobatic capability, only positive G maneuvers and ven~engines, Textron Lycoming also overhauls engines at the brief periods of invened flight are possible.Lycoming factory. These overhauled engines exceed industrystandards for quality through the use ofgenuine Textron Lycom-

To operate correctly, an engine must have fuel which is

ing pans and full factory support. Although these engines doproperly metered in proportion to the air entering the engine

not become zero time as when remanufactured, a policy of ex-induction system. The fuel injector measures air flow and meters

tensive parts replacement insures a quality product which hasfuel to the inlet ports of each cylinder. Unlike the carburetor,

a full year parts and labor warranty against defects in materiala fuel injector is not affected by unusual aircraft attitudes.

and workmanship.Therefore, all Lycoming engines which are designed foraerobatic flight are equipped with a fuel injector.

TOP OVERHAUL VS. MAJOR OVERHAUL Delivery ofmetered fuel to the combustion chamber is notThe industry originated the terms Top Overhaul and Ma- the only challenge addressed in designing an aerobatic aircraft

jor Overhaul years ago to identify and make a distinction be- engine. It is also necessary to provide lubricating oil to manytween the degrees of work done on an engine. Textron points in an operating engine regardless ofthe aircraft attitude.Lycoming-Williamsport defines a top overhaul as the repair or Two different methods have been used to provide oil foroverhaul of those parts on the outside of the crankcase without aerobatic engines manufactured by Textron Lycoming.completely disassembling the entire engine._It includes the

removal of the cylinders and degiazing the cylinder walls, in-The flat, opposed cylinder aerobatic engines first offered

spcction of the pistons, valve operating mechanism, valveby Lycoming were designated AIO-320 or AIO-360. These

guides, and replacing piston rings. A major overhaul consists engines were the dry sump type with appropriate oil inlet and

of the co_mplete disassembly of an engine, its repair, reassemblyoutlet connections as well as two crankcase breather connec-

and testing to assure proper operation. Nevertheless, whethertions. Necessary lines and an external oil tank with a revolving

the work accomplished is a top or major overhaul, Federal Avia- pickup capable of reaching oil in almost any aircraft attitude

tion Regulations require that it meet regulations, which werewere then supplied by the aircraft manufacturer. This type of

-quoted at the very beginning of this discussion of overhaul. installation provided aerobatic capability but it was complicatedenough to be very expensive. A simpler, more universally usable

OVERHAUL A SUMMARY system was needed.

Textron Lycoming does overhaul engines at the factory. Most Lycoming engines are termed "wet sump" enginesAn overhauled engine carries forward all previous time in the because oil is stored internally in a sump at the bottom of theengine logbook; a factory remanufactured engine goes back to crankcase. When the engine is inverted, the oil will be in thezero time. The cheapest overhaul may not be the best. There top of the crankcase rather than in the oil sump. To maintainshould be no compromise with safety. A good overhaul has a a continuous flow of oil during inverted flight, an oil pick-updisadvantage for the owner in that unless he has a spare engine, line must be provided near the top of the engine as well as indown time of the airplane is often undesirable. First overhauls the oil sump. Lycoming aerobatic engines carrying an AEIOon a well-maintained and properly operated engine are generally designation use inverted oil system hardware to adapt oil pick-economical in cost. Subsequent overhauls tend to be more ex- up lines at the top and bottom of the wet sump engine.pensive. Lycoming provides overhaul manuals and related ser-

vice publications to aid operators in the field accomplish a topThis inverted oil system is comprised of two major com-

overhaul or the more complete major overhaul; but the overhaul- ponents, the oil valve and the oil separator. Several other items

ing agency must comply with the performance rules set forthof hardware adapt the system to the Lycoming engine so that

in Section 43.13 of the Federal Aviation Regulations.oil is available to the oil pump in either the upright or inverted

position. These hardware items include a standpipe in the sumpwhich acts as the engine breather during inverted flight, a specialadapter or plug at the oil sump suction screen, and other hoses

What Is An Aerobatic Engine? and fittings.

A Fiver reader wrote to express interest in a Lycoming In addition to the inverted oil system Lycoming makes other

10-360 engine. He went on to say that the engine would be engine modifications to adapt standard engine models to

used in an aircraft capable ofunlimited aerobatics. A statement aerobatic use. Some models of the AEIO-540 engine have a bat‘-

like this indicates a need for explanation of the differences be- fle added in the oil sump to eliminate oil loss through the oil

tween the standard Lycoming engine and the aerobatic Lycom- separator. Also the flow ofoii to the oil pickup in the accessorying engine. Unlimited aerobatic flight with a non-aerobatic case is limited in the inverted position. To improve this oil flow.

engine could result in engine stoppage from either fuel or oil holes are machined in the upper rear wall of the crankcase.

starvation. With these changes completed, the engine is capable of

It should first be explained that unlimited aerobatic flight unlimited periods of inverted flight in addition to normal uprightimplies that the aircraft may be flown in any attitude with no flight. Because the oil pick up points are at the top and bottom

limitations. For this reason, any engine which employs a float of the engine, knife edge flight or flight at very high up or down

type carburetor for fuel metering is immediately eliminated from pitch angles have some limitations; the limitations do not pre-use in a fully aerobatic aircraft. Inverted flight would quickly vent engines from being used in aircraft which perform all the

cause the carburetor to stop metering fuel and the engine to stop maneuvers required for international aerobatic competition.running. While carbureted engines are used in some aircraft with Engines built with the inverted oil system and incorporating the

other modifications discussed earlier are cenified by the FAA A. GENERAL RULES

as acrobatic engines. i. Never lean the mixture from full rich dunng take-off, climb

The meanings of the letters and numbers in the Lycoming or high performance cruise operation unless the airplane

engine designation are fully explained elsewhere in this publica- owners manual advises othenvrse. However, during take-

tion, but the AE part of the AEIO indicates "aerobatic engine." off from high elevation airports or during climb at higher

Lycoming is currently producing AEIO-320, AEIO-360 and altitudes, roughness or reduction of power may occur at

AEIO-540 acrobatic engines which range from 150 to 300 full rich mixture. In such a case the mixture may be

horsepower. One of these models should be installed in a general adjusted only enough to obtain smooth engine operaaon.

aviation aircraft which is designed for acrobatic flight. Careful observation of temperaturt instruments should be

practiced.2. Operate the engine at maximum power nurture for per-

The Use of Higher Octane Aviation Fuel, formance cruise powers and at best eronomv mixture for

100 ]LL Blue Or 100 Green, For Engines economy cruise power; unless otherwise specified m the

airplane owners manual.

Rated For 80/87 Octane Fuel3. Always return the mixture to full rich before increaslnp

(A Reprint of Texuon Lycoming Service Lener power settings.

No. L185) 4. During let-down and reduced power flight operations n

We have received many inquiries from the field express- may be necessary to manually lean or leave mixture set-

ing concern over the limited availability of 80/87 grade fuel, ting at cruise position prior to landing. During the land-

and associated questions about use of higher leaded fuel in ing sequence the mixture control should then be placed

engines rated for grade 80/87 fuel. The leading fuel suppliers in the full rich position, unless landing at high elevation

indicate that in some areas 80/87 grade aviation fuel is notfields where leaning may be necessary.

available. It is further indicated that the vend is toward phase 5. Methods for manually setting maximum power or best

out of 80/87 aviation grade fuel. The low lead 100 LL Avgas, economy mixture.

blue color, which is limited to 2ml tetraethyl lead per gallon a. Engine Tachometer--Airspeed indicator Method: The

will gradually become the only fuel available for piston engines. tachometer andlor the airspeed indicator may be used

Whenever 80/87 is not available you should use the lowest lead to locate, approximately, maximum power and best

100 grade fuel available. Automotive fuels should never be us- economy mixture ranges. When a fixed pitch propellered as a substitute for aviation fuel in aircraft engines. is used, either or both insvuments are useful m-

The continuous use, more than 25R of the operating time, dicators. If the airplane uses a constant speed propeller,

with the higher leaded fuels in engines certified for 80 octane the airspeed indicator is useful. Regardless of the pro-

fuel can result in increased engine deposits both in the com- peller type, set the controls for the desired cruise power

bustion chamber and in the engine oil. It may require increas- as shown in the owners manual. Gradually lean the

ed spark plug maintenance and more frequent oil changes. The mixture from full rich until either the tachometer or

frequency of spark plug maintenance and oil drain periods will the airspeed indicator are reading peaks. At peak indica-

be governed by the amount of lead per gallon and the type of tion the engine is operating in the maximum power

operation. Operation at full rich mixture requires more frequent range.

maintenance periods; therefore it is important to use properly b. For Cruise Power: Where best economy operation is

approved mixture leaning procedures, allowed by the manufacturer, the mixture is first lean-

To reduce or keep engine deposits at a minimum when us- ed from full rich to maximum power, then leaning a

ing the higher leaded fuels, blue 100 LL Avgas or green 100 slowly continued until engine operation becomes rouph

grade Avgas, it is essential that the following four conditions or until engine power is rapidly diminishing as noted

of operation and maintenance are applied. by an undesirable decrease in airspeed. When either

condition occurs, enricfi the mixture sufficiently to ob-A. Fuel management required in all modes of flight opera-

tain an evenly firing engine or to regain most of thetion. (See A, General Rules).

lost ah-speed or engine RPM. Some slight engine powerB. Prior to engine shutdown run up to 1800 RPM for 15

and airspeed must be sacrificed to gain a best econom)´•to 20 seconds to clean out any unburned fuel after taxlmg in.

mixture setting.(See B, Engine Shut-Down).

c. Exhaust Gas Temperature Method (EGT): Refer to

C. Replace, lubricating oil and filters each 50 hours ofService Instruction No. 1094 for procedure.

operation, under normal environmental conditions. (See C,

Lubrication Recommendations). Recommended fuel management-manual leaning, will not

D~ Proper selection of spark plug types and good only result in less engine deposits and reduced maintenance cost.

maintenance are necessary. (See D, Spark Plugs).but will provide more economic operation and fuel saving.

The use ofeconomy cruise engine leaning whenever possi- B. ENGINE SHUT-DOWNble will keep deposits to a minimum. Pertinent portions of the

manual leaning procedures as recommended in Textron Lycom- The deposit formation rate can be greatly retarded by con-

ing Service Instruction No. 1094 are reprinted here for wlling ground operation to minimize sepatation of the non-

reference.volatile components of the higher leaded aviation fuels. This

rate can be accelerated by (1) Low mixture temperatures and detonation. "Knock" is much more obvious in an automobile

(2) Excessively rich fuel/air mixtures associated with idling and engine when a lower octane fuel than that specified by the

taxiing operations. Therefore, it is important that engine idling manufacturer is used, and the engine has a load or pull on it.

speeds should be set at their proper 600 to 650 RPM range with there is a definite knocking sound as a result. This is a typethe idle mixture adjusted properly to provide smooth idling of detonation. The proper fuel will burn smoothly from the sparkoperation. Shut down procedure recommends setting RPM at plug outward, exerting a similar smooth pressure downward1800 for 15-20 seconds prior to shut down.

on the piston. Detonation or "knock’’, instead of smooth burn-

ing ofthe fuel, results in an explosion or shock, producing veryC. LUBRICATION RECOMMENDATIONS

high heat and an abrupt hammer-like explosion to the piston.Many of the engine deposits formed by combustion of all

In aircraft engines, detonation is almost impossible to hearleaded fuels are in suspension within the engine oil and are not until it has reached proportions where it is frequently too late.removed by a full flow frlter. When sufficient amounts of these

The rush of air, sound of the engine and prop, and sound-contaminants in the oil reach high temperature areas of the

proofing of modern aircraft cabins all tend to muffle the earlyengine they can be baked out, resulting in possible malfunc-

tions such as in exhaust valve guides, causing sticking valves, stages of detonation. Similarly, in most cases, by the time the

The recommended periods of 50-hour interval oil change and cylinder head temperature shoots upward indicating detonation.

filter replacement for all engines using full-flow fiitration systemit may be too late because these obvious symptoms tend to in-

and 25-hour intervals for oil change and screen cleaning fordicate detonation or "knock" has reached serious levels, often

pressure screen systems must be followed. If valve sticking is progressing into preignition,with subsequent piston damage.

noted, all guides should be reamed using the procedures as stated Lead in aviation fuel has an additional role of preventingin latest editions of Service Instruction No. 1116 and/or Ser- small welds that can form between the hot valve and its seat.

vice Instruction No. 1425, and time between oil drain, and oil The experts tell us that with no lead at all, valve action wouldfilter replacement should be reduced. gradually erode the valve seat, resulting in a loss of compres-

sion. Lead provides a thin layer of protective material whichD. SPARKPLUGS

prevents the undesirable erosion.

Spark plugs should be rotated from top to bottom on a 50 Although we have seen that lead is extremely helpful inhour basis, and serviced on a 100 hour basis. If excessive spark the fuel, it can create problems in the cylinder if the fuel didplug lead fouling occurs, the selection of a hotter plug from

not have a scavenging agent in it to cope with this problem aspectthe approved list in Service instruction No. 1042 may be of TEL. Without the scavenging agent, the resulting lead ox-

necessary. However, depending on the type of lead deposit ide deposits from combustion would collect in the cylinder informed, a colder plug from the approved list may better resolve

large amounts, resulting in glowing horspots, preignition andthe problem. Depending on the lead content of the fuel and the

early engine failure. Bromides are added to the fuel to com-

type of operation, more frequent cleaning of the spark plugs bine with the lead so that most of the lead is carried off withmay be necessary. Where the majority of operation is at low

the exhaust gases as lead bromide.power, such as patrol, a hotter plug would be advantageous.If the majority of operation is at high cruise power, a colder Fuel dyes are added to the fuel to show that the commer-

plug is recommended, cial aviation fuel contains lead, and to easily identify its octane

raring. They are colored as follows:

80 Octane Low Lead Red

100 Octane Low Lead Blue

What is Avgas~ 100 Octane High Lead Green

Avgas (aviation gasoline) is energy that we have tended toAviation Grade 80 octane has 0.5 mi. TEL/U.S. gallon:

take for granted. Aviation gasoline is really an excellent fuei.100 octane low lead has 2 mi. TEL/U.S. gallon; and 100 oc-

It is easily stored in routine containers. Furthermore, its freez-tane high lead may have anywhere from 3.0 to 4.0 mi.

ing point (below-760 Fl and boiling point (3380 Fl are separ-dtedTEL/U.S. gallon.

by a wide temperature range, which make it quite a practical Dye colors are also used in the coding of aviation fuel

fuel, storage tanks and transfer lines, and are standard throughout

The layman pilot or mechanic need only know that’he world. The dyes burn Eomp]etely during combustion oirhe

fi~ei.technically, Avgas is a careful blending of paraffins, aromatics,

napthenes and olefins, to which the refinery adds tetraethyl lead By knowing more about the fuel used in his or her engine.(TEL). It also has dyes added to indicate the fuel has lead, and the pilot or mechanic is better informed to cope with any fuel

to distinguish octane ratings by color. Stabilizers are included related problems that might occur in the engine.to aid during long storage periods, and a scavenging agent to

help eliminate the combustion products of lead.

The oil companies tell us that addition of lead to the fuel

is the best, most economical way to a higher octane fuel. In

the petroleum industry jargon, a higher octane rating would

make the fuel more "knock" resistant--or more resistant to

80 ~ctane Engine-- carrying Lycoming parr number 75068 and operated more than 25~’0

Grade 100 Aviation Fuel of the time with fuels graded higher than 80. It also recommended

that these valves be replaced at overhaul with Lycoming part numberMany aircraft owners still ask questions about the effect

74541, an exhaust valve which is identical to the 75068 valve ex-of using a higher grade fuel in engines which were originallycertified for 80´•octane aviation gasoline. Since this question cept for the highly corrosion resistant material in the valve head.

revolves around the gasoline usedin aircraft, it is appropriate Since early 1976, new and remanufactured engines shipped from

to first discuss the subject of aviation fuel grades, octane levels the factory have had this change incorporated in them.

and designations before getting to the central question of the If you are the owner of an aircraft with a low-compressionengine and the fuel used it it. engine which still has the 75068 exhaust valves, there may still be

Most individuals associated ;vith aviation for a number of no reason for concern. Higher leaded fuel is defined for purposes

years tend to recall four aviation fuel grades in terms of the of this discussion as fuel with more than two mi of lead per gallon.lean/rich octane ratings used by the American Society for This includes only the grade 100 green fuel. The blue, grade 100LL

Testing and Materials (ASTM) and by the military. These fuelfuel which is found in most areas of the United States contains a

grades are listed in the second column of the table under "Oldmaximum of two mi of lead per gallon and is approved for use in

Designation." Two things have happened over the years which

require explanation. First, the oil companies indicated an in-all Lycoming engines. Several years of experience with grade 100LL

tention to produce only a single grade, 100 low lead fuel, which fuel in engines rated for use ofgrade 80 aviation gasoline has shown

would be used for all aircraft piston engines. Second, the ASTM that use of grade 100LL does not cause measurable erosion of the

specification for aviation gasoline was recently updated and new 75068 exhaust valve.

"Grade Number" desi~nations were assigned to each level of It is true that use of fuel with a lead content higher than that

aviation fuel which is presently available from commercial of grade 80 is more likely to cause lead fouling of the spark plugssources. The new designations have a single number, but the

and combustion chamber. Them are basic operational andoctane level requirements for lean and rich mixture still exist.

maintenance procedures which can be used to help cope with theThe table shown here applies to fuel standards in the United

States and will allow easy comparison of the old and new fuel higher lead content ofgrade 100 or grade 100LL. Textron Lycom-

designations when the term "grade" is referred to throughout ing issued Service Lener L185 to provide guidance.

the remainder of this article. The advice in Service Letter L185 touches four areas. First.

general rules for proper leaning since an over-rich fuel/air mixtureOctane or Maximum contributes to lead deposits in the combustion chamber and on the

Nevj Performance Milliliters

ASTM Old Number of Lead spark plugs. The second item was an excess fuel "clearing pro-

Designation Designation LeanlRich Color per U.S. Gallon cedure" to be used before engine shutdown. Third, because the

Grade 80 80/87 80/87 Red .5 mi higher leaded fuels also cause more lead to be suspended in the

Grade 100LL 1001130 Blue 2.0 mi oil, a maximum time between oil changes of 50 hours was recom-

Grade 100 1001130 1001130 Green 4.0 mi mended. The final point suggested rotation of spark plugs from top

None 91196 91/96 Blue No longer to boaom at 50 hour intervals and possible change to a different

’None 115/145 115/145 Purple available heat range spark plug if the type of operation made this changeappropriate.

The annduncement of a single grade aviation fuel for allWhenever the subject of using higher octane fuels in engines

reciprocating aircraft engines created a furor which gradually fad-certified for grade 80 comes up, someone is sure to ask if this will

ed away as pilots and mechanics became more knowledgeable ofcause these engines to run hotter. Tests were run in the Lycoming

’the actual effects of using gradd 100LL fuel. To respond to thosetest cells using a low-compression 0-320, 4 cylinder engine. In-

questions which are still asked, a brief summary of the policies ad-itially, the engine was run with grade 80 fuel at 55 power. 65 ro

vocated and instructions issued by Textron Lycoming during thepower, and 75% power. At each power sening, the fuel flows were

past 10 years may clear up the fuel issue for readers who ownadjusted from rich to lean and a curve ofcylinder head temperature

engines certified for grade 80.was pioned against the fuel flow. This test was repeated using grade

Textron Lycoming Service Instruction 1246 dated January 14, 100 aviation gasoline. The results essentially showed no differences.

1972, provided information on conversion of0-235 and 0-290 engine The temperature curves in the drawing below show the pioned pointsmodels to the use of grade 100 fuel. These smaller, low compres- for the two fuels.

sion engines were manufactured with solid stem exhaust valves and 0-320 (150 HP)

bronze valve guides. They were certified with grade 80 fuel. Valve CIL HEAD TEMPS.

erosion and accelerated valve guide wear occurred when operators FUE;SROWwere forced to use highly leaded fuels instead of the grade 80

cn Ha TD1PS

designated for the engines. The erosion problem could be alleviatedb

by replacing the original parts with sodium cooled exhaust valvesI

and valve guides made of ni-resist alloy. E 1 ~07 6sX2450 RPN

As grade 80 f~el was eliminated from the inventory at manyato RP~

55X

airports, it became necessary for some owners of low-compressionB

d

engines to utilize the highly leaded green fuel extensively. The most gapparent result associated with continuous use of this fuel in low-

compression engines was the possible erosion of the exhaust valveNEL FLOW-LB./HR.

head. Textron Lycoming Service Bulletin 404 required inspectionof those low-compression engines manufactured with exhaust valves

o-O 80/87 D(XON GdSOLI~JE-OUce PB/GOL.

x-x 100/130 EXXON G1ISOUNE-~.OSes PB/CIIIL.

To summarize the contents of this article, low compres- 3. During descents to the traffic pattern, we recommendedsion engines which are rated for use with grade 80 fuel should be maintaining the mixture at the leaned cruise condition with

operated with the available aviation gasoline in this order of a gradual richening of the mixture, carrying some power.priority: (1) Grade 80, (2) Grade 100LL, (3) Grade 100. Only and at a sensible air-speed to maintain the most efficientthe third choice, grade 100 "high lead’’ aviation gasoline could engine temperatures possible. Avoid low power--highcause any problem. Even this fuel is only a problem in engines speed descents which cause sudden cooling, severe leadwhich have the 75068 exhaust valves and only then ifhigh lead fouling, cracked cylinder heads and warped exhaust valves.fuel is used more than 25% of the time. The recommendations 4. If the magneto check before or after flight reveals anyin Service Letter L185 will aid in reducing lead induced prob- roughness caused by a fouled spark plug, open the throttlelems. Considering all possibilities, there should be very few slowly and smoothly to cruise RPM and lean the mixtureowners who have any reason for concern with the aviation fuel

as far as possible, Olet with a smooth engine). After severalavailable to them. If only grade 100 fuel is used, then the ex- seconds leaned, return to the proper mixture position forhaust valves should be checked. If either grade 80 or grade takeoff and recheck the magneto. if two such attempts do100Li is used, these low compression engines should reach

not clear the fouled plug, then return to the line and reportTBO without difficulty, the problem to maintenance.

RECOMMENDATIONS ON MAINTENANCE TO

Minimizing The Spark Plug MINIMIZE SPARK PLUG FOULING

Fouling Problem I. Rotate spark plugs from top to bottom on a 50rhour basis.and service plugs every 100 hours, particularly in an engine

Perhaps it’s tbo cliche to say that using proper operatingcertified for 80 octane aviation fuel, but using a higher lead-

ed fuel such as 100 LL.and maintenance procedures will minimize spark plug fouling,according to engineers at Textron Lycoming and the spark plug 2. Make sure the correct heat range spark plug is being used

manufacturers. However, this is the best known method of cop in your engine if you are experiencing plug problems.ing with the problem. Textron Lycoming Service Instruction No. 1042 is the basic

reference source concerning the proper spark plug for the

RECOMMENDATIONS ON OPERATION TO specific engine. Do not simply replace plugs with same

MINIMIZE SPARK PLUG FOULING model number that were in the engine. The previous in-

i. Use helpful ground operating techniques such as:staller may have used the wrong plug. Don’t be trapped!Use the chart.

a. Idle engines in the 1000-1200 RPM range so that the

lead scavenger in the fuel can operate.3. Oil land filter) should be changed at a maximum of 50

b. Avoid closed throttle idle. hours, particularly when using the higher leaded fuels. Oil

filters do not filter the lead sludge which accumulates fromc. After flight, before shutdown, run engine one minute

combustion. Controlled programs have revealed that theat 1200 RPM, increase to 1800 RPM for 15 to 20

higher leaded fuels build an accumulation of lead in the oilseconds, reduce to 1200 RPM and cut engine with mix-

from combustion. If the oil is continued in use beyond 50ture control.

hours time, it has caused sticking exhaust valves.d. Check magnetos on fixed pitch direct drive engines at

4. If idle mixture is too rich on the ground, have maintenance1800 RPM to help prevent lead fouling, and generally

adjust it properly.at 2200 RPM with a constant speed prop.

e. Avoid abrupt throttle movements on the ground as it tuM,

invites spark plug fouling. LEAD EOULlNG

2. Use efficient fuel management (good leaning techniques) ICM*x

at cruise power:DEPOSITSLEAST "00

ADYERSE TO GOOD cuma

a. Lean at any altitude at the manufacturers’ recornmend-Ilw *ND

SPARK PLUG cnuaE

spark plug fouling and save fuel: AHD soo

ed cruise power. OPERATION lax,

b. Lean as close to best economy mixture as the engine I900

HOLD

will permit by rulining smoothly, it will help prevent LEAD BROMIDE

CARBON FOULING700

(1) WithanEGTsystem, thismeansoperateatpeak I ~ooEGT at cruise power of75% or less on the small

direct drive engine. IDLECONOUCINE P~TH K)PMED

(2) With a float-type carburetor, it means leaning BI COMBVnlON PPODVCIS

to roughness at cruise power, then enriching just TEMP P ’B’

enough to remove the roughness.(3) With a fuel injection engine, it means leaning to Combustion deposit fouling fundamentals

the bottom of the percent of power point on the5. Low ambient temperatures can be a cause ofspark plug foul-

fuel flow gage, with a smooth engine result.ing. Lead from the fuel should become vaporized during

cdmbustion and converted into a powder form which is nor- Do Not Use Automotive Gasoline In

m8lly blown out the -haust. In order to achieve theTextron Lycoming Aircraft Engines

proper vaporization, suitable engine operatingtemperatures should be maintained. Note in the chart that Which are Certified for Aviation Gasoline

the most desirable range to avoid spark plug fouling is the

temperature range 9000 -´•13000 F. (AUTOMOTIVE GASOLINE COULD BE DANGEROUS

Oil temperature is also an’important factor in preventing TO YOUR HEALTH REWRITTEN MAY 1986)

plug foiling. It has been our experience that a desirable oil In the issue of Flyer No. 25, dated February 1976. we told

temperature during flight should be in the range of 1650 F to operators not to use automotive gasoline in our aircraft engines.2000 F. For low ambient outside temperature operations, one and listed seven reasons against its use. Service Leaer No. L199,

method to keep oil libt is by closing off at least some of the dated January 1983, reiterated that policy by stating: "Textron

air flow to the oil cooler. Airftrlme manufacturers make available Lycoming does not approve the use ofany fuel other than those

a winterization kit that can be used to raise oil temperatures to ...specified in our latest edition of Service Instruction No. 1070.

the desired range. If a kit is not available, use any accepted Although Supplemental Type’Certificates (STC) now makemeans bf~locking the cooler such as with a good grade of tape, the use ofautomotive fuel, which meets minimum specified stan-

ap-Remove kit or tape in spring or you’ll be calling for help dards, legal for use in some aircraft, reciprocating enginein-~egards to high oil temperature. manufacturers and most major oil companies do not approve.

While it is true that octane levels appear adequate, theseSUMMARY: organizations are of the opinion that the varying quality con-

Spark plug fouling is not limited to engines that were cer- trol standards applicable to automobile gasoline produce undue

tiffed for 80 octane aviation fuel, but which aI~using the higher risk when it is used in aircraft. Several specific reasons are givenleaded 100 octane as well. ~herefore, the techniques recom- for the non-approval of automobile fuel:

mcndea herein for operation and maintenance apply to all our I. Its use reduces safety. Although an operator may find that

engines, but with emphasis on the 80 octane engine using 100 the engine runs wellon a specific grade of auto fuel, there

octane fuel. is no assurance that fuel from the same tank will be of the

same quality when purchased the next time. Risk is

increased.

2. Its use can void warranty, or result in cancellation of theFuel Contamination

owner’s insurance.

With the increase in recent years of the number of fuel in-3. The storage characteristics of automotive fuel are less

desirable in comparison with the good storagejectors on our engines, has been a number of complaints about

characteristics of aviation gasoline. After several months,"miss" in flight. We have beena mysterious occasional engme stored automotive fuel may suffer loss of octane rating, and

able to verify that the majority of these complaints on fuel in-tends to deteriorate into hard starting, along with forming

jected powerplants are from contamination in the fuel--gum deposits that cause sticking exhaust and intake valves.

principally water. We have bekn telling operators for many years

that fuel injectors and their systems are more vulnerable to con-and fuel metering problems, resulting in rough running

tamination than are carburetors. Since water and other con-engines. The turnover of automotive fuel is so fast that

longlasting storage characteristics are not required.taminants collect on the bottom of the airplane fuel tank, it also

makes good sense not to make a practice of running a fuel tank 4. The additives in automotive fuels are chemically different

from those designed for aviation, and contain auxiliarydry.

scavengers which are very corrosive, and under continuedCareful draining of fuel sumps for water will help alleviate

use can lead to exhaust valve failures. They also cause rust

the "miss" problem. A sufficient amount of fuel must be drainedand corrosion in the internal parts of the engine. The

to ensure getting the water. Experience indicates that draining allowable additives for aviation gasoline are rigidly testedshould be accomplished before refueling because fuel servic-

and controlled. There is no uniform control of additives

ing mixes the water and fuel, and the water may not have set-in automotive gasoline. Many different additives are used,

tied to the bottom of the tank until the airplane is airborne. Learndepending on the fuel manufacturer. For example, one fuel

to identify suspended water droplets in the fuel which causescompany adds a detergent to clean carburetors. This ad_

the fuel to have a cloudy appearance; or the clear separation ditive creates a significant increase in the affinity of theof water from the colored fuel after the water has sealed to the

gasoline for water which can cause fuel Nter icing problemsbottom of the fuel tank, in flight if outside temperatures are cold enough.

5. Automotive fuels have higher vapor pressures than avia-

tion fuel. This can lead to vapor lock during flight because

FUEL CONTAMINATIbN--Water (says the FAA) is thethe fuel companies advise that automotive fuels can have

double the vapor lock pressures of aviation gasoline.principal contamination of aviation fuel. For a safe flight,

depending on the seasons of the year, and the locationcarefully drain fuel sumps at each preflight.

because of climatic conditions. In addition, automotive fuel

also increases the possibility of vapor lock on the groundwith a warm engine on a hot day.

6. Although the fuel octane numbers shown on the pump of ing on the engine, and why an engine must be designed for a

automotive and aircraft gasolines may be similar, the turbocharger; also the operation of turbocharged engines, and

actual octane ratingsare not comparable due to the different the maintenance and trouble shooting procedures for turbocharg-methods used to rate the two types of fuels. Furthermore, ed powerplants.aviation gasolines have a lean and rich rating i.e. 1001130, The advent of the lightweight turbocharger has been call-whereas motor gas is not tested for a rich rating. ed the shot of adrenalin which the piston engine needed to re-

7. Automotive fuel used in an aircraft engine may lead to main the prime method of powering general aviation type air-desiructive deionation or pre-iginition and potential engine craft. Although in some respects this may be an overstatement,failure at high power conditions. it does have much merit, and it is the lightweight turbocharger

8. The actual Mo-Gas fuel requirements range from meeting that has enabled general aviation aircraft to operate above

ASTM or government specifications only in six states, to adverse weather in the smooth air of the higher altitudes, and

few or no minimum requirements in the remaining 44 states, to realize the increased true air speed not possible with nor-

as opposed to the uniform strict requirements for aviation mally aspirated engines. So this is the "why" of turbocharg-fuel, ing, and since it is possible that there is a turbocharged Lycom-

SUMMARY: ing engine in your present or future, we are going to review

the very basics of turbocharging and bring the reader up to theAuto fuel is now beiiig used as a substitute for Grade 80

present "state of the art" of it.aviation gasoline under STC’s issued by the FAA. Most majoroil companies and engine manufacturers continue to recommend

The aircraft engine, as any reciprocating engine, is a heat

that aircraft piston engines be operated only on aviation gasoline. engine which derives its power from the burning of a mixture

Deterioration ofengine and fuel system parts have been reportedof air and fUel, which has been mixed in the proper propor-

in auto fuel. Operators shduld consider the add- tions by a fuel metering device. The amount ofpower the engineed risk of using auto fuel in aircraft. Remember--a pilot can’t develops will be directly proportional to the total mass of air

pull over to the side of the road when fuel creates a problem pumped through the engine, providing the fuel/air ratio is keptwith the engine. constant. This can be varied in a normally aspirated (un-

turbocharged) engine by changing the throttle setting and/or

changing the RPM. Let us go over that again. Changing the

Understanding The AD throttle will vary the manifold pressure available to the cylinderduring the intake stroke. As a result the cylinder will develop

The Federal Air~Regulations state that no person maya given amount of power on each power stroke. So if we in-

operate a product to which an Airworthiness Directive applies crease manifold pressure to the cylinder. we will in turn receive

except in accordance with~ the requirements of that airworthiness more power from the engine. Now if we keep the manifold

directive, pressure constant, but increase the number of power strokes byincreasing the RPM, we will also receive more power from the

The custom on Airworthiness Directives (AD) for Lycom- engine. We see that changing either the throttle setting (manifolding engines involves a close’working relationship between us pressure) or the number of power strokes per minute (RPM).and the FAA. The AD is usually preceded by a Service Bulletin, will result in varying the total air mass flow through the enginebut the AD helps insuie the broadest possible circulation. and will determine the horsepower the engine will develop. So

The AD should be carefully followed because it is the best in essence, a reciprocating engine is also an air pump, and if

information available: It has been reviewed by the manufac- the fuel/air ratio is kept constant the power developed will vary

turer, both from an engineering and service standpoint, and will directly with the mass of air consumed.

allow the owner to gain the most utility from the product with We are limited in the speed at which we can operate thethe least rimount of expense and down time. An AD should not engine because of engine and prop mechanical limitations. Socause a panic reaction by oper~tors where it insists on immediate the only other way to change the mass flow is to increase the

compliance. Many AD’s, if read carefully, merely require in- manifold pressure. We all know, however, that as we ascend

spection from time to time, and the actual change only at in altitude the air becomes less dense which reduces the mass

overhaul, flow through the engine with the result of a power loss that is

Always check your engine serial number when concerned proportional to the reduced mass air flow through the engine.about an AD. Similarly, any contact concerning an engine with You have noted that in climb with a normally aspirated engine.

an PEG, Textron Lycoming Distributor, or the factory, should it is necessary to keep opening the throttle if you are to keepinclude the engine serial number, the air speed and the rate of climb constant. So we see that if

there was a way we could put the engine into a container so

it could be kept at sea level conditions, we could maintain the

same performance regardless of ambient conditions and altitude.

A long time ago, a smart engineer who was thinking alongLet’s Talk Turbocharging these same lines reasoned that if he built an air pump into the

engine that could pump the less dense air at altitude up to the

Editor’s Note: This is the first in a series of articles on tur- same pressure he had at sea level. he would be able to maintain

t!ocharging in which we will try to cover the general spectrum sea level horsepower. So he designed a centrifural air com-

of this improvement in the lightweight piston engine. We will presser and placed it between the fuel metering system and the

deal with the theory of turbochar_eing, the effects of turbocharg- intake pipes. The pump consisted of an impeller, diffuser and

collector. The impeller was driven at about twelve times is complete and automatic and except in cases of poor or abruptcnnkshaft speed and this high rotational speed imparted a large throttle management, it does not overboost.

velocity of energy to the air passing through. Now as the fuel/air The automatic control system just described is basic, but

charge leaves the impeller, it goes to the diffuser where vanes it is the basis for most control systems used on Lycomingsmooth out the air flow while allowing the mixture to slow down

engines. In another article we will also talk about the changesso that the velocity pressure acquired from the rapid rotational required in an engine to make it suitable for Nrbocharging. and

speed of the impeller is transformed into static pressure. This the difference between an engine designed for turbochargingair mass is then stored momentarily and equalized in the col- and the one that has just had a turbocharger added. We willlector and is then drawn into the cylinders. Our engineer now also discuss turbocharging to increase power at sea level in-has his air pump, but how was he to drive it? Well he could stead of only using it to maintain sea level pressure at altitude.drive it from the accessory gear train or from the rear of the (See "The Pilot and Turbocharging").crankshaft, but both of these methods robbed the engine of

horsepower it could deliver to the propeller. Although super-

chargers for many years have been driven mechanically off the

crankshaft, our engineer realized he had not reached the ultimate

inlhe "state of the an" of supercharging, so he began looking The Dual Magnetofor another means of driving his air. pump.

Our hypothetical engineer realized that the largest percent Several models of Lycoming engines use the Bendix dual

of energy released by burning the fuellair mixture was going magneto now produced by the Ignition Systems Products Divi-

out of the exhaust pipe in the form ofheat. Realizing if he could sion of Teledyne Continental Motors. This single unit magneto

in some way7larness this wasted energy to drive his air pump, design had as its first goal, reliability, with simplification, no

the horsepower normally robbed from the engine to drive the increase in cost, and weight reduction as other desirable design

impeller could be used by the propeller. features. As a result, the magneto system itself is five to six

-We have all noted a windmill turning in the breeze, so ourIbs. lighter than other present day mags. There is an additional

weight saving by eliminating one magneto drive and itsengineer rightfully reasoned ifhe put a turbine wheel in the ex-

associated hardware from the engine. As an alternative, thishaust stream he could take the hot exhaust gas under pressure

drive can be.retained and used for another accessory or com-and expand it as it passed through the wheel to extract energy.

He took an impeller, connected it by a commdn shaft to the tur- ponent without the weight penalty ofan added drive. New designfeatures and simplification of the combined magnetos and engine

bine and he had a means ofdriving his air pump by energy whichaccessory case should prevent any cost increase for the new

was formerly going to waste. Supercharging by means of us-

ing exhaust gases to drive the air pump is called turbocharg- system.

ing. Now our engineer hadqrogressed to the point where he Some less obvious advantages whichjustified the design are:

required a means of contrdlling his turbocharger. As he climb-1. A considerable saving in installation time. Only one

ed in altitude the pump must constantly put out a higher pressure magneto has to be mounted and timed to the engine: the

ratio in order to maintain sea level conditions. He reasoned that synchronization of the two magnetos has already been done

if he can dump the exhaust gas at sea level through a butterfly within the unit itself.valve in a leg off the exhaust pipe and ahead of the trrbine wheel,

he will be able to control the amount of energy being used to2. Improved maintainability because of fewer pans and the

drive the turbine and thus control the speed of the compressor,ease of setting internal timing in the unit.

’The butterfly valve (wastegate) can be positioned by means of 3. Reduced inventory with one integral ignition system replac-mechanical linkage, but the disadvantage in this system is that ing two magnetos.the engine can be overboosted, causing detonation and severe

4. Better synchronization of the two sparks in each cylinderengine damage if someone "forgets" and leaves the wastegate because the two main breakers are operated by a common

in the’ closed position. So dur engineer was looking for ancam rather than being separated by two engine drive trains

automatic means for control which would eliminate someoneincorporating gear backlash and "float".

putting "Murphy’s Law" into practice. (Murphy’s Law states

that if something can be done incorrectly, someone is bound 5. If it sh~uld become necessary for reasons of engine per-

to do it.) So he came up with an automatic system that sensed formance or exhaust emission reduction, an automatic

compressor discharge pressure and positioned the wastegate to advance can be used.

maintain the correct manifold pressure. The system contains 6. The dual magneto has altitude capabilities of better than

two basic components. The controller, which senses the com- 20,000 feet and can withstand high temperatures.

presser discharge pressure and regulates engine oil pressure used7. The dual magnetos have been FAA approved for either

as the muscle for the actuator on the wastegate. When the con-retard or impulse coupling.

troller calls for more compressor discharge pressure, it closes

the oil bleed line from the w~stegate so ihe wastegate actuator The most obvious difference between dual and single

sees higher engine oil pressure and thus closes the butterfly. magnetos is that the dual units contain two each of several pans

When the compressor dischaI’ge pressure comes up to the desired such as coils, distributor gears, capacitors, breakers, and

control pressure, the controller will bleed oil from the wastegate distributor electrode sets. Insofar as the electrical and major por-

to maintain the correct butterfly position which in rum will main- tions of the magneto circuit are concerned, a dual ma_eneto is

rain the correct compressor discharge pressure. Now the system actually two separate units in a common housing.

Use of the dual magneto does, of course, require a newly "can opener’’ service tool for the aviation mechanic. The tool

designed engine accessory housing. This new housing require- easily cuts open the filter without contaminating it so the ele-

ment has made it possible for Lycoming engineers to make some ment can be examined for any signs of engine deterioration.worthwhile new improvements in the accessory housing. Before discarding the filter elements of the AC or the Cham-

Although the dual magneto is an innovation with opposed pion filters, an examination of the filter element should be made

powerplants, it has an eaily successful history of use with the by unfolding the pleated element and examining the material

old Lycoming R-680 engines, and also was used with P W trapped for evidence of internal engine damage. In new or newlyR-2800 powerplants as well as the Wright R 3350 BA series overhauled engines, some small particles of metallic shavingengines. might be found; these are generally caused during manufacture

and should not be cause for alarm. However, positive evidence

of internal engine damage found in the filter element justifiesfurther examination to determine the cause.

Information About Lycoming To examine the AC filter element, remove the outer per-

Approved Full-Flow Oil Filters forated paper cover, and using a sharp knife, cut through the

folds of the element at both ends close to the metal caps. ForAlthough Textron LXcoming publication SSP-885-1 covers

examination of the Champion spin-on filter, Tool CT-470 must-.the latest information concerning full-flow oi~filters for our

be used to cut top of can.engines, we feel it is also important to emphasize and explainkey aspects of the publication in the "Flyer" to help people Clean engine oil is essential to long engine life. Consequent-in the field. SSP-885-1 is concerned with full-flow oil filters ly, the quest for better ways to keep the lubricating oil free from

in our direct drive engines, but does include one exception contaminants is endless.

the geared TIGO-541 which powers tk4´• Piper Pressurized

Navajo.Detonation And Pre-Ignition

Operators and meclianics must carefully read SSP-885-1

before handling the various types of Lycoming approved filters.Although knowledge ofdetonation and pre-ignition may be

Special note should be made of the differences of installing the"old hat" to the old timers in aviation, lots of people in our

AC vs. Champion filters. The AC is installed with the housingindustry are still somewhat confused over the difference bet-

not turned, but with an attaching bolt through the center of theween the two, and what causeseither of them.

housing, torqued to 20-25 foot pounds.The Champion spin-on filter calls for a different installa- DETONATION

tion in that the filter housing itself is turned to a torque of 18-20 There is a limit to the amount of compression and the

foot pounds. Never exceed the maximum torque limit. degree of temperature rise that can be tolerated within an engineMaintenance people in tke field using both types of filters must cylinder and still permit normal conbustion. When this limit

be very careful during installation of this part. is exceeded, detonation can take place. Piston engines are

SSP-885-1 includes the new Champion Full-flow Spin-Onvulnerable to detonation at high power output because combus-

Filter. The latter is an added improvement over older methods tion temperature and pressure are, of course, higher than they

of filtration, and is installed as optional equipment on all direct are at low or medium powers. Leaning the mixture at high power

drive Textron Lycoming aircraft engines. Some of the advan- can cause it.

tages of the. Champion Spin-On Filter include a resin- Unless detonation is heavy, there is no cockpit evidence

impregnated paper that constitutes the filter element, which is of its presence. Light to medium detonation may not cause

heat cured, acid resistant, and capable of removing contaminants noticeable roughness, observable cylinder head or oil

that would be injurious to the engine. The spin-on was design- temperature increase, or loss of power. However, when an

ed to save weight and also shorten maintenance time, and is engine has experienced detonation we see evidence of it at tear-

available in long and short sizes. There is no need to replace down as indicated by dished piston heads, collapsed valve heads.

elements, O-rings, and various nuts and bolts and washers, or broken ring lands, or eroded portions of valves, pistons and

to clean the filtering units. cylinder heads. Severe detonation can cause a rough running

All models of Textron Lycoming direct dhve engines canengine and high cylinder head temperature.

be converted to use the Lycoming approved full-flow filter ele- PRE-IGNITIONment or full-flow spin-on oil filter; however, before installing,

Pre-ignition, as the name implies, means that combustioncheck the distance between the firewall and the mounting padon the accessory housing. Do not over-torque the filter at in-

takes place within the cylinder before the timed spark jumpsacross the spark plug terminals. This condition can often be

stallation. After installation of the full-flow filter, always ground traced to excessive combustion deposits or other deposits (suchrun the engine before flight and get oil temperature into the bot-

as lead) which cause local hot spots. Detonation often leads totom of the green are on the gage. After a good runup, shut engine

pre-ignition. However, pre-ignition may also be caused by highdown and inspect the frlter area for oil leaks. Also check engine

power operation at excessively leaned mixtures. Pre-ignitionoil level; addition of the filter assembly will require adding ap- is usually indicated in the cockpit by engine roughness, backfir-proximately one quart of oil.

ing, and by a sudden increase in cylinder head temperature. It

Along with the filter and converter (a simple converter kitmay also be caused by a cracked valve or piston, or a broken

is required with some engines), Champion has developed a new spark plug insulator which creates a hot point and serves as a

glow spot. Specifically, preignition is a condition similar to early These worthwhile features in the powerplants have meant

timing of the spark. Pre-ignition is a serious condition in theeven longer operating life than standard steel barrels, and they

combustion chamber and will cause burnt pistons and tuiiped mean dependability and economy.intake valves.

The identification for chrome plated cylinders has been the

The best temporary in-flight methods for correcting pre- orange band around the cylinder base, or the equivalent color

ignitibn and detonation are to reduce the cylinder temperature on the edges of the top cylinder head fins between the two valve

by retarding the throttle, enriching the mixture, opening cowlpush rod shroud tubes. The color coding for the nitrided

flaps if available, or a combination of all of these, cylinders is azure blue and will appear in either of the two loca-

tions indicated above. The band around the cylinder base is us-

ed when cylinders are painted black as a separate operation priorThe Pilots’ Operating Handbook is the final authority to engine assembly. The color coding on the top edges of the

regarding operation of your Lycoming engine. cylinder head fins has been used on engines painted all gray

Study~it thoroughly. after assembly.

From the service standpoint on nitrided cylinders, there are

three methods of handling a full time engine at overhaul.

Nitriding 1 What Is It? i. The barrels can simply be reworked and returned to

service if they are not beyond service limits.

Lycoming Engineering, in their continuing effort to improve 2. The barrel can be reground and then chrome plated.

our engines, developed a better method of manufacturing 3. The old cylinder may be discarded and replaced with a new

hardened alloy steel cylinder barrels a number of years ago by one as in the Lycoming factory overhaul and remanufac-

means of a method known as nitriding. Simply described, the rum programs.addition of nitrogen to the surface of an alloy steel produced

CHROME vs. NITRIDINGa hard, wear resistant surface. Commercially, the introduction

of nitrogen into the surface layers ofalloy steel is brought about Either method provides a satisfactory hard wearing surface.

by subjecting the practically finished parts to an atmosphere of Engines with chrome or nitride hardened barrels have a good

ammonia gas. The process requires special heat treating fur- wear characteristic, and are more rugged than standard steel

naces which are air tight and capable of holding the parts at barrels. In spite of hardened barrels, a’good, properly main-

a high temperature. At this heat level (9750 Fl, the ammonia rained air filter is still a must. Pistons are moving up and down

gas flowing into the furnace is broken down into its elements at a rate of more than two thousand times per minute, and when

of hydrogen and nitrogen, and this is the source of the nitrogen dirt or any abrasive is introduced into the combustion chambers.

which penetrates the surfaces of the steel. In order to produce it causes a lapping process which rapidly wears metal away.

a satisfactory nitrid~d surface, the process must be operated for No engine can digest dirt and provide a satisfactory service life.

an extended period of time, generally from 25 to 80 hours.

Along with cylinder barrels, Lycoming nitrides all its

crankshafts and some gears.

The nitriding process applied to cylinder barrels has been Compression Ratio An Explanationthoroughly service tested in military as well as commercial ser-

vice. After having been FAA type tested, we began production AS It Relates To Textron Lycoming Enginesof engines using nitrided cylinders in 1960. The service record

of these cylinders has been excellent. In fact, our Management We aren’t attempting to make mechanics out of pilots by

was so impressed with the favorable service record of the nitrid- writing about compression ratio in aircraft engines, but we desire

ed cylinder that they changed from chrome to nitrided cylinders to help both groups by providing a simplified description as it

in all our higher powered turbocharged and supercharged relates to our engines.

engines. Some favorable ’characteristics of nitrided barrels are In order to gain a reasonable amount of work from an in-

as follows: ternal combustion engine, we must compress the fuel/air mix-

I. Reduced cylinder wall wear--the harder a surface the more ture during each power stroke. The fuel/air charge in the

difficult to wear down, cylinder can be compared to a coil spring in that the more it

is compressed, (within limits), the more work it is potentially2. Natural choked barrels providing improved piston ring life

capable of doing.due to a resulting straight cylinder wall when engine is hot

or operating, and a better job of sealing. Engineering tells us that the compression ratio of an engineis a comparison of the volume of space in a cylinder when the

3. Nitriding permits use of chrome plated piston rings whichpiston is at the bottom of the stroke to the volume of space when

are more wear resistant and quite compatible with hard-the piston is at the top of the stroke. For example, if there are

ened sttel.140 cubic inches of space in the cylinder when the piston is at

4. Nitriding provides a hardened surface with an increased the bottom and 20 cubic inches of space when the piston is at

fatigue strength, the top of the stroke, the compression ratio would be 140 to

5. It also has the ability to resist softening when excessively 20 or usually represented at 7:1.

heated during engine operation.

Low Compression High Compression recommended cruise power. We have observed too many pilotswho consistently operate at full rich mixture at cruise power.It is a needless waste of money and fuel to routinely operateat full rich at cruise. Rich running engines tend to be on the

rough side, thereby creating vibration, which causes a deteriora-

tion of engine accessories and engine mounts--another con-

trollable cost factor. Proper leaning at cruise and during de-

scent means less spark plug fouling, longer life for the plugs.and reduced maintenance cost as a result. Good leaning techni-

ques likewise result in cleaner combustion chambers with fewer

’~Zt f lead salt deposits on the piston and exhaust valve heads. Under

certain conditions these deposits invite pre-ignition and highermaintenance costs. Proper leaning at cruise during cool or cold

weather, aids in raising engine and oil temperatures to desirable

minimums in order to boil the water and acids out of the oil.

Water and acids attack the insides of an engine, causing rust

and corrosion, another controllable maintenance cost.

Although we can create a more efficient engine by increas- An additional oppormnity for the licensed pilot to help with

ing the compression ratio, there are limits and a compromise the cost of flying is in the area of preventive maintenance. The

is needed. If the pressure is too high, premature ignition will FAA defines the term in FAR Part I as follows:

occur and prodlice overheating. Compression ratio is a con- "Preventive Maintenance’ means simple or minor preser-trolling factor in the maximum horsepower developed by an vation operations and the replacement of small standard pansengine, but it is limited by present day fuel grades and the high not involving complex assembly operations."engine speeds and manifold pressures required for takeoff. Then in Part 43.3 paragraph 01), it defines persons authoriz-

Our normally aspirated engines are generally categorized ed to perform preventive maintenance:

as either low compression or high compression powerplants. "The holder of a pilot certificate issued under Part 61 mayIn surveying the complete range of all Lycoming engine models, perform preventive maintenance on any aircraft owned or

we note that they vary all the way from a low 6.5:1 to a high operated by him (or her) that is not used in air carrier service."of 10:1. Engineering has generally established the low com-

Just a reminder that FAR No. 43.9 requires that you makepression group as those with a compression ratio of 6.5:1 to

an envy in the engine logbook or maintenance record of7.9:1; and the high compression group from 8:1 and higher. whatever preventive maintenance, the pilot accomplished. Along

All Lycoming engines in the high compression category with these responsibilities. FAR 43.13-1A reminds the pilot that

require a minimum of Grade 100LL (blue) or 100/130 (green) after completion of preventive maintenance, he or she should

octane, FAA approved aviation fuel, and nothing less. We are do a good complete ground run, and then shut the engine down

stressing with high compression engines the importance of the to inspect the engine for proper condition. If everything is nor-

manufacturer’s recommendations as outlined in the Engine mal, the engine should have a preflight runup and test flight.Operator’s Manual or in the Airframe Owner’s Manual. With

Appendix A ofPart 43 of the FAR’s, lists examples of workhigh compression engines, not only do we require the correct defined as preventive maintenance (a few were selected by yourfuel, but the proper oil, precise timing and a good air filter.

Editor as representative).All are very important in order to protect this high performancepowerplant. i. Replacing defective safety wiring or cotter keys.

2. Replacing any cowling not requiring removal of the prop,or disconnection of flight controls.

3. Replacing or cleaning spark plugs and setting spark pluggap clearances.

How To Keep Engine Costs Down4. Replacing any hose connection except hydraulic

Through Do-It-Yourself Preventive connections.

Maintenance And Sound Operation 5. Replacing prefabricated fuel lines.

6. Cleaning fuel and oil strainers.

Some owners and operators of engines certified for 80/87Now there is more to properly accomplishing preventive

octane aviation fuel faced with having to use aviation grade maintenance on your engine than meets the eye in a quick100LL fuel have complained about the added maintenance ex-

reading here. Apparently, other organizations have had similarpense, and cost of operation with the higher leaded (higher than

concern for this aspect of the situation. The National Pilots80/87) fuel. However,there are some things the owner or Association and the Aviation Maintenance Foundation haveoperator can dd to hold down expenses where they are iorced

coordinated their efforts in a program ofnew series of preven-to use grade 100LL.

tive maintenance.meetings "to teach general aviation pilots and

A very imponant economy measure penaining to opera- aircraft owners the rudiments ofbasic aircraft care." If vou can’t

tion is that of proper leaning ofthe mixture at the manufacturer’s attend this kind of instruction before you jump into preventive

maintenance on the simpler general aviation airplanes as a pilot. The methodical physicist experimenting with draft horses

we recommend consulting a licensed A and P intially. There used to operate mine pumps found that, on an average, a horse

are important items to know about, such as specific service pulling with a force equal to a weight of 150 pounds walked

manuals, availability of tools, torque limits on spark plugs and 2’h miles per hour. Since work is force exerted through a givenoil screens, etc. It’s your responsibility when you do preven- distance, it is measured in terms of feet pounds. Thus, on an

tive maintenance on your aircraft engine, so use care. average, one horse could do work at the rate of 33,000 feet

In summing it all.up, the best approach to keeping cost down pounds per minute or 550 feet pounds per second.

on your aircraft engine is by means of good operation and sound Watt’s definition for one horsepower, which has now

maintenance. We have outlined how the pilot can personally become univeral, was, therefore, the doing of work at the rate

accomplish important aspects of both operation and of33,000 feet~pounds per minute. Today, all conventional power

maintenance. producing units are rated on this basis.

The modern light plane 250 horsepower engine is capable

"Watts" Horsepower of doing work at the same rate as that of 250 average horses.

From an interested engineer’s point of view, it is capable ofby: F. G. Rohm

moving 137,500 pounds of weight one foot in one second. Yet,Chief Qualification Engineer ~et.) what a difference there is in its size and weight (approximately

This interesting article was written for us by Fred Rohm, 400 pounds) when compared to the horses it replaces!who was our Chief Qualification Engineer when he retired.

Fred had a career of 44 years in the industry, with a

majo~y of those years spent at Textyon Lycoming. Most Cut-Away Of A Four Cylinderof his career at Lycoming was as ~bief Experimental PowerplantEngineer, which establishes his qualifications to author this

FRONT VIEW OF A FOUR CYLINDERkind of article.

TEXTRON LYCOMING POWER PLANT.

James Watt, Scottish physicist, had an engine problemeven in 1769. Although steam engines had been invented before

he was born, they were crude, inefficient machines and onlya few were in use. So he had, after much experimental work,

developed a relatively efficient condensing steam engine, the

forerunner of the present day type.

Being a good business man, Watt tried to sell his engineto coal mine operators whb were then using draft horses to sup-

ply power to drive the pumps which kept the mines free ofwater.

But the mine owners had sales resistance! They insisted on

knowing exactly how many horses each engine would replace,or, in other words, the horsepower of the engine. How much

work would his steam engine do? This, then, was James Watt’s

problem. PY

Although simple machines such as sailing vessels, wind-

mills and waterwheels had been used for centuries, Watt realized

that for the most part, the majority of work in the world had

been done by man and his domesticated animals. Work was SIDE VIEW OF THE

measured and paid for by the day, from "sun to sun". With FOUR CYLINDER ENGINE.

the advent of reliable clocks, work was then accounted and paidfor by the hour. Evaluating work by this time method, it was r~l oYuun

assumed that all nien and animals could and did perform the naoucnl

same amount of work. This was far from being true.

Watt realized that in older to have his steam engine used

by the coal mine operators he would have to answer their ques-

tions "how much work will it do, and how many men and

horses will it rei~lace?" Since the "power" of one horse was

a generally known and a constant quantity, he would have to

determine the "power" of his engine in order to compare it

with the horses which it was to replace. His problem then was

to define "power".Power did not mean force. The mine owners cared nothing

about the force Watt)s engine might exert. They wanted to knowm turow w~m.

how fast the engine would pump water out of the mine: in other

words, how fast will the engine do the work? Simply, that was

the definition of "power".

Your Engine And The mathematics to arrive at this fuel usage are simple:

Fixed,Pitch Propeller 180 HP X 75% of power 135 HP

135 HP X .435 BSFC 58.7 Ibs. of fuelThe effect the propeller has on engine operation and on air-

craft performance is quite significant. Based on questions which58.7 Ibs. of fuel s 6 Ibs. per gal. 9.8 gal. per hour

have been asked by aircraft owners and from experience gain- Having made some assessments about what can happen withed at the Textron Lycoming service hangar, there are several a standard propeller, now we will try to see what happens when

areas of propeller related information which may be of interest. a cruise propeller is installed in place of the original. The first

Aircraft equipped with a fixed pitch propeller will usually thing we must know about the cruise propeller is that it has more

have static RPM (full throttle with aircraft standing still) limita- pitch than the standard propeller. This means it will take a big-tions and full power in flight RPM limitations spelled out in ger "bite" of air than the original propeller with each revolu-

the Pilot’s Operating Handbook. If static RPM is below the tion. This bigger bite of air will have an effect on aircraft per-

minimum specified, the engine could be low in power.formance and on how the engine may be operated.

However, experience has shown that this is not always true. Taking a bigger bite of air increases the resistance to theFaulty induction air systems and/or faulty exhaust systems have turning propeller. Perhaps it may be easiest to imagine what

-been shown to contribute to indications of low power. A pro- happens by considering your hand when held in the airstreampeller which is ever so slightly less than perfect may cause the outside a moving automobile with the palm forward as com-

static RPM to be outside the designated full throttle static RPM pared to having the side of the hand forward. Because of thiszone. In addition to these other factors, it is not unusual to find increased resistance, the static RPM will be lower than witha tachometer which is inaccurate. If an incorrect static RPM the original propeller. The same thing will be true when fullreading is observed during the engine che~k, any one or all of throttle, in flight RPM, is compared to that of the standard pro-these components could be at fault. The tachometer may be the peller at a similar altitude and temperature. This will reduceeasiest to check if a reed tachometer is placed in the aircraft. takeoff performance of any aircraft. Using the earlier exam-

This "little box" is not permanently attached to the aircraft, pie, the engine was rated at 180 horsepower at full throttle andbut it can quickly verify the accuracy of the standard aircraft 2700 RPM. Now, in spite of applying full throttle, the increas-instrument. Knowing the accuracy limits of the aircraft ed resistance reduces the maximum attainable RPM to somethingtachometer may eliminate the need for further examination of less than 2700. As a result of not developing the rated 2700the engine and propeller or it may confirm the need for further RPM, the engine also will not develop the power for which ittroubleshooting. In any case, consider each component of the was rated. Since maximum power is less than full rated, air-system before blaming a_low static RPM reading on any one craft performance will suffer. This should be considered beforeof them, a fixed pitch propeller is chosen or exchanged for a different

Another aspect of op~ration with a fixed pitch propeller model.

came in the form of a question from a Lycoming engine owner. At this point we must return to the original question. WhyHe indicated that the propeller provided by the airframe does the engine require more fuel with the cruise propeller? Itmanufacturer had been exchanged for a cruise propeller. (This is an accepted fact that the cruise propeller is more efficientexchange should only be done with FAA approval.) With the for cruise operation, so it would not be unusual to follow thisnew cruise propeller is use, an increase in fuel usage was soon line of thinking. Seventy-five percent of rated power using the

apparent. Operating costs increased and an explanation was original propeller at sea level and standard temperature requiredrequested. a throttle setting to achieve 2450 RPM. Therefore. without more

It is well known that the amount of horsepower taken from thoughtful consideration, it seems logical that the cruise pro-

an engine will have a direct relationship to the amount of fuel peller might also be set for 2450 RPM when 75% power is

used. Therefore, it can be deduced that use of the cruise pro-desired. Of course there is an increase in performance, but this

peller increased the horsepower requirement. This deduction can be attributed to~the more efficient cruise propeller. Next

deserves some additional explanation, comes the realization that the improved cruise performance isn’tall efficiency. Instead of 9.8 gallons of fuel, the engine is now

As an example, the standard propeller supplied with an air- using a greater amount of fuel per hour. For purposes of thiscraft may allow the engine to develop 180 horsepower at 2700 illustration, let us assume that the number is 11 GPH. By rever-RPM at full throttle, in flight at sea level, with a standard sing the mathematics used earlier, it is possible to estimate thetemperature. The Lycoming 0-360-A Series normally aspirated horsepower and percentage of power actually being used as aengine illustrates this example, result of operating the cruise prop at 2450 RPM with a best

Next, let us assume that this same engine/propeller com- economy fuel air mixture.

bination is operated at 75 power with a "best economy’’ fuel

air mixture setting. Again, assume sea level and standard11 GPH X 6 Ibs. per gallon 66 pounds

temperature to simplify and standardize the discussion. Seventy- 66 pounds t .435 BSFC 151.7 horsepowerfive percent power will require about 2450 RPM with a brake 151.7 HP s 180 rated HP 84.3% of powerspecific fuel consumption of.435 pounds per brake horsepower Assuming a fuel usage of 11 gallons per hour for this pro-hour. Also, 75% of the 180 rated horsepower is equal to 135 blem provides a reasonably realistic example of the changehorsepower. Fuel usagcat this power and mixture setting will which a different fixed pitch propeller might create. It also il-be 58.7 pounds per hour or 9.8 gallons per hour. The lustrates the need for pilots to change their habits when a pro-

peller is changed. In addition to the change of habits, the discus- combustion engine like the Textron Lycoming aircraft pistonsion shows a real need tore-evaluate the take-off, climb, and engines, detonation indicates abnormal combustion. Essential-

cruise performance of an aircraft if the fixed pitch propeller is ly, detonation is an uncontrolled explosion of the unburned gases

changed for a different model. in the engine combustion chamber. Some engines are more

susceptible to detonation than others. For example, NrbochargedAnother very important point concerns leaning. Remember engines are more susceptible than similar non-turbocharged

that Lycoming recommends leaning to best economy only at models and engines with higher compression ratios are more

75% of rated horsepower or less. It is very possible that lean- likely to exhibit detonation than engines with lower compres-

ing to roughness or to peak on the EGT gage could cause serious sion ratios.

damage ifthe engine is actually producing more than 75% of Detonation may occur in an aircraft engine as a result of

rated horsepower as shown in this illustration. maintaining a manifold pressure which is too high for the

With this information as background, it is easy to see that specific engine speed and mixture setting being used. The engine

setting a desired’p;jwer with a fixed pitch propeller can only power (i. e. speed and manifold pressure) and mixture settingsrecommended in the Pilots’ Operating Handbook (POH) for a

be accomplished if the‘pilot has a chart which applies to theparticular aircraft model have been determined by a detonation

specific aircraftlengine/propeller ~combination. Although thesurvey. These surveys use special instrumentation to detect and

power chart for a new aircraft may come from data obtainedrecord detonation as it occurs. Based on these surveys, the

by test flying with torque meter, a fairly accurate detonation limiting conditions are defined. Data from the surveyschart can be derived for any fixed pitch propeller and engine indicate that detonation occurs in varying degrees; it is

combination. Briefly, this is done by finding the maximum sometimes possible to operate an engine for relatively longavailable RPM at any particular altitude and applying data from periods in the first minor phase of detonation without inducing

the propeller load curve. damage. Textron Lycoming does not recommend or condone

engine operation which even approaches conditions which mightTo conclude, the purpose of this article is to make readers

cause detonation. The laboratory quality equipment used for themore aware of some operational aspects of the fixed pitch pro- detonation survey is not practical for use in an aircraft engagedpeller. Usually it is only necessary to accept the material pro- in normal flight operations. Without this equipment, the pilotvidcd by the airframe manufacturer and to use the engine/pro-

may not know that detonation is occurring, and it is impossiblepcller as directed. If a propeller change is made, or on those to establish the fine line between the first phase ofminor detona-

rare occasions when we question the power available to the pro- tion and the detonation magnitude which induces preignition

pe!ler, the material presented here could prove to be helpful. and/or engine damage. For this reason it is imperative that power

and mixture recommendations of the POH be carefullyobserved.

Preignition is a circumstance which causes destructive

engine damage and will be examined here briefly. Most Lycom-Induced Engine Damage ing engines are designed for ignition of the fuel/air mixture at

20 crankshaft angle degrees before the piston reaches top dead

From time to time a field service report states that an engine center during the compression stroke. Some engine models

has~ damage. After further examination of the engine, this specify ignition at 180, 230 or 250 before top dead center. If

damage may be classified as ’’induced damage’’. To clarify what ignition of the fueyair mixture occurs before the scheduled pointis meant by this term, induced engine damage is a failure or in the operational sequence of events, preignition exists and the

unsatisfactory condition which results from operational or compression stroke continues as the burning fuel/air mixture

maintenance practices employed after the engine is placed in is trying to expand. This subjects the combustion chamber and

service. Although there are a variety of conditions which may pistons to temperatures and pressures far in excess of those ex-

fall into the induced damage category, this article will discuss perienced during normal combustion. These excessive

two panitular types of failure and the circumstances which can temperatures and pressures cause damage to pistons and valves.

induce them. In some cases both burned pistons and stretched valves will be

Examination’ of an engine which is reported to have low found in an engine which has been subjected to preignition.

compression, loss of power, errati~ operation, metal.contamina- Considering the millions of hours flown each year in pistontion, or even complete engine stoppage may result in a deter- powered aircraft, engine damage from detonation and preigni-mination that pistons are burned or valves stretched. (Stretch- tion is quite rare. The infrequency of the happening means lit-

ed valves are sometimes sai’h to be tuliped.) These two types tie if your engine is the one affected. Therefore it seems ap-

of damage can be initiated in a number of ways, but the chain propriate to look more closely at some of the factors which lead

of events is often the same; detonation is followed by preigni- to detonation and preignition.tion and the engine damage has begun. To prevent burned The possibility of overboost is a characteristic of all super-

pistons and tuli~ed,(or stretched) valves, action must be takencharged and turbocharged engines. Generally, overboost means

to eliminate the possibility of detonation and preignition. the application of manifold pressure which exceeds the limit

Detonation is a phenomena which can occur in any inter- specified by the manufacturer. Early versions of the manually

nal combustion engine. The possibility of detonation cannot be controlled turbocharger allowed quite a few pilots to inadvenent-

completely eliminated. By definition, detonation is a violent ex- ly induce damage by overboost. With this system. the tur-

plosion. When used with reference to a spark ignition internal bochar_per wastegate was normally left full open for takeoff:

full throttle would produce 28 to 30 inches of manifold pressure. or at a power setting in the high cruise range need a relativelyAfter takeoff at full throttle, gradual closing of the wastegate rich fuel/air mixture to help cool the engine and reducewould slowly increase speed and manifold pressure possibilites of detonation. Since lean fueYair mixtures and highto maintain climb power.to cruise altitude or to the critical power settings promote detonation, it is recommended thataltitude of the engine. The system worked fine until the Lycoming engines not be leaned at power settings which pro-wastegate was inadvertently left in the closed position. If the duce more than 75% of rated engine power unless this opera-

pilot then applied full throttle for takeoffor a go-round, it could tion is approved in the POH. The pilot, by simply leaning the

produce 60 inches or more of manifold pressure and failure of mixture excessively at power settings above the cruise ranges,the engine, may be responsible for inducing the detonation and preignition

More recent turbocharger installations usually include a which leads to tuliped valves and burned pistons.pressure relief valve and/or an automatic wastegate control And finally, a small amount of dirt in the fuel system maywhich helps to avoid the possibility of overboost. Even with be responsible for clogging a fuel injector nozzle or nozzles.these prqtective devices, it is still possible to overboost by rapid A partially clogged fuel injection nozzle will reduce fuel flowthrottle operation and/or inattention to limiting manifold to that cylinder and will cause a lean fuel/air mixture. A noule

pressures at low engine speeds. which is partially clogged in an aircraft which has a pressureAutomatic controllers may not be capable of preventing operated fuel flow indicator will cause that indicator to display

overboost if full throttle operation is attempted before engine a higher than normal fuel flow. Leaning in an attempt to cor-

oil is warmed up sufficiently. Textron Lycoming Service In- rect the high indicated fuel flow will result in an even leaner

struction 369F addresses the problem of overboost and recom- mixture in the affected cylinder. Again it is possible that a burn-

mends, depending on the severity and duration of the overboost, ed piston or Nliped valve will be the final result.

a log book entry, engine inspection, or complete engine overhaul Understanding and avoiding those factors which lead to in-including replacement of the crankshaft. duced engine damage is certainly preferable to the discovery

As stated earlier, ignition of the fueyair mixture must take of tuliped valves or burned pistons in your engine. This entire

place at precisely the right time. A spark plug which has been discussion is aimed at promoting an understanding which will

dropped, or damaged in some other way, may induce preigni- allow pilots and maintenance personnel to direct their effortstion by causing a ’’hot spot" in the combustion chamber which to those elements which will reduce the possibility of induced

self ignites the fuel/air mixture. This could also occur from use engine damage. Observing the refueling of the aircraft and

of unapproved spark plugs. Flight with defective magnetos or checking the fuel system for indications of contamination are

flight in excess of certified aircraft limits may allow cross fir- tasks expected of the pilot. Meticulous management of powering within the magneto, improperly sequenced ignition of the and fuel/air mixture as recommended by the POH is also a pilotfuellair mixture, and engine damage. Proper magneto to engine activity which will enhance the possibility of avoiding induced

timing is also an important factor. The timing is affected by damage.wear and therefore should be checked and reset at specified in- Maintenance personnel play an equally important role.tervals. Regular, meticulous spark plug and magneto Troubleshooting a fuel injected engine for rough idle may leadmaintenance will help to avoid preignition and possible engine to the cleaning or changing of partially clogged fuel injectordamage from these sources, nozzles. Damage could result if the engine were operated at

Although overboost and incorrect ignition timing are causes takeoff or climb power with reduced fuel flow to one or more

of induced engine damage, this damage can often be attributed cylinders. A close check of magneto timing and magneto con-

to fuel and the fuel/air mixture. The frrst problem related to dition at regular inspection intentals will help to insure the con-

fuel is simply having improper fuel in the aircraft tanks. A piston tinued satisfactory operation of any engine.powered aircraft refueled with jet fuel would have a fuel blend

There are some "after the damage" factors thatwith greatly reduced octane level. A piston engine should not maintenance personnel should consider. Suppose that a powerbe started when even small amounts ofjet fuel have been add-

loss has been reported. A compression check reveals low com-ed to aviation gasoline because engine contamination and detona-

pression; a stretched or tuliped valve may be found. This is antion are likely; attempted flight under these conditions will cer- indication that the engine has experienced detonation andtainly result in destructive detonation and preignition. The use

preignition. A borescope examination should be conducted toof 80 octane aviation fuel in an engine certified for 100 octane

see if a piston has been burned. A burned piston often resultsaviation fuel will produce similar results.

in damage to cylinder walls and piston skirts; it also may con-

The lubricating oil may be a source of octane reducing fuel taminate the engine with metal particles. There is no healingcontamination. Excessively worn piston rings may allow enough process for this damage. In some cases it is possible to repairoil into the combustion chamber to dilute the fuel/air mixture. the engine by removing the metal contamination from the engineThe dilution will reduce the octane rating of the fuel and can and oil system, including the oil cooler, and by replacing alllead to detonation and engine damage. While this scenario is damaged parts, but often it is necessary to replace the entirenot entirely typical of the engine which uses large amounts of engine. If an engine is to be repaired, it must be rememberedoil because of worn or broken piston rings, it is possible for that repairing the damage is not enough; the cause of thethis situation to occur. r~glfunction which induced detonation and preignition must also

Even the use of 100 octane fuel in an engine in good be found and corrected. Did a magneto malfunction producemechanical condition‘ddes not eliminate all the possibilities of ignition outside the normal firing sequence’! Were manufacturer

induced engine damage. Most engines operated at takeoffpower approved spark plugs installed in the engine? Did a cracked

spark plug induce preignition? Was an approved fuel used, and The Flyer may have carried information on this subject in

if so, is there evidence of fuel contamination? Whatever the the past, but the reminder from someone who had an unfor-

malfunction, it musi be coiiected along with the damage or the tunate incident prompted this story. Preventing possible freez-

same problem could reoccur, ing of the crankcase breather tube by use of a whistle slot or

To conclude, induiced damage in the form of tuliped valves other means is an important little detail which all of our readers

and burned pistons can usually be avoided by understanding the should be aware of. Many may benefit from the knowledge.

sequence of events which lead to this form of engine damage.CarefUl attention to detail is required of pilots and maintenance

personnkl. Compared tp the expense of repairing or replacingWelding Is Wasteful

a damaged engine, it is worth the time and effort necessary to

avoid induced engine damage.Ifyou are told that your crankcase or a cylinder head should

be welded because of a crack, think long and hard about the

step you are about to take. The argument is that it is less ex-

The Whistle Slot pensive to have your old case welded than to buy a new one.

This is true when the only consideration is getting your aircraftWe often tend to believe--what we know, everyone knows. back in the air as cheaply as possible. For the long run, welding

While participating in a flight instructor refresher recently, a the aluminum parts of an aircraft engine to repair cracks may

young lady from Maine provided a reminder that this is oftencause you so many headaches that you will wish you had decided

not the case. on replacement as recommended by Textron Lycoming.This-lady and her husband fly in Maine throughout the The recommendation to replace rather than weld is based

year. During the winter, they and their aireraft are frequentlyon years of experience and thousands of examinations in the

exposed to extremely cold temperatures. During the past winter, Williamsport Plant Metallurgical Laboratory. Based on this ex-

th_ey had an unfortunate experience. The end of the engine perience, the vast Icnowledge of the individuals who work inbreather tube froze over, a pressure build up occurred in the this Met Lab should not be ignored. The brief explanation whichcrankcase, and the crankshaft nose seal reptured. The oil leak follows will attempt to relate some of this experience and to

that resulted covered the aircraft with oil-from nose to tail. For-explain why welding is wasteful.

yunately, a safe landing was made before all oil was lost.Starting with two very basic but critical items in the welding

As she related her story, another flight instructor quicklyprocess, we look at the material to be welded and the welder.

indicated that he had also experienced the same problem severalThe material is an aluminum alloy. Exactly which alloy is very

years earlier. The safe landingsin both cases are good news.important, and since this is proprietary information, the welder

The bad news is the expense incurred to repair the engine. in the field may ormay not know exactly which alloy a crankcase

An incident like this and for that reason it is made of. Also, it takes more than just a very good welder

is important that we repeat ourselves from time to time. We to successfully weld aluminum. The experience in qualifyingshould not assume that everyone knows about the ’’whistle slot’’ welders at the factory shows that only the most outstanding can

or other methods of insuring adequate crankcase venting. pass the annual FAA qualifying examination for Aircraft Cer-

First, the cause of this incident. Moisture is expelled from tified Welder. Even a good welder may leave tungsten in the

the engine crankcase through the breather Nbe which often ex- weld which causes it to be unsatisfactory.

tends through the bottom of the engine cowling into the air A complete knowledge of the material and the expert welder

stream. Under very cold conditions, this moisture may freeze cannot assure a satisfactory weld in a cracked crankcase or

and continue a buildup of ice until the tube is completely cylinder head because there are many other inherent pitfalls over

blocked. which the welder has no control. A new crankcase is heat treated

It is normal practice for the airframe manufacturer to pro- to give it strength and is then machined to the exact tolerances

vide some means of.preventing freeze-up of the crankcase needed for a perfect match of the two halves and appropriatebreather tube. The breather tube may be insulated, it may be crush on the bearings. Welding a crankcase may cause distor-

designed so the end is located in a hot area, it may be equipped tion and most certainly will weaken it. Unformanately, heat

with an electric heater, or it may incorporate a hole, notch or treating to regain this strength is not a practical solution because

slot which is often called a ’’whistle slot." The operator of any thl’heat treating will distort the case and mating surfaces will

aircraft should know which method is used for preventing freez- not fit as designed. This is why welded crankcases are often

ing of the breather tube, and should insure that the configura- plagued with oil leaks.

tion is maintained as specified by the airframe manufacturer.A welded case which is weak and slightly distorted from

Because of its simplicity, the "whistle slot" is often used. the welding may not be the worst of the problems created. We

Although the end of the tube may extend into the airstream, should keep in mind that a crankcase cracks in the first placea notch or hole in the tube is located in a warm area near the from fatigue, and lack ofstrength in a critical area. After welding

engine where freezing is extremely unlikely. When a breather there may be porosity at the weld or subsurface cracks which

tube with whistle slot is changed, the n’ew tube must be of the are not visible. Even a dye penetrant inspection will not reveal

same design. Replacing a slotted tube with a non-slotted tube these defects. The welded part should be inspected by X-ray.could result in an incident like the one described by the lady but many shops that weld do not have this capability. So now

from Maine. we have a crankcase which cracked in a critical area because

of overstress and fatigue. The crack has been welded, but con- Before getting to specifics, it would be well to establish

ditions~ leading to fatigue may still be there, and the subsurface a background for this discussion. Think for a moment about

defects which go undetected will act as stress concentrators. how heavily you rely on that Lycoming engine every time you

Many times a new failure occurs in the critical area near the fly. How can you be so comfortable, and so sure the engineweld. For the aircraft owner, this creates a new headache, and will continue to give you power for flight--hour after hour? Isn’t

for the matallurgists who have seen the problem many times it the excellent reputation of the company, and the solid enginebefore, it is one more reason to continue saying, "We don’t that you place your confidence in? This does not mean that ab-

recommend the welding of cracked crankcases." solute perfection has been achieved. Any mechanical device may

Cylinder heads are also made of aluminum alloy. Cracks malfunction, wear out, or at some time cause a problem for its

sometimes occur inside the dome area and there are individuals owner. All of these things may occasionally apply to a Lycom-

who recommend welding. The metallurgists consider repair by ing reciprac~iting engine, but we know that any problem we ex-

welding to be absolutely foolish and their experience provides perience with a factory engine will probably not be life

them with good reasons. The surface area in the dome is af- threatening.

fected by a thermo-chemical attack--to put it simply--corrosion. Did this reputation for reliability just happen? No, it is the

This corrosion is a form of oxidation which will not fuse pro- result of60 years ofexperience with aircraft engines. That does

_

perly during weldingi It is not practical to remove all of the not mean that the same individuals who engineered the Lycom--corrosion because this would entail remachining the entire in- ing engines of the 1930s and 1940s are still at Lycoming. It

terior surface which would change the designed compression does mean that their experience has been passed on. What has

ratio of the engine, in an effort to weld this area, those who been learned from thousands and thousands ofhours of test stand

do it make an effort to clean the crack thoroughly. Unformnate- running and engineering flight tests over all of those years pro-

ly, this isaflittle help because the area adjacent to the cleaned vides a solid data base of knowledge which is used to insure

out clack will still’ be affected by thermo-chemical attack. that a certified Lycoming engine is a safe and reliable device

Because this corrosion will not allow the weld to fuse complete- when opeI-dted and maintained as recommended by the

~y, new cracks are almost certain to occur. manufacturer.

Thermo-chemical attack is not something we can see. To With this background, take a look at some of the modifica-

the novice, a welded crack in a cylind_er head may look great. tions being advocated today: for example, "Change pistons and

It may not even be possible to identify the weld. But when the increase the compression ratio of the engine." This does in-

pan is dissected by a metallurgist for examination under a high- crease the horsepower an engine is capable of producing. It is

powered microscope, the weld and the poor fusion and cracks a tactic Lycoming engineers have used for years. Any Lycom-around the weld are immediately identified. ing engine with a compression ratio of 8.00:1 or higher requires

Based on this explanation, readers should now understand100 octane aviation gasoline and has undergone extensive flight

why Textron Lycoming does not recommend the welding of testing to establish an adequate detonation margin.

cracks in aluminum crankcases and cylinder heads. These cracks An individual or company who proposes to make your

usually occur as the result of fatigue over long hours of use, engine more powerful, by whatever means, will usually con-

and the odds of achieving long term satisfaction by welding are centrate on selling the benefits the modification will bring. You

extremely remote. If you are buying an aircraft, watch out for have an airplane powered by a Lycoming 0-235-K, L, or M

the engine which has been repaired by welding, and if you own engine, for example, and are told that by simply changing the

an engine which has experienced cracks, remember that you pistons it will be possible to get your aircraft off the groundprobably are wasting money by having those cracks welded.Ex- more quickly, to climb faster, and to cruise faster. This sounds

perience has shown that replacement of these parts is likely to wonderful, and it is true. You ask, why didn’t Lycoming make

be most economical and is likely to cause fewer headaches over the engine like this to start with? Well remember this, it ,vas

the long run, made that way, but it proved to be less than satisfactory.

By looking at the engine model certification sequence, we

find that the 0-235-engine started as a low compression engine.Look What They Are Doing To Our Engines The C and E models had a compression ratio (CR) of 6.75:1

and used 80 octane aviation gasoline. Knowing that higher com-

Modification of aircraft, and the engines that power them, pression ratios (CR) increase engine efficiency and that 100 oc-

is a very popular activiiy today. Magazine articles frequently tane fuel would help to prevent detonation at the higher CR.tell us of the wonderful changes which occur when a modifica- Lycoming certified the 0-235-F and G models in 1971. Thetion has been incorporated; unfortunately, these articles and 9.70:1 CR gained 10 horsepower which allowed the new modelsthose who develop and sell modifications often do not touch

to be certified at 125 HP. It did not take long to find that althoughon the detrimental side effects which may result from the these engines ran well in the test cell, installing them in air-modification. Without question, there are modifications which craft and turning them over to pilots in the field produced poorare well engineered and which provide a positive benefit. The results. Failure to follow critical fuel management proceduresproblem is that when we get excited about the prospects of the resulted, in some cases, in detonation, preignition, and burnedbenefit side, we tend to forget that there is no free lunch--we pistons. Not many of these engines were installed in airplanes.don’t get the benefit for nothing. The purpose of this discus-

sion.is.to.point r,ut.some Df.the. hidden problems and.costs~ofThe next step for Lycoming was to find a compromise bet-

engine modification. ween a 6.75: i and a 9.70:1 CR which provided acceptable per-formance and increased detonation margin. The testing which

followed led to cenif~cation of the O-235-K, L, and M series detonation characteristics of that engine are carefully checked.

engines with a CR of 8.50:1. When the recommended 100 oc- This detonation survey insures that power settings specified in

tane aviation gasoline isused in these engine models, burned the Pilots Operating Handbook provide an adequate margin so

pistons are rarely ever encountered. that detonation and associated engine damage will not occur

under any normal operating circumstances.The 0-235 is just one example ofan engine being modified

to something Lycoming engineers already know will demand When a Supplemental Type Certificate (STC) is issued to

much closer attention to proper operating technique than the allow addition of a turbocharger to a Lycoming engine, the high

original. An individual called the factory recently and said that compression pistons usually stay in the engine and oil squirtshe intended to modify a 290 horsepower 10-540 engine by are often not available for cooling. On the surface, it may seem

replacing the 8.70:1 CR pistons with 10.00:1 CR pistons. This that maintaining a manifold pressure of 30 inches or less should

engine would certainly produce more horsepower, but there are cause the engine to operate about the same as a normallyat least three problems. First, the modified engine would not aspirated engine. In fact, the engine runs much hotter because

be a certified model and therefore could only be used in an the turbocharger heats the air as it compresses it. Because the

airplane which is operated in the EXPERIMENTAL category. turbocharger must work harder and harder as the air becomes

Second, the engine would require a full rich mixture setting over less dense with an increase in altitude, the engine may run very

much of its operating envelope in order to avoid detonation. hot during climb and during cruise at altitude. The hot runningAnd third, Lycoming models certified for more than 290 engine with high compression pistons must depend heavily on

horsepower are designed with a heavier crankshaft. Both the excess fuel for cooling; this makes correct leaning a critical pilot

higher horsepower with the lighter crankshaft and the increas- task. Over the years, Lycoming has received numerous reports

ed exposure to detonation make the engine less reliable. This of burned pistons in engines which have field installed tur-

is a modification which is unacceptable in view of Lycoming bochargers. From this, and for the reasons stated earlier, it has

experience. been concluded that in many cases there has been no detona-

tion survey or the survey did not provide enough data to establishThe point of this discussion is to show our readers that

reliable power setting and leaning procedures. It can be veryLycoming, as a company, has expended a great deal of effort,

expensive to learn about the detrimental effects a turbochargerand has gained a great deal of experience. The result is enginemodels which generally can be expected to operate reliably-- may have on an engine afterthe installation is already in your

as they are certified. When it is suggested that one of these airplane.

engines shduld be modified by installing high compression If you are considering the addition of a turbocharger to your

pistons, remember that it was done years ago with poor results. Lycoming engine, be prepared to ask a lot of hard questionsWhen a modifier with much less experience than Lycoming pro- (a list is printed with this article) before putting your money

poses a change which is almost certain to produce the same poor and your engine on the line. You can help yourself by obtain-

results, Lycoming is concerned for the engine owner who may ing a copy of FAA Advisory Circular 23.909-1. The subjectbelieve that this simple change can have no harmful effect. of this AC is "Installation ofTurbochargers in Small Airplanes

Another favorite modification is the add-on turbocharger.with Reciprocating Engines." This circular reinforces previous

Are there benefits whichbecome available when this is done? paragraphs of this article when it states that "induction air

temperature may become ciritical at altitude because of the in-Of course, and anyone who might consider adding a tur-

creased compression of air required’’ and ’’the addition of thebocharger will be well aware of those benefits as well as the

turbocharger to an engine not specifically designed for it mayprice of the installation. But will they be aware of hidden costs

affect carburetor inlet and induction air temperature to AP-such as the possibility that a turbocharger may cause problems

PRECIABLY REDUCE THE I)ETONATION MARGIN."which will void the engine warranty, or that modifications to

Several other related items in the AC include such statementsany engine invalidate manufacturer TBO recommendations. At

as detonation characteristics may be unsatisfactory, a newfirst glance, these policies may s’eem somewhat unfair to the

recommended overhaul period should be established, the stan-engine owner who wants to add a turbocharger. But again, the

dard diaphragm type fuel pump is not adequate to supply a tur-engine manufacturer must rely on the lessons learned from many

bocharged engine with fuel under all operating conditions, andyears of experience.

the change in the engine power to altitude realationship should

The first Textron Lycoming model to be turbocharged was be evaluated to determine if propeller certification is valid.

FAA certificated in 1961. Since that time, about 60 additionalAdvisory Circular 23.909-1 also mentions the installation

turbocharged engine models have been certificated. The fac-of an intercooler which is another popular addition to the tur-

tory turbocharged engine has a number of design features not

bocharged engine installation. The AC warns of several itemsusually included on factory built normally aspirated engines.

which must be considered when an intercooler is installed. ItThese features are incorporated to help the engine withstand

recommends careful evaluation of changes to engine power,the additionalheat and pressure generated by the turbocharger

cooling characteristics, operating limits, and operating pro-and to reduce the possibility of detonation. Low compressionpistons help to deal with detonation. Valves and valve guides

cedures. It also states that addition of an intercooler is likely

are made of materials which are more heat resistant. Heat isto significantly affect engine horsepower.

also carried away from the pistons by oil which is delivered If engineered and controlled properly, an intercooler in-

to the back of the piston by oil squirts which are placed in the stallation can provide benefits such as a cooler running engine

engine especially for this purpose. And finally, before an air- and higher altitude capability. Engine owners should be wary

frame is certified with any factory engine, the fuel flow and of an add-on intercooler installation from which improved take-

off and climb performance are claimed. Only increased power Questions To Ask The Engine Modifiercan improve take-off and climb performance, and this would

indicate that rated engini power is being exceeded as a resultAs stated in the companion article "Look What They Are

of the power which cgn be generated from cooler induction air. Doing To Our Engines," a Lycoming engine owner should ask

To stay within the FAA certified limits for the engine, manifold questions before agreeing to an engine modification. The pur-

pressure and/or RPM settings may need to be reduced when pose of this brief discussion is to provide background and

an intercooler is installed. The exact power settings to be used specific questions. The various modifications have one item in

can only be determined by extensive in-flight testing and carefi~lcommon they generally propose to improve some or all of

torque meter measurement of the power being produced. If thisthe aircraft performance envelope. This generally translates to

is not done, the reliability of the engine becomes questionable. getting more power from the engine than it was designed for.

This is the reason that Textron Lycoming Service Letter No.As a result, there are similar questions to be asked about each

L201B states, "Reliability and average service life cannot beof the various types of modifications. These may help you:

predicted when an engine has undergone any modification not GENERQL

approved by Textron Lycoming." I. Will the modification cause the engine to produce more

Polishing and porting is yet another fad which is receiving horsepower?a great deal of attention these days. If you are sold on the idea How much?

that this type ofengine modifying is done in automobile racing 2, If the answer is No. 1 is no, why modify?circles all the time, consider that the TBO on an automobile 3. If the answer to No. 1 is yes, is the modified engine legalracing engine may be less than 100 hours; would you be satisfied for the aircraft in which it was originally certified?if that were all you could expect from your aircraft engine? 4. Has the modification been tested thoroughly enough so thatMagazine advertisements have claimed that cylinder porting will the modifier can define a reduced TBO? Has the new TBOadd five horsepower per cylinder. If the added five horsepower been stated in writing?per cylinder is a fact, this engtne is outside its certified limits

5. Will the modifier pick up warranty on the engine after it isand would be illegal except in an experimental category aircraft.

modified? What are the terms of that warranty and are theyWhat modifications can be made to a cylinder to achieve stated in written form?

the power increases which are claimed? Polishing alone might COMPRESSION R4TIO INCREASEimprove airflow and efficiency slightly, but it is not likely that

this improvement would change the power of the engine enough I. Ask to see all data from the detonation survey.

to be noticeable in the aircraft performance. To go a step fur- a. Are detonation characteristics satisfactory?ther, if the cylinder head ports were ground out just a bit, a

b. How do fuel flow schedules compare with those for the

larger charge of fuel and air wi~uld generate additional power,unmodified engine?

Again, this kind of change would affect the legal certification 2. Since torsional vibration levels will be affected, was a surveyof the engine. It would also affect reliability because less material done to insure that new characteristics are acceptable?in the cylinder head results in reduced strength. A recent report a. If no survey was done why?in the aviation press indicates that at least two sets of cylinders b. If survey was done, are the results acceptable?subjected to this procedure were found to be unairworthy when 3. Was a survey done to determine the cooling margin duringinBpectea by A P mechanics and FAA inspectors. One of these climb? Is the margin still sufficient?sets of cylinders had been flown at least through a normal engine 4. Will a new power setting chart be provided?break-in period. Cracks were found in the port areas of these

cylinders when they were inspected. TURBOCHARGER ADD-ON

To conclude, this article is not intended to discourage in- I. Has a detonation survey been done for your aircraft model?

novation. It is meant to educate readers who can easily see and 2. Has a cooling climb survey been done for your aircraftunderstand the benefits of an engine modification, but who may model?

not be aware of the effect a modification can have on reliabili- 3. What does the data from surveys in question 1 2 show?ty and life expectancy of the engine. Years of experimentation Ask to see the data and have it explained.and thousands of engines in the freld have given Lycomingengineers and~service representatives an excellent knowledge

4. If engine power changes at any altitude, is the propeller cer-

of what will work, and what will not work. This knowledgetification still valid?

comes from problems and failures as well as sudcesses. It is 5. Does the modification replace the low pressure fuel pumpfrom this experience thit reliable engine models are developed. with a fuel pump capable of delivering the higher fuel

The information shared in this article is provided to help engine pressure needed for a turbocharged installation?

owners. If you own a Lycoming engine and are contemplating 6. if your engine has a compression ratio higher than 8.5: i,a modification of any kind, use the list of questions provided do leaning instructions reflect the critical fuel managementto help get all the facts. Be sure you are completely satisfied procedures necessary to avoid detonation?that the modification will leave you with an engine which is

INTERCOOLER ADD-ONlegal, safe, and reliable.

i. Are new power setting charts available?

DO these charts recommend lower power settings to com-

pensate for the additional power generated by cooler intake

air?

If you are an engine owner contemplating an engine matched sets, by weight, before installation in a Lycomingmodification, thes~ questions should be answered to your engine. Should it be necessary to replace one of these matched

satisfaction since the reliability and longevity of your engine parts during the service life of the engine, there is a system to

may be affected. Should you desire assistance or have ques- keep the balance within specified tolerances. (See "Notes

tions about engine modifications, call Lycoming. We will be on Replacing Rods or Pistons" in the Maintenance Section.)

happy to provide assistance if possible. Lycoming engineering Perbaps the engineering answer to other questions may be

717-327-7119. enlightening or to the non-engineers, confusing. The pointis, Lycoming engineers are well aware ofwhat is needed to make

a Lycoming engine safe and reliable for the long TBO times

Engine Balance which are recommended for these engines. Thousands of hours

After certifying hundreds of flat, opposed cylinder aircraftof engine testing followed by days and weeks of data analysis

engines, and after building more than a quarter million engines provide the basis for the Lycoming engine design.

for general aviation, is it possible that Lycoming engineers have The engineering answer as to why there is a need for mat-

not learned what it takes to produce an engine which is proper- ching and balancing of engine parts in this: "As a matter of

ly balanced? Many engines have been tested over the years and sound design practice, matching and balancing components will

~agreat deal of data is availabre to support the building of engines load crankshaft bearings in a predictable manner and reduce the

to factory specifications. To put it simply, the subject of engine reaction loads at the engihe mounts." Just as we suspected

balance is well understood by Lycoming and is a consideration right!in the design and manufacturer of all Lycoming engines. Since those engineers did such a good job on that last ques-

These~Ltatements are contray to what has been implied by tion, another was ventured, "Is there any danger or problem

several advertisements and magazine article~Cilowing reports with additional balancing by non-factory activities?" Those of

have appeared in several industry publications; they say your us who are pilots will understand some of the response, but it

Lycoming engine would be so much better if you would just will take those who sepak the language of engineering to com-

take the time and spend the money to have it "custom balanc- prehend the rest. Here it is: "There are occasions when dynamic

ed". The implication is that the manufacturer knows noti~ing balance of the prop/engine combination can provide reduced

about balancing an engine and simply throws the parts together first order vibration, but additional internal balancing of Lycom-

without consideration of the importance of balancing. This is ing engines-is not required nor recommended. The rotating and

absolutely false. Lycoming engines are very carefully balanc- reciprocating masses of the six and eight cylinder opposed

ed to the degree which is necessary. They are not balanced to engines are inherently balanced. The rotating masses of the four

a point of absolute perfection because they rnn at relatively low cylinder opposed design are balanced. The reciprocating masses

speeds (compared to some automobile engines) and therefore of the four cylinder engine are not balanced as a vibratory in-

do not require the degree ofbalancing being advocated by shops enia moment at second order exists in the plane of the cylinder

which deal in this specialty, center lines. Matching the weights of components closer will

not reduce the second order moments. A redesign incorporatingTo justify this excessive emphasis on balancing, the

counterrotating layshafts rotating at twice engine speed couldautomobile racing engine is often cited as another place where

be implemented. However, the magnitude of the second orderbalancing is important. This is like comparing apples to oranges;

moments is insignificant with respect to other harmonics of thethe two types of engines are not the same. A typical Lycomingdirect drive engine is redlined at 2700 or 2800 RPM while an

engine mount reactions. In light of the contribution of the se-

cond order moment, redesign is not practical. In fact, all iner-auto racing engine may operate at more than three times this

tia loads due to any slight unbalances from matched weightspeed.

groups are a very small portion of the total reaction at the engineIn order to delve into the subject a little deeper, several

mounts. The largest contributor is due to the engine firing.questions were directed to the Senior Analytical Engineer at

Additional internal balancing contributes little to engineLycoming. His responses may help those who have doubts about

smoothness, and it may even be harmful when material isthe quality of engine balancing done at the factory. removed from highly stressed parts of the engine.

Several Lycoming engine components are dynamically To summarize, these are the points we have attempted toballinced. For non-engineers, that means that the proper balance

communicate by providing information about the balancing ofis determined while the part is in motion; it is spinning as it

Lycoming reciprocating engines. First, Lycoming engineerswould be during operation. These parts are the supercharger have acquired vast amounts of data through years of engineiinpellers, starter slpports, and the crankshaft. In addition,

testing. This knowledge is used to insure that Lycoming enginesdynamic counterweights are statically balanced to control the

are carefully balanced during manufacture. It is also used to

location of the very critical center of gravity, formulate a system which allows satisfactory engine balance to

Balance also includes the control of weights for a number be maintained when weight matched parts are replaced duringof moving engine components. Items such as piston pins, piston the operational life of the engine. The engine balancing done

plugs, and piston rings are 100% machined to close tolerances by Lycoming is part of an organized system which is intended

which provide consistent weights. The weight of dynamic to provide a quality product.counterweights is also carefully controlled.

The second point is that additional internal custom balanc-

A second aspect of engine balancing is accomplished by ing is not recommended by Lycoming. It simply is not

matching some engine pans by weight. Pistons and connecting necessary, and therefore engine owners would be well advised

rods are in this category. Both of these parts are organized into save their money.

Low Time Engine May Not Mean deterioration as a result of not being used. When the engine

Quality and Value does not achieve flight operating temperatures on a regular basis,the moisture and acids which form as a result of combustion

Reading the ’’Aircraft for Sale’’ advertisements can be in- and condensation are not vaporized and eliminated through the

teresting and misleading. As aviation-oriented people, we are exhaust and crankcase breather. As moisture and acids collect

conditioned’to look for certain bits of information which we in the engine, they contribute to the formation of rust on the

believe will allow us to evaluate the product offered for sale, cylinder walls,.camshaft, and tappets.In the case of airplanes, this information can generally be As the engine is run after rust has formed, the rust becomes

segregated in three categories-airframe, avionics, and engine. a very fine abrasive causing internal engine wear, particularlyFor purposes of this article, you are on your own with respect to the camshaft and tappets. As these components wear, theyto airframe and avionics. There does seem to-be information make more metal which attacks the softer metals in the engine.on engines which cannot be emphasized too strongly. Piston pin plugs are examples of parts which may wear rapidly

Engine information is usually provided as hours of opera- when rust becomes an abrasive inside the engine. This wear

tion since new or from some major maintenance event. For ex- could eventually lead to failure.

ample, 700 TTSN would indicate that this aircraft and engine The infrequently flown engine is just one example of a lowhave been flown for 700 hours since new from the factory. time engine not meeting the expectations of a buyer or new

-Other, but not all, engine related abbreviations include SMOH owner. The term zero SMOH is always enticing since it indicates

Thours since major overhaul, SPOH Olours since prop overhaul), the engine has been overhauled, has zero hours since overhaul.STOH (hours since top overhaul), and SFRM (hours since fac- and now may be expected to fly happily on through a full

tory remanufacture). Assuming that the recommended TBO of manufacturer recommended TBO. This will happen in some

the engine being considered is 1800 or 2000 hours, it would cases, but in others, there will not be a chance of this happen-appear that hours of use in the 400 to 800 hour range would ing. It depends on the quality of the overhaul.

automatically make this engine a very valua~e commodity. Un- Textron Lycoming Service Bulletin No. 240 recommendsfortunately this is not always true, and therefore an advertise-

parts to be replaced at overhaul regardless of the apparent con-

ment like those discussed earlier may state numbers and facts dition of the old parts. The number of these new parts used inwhich are absolutely correct, but still misleading, the engine at overhaul will probably determine the possibilities

Consider a situation which occurred recently. A Lycom- of achieving a full TBO. Consider that most overhaulers install

ing 10-360 engine with less than 700 hours since new was reconditioned cylinders on the engines they overhaul. These

reponed to be using oil at the rate of two-thirds quart per hour cylinders are not traceable. There is no requirement to main-and losing oil pressure during flight. On closer examination, tain a record of their previous histoIy. They may have only 2000it was determined that deterioration and wear had caused metal hours of operation, but they could just as easily have 5000, 7000,contamination throughout-the engine. An engine overhaul was

or more hours of operation. Those cylinders may have beennecessary and it included replacement of items such as the cam- cracked and repaired by welding--a procedure which Lycom-shaft, oil pump gears, and-pistons. Why should an engine with ing metallurgists do not recommend because the strength of aless than 700 hours since new be in this sad state?

repaired cylinder head may be significantly less than that of a

It should be apparent that the number of hours the engine new head. There is no requirement to let a prospective enginehas operated is only pan of the story. We need to know all the buyer know if cylinders have been welded and this cannot befacts if we are to understand what may have happened to this determined even by close examination. The possibility of find-

normally reliable engine and also if we are to determine the value ing a reconditioned cylinder with cracks after a few hundredof a low time engine in a pre-owned airplane, hours of operation is very real. Should this happen, it will be

The engine with metal contamination and less than 700 a costly experience.hours of operation had been installed brand new from the The lesson to be learned here is a very old one-"Buyerfactory--MORE THAN 12 YEARS before. The engine log Beware’’. Whether you are looking at those ’’Aircraft for Sale’’book shows that during the first 10 years of service this engine advertisements or looking for a replacement engine for an air-had averaged less than four hours of flight time each month. craft you already own, consider carefUlly what you are aboutChances are excellent that there were some months when the to buy. What do you really know about the engine other thanengine was not flown at all, the low time number? How much validity does that number real-

Textron Lycoming Serj~ice Letter No. L201B states that ly have? What questions can you ask which may help you to

the recommended TBO is based on the use of genuine Lycom- insure that this engine will meet your expectations?ing pans,~ average experience in operation, and continuous ser- Perhaps simply re-reading the paragraphs you have just readvice, Continuous service assumes that the aircraft will not be

may help you to formulate questions you want answered beforeout of service for any extended period of time. If an engine is taking the plunge. In the case of a low time engine with a historyto be out of service for longer than 30 days, it should be preserv- of infrequent flight, borescope examination of thecylinders anded as specified in Textron Lycoming Service Letter No. L180.

an inspection of cam and tappet surfaces by a competent andService Letter No. 201B also states that because of the varia- knowledgeable A P mechanic would be a very wise move.

tions in operation and maintenance, there can be no assurance Always remember that low numbers in the hours of operationthat an individual operator will achieve the recommended TBO. records do not guarantee reaching TBO with many long hours

The point of this discussion is simple. A low time engine of trouble free operation. The buyer must investigate every detail

may not add value to an aircraft. and the buver should be aware of engine history as closely as possible, and be satisfied that

of all frictors which ii~ay affect the condition and value of the the product does have the value which the low hours of open-

engine. An engine which is not flown frequently is subject to tion number suggests.

OPERATIOI\T

Hard Ffacts About Engine Break-In slightly and allow some wear to occur. This wear, or seatingof the ring with the cylinder wall will only occur when pressures

Most people seem to-operate on the philosophy that they inside the cylinder are great enough to cause expansion of thecan best get their money’s worth from any mechanical device piston rings. Pressures in the cylinder only become great enoughby treating it with great care. This is probably true, but in many for a good break-in when power settings above 65% are used.cases it is necessary to interpret what great care really means. Full power for take-off and climb during the break-in periodThis is particularly applicable when considering the break-in

is not harmful; it is beneficial, although engine temperaturesofa modern, reciprocating aircraft engine. Aircraft owners fre-

should be monitored closely to insure that overheating does not

quently ask about the proper procedures for run-in of a newoccur. Cruise power settings of 70% to 75% of rated power

or remanufactured engine so they can carefully complete theshould be used for a good engine break-in.

required steps. Many ofthese recommended break-in proceduresIt should be remembered that if the new or remanufactured

also apply to engines which have been overhauled or had a

cylinder replaced.engine is normally aspirated (non-turbocharged), it will be

necessary to cruise at the lower altitudes to obtain the requiredThe first careful consideration for engine run-in is the oil

cruise power levels. Density altitudes in excess of 8000 feetto be used. The latest revision of Textron Lycoming Service

will not allow the engine to develop sufficient cruise power forinstruction Number 1014 should be consulted for this informa-

a good break-in.tion. The basic rule which applies to most Lycoming piston

For those who still think that running the engine hard dur-engines is simple; use straight mineral oil of the proper viscosity

ing break-in falls into the category of cruel and unusual punish-for the first fifty hours or until oil consumption stabilizes. Thenment, there is one more argument for high power settings dur-

switch to ashless dispersant (AD) oil. But don’t stop readinging engine break-in. As stated earlier, the use of low power set-

now because there may be an exception or note ofcaution whichtings does not expand the piston rings enough to break down

applies to your particular situation.the film of oil on the cylinder walls. The high temperatures in

The exception to the basic rule on break-in oil applies to the combustion chamber will oxidize small amounts of the oilthese engine models: TO-360-C, TO-360-F, TIO-360C, film which often creates a condition commonly known as glaz-TIO-541- and TIGO-541-. These engine models are to be ser-

ing of the cylinder walls.When this happens, the ring break-inviced with ashless dispersant oil for the entire life of the engine,

process stops, and excessive oil consumption frequently occurs.

including the break-in period. The bad news is that extensive glazing can only be correctedTextron Lycoming "76" Series engines fall into a category by removing the cylinders and rehoning the walls. This is ex-

different from all others. These models include the 0-320-11, pensive and it is an expense that can be avoided by proper break-the O/LO-360-E and the TO/LTO-360-E. Although these in procedures.engines should be run in with straight mineral oil, Textron

To summarize, there are just a few items to remember aboutLycoming oil additive LW-16702 must be added to the oil for

engine break-in. (1) If a preservative oil has been added by thebreak-in, and every 50 hours thereafter or at every oil change. aircraft manufacturer, drain it after the first 25 hours of opera-After engine break-in, AD oil with LW-16702 is recommended.

tion. (2) Follow the engine manufacturers recommendationWhen taking delivery of a new aircraft, there is another regarding the oil to be used for break-in and the period be-

point which must be emphasized. Some aircraft manufacturers tween changes. (3) Run the engine at high cruise power levelsadd approved preservative lubricating oil to protect new engines for best piston ring/cylinder wall mating. (4) Continue break-from rust and corrosion at the time the aircraft leaves the fac- in operation for 50 hours or until oil consumption stabilizes.

tory. This preservative oil mrcst be removed at the end of the These simple procedures should eliminate the possibility offirst 25 hours of operation. cylinder wall glazing and should prepare the engine for a long

Each new or remanufactured engine is given a production and satisfactory service life.

test run at the factory before the engine is delivered to an air-

craft manufacturer or other customer. After installation in the

aircraft, the engine is run again during the test flights. These Leaning Textron Lycoming Enginestest runs will insure that the engine is operating normally and

will provide an opportunity to locate small oil leaks or other (How to use this outline presentation: All operators should

minor discrepancies, in addition, these test runs do the initial read the General Introduction and Summary Recommendations,

seating of the piston rings. The rest of the break-in is the respon-but should carefully study the section that applies to his or her

sibility of the pilot who flies the aircraft during the next 50 hours. specific powerpiant.)

A new or remanufactured engine should receive the same GENERAL INTRODUCTION

start, warm-up, and preflight checks as any other engine. There The information outlined in this presentation has been

are some aircraft owners and pilots who would prefer to use reduced to minimum essential facts, and is based on leaninglow power settings for cruise during the break-in period. This as described in the various Lycoming "Engine Operator’sis not recommended. A good break-in requires that the oil film Manuals", and Service Instruction No. 1094. "Fuel Mixture

which lubricates the piston rings and cyiinder walls break down Leaning Procedures".

Although the above documents are authentic basic 8. Proper leaning at cruise power results in more normal

references 6n leaning, and including the related write-ups in engine temperatures in cool weather or at the cooler

pist issues of the’"Flyer", we see the need to review all of temperatures of altitude. Rich mixtures cause undesirable

these and outline the basic combined information in one article cool engine temperatures in cool or cold weather.

for the following reasons:a. Oil temperatures should be at least 1650 F minimum

I. The basic leaning information needs to be repeated from in order to reduce moisture forming vapors and

time to time. undesirable acids in the engine oil.

2. We need ib update our information on new engine models, The Three Basic Types of Fuel Metering Devices Used with

or concerning new and i;nproved engine instrumentation. Lycoming Engines In General Aviation; and the General Pro-

3. Operators in the field have stated that some of the Pilot’s cedures for Leaning at Manufacturers’ Recommended Cruise

Operating Handbooks lack sufficient information onPower:

leaning. 1. Floattype carburetor.

4. The engine manufacturer with the approval ofthe FAA and a. Fixed pitch propeller lean to a maximum increasein cooperation with the airframe manufacturer, is the in RPM and airspeed or just before engineauthority on the operation of his product. roughness.

5. Small aircraft, such as the typi’cal General Aviation trainer, (1) Engineroughness isnotdetonationat cruisepower,have limited engine instrumentation. Therefore, we pro- but is caused by the leanest cylinder not firing duevide the operator with certain basic leaning rules to pro- to a very lean fuel-air mixture which will not

teet the powerplant and yet operate it efficiently. Damage support combustion in that cylinder.to this type of engine results from i~ing at higher than

the manufacturer’s recommended cruise power.b. Controllable propeller lean the mixture until

roughness encountered, and then enrich slightly until6. The more complex powerplants of higher horsepower or roughness is eliminated and engine is smooth. There

higher compression ratios (200 HP and higher), are general- may be a slight increase of airspeed noted in smooth

ly accompanied by sufficient engine instrumentation to pro- air when properly leaned at cruise when compared to

teet the powerplants while operating at approved higher than full rich.routine power settings. However, the engine manufacturer

helps protect these engines by establishing certain re-c. The EGT offers little improvement in leaning the float-

quirements for leaning at higher than average cruise powertype carburetor over the procedures outlined above

by reference to.fuel flow, exhaust gas temperature, or tur-because of the problem of imperfect distribution.

bine inlet temperature, cylinder head temperature, oil However, if the EGT is installed, a good rule of thumb

temperatures and pressures. The airplane pilot’s manual willis lean the mixture plus 500 on the rich side ofpeak EGT

specify this information for these more complex high per-with this type of fuel metering device.

formance powerplants. d. With the application of carburetor heat, the mixture

is richer; check and adjust mixture leaner.

WHY LEAN THE ENGINES?2. Fuel Injection.

In spite ofa number of variations in the different modelsa. Becauseofthevaried modelsoffuelinjectorsused with

of our powerplants, there are some general recommendationsLycoming engines, the operator must consult the

on leaning’we can dffer for all Lycoming piston engines. specific Pilot’s Operating Handbook for specifici. Most carburetors or fuel injectors are set slightly on the leaning instructions.

rich side--this calls for leaning at any altitude at theb. However, as a basic technique, at the manufacturer’s

manufacturer’s recommended cruise power. recommended cruise power limitation, with a manual

2. Proper leaning means economy of fuel, which results in mixture control, lean initially by reference to the fuel

lower cost of operation. flow (if available) for the percent of cruise power with-

3. Rich running engines cause roughness proper leaning out exceeding manufacterer’s recommended limits.

makes them smooth, which protects engine mounts and Then for more precise leaning, if an exhaust gas

engine accessories from undesirable vibration and possi- temperature is available, find peak EGT without ex-

ble failure. ceeding limits, and operate there, or by the rule of thumb

of plus 500 F on the rich side of peak EGT.4. An engine properly leaned is a more efficient powerplant.

(1) Monitor cylinder head temperatures.5. Leaning at cruise can exiend the range of the aircraft--

a safety factor. (2) The EGT is a helpful instrument for precise lean-

ing with fuel injection.6, Proper leaning means less spark plug fouling and longer

life for plugs also a safety factor, as well as lower (3) If EGT and fuel flow are not available, then lean

maintenance cost. to just outside roughness, or to a slight airspeed7. Correct leaning means cleaner combustion chambers and loss, then as desired by the pilot.

less likelihead of pre-ignition from undesirable combus-

tion deposits.

LEANING RECOMMENDATIONS FOR TYPES full rich mixture regardless of the airport elevation. The

OF TEXTRON LYCOMING ENGINES supercharged engine needs the extra fuel for coolingi. Direct drive normalljr aspirated engines, (carbureted or because of the high induction air temperatures created

fuel injection): by supercharging, and because it is operating at sea level

a. May beleanedatany altitude, atmanufacturer’s recom- horsepower.mended cruise power iusually 75% or less), provided b. If leaning by means of manual mixture is permitted at

there is a manual mixture control. climb power, it will be specified in the Pilot’s Operatingb. In climb from sea level through 5,000 ft. density Handbook, and will list required ranges for fuel flow.

altitude, mixture must be full rich. Continued climb power settings, and temperature limitations.

above 5,000 ft., mixture may be leaned for smoothc. The exhaust gas temperature gage is a helpful instru-

engine operation. DO NOT confuse the 5,000 ft.

reference for climb with the cruise configuration. ment for leaning the supercharged engine at cruise

power with a manual mixture control.c. Operation at higherthan 75% power withoutreference

to fuel flow, cylinder head temperatures, and without d. Recommended standard cruise power for the super-

knowledge of specific powef, requires full rich mixture. charged engine is 65 At 65 power or less this type

(1) Leaning at recommended cruise power does notofengine may be leaned as desired as long as the engine

damage a normally healthy engine, but leaning at operates smoothly, and temperatures and pressures are

higher than 75 cruise power in this type ofengine within manufacturer’s prescribed limits.

can cause engine damage when complete engine in- SUMMARY RECOMMENDATIONS-strumentation is not available(CHT and fuel flow

minimum), and’limitations ffet spelled out in1. This presentation has merely covered the minimum basics

airplane pilot’s operating handbook,of the various types of Textron Lycoming powerplants. For

a more detailed description of the leaning procedures, par-2. Leaning the turi~ocharged Lycpming powerplant, ticularly the higher powered more complex engines, refer

a. The turbine inlet temperature gage (TIT) is a required to the Pilot’s Operating Handbook. If the manual is in-instrument with turbochargingby Lycoming. complete, refer to Textron Lycoming Service Instruction

b. During manual leaning, the maximum allowable TIT No. 1094.

for the particular engine and installation must not be2. For maximum service life, where there is a cylinder head

exceeded. Check the Pilots’ Operating Handbook (POH)temperature installed, maintain cylinder head temperature

or The Engine Operator’s Manual to determine this

temperature limit. (for continuous operation), below recommended 4350 F

(2240 C). If cylinder head temperature is higher than recom-

c. At cruise power wken leaning the mixture, ifm reach-mended during flight, in order to complete the flight as safe-

es the maximum allowable limit before peaking, doly as possible, reduce head temperature to within recom-

not exceed the limit to find peak.mended operating range by enriching the mixture, or by

d. Operation may be at peak during.cruise provided TITadjusting cowl flaps if available, or by reducing power, or

does not exceed red line maximum and cylinder headby use of any combinations of these methods.

should not exceed 4350 F (2240 C), for continuous

operation. Mixture may be operated anywhere on the 3. Some leaning during descent to traffic pattern may be in

rich side of peak. CHT, fuel flow, and TIT will decide order to prevent roughness or sudden engine cooling. The

where the pilot will operate his mixture control as before-landing check should prevent overlooking the mix-

specified in the Pilot’s Operating Handbook. ture for landing.e, Very high altitudes may result in high temperatures 4. Always return mixture to rich before increasing power.

which will require adequate fuel, cowl flaps, or air5. Leaning the mixture in accordance with the engine manufac-

speed for cooling. turer’s recommendations is practical and economical.f. All takeoffs with turbocharged powerplants (where tur-

6. Normally aspirati~d, direct drive Lycoming engines operatedbo is operating) must be at full rich mixture regardlessof airport elevation. The turbocharged engine needs the at manufacturer’s cruise power (usually 75% power or less)

extra fuel for cooling because of the high induction air may be leaned at any altitude. Do not confuse the 5.000

temperatures created by turbocharging, and because the ft. reference for climb with this type. If cruise (for exam-

engine is operating at sea level horsepower. pie) is 2500 ft., and 75% power or less is used, then the

g. Always consult the Pilot’s Operating Handbook for anymixture should be leaned for all routine cruise operations

variations for the specific aircraft. If leaning by meansoutside the traffic pattern.

of manual mixture is permitted at climb power, it will 7. Leaning techniques vary because of differences in fuel

be specified in the Pilot’s Operating Handbook and will metering devices (carburetor or fuel injector), turbocharg-list required ranges for fuel flow, power settings, and ing or supercharging, fixed pitch or constant speed prop,temperature limitations.

_etc. Read the airplane Pilot’s Operating Handbook and

3. Leaning the supercharged Lycoming powerplants. determine the proper operating technique. Get a proper

a. All takeoffs with supercharged powerplants must be at check-out in the aircraft.

Proper Leaning At Cruise Aids Safe vs. lean at cruise. in the illustration of the 180 HP engine there

is one additional hour of flight when properly leaned. This Is

Flight And Saves Dollars a very real safety of flight fact.

These are some of the more important facts that illustrate

In previous issues ofour Lycoming Flyer, we have always how proper leaning at cruise power aids safe flight--and saves

emphasized proper leaning at the manufacturer’s recommend- dollars.

ed cruise power at any altitude; however, in this article we will

expand our continuing discussion of leaning and explain (1)

how it saves dollars, and (2) how it aids safe flight. In a prac-

tical approach to our subject, let’s look closely at the chart listed Operating The Direct Drivebelow:

Fixed Pitch Lycoming EngineLeaning the normally.aspirated, direct drive

Lycoming engine at cruise vs, full richThere is an area of confusion concerned with operating the

at 4,000 feet density altitude, 75% power. direct drive fu~ed pitch normally aspirated powerplants amongEngine Airplane

some pilots. If there is a power chart provided, it will indicateModel Model

that as the airplane is flown at different altitudes above sea level,300 HP Piper Cherokee 300

it is necessary to use a higher RPM for adequate cruise perfor-Full Best Economy Hours Hours

mance with an increase in altitude. A typical example mightRich (Peak EGT) Rich Lean

be the 0-360, 180 HP Lycoming powerplant. The power chart

19$ gals. 15.6 gals. 4.2 hrs. 5.1 hrs.by the airfnune manufacmrer for this fixed landing gear air-

Engine Airplane craft lists 75% power at 7500 feet at 2675 RPM (00 manifold

Model Modelpressure gage in their airplane). The confused pilot observes

250 HP Piper Aztec that red line takeoff RPM is 2700 RPM, and is afraid to lean

Full Best Economy Hours Hours either for cruise or climb despite the altitude because he is pull-Rich (Peak EGT) Rich Lean ing almost takeoff RPM.

16.2gals. 13.6gals. 4.3 hrs. 5.1 hrs. However, he can and should lean the engine at these

Engine Airplane altitudes despite the high RPM, for the horsepower is down to

Model Model 75% because of the thinner air. On the other hand, with any

180 HP Cessna Cardinal direct drive normally aspirated Lycoming engine, he can and

Full Best Economy Hours Hours should lean the mixnre at any altitude as long as he is in cruise

Rich (peak EGT) Rich Lean configuration at 75% power or less.

11.9 gals. 9.7 gals. 4.1 hrs. 5.1 hrs. Let’s take a look at the airframe manufacturer’s power chart

Observe the fuel flows at "Full Rich" vs. "Best economy", for the 0-360, 180 HP engine and observe the gradual increase

and note that the higher horsepowered engine uses almost 3’h in RPM required with the increase in altitude, but maintaining

gallons per hour more fuel at full rich cruise power. Now multip 75% for cruise at each altitude. What the chart will not show

ly 3 H, times the cost of aviation gasoline per gallon, and con- here is that for flight above 7500 feet, it is not possible to achieve

ciude how much unnecessary additional cost per hour of flight 754~ power with a normally aspirated engine (meaning not tur-

time you are incurring by operating at full iich mixture at cruise bocharged or supercharged).

power. POWER CHART

While we are on a discussion of unne~essary cost of opera- Percent Endurance on

tion, another important factor is the damage often done to engine Altitude RPM of H. P. 59 gals. fuel

accessories by operating at full rich at cruise power. Engines 2500 2550 75% 4.8 hours

operating at full rich in cruise tend to be rough, resulting in 3500 2575 75C/o 4.8 hours

shaking engine accessories and engine mounts. thereby con- 4500 2600 75X 4.8 hours

siderably reducing their life and often resulting in expensive 5500 2625 75% 4.8 hours

early replacement. A properly leaned engine at cruise power 6500 2650 75~ 4.8 hours

is a smooth engine and will save money. 7500 2675 752 4.8 hours

We have been telling all concerned about the benefits to

the spark plug by proper leaning at cruise power in earlier issues

of the Flyer, and it can be repeated in this discussion becauseOperating Your Lycoming Engines

it well illustrates our point on saving dollars. Proper leaningat cruise helps prevent spark plug fouling. The maintenance cost At Takeoff And Climbto remove and clean spark plugs can be reduced by good lean-

ing techniques. Frequent cleaning of spark plugs reduces their In reviewing a number of the airframe manuals, it reveal-

life and requires early replacement. Furthermore, badly fouled ed that there is a certain amount of implied operation concern-

spark plugs could also become a safety of flight problem too. ing rakeoff and climb. Therefore, from an engine point of view,

For a very interesting safety of flight item, let’s look at the we would like to discuss the take-off and climb in greater detail

chart again. Notice the difference in hours of flight at full rich herein.

DIRECT DRIVE ENGINES NORMALLY ASPIRATED

Most normally aspirated engines are rated at full power for

takeoff and climb indtfinirely, provided engine temperaturesThe normally aspirated engine performs and reacts to den-

and pressures are within the green are area of the engine in- sity altitude. As an example, this type powerplant at takeoff from

struments. Extra fuel, sensible airspeed, and cowi flaps, if an airport with a 3,000 ft. indicated altitude, but with an am-

available, are all helpful in keeping cylinder head temperaturesbient temperature at 850F, would have a density altitude of more

within desired limits during takeoff or climb, than 5,000 ft. The engine would lack some 20 to 25Lic of us

Climb requirements may vary as an example on apower and also probably run rough because of a nch mixture

warm day with the airplane close to gross weight. and a directon the ground at full rich. Therefore, the typical normally

drive engine with a fixed pitch prop, the pilot will need full aspirated direct drive engine requires the mixture be leaned on

throttle all the way to cruise altitude. The same airplane on athe ground for efficient takeoff performance where arrports are

cold day and lightly loadtd, after full throttle at takeoff the pilot 5.000 ft. (density altitude) or higher. The over rich condition

may want to reduce power 100 or 200 RPM and still not see is something the pilot can compensate by leaning. However.

performance suffer. the higher density altitude with its thinner air cannot be com-

Those direct drive normally aspirated engines with a proppensated for with a normally aspirated engine unless a super-

governor are also rated indefinitely at full power, and the charger or mrbocharger unit is added to the powerplant. Thus,

manuals all recommend full power for takeoff, but specify aat density altitudes of5,000 6,000 feet, the pilot of a normal-

small reduction in power, generally to 8596 power climb. Study ly aspirated engine has available to him approximately 75k of

the specific airplane Pilot’s Operating Handbook for detailed the engine power, and must plan his takeoff accordingly after

power settings. setting the mixture.

GEARED, TURBOCHARGED AND

SUPERCHARGED ENGINES PROCEDURE FOR LEANING

Turning to the more complex powerplants such as the

geared, turbocharged and supercharged models, the manuals i. The fixed pitch propeller lean to maximum RPM at full

are quite specific in their description of takeoff and climb rech- throttle prior to takeoff where airports are 5.000 ft. densl-

niqucs. Our geared and supercharged powerplants have a limit ty altitude or higher. Limit operation at full throttle on the

of five minutes at takeoff power. However, it is advisable to ground to a minimum rime.

throttle power to the recommended climb power as stipulatedin the manual as soon as rakeoff obstructions have been cleared

2. The direct drive normally aspirated engine with a propgovernor but without fuel flow or EGT, set throttle at full

and proper airspeed attmed.power and lean mixture at maximum RPM with smooth

The turbocharged Lycoming’s (including the TIGO-541-E operation of the engine as a deciding factor.

series) do not have a five minute limit at takeoff power.However. the manual clearly stipulates a reduction to a proper

3. With fuel injection, if the powerpiant has a marked fuel flow

climb power when citar of obstaclts, and when climb speed gage, then set mixture in accordance with instructions on

has been established, and cylinder head, oil and turbine inletthe fuel flow gage and/or in accordance with the airplane

tcmperamns art within limits. Due to the more complete enginePilot’s Operating Handbook.

instrumentation in the airplane, the manuals allow some lean- 4. With an EGT gage, at full throttle, lean mixture to plusing at climb. but with the engine insruments indicating within 1000 on the rich side ofpeak of a normally aspirated engine.specified limits listed in the airplane manual.

5. Pressure carburetor Ail Lycoming engines have anThe more complex powerplants (geared, supercharged, and automatic mixture controi which does not require leaning

turbocharged) demand smooth, careful operation of the throt- for takeoff.tie at all times, particularly at high power, but especially when

engines and oil are not up to normal operating temperatures such 6. Turbocharged and supercharged engines All takeoffs

as for the initial takeoff. Overboost or erratic engine operation must be at full rich mixture because the engine is broughtwill result from abrupt movements of the throttle. All super-

back to sea level horsepower which does not permit leamng.charged and turbocharged engines must use full rich mixture

for all takeoffs regardless of field elevation. DESCENT

Landings And Takeoffs From Regardless of the field elevation where the pilot intends to

land, the descent from cruise altitude to traffic pattern altitude

High EIevation Airports should include some leaning for smooth engine operation. LOW

elevation fields @elow 5,000 ft. density altidude) will requirePilots frequently ask us for information and guidance con- that the mixture be moved to full rich in the "before landing

ccming landings and takeoffs from high elevation airports. Our checklist". Landing at airports above 5,000 ft. density altitude,reference point in this discussion will be based on density the mixture must be leaned to smooth engine operation duringaltitude. The discussion also requires that we treat separately traffic pattern flight and landing; otherwise, the engine may stall

operation ofnormally aspirated, supercharged on the runway because-of excessive richness.

engines at high elevation airports.

The Need For Good Fuel Management

One phase of Textron Lycoming’s interest in safety is a

constant review of accidents involving our engines. It appearsthat one of the advantages in reviewing these accidents in five

year divisions, is that some patterns emerge. After a recent

review, the pattern of poor fuel management was obviously a

serious problem.

These accident reports list such poor fuel management

techniques as switching to another fuel tank after the before

takeoff Nnup was completed, and then experiencing engine pro-blems on takeoff. There are other reports of pilots switchingfuel tanks at a critical point on the approach to a landing, with

"EGT Probe and Gage"

the result that the pilot turned the fuel valve to an empty tank

but couldn’t compensate in time and crashed. It is also painful INSTALLATION INFORMATION-ta read about pilots flying low on day cross-country, or

The mechanic must carefUlly follow the installation instruc-moderately low at night, and running a tank dry. By the time

tions concerning placing the probe in the exhaust stack. If itthey realized what caused the engine stoppage and attempted

is closer than I’h inches to the cylinder head, probe life willto see the correct fuel selector position, the aircraft had lost too

be limited, or if too far down toward the end of the exhaustmuch altitude and made contact with the ground.

stack, the response on the gage will be slow. Should there beThere are several other examples ofpo~ fuel management doubt concerning in which stack a single probe is to be in-

in this particular five year study, but those listed herein should stalled, that information is available from the airframe dealer’smake a point with pilots. Be thoroughly familiar with your service department. The operator might desire the more expen-airplane fuel system and tank switching procedure. Furthermore, sive installation of probes in ail cylinders, therefore the accom-

it is unsafe pilot technique to run a tank dry as a routine pro- panying gage will generally have a selector switch for individualcedure. We realize there is the occasional exception, but to readings on all cylinder exhaust stacks. Again, it is mast im-

routinely run a fuel tank dry asks for trouble. Our records show portant that the installation instructions are carefully followed

a number of accidents where the fuel selector broke off, or was In order to get reliable readings.frozen or jammed into one position, or caused sediment in the

INTERPRETING THE SYSTEMbottom of the fuel tank to be sucked into the fuel system. Fuel

injection is more difficult to restart in the air than most car-Most of the EGT manufacturers have standardized on gage

buretion because of its vulnerability to vapor lock. increment markings of 250 F (see illustration). A few EGT

manufacturers will go further and show the temperature rangeGood judgment and sound fuel management go on the gage as 12000 F to 1750" F. Lycoming engines normal-

hand-in-hand.ly operate within an EGT range of 12000 F 16000 F.

The simple gage shown in the illustration is quite satisfac-

tory for the less complex engines. An advantage of the EGT

over the cylinder head temperature gage is one of an almost

The Exhaust Gas Temperature (EGT) immediate response to manual movement of the mixture con-

And Fuel Managementtrol. as long as it is not a rapid movement of the control.

Remember that the peak or point of maximum needle detlec-

tion of the EGT gage is the basic reference for fuel manage-Since so many operators of our engines frequently ask us

ment. If an operator has experimented with the EGT at theabout the use of an exhaust gas temperature with our

engine manufacturer’s recommended cruise power, he observespowerplants, perhaps we should examine the system, and also

that gradual leaning does result in peak EGT. The location ofset how it relates to fuel management. peak EGT on the gage will also vary with different power set-

One of the better publications describing the EGT that we tings, changes in altitude, and change in ambient temperature.have seen was put out by Alcor Aviation, Inc., P. O. Box 32516

From peak EGT, either increasing or decreasing the fuelof San Antonio, Texas 78284. This excellent booklet is titled, flow causes a decrease in EGT. When richer than peak EGT"EGT and Combustion Analysis In A Nutshell", and is

there is excess fuel, and when leaner than peak, there is excess

available free to interested operators. air.An EGT system is not a complex or expensive item to in-

Peak EGT with a float-type carbureted engine is frequent-htall. The more economical kit consists basically of the gage, ly a vague point because of less efficient distribution (than fuelwiring, and probe (see illustration). The system generates its

injection) to the individual cylinders by this type of metenngown electricity to operate the instn~ment.

device. As a result, float-type carbureted engines tend to operatesmoother at +250 to +500 F on the rich side of peak EGT.

Whereas, the fuel injected engines at 250 H.P, and higher will

provide a precise peak, and theretbre the EGT system is likewise

a more precise method of fuel management with fuel injection

DEFINITION OF PEAK EGT the pilot attempts to go leaner than peak EGT, (with fuel InJt~c-A simple definition of peak EGT is given us by engineer- tion only), the power decreases rapidly as fuel flow decreases.

ing as the chemically correct mixture of fuel and airwhich BEST POWER MIXTUREgives 100% utilization of all the fuel and all the air. Remember,we said earlier that at mixtures leaner than peak EGT there is

Best Power Mixture, or sometimes termed Maximum

excess air, and at richer mixtures, excess fuel. Operation at peakPower Range, as depicted on the EGT gage, is in the nn4e of

EGT, particularly on long flights, can be an advantage not on-plus 1000 F to 1500 F on the rich side of peak. Best Powlrhlix-

ly for purposes of increased range, but there is less likelihood ture will provide fastest indicated airspeed for a cruise power

of spark plug fouling as well, setting, although it is generally not considered a practicaleconomic mixture for cruise purposes. However, Best Power

Don’t be surprised to see variations in temperature between Mixture generally provides a safe amount of fuel for a powerindividual cylinders where there is a probe for every cylinder. setting higher than the engine manufacturers recommendedIt is fairly typical to see an average 1000 F variation with fuel cruise, except that needed for takeoff power. Satisfactory ’’Nleinjection, and as much as 2000 F variation with a float-type car- of thumb" compromise between Best Economy and Best Powerburetor, The latter (carburetor) variation tends to be greater Mixtures has been at plus 500 F on the rich side of peak EGT.because fuel/air distribution is not as good as with fuel injec-tion, In cold outside air temperature flight conditions, the mix- Again we repeat that maximum leaning (peak EGT) does

tTure distribution is poorer for both fuel injected and carburetednot damage an engine at the engine manufacturers recommended

engines. However, with the float-type carburetor operating incruise power. Damage is caused by maximum leaning at higher

below freezing ambient temperatures, the fuel/air distributionthan recommended cruise power where the manuals do not spell

is definitely worsened, resulting in noticeable variations init out or allow it, and when the aircraft does not have 3 com-

temperature between individual exhaust stacks. plete set of reliable engine instruments to protect the

powerplants. Excessive leaning under the latter high power con-It is also important to understand that leaning to roughness ditions can cause detonation and/or preignition and possible

at the engine manufacturers recommended cruise power is not engine failure.an indication of detonation, but indicates normal characteristicsof distribution to the individual cylinders. The roughness in-

The exhaust gas temperature system can be a valuable aid

dicates that the leanest cylinder has become so lean it is begin-in proper leaning at cruise power, particularly with fuel injec-

ning to miss. This is typical of an engine with a float-type car-tion powerplants. It is hoped that this write-up will help the

buretor. Damage to an engine from leaning does not occur at operators of Lycoming engines achieve the best possible effi-

the manufacturers recommended cruise power, but takes placecient use of the EGT system.

at higher than cruise power. If we were to sum up the major advantages of an EGT to

As far as the pilot is concerned, operating on the lean sidethe operator, they are as follows:

ofpeak EGT can only be accomplished with fuel injected engines I. Saves fuel an economy aid.

ofat least 250 HP or higherbecause the fuel flows in the lower 2. Aids proper mixture control more precise fuelhorsepower engines are so small. It isn’t possible with float- management.type carburetors because of the fuel/air distribution problem. 3. Helps increase range.Leaning past the peak is not recommended.

4. Detects some types of engine troubles.LIMITATIONS OF POWER AT PEAK EGT 5. Aids peak engine performance at cruise.

Textron Lycoming allows leaning to peak EGT at 75% 6. Helps prevent spark plug fouling.power and below on our direct drive normally aspirated engines.We limit operation at peak EGT on our geared, supercharged

7. Fits any General Aviation piston aircraft engine.

powerplants at 65% power or below. With Lycoming tur- 8. Can be used with carbureted or fuel injected engines.bocharged engines, where the EGT gage is used to interpretturbine inlet temperature (TIT), the maximum allowable TTT

specified in the POH should not be exceeded when attemptingto find a peak temperature by manual leaning. Where a cylinder An Explanation Of Power Settingshead temperature is also available, the operator ought alwaysto cross-check the head temperature as a routine procedure when

A recent letter received here at the factory asked a ques-

leaning, and remember that whenever CHT reaches the max-tion we are hearing more often in recent months:

imum before reaching peak EGT, then CHT rather than EGT "Is it a fact, or is it fiction, that engines with constant speedshould dictate the leaning. props should not use power settings where inches of mercury

exceed RPM in hundreds? I am referring of course to non-BEST ECONOMY MIXTURE turbocharged engines in general--".

Best Economy Mixture as it relates to the EGT system The answer to this question is easily found in cruise powerbegins at peak. For all practical purposes with Lycoming charts of the airframe Pilot’s Operating Handbook. Whateverengines, peak EGT is right at the edge of Best Economy mix- the combinations of RPM and MP listed in the charts thevture, and is our only practical point of reference in the Best have been flight tested and approved by the airframe anhEconomy Mixture range. At the manufacturers recommended powerplant engineers. Therefore, if there are power settingscruise power. peak EGT causes a slight loss of horsepower such as 2100 RPM and 24" MP in the power chart, they are

usually reflected in two or three miles per hour of airspeed. If approved for use.

The confusion over so-called "squared" power settings Then, follow with the appropriate manifold pressure now

(i. e. 2400 x 24" MP), appears to have been a carry-over from that the mixture and RPM have been correctly set to accom-

some models of the old iadial engines which were vulnerable modate the increased throttle.to excessive bearing wear where a MP higher than "squared"

DECREASING POWER--Most models of our engines re-was used. More pressure on the bearings with the higher than

quire the basic procedure for decrease of power by retarding"squared" MP was the cause of their problem. However,

throttle, followed by RPM. However, we do have an excep-changes in design, metals and lubricants permit changes intion in several older models of our geared normally aspirated

operation in the more modern flat opposed powerplants.powerplants such as the GO-480 and GO-435 series. In the climb

Let’s look at the power charts in a couple of the Pilot’sconfiguration, we recommended full throttle throughout the

Operating Handbooks of two different aircraft manufacturers, climb for internal fuel cooling with RPM reductions initiallybut where both are using the four cylinder 200 HP Lycoming to 3000 RPM and then 2750 RPM for prolonged climb.engine,

Turbocharged and Supercharged engines require careful apCessna’s Model 177 RG, using the Lycoming plication ofthe basic power sequences as outlined in the begin-

1O-360-A1B6D, in the cruise range at 6,000 feet lists a cruisening. It is also possible to create a "like" overboost on these

power setting range at that altitude of anywhere from 2100 RPMengines by going to takeoff manifold pressure at cruise RPM.

to 2500 RPM with variations all the way from 18" MP to 24"such as might take place in an unexpected go-around. The

MP. They list a recommended Power setting for 664% power stresses and pressures on prop and engine would create a threatat 2100 RPM at 24 n MP.

to both.The Piper Arrow, powered by the Lycoming 1O-360-C

series engine, lists the following cruise power settings at 6,000feet in their chart at 65% power at full throttle (about 23 MP) Considerations For Low Powerx 2100 RPM.

The complete chart for 65% power is shown as follows: Low RPM Cruise

Altitude 2100 RPM 2400 RPM The high price of aviation fuel is causing aircraft owners

SL 25.9 MP 22.9 MP and pilots to review their operations in search of ways to keep1,000 25.6 MP 22.7 MP operating costs down. Those operating aircraft with controllable

2,000 25.4 MP 22.5 MP propellers have been requesting information on cruise opera-

3,000 25.1 MP 22.2 MP tion in the low RPM range 1800 or 1900 RPM for example.4,000 24.8 MP 22.0 MP The number of queries received indicates a great deal of interest

5,000 F. T. MP 21.7 MP and, therefore, it seems appropriate to share the information

6,000 F. T. MP 21.5 MP on this subject with all of our readers.

The Textron Lycoming Engine Operator’s Manual has per-After studying the power chart, the pilot would undoubtedly formance curves applicable to each engine series. The curve

then ask what combination of RPM and MP would be best to for the 1O-540-K series, 300 horsepower engine is printed hereuse at cruise. We recommend the pilot try the various combina-

as a reference for this article. The curve does provide data on

tions offered by the power chart over a five-minute period whenthe maximum manifold pressure (MP) which may be used with

flying in smooth air, and use the listed RPM and MP Combina-any particular RPM at sea level and at altitude. The limiting

tion which gave the least vibration and the lowest noise level. manifold pressure line clearly restricts high manifold pressuresThe Pilot’s Operating Handbook is the basic reference for with low RPM settings. There is a good reason for this; high

the pilot as this subject illustrates. manifold pressure and low RPM is similar to allowing yourautomobile to lug up hill in fourth gear. The pinging you hear

in your automobile tells you that detonation is occurring and

you should shift down to a lower gear. In an aircraft, detona-

tion is not likely to be heard, damage occurs in the engine and

Basic Power Sequence it is then too late for preventive measures. For this reason.

(Governed Engines) engine operation should be within the limitations established

in the Pilot’s Operating Handbook (POH).

TQ INCREASE POWER first, enrich mixture, increase Although there are restrictions, it is quite apparent that

RPM, then follow with throale. operation is possible in the 1800 to 1900 RPM range. The real

TO DECREASE POWER first, reduce throttle, reduce question is whether there is any actual benefit.

RPM, and then adjust mixture. One of the first considerations of low RPM cruise is that

INCREASING POWER enrich mixture first to ensure power settings this low should not be used during the engine

protecting the engine against damage from higher power when break-in period. During the break-in period, power settings of

previously leaned out for a lower power setting. at least 7546 or more should be used for climb and cruise. Low

power for break-in may result in glazed cylinder walls and highNext, increase RPM because the engine and propeller would

oil consumption which can only be cured by cylinder removalhave undesirable pressure and stresses with a high manifold

and rehoning.pressure and lower RPM in some models.

CUIM Y) 1YJ3 moving vertically down the curve to 1900mrMICTWC I~ltFmR TrrY Y1 UI[C

R*Os~IPr*au~ I I I I I LMYI)K RPM while maintaining 24 inches of MP will1(4 au URCRIFT UWIE

lamor i ruru*mi PERFORY"WCE DLTI feSUlf i, a loss of about 30 horsepower andur~ra o*l* rru v*roo nm YUYUI P(I~R YXIICIEI i Inllm~l\a I I_l.uraru*rao I II IllunmonrmarnorPo therefore arevised powerof5546. BecauseIW(II´•’n~rUUrll(YO´• fC sauF´•* ~4 MCm

cap~Essw amo this power setting is near the limiting*UL(I1IHLlw tllY NELIIXtTWIrUUm~ r~ rRDn~l %nax RU-IOW manifold pressure line, it would be inap-NawoE.uuu

N1ID

310 mrrauL urmRE propriate to increase the manifold pressure

MlulIUI* amnD* rOIWED

setting at 1900 RPM since the limitingru* lo’r uu~a rru 5

1~’" manifold pressure might be exceeded.*w

Quite frequently, someone will ask if thet engine will last longer if it is run at a slower

RPM setting. The answer is "No". Open-tion at the recommended cruise RPM settingsshould allow the engine to reach TBO if ithas regular oil changes, is operated withinnormal temperature ranges, and is well cared

KI I ;I I r hll~n 1 I IIl I Ifo’ by pilots and maintenance personnel.

rulromrIn summary, it is possible to run an

g engine at cruise using 1800 or 1~00 RPM.A curve from the Engine Operator’s Manualshould be consulted to insure that manifold

pressure limits are not exceeded. In reality,~P*oaumur h´•

I, n Ic ,I I~ tJ 2) n n n t( n lad i r I II b IJ u ii ´•saoiiiinii operation at these low RPM settings is nots11594 ILllr(IY H1 r*aa~*or n´•n I very practical because the very low power

operation may induce drag and inefficiency.Sea Level and Altitude Performance Curve IO´•540-K, -L, ´•M, -S The recommendations of the Pilot’s

Operating Handbook provide the bestThere are some other considerations of low power cruise opera- guidance for operation of an aircraftlengine

tion. Low manifold pressures, below an arbitrary point of perhaps combination and therefore the limitations of18 inches for continuous cruise, may cause excessive oil usage, the POH should be observed.and oil build-up in the valve guides which could lead to stickingvalves.

Particularly during cold weather operation, low power opera-tion may allow both the oil and cylinder head temperatures to fallbelow the normal range. This is detrimentalto good engine health. Oil temperature in POWER TABLE SETTING

particular must be maintained at a minimum LYCOMING ;MODEL IO-540-K, -L, -M SERIES, 300 HP ENGINEof 1650 F. At lower temperatures, the

moisture which gathers as a result of com- P"". ~d´• HP jj~ Riled 19j HP 6SL~ R~cd 225 HP ~j4 R´•lcdAir. fcmp RPY end MAN. PeI* RPM end MAN. Pm.. RPM end M4N Rc´•rbustion will not vaporize and be expelled. F,,I I ´•F 2100 2200 u00 2400 2100 poe 2300 2~00 2200 uno 2~00

This can cause dilution of the oil whichdetracts from the lubricating properties.

SL 39 22..3 21.8 21.2 20.; 25.6 21.7 23.8 23.2 27.6 26.6 25.81.000 33 22.3 21.6 21.0 20.5 2.5´•.3 2´•1.1 23..5 22.9 27.3 26.3 23.~

The Pilot’s Operating Handbook for 2.000 32 22.1 21.-1 20.7 20.2 25.1 21.2 23.3 22.7 27. 1 26. 1 .,.i.2each aircraft provides a variety of power set- 3.000 21.9 21.2 20.5 20.0 21.8 23.9 23.0 22..5 26.8 23.8 ?j.9

tings which most often show 2100 or 2200 aooo 33 21.; 21.0 20.3 19.8 21.6 23.7 22.8 22.2 26.3 23.6 9-1.6RPM as the minimum for cruise. The table ~I 21.3 20.8 20.1 lc).6 2´•2.3 23.3 22..5´• 22.0 25.3 21.´•1shown here is for the IO-540-K series engine 6.000 38 21.3 20.6 19.8 19.3 21.0 23.2 22.3 21.7 23.0 "1.1which was illustrated in the curve shown 7.000 3-1 21.0 20.1 19.6 19.1 23.7 22.9 22.0 21.3 23.8earlier. The power which may be obtained 8.000 31 20.8-20.2 19.1 18.9 22.i 21.8 21.2when using 1800 or 1900 RPM is generally 9.000 27 20.6 20.0 19.2 18.6 21.3 21.0not practical for continuous cruise because Io.ooo 23 20.1 19.8 19.0 18.4 21.2 20.7the aircraft must be flown at a high angle of Il.ooo 19 20.2 19.6 18.7 18.2 20.-1attack which may have a detrimental effect 12~000 16 20.0 19.1 18.5 18.0on cooling air flow and which also induces 13.000 12 19.2 l8.J 1;.7more drag and, therefore, inefficiency. 14.000 9 18.0 17.3

As an example, the power setting table 1.’.000 I 16.9

shows 2100 RPM and 24 inches of MP to To maintain constant power, correct manifold pressure approumately 0.18" HR for eachbe 65~ power at cSOIW) feet on a standard day. 10"F variation In induction air temperature from standard altitude temperature. AddPicking this same point on the altitude per- manifold pressure for air temperature above standard: subtract for temperature belowfbrmance curve, it is possible to see that standard.

Engine Operational Tip and himself.

We will emphasize here again, as we have in the past, thatLycoming does not recommend running a fuel tank dry as these normally aspirated (not supercharged or turbocharged)

routine procedure. Operators have related to us many of their direct drive engines with a manual mixture control should beexperiences where using this undesirable technique has resulted leaned at cruise powers of 7546 or less at any altitude whilein forced landings when the fuel selector broke and a tank with cruising. With this type ofpower plant, the 5,000 feet referencefuel could not be selected, and in another instance where the

was only for climb purposes. The recommendation during climbfuel selector was frozen in one position. was to maintain full rich in the climb from sea level through

However, a flight instructor recently recounted to us a "hair 5,000 ft. density altitude. If the climb was to continue higherraiser" during a flight in a borrowed single engine turbo- than 5,000 ft., mixture should be leaned for engine efficiencycharged aircraft over the Rockies. Fortnnately, he was aware and smoothness.

of his friend’s habit of running a tank dry. When the instructor Damage to a direct drive normally aspirated engine fromrefueled the aircraft before flight, he observed that both out- excessive leaning is done at higher than cruise power, or aboveboard tanks were completely empty. After filling them, he 7596 on the direct drive engines we have been discussine, andclimbed the aircraft eastbound to 22,000 feet in order to top above 6596 power on the geared and supercharged engines.a heavy overcast which had dangerous icing. Part way on this Therefore, the principal consideration in leaning is the percenttrip the instructor switched to one of the ouf60ard tanks--at ofpower at cruise, and secondly altitude. Even though the pilotwhich point the engine temporarily quit. After all the necessary of a direct drive nounally aspirated powerplant is only flyingmoves under this emergency, he was finally able to restart his 1,000 feet above sea level (for example), if he is at 75 Z powerengine; but in the meantime he had lost precious altitude down

or less he should lean the mixture.to 19,00~feet which put him in the overcast. The aircraft beganto ice up, and gain weight, and the wastegate had Leaning is not the easiest subject to write about when a

warped in a slightly open position due to sudden cooling, whichmanufacturer has as many varieties of engines and fuel meter-

created a reduced power condition. These two factors made it ing devices as Lycoming offers. Our Service Instruction 1093

impossible for him to climb out of the icing in the clouds.covers most aspects of leaning our engines across the board.

This discussion has been largely limited to the misunderstoodWith high mountains below him the pilot declared an 5,000 ft. reference with normally aspirated direct drive engines

emergency, and fortunately received a radar steer to an airport with a manual mixture control, and limited engine instrumen-above minimums. A later test showed he had a vapor lock in tation, in order to help prevent any similar accidents in this typethe lengthy fuel line from the outboard tank to the engine. Fuel of equipment. The more complex engines and aircraft are pro-injection, particularly, is vulnerable to vapor lock from empty vided with more complete engine instrumentation to protect thefuel tanks. So don’t runa fuel tank dry as routine procedure. powerplants.

A Special On Fuel ManagementFuel Starvation Accidents

While reading the report ofa recent accident that could have

been prevented, it occurred to us that despite all our efforts and Pilots are generally interested in reading about the causes

those of others to inform people who operate our engines, peo- and prevention of aircraft accidents because there is a basic sur-

pie are still confused or they misunderstand some basic aspects vival instinct characteristic in most people. As a result, pilotsof leaning. In this particular accident, it was caused either by are curious to learn what caused accidents so they can avoid

lack ofunderstanding, or confusion over the 5,000 ft. reference a similar experience. There is much to be learned from the

in leaning. We will attempt to clarify this area ofmisunderstan- unhappy experiences of other pilots in a special National

ding; but first let’s review the facts concerning the accident to Transportation Safety Board study ofU. S. general aviation ac-

observe how it happened and then learn how to prevent a cidents involving fuel starvation. The report is interesting and

similar accident, can be helpful to those who fly.

The private pilot involved had planned the same VFR 4:30 As an engine manufacturer we are sensitive to any state-

hour cross-country which he had made several times previous- ment or report concerning an accident which cites "enginely without refueling enroute. During his training, the pilot had failure" as the cause, when the facts reveal it to be engine stagbeen told erroneously not to lean his direct drive, normally page caused by fuel starvation, and not the "failure" of the

aspirated Lycoming engine below 5,000 feet. Until the day of engine as such. However, the principal purpose in reviewingthe accident, all flights to his same destination had been made this report and bringing it to other attention, is to prevent this

at 5,000 feet or higher, and as a result he had leaned the mix- kind of accident from continuing.ture and always made the trip without refueling. This report entitled "Fuel Starvation", analyzes fuel star-

On the day of the accident, about halfof the return trip was vation accidents involving 29 selected makes and models of

made at 7500 feet with the mixture leaned. However, the rest fixed-wing General Aviation airctft. Of the selected group. 12

of the flight was made at 2300 to 3000 feet with the mixture aircraft were found to be more susceptible to fuel starvation than

rich. He ran out of fuel and crashed a mile short of the airport, the others. Accidents involving these 12 aircraft were review-

killing two passengers and seriously injuring another passenger ed in detail to define the primary causes of fuel starvation and

other associated causal factors. Chronic difficulties and influen- noticeable change in engine temperatures. However. enginler-tial factors, found in the accident file review and technical ing people deal in facts and not limited observations, so Lvcom-research, were discussed ~with representatives of the Federal ing Engineering ran a test in their test cells with our O-32b (150Aviation Administration and three manufacturers of general HP) four cylinder engine certified for 80 octane fuel. Thev testedaviation aircraft. From these discussions, remedial measures the engine with 80 octane, then ran the engine again with 10Qto reduce the number of fuel starvation accidents were octane. and charted the results as shown in the illustration. Noteformulated, that O represents 80/87 octane fuel, and X represents 100/130

Recognizing that fuel starvation has remained a significant low lead fuel. The fuel flows and temperatures were charted

problem in general aviation safety, the NTSB examined 192 ac-at 55ro, 65%, and 75% powers.

cident reports for a two year period. For the purposes of this There were no cylinder head temperature differences be-study, fuel starvation is defined as the interruption, reduction, tween the two fuels.or complete termination of fuel flow to the engine, althoughample fuel for normal operation remains aboard the aircraft.

FUEL STORAGE

While manufacturers expressed the general opinion that fUelAnother question we have been asked concerned storage

system design improvements and operational procedure im-ofaviation gasoline. We contacted a senior engineer of the Shel I

provements could diminish fuel starvation problems, they stress- Company who gave us some answers. Shell’s experience in-

ed the importance ofpilot awareness with regard t~iproper fueldicated that 100 octane aviation fuel kept in sealed drums is

system maintenance and operation. The industry, through the good for five (5) years. The same 100 octane stored undergronndGeneral Aviation Manufacturers Association, completed two

with occasional use, and good housekeeping, is good for use

fine projects which could lead to the elimination ofseveral fac- up to two (2) years. Beyond the time shown here, a gum

tors which contribute to fuel starvation. One was a study of thesubstance develops that sticks to the carbuertor or fuel injector

feasibility of fuel system design standardizati~n in general avia-and disturbs proper fuel/air distribution--which means rough

tion airplanes; the second is a standardization of the format and running and some loss of power. Old fuel also causes hard

content of the Pilot’s Operating Handbook. starting.

NO MIXING OF FUELS

Our experience as an engine manufacturer has proven timeafter time that mixing aviation octane fuels in the airplane tank

0-320 (150 HP)creates trouble. The one best place for blending fuels is at the

CIL HEAD TEMPS refinery. The fuel people confirm our experience that differentvs octane fuels when mixed do not necessarily give some in-

FUEL FLOW termediate numbered, fuel, i. e. 100 octane mixed with 80 oc-

tome does not provide a 91 octane fuel. The pilot cannot be sure

cut HD TEUPS of knowing what octane he has when mixing fuels.

Q L320RPN

SSX Induction Icing8

nmnsu

We used to talk about carburetor icing in past years, butwith all the modern fuel metering devices used today, a more

Fun FLOW LB /nR up-to-date terminology describes this flight condition as induc-

LEGENOtion system icing. The latter term includes all types of fuel meter-

Q-0 W/I~ EXXON G*SOLINE-OSJse PB/GaL ing (fuel injection as well as carburetion), and also the pansI-x 100/1~0 EXXON GISWCE.Z Os,, PB/GIL of the induction system where ice can accumulate such as the

air filter, or bends in the system, as well as the critical areas

of the fuel metering device like the throttle plate in the floatMore About Fuels

type carburetor.

In a previous "Flyer", we answered a question concern-If operators understand what happens when the fuel meter-

ing fnels which a number of operators had asked. They ing device (carburetor or fuel injector) inject fuel into the air

wondered if the new low lead Grade 100LL was used in ourbeing sucked into the induction system by the engine as it

engines certified for 80 octane aviation fuel, would the engine operates, they can take suitable precautions to preferably avoid

run hotter? We pointed out that this was a good question becauseor eliminate induction system ice. But they also need to under-

many small airplanes requiring 80 octane fuel do not havestand how the engine reacts when heat is applied to prevent in-

cylinder head temperature gages, and oil temperature changeduction icing.

tends to be slow and also difficult to read unless there is a marked There are two types of induction system ice:rise in temperature. 1. Impact ice--forms on the air filter and bends in system.

When we flew a few airplanes requiring 80 octane fuel. 2. Refrigeration ice forms in float type carburetor as resultbut used Grade 100LL (blue) we could not observe any of fuel vaporization and low pressure.

goes through the engine as water, causing some of the roughnessand more power loss. Therefore, unless the pilot knows what

i" is actually happening, the stress and confusion of the situation

will tend to frighten him out of using heat, and thereby could

result in losing his engine to icing. But most ofall he must realize

that despite temporary roughness and attendent moderate power

loss, the pilot is not damaging his engine at a cruise power of

7545 or less with any amount of heat.

RELATED FACTORS WHEN USING

CARBURETOR HEAT

When using heat, there are related factors or influences to

remember. The engine loses about 151 of its power when full

heat is applied. Carburetor heat also creates a richer mixture

which may cause the engine to run rough, particularly at fullI c~e_ heat. If there is any throttle available, the power may be in-

creased 2 inches of MP over that previously shown with a

governed engine, and an increase of 100 RPM with a fixed pitch

prop. The mixture should be adjusted lean (at cruise power or

CARBURETOR ICE less) whenever heat is applied. Furthermore, any applicationor removal of heat would call for an appropriate adjustment of

the mixture during cruise. At lower power conditions such as

ICING INDICATIONS required during flight in the traffic pattern, it may be imprac-

Typical icing indications to the pilot, where he failed to tical to lean the mixture. Do not use heat for takeoff or climb

anticipate the need for heat, vary from a gradual loss of power, on Lycoming engines as it is not necessary, and it may bring

to vibration and roughness. it simply depends on how the ice on detonation and possible engine damage. An exception to the

forms in the induction system. With the float-type carburetor, latter might be in the severe temperatures of the Arctic which

since ice forms on the throttle plate, the pilot might note somecalls for a special knowledge, or a special severe weather

stickiness when he attempts to move the throttle. Where there condition.

is a fixed pitch prop and the float-type carburetor, the pilot will Ifyou are wondering how long to continue the use of heat,

note a gradual loss of RPM and airspeed as ice forms. The same it would depend on the icing conditions. If icing happened to

model engine, but with a constant speed prop, will indicate car- be severe, then heat should be used as flight continues in known

burctor ice by means of a loss of manifold pressure and the ac- or suspected icing conditions. We have found in our flight tests

companying loss of airspeed. on various models of Lycoming engines, and with special

THE FLOAT-TYPE CARBURETOR AND ICINGdetonation pickups, that at cruise power with full heat or alter-

nate air, we have never experienced detonation or damage to

Under certain moist land "moist" is a key word here) at- the engine. If that is difficult to believe, a turbocharger heats

mospheric conditions, when the relative humidity is more than the induction air hotter at high altitude than the typical carburetor

50%, with air temperatures ranging anywhere from 200 to 900 heat or alternate air, without causing any detonation or damageF, it is possible for ice to form in the carburetor. The rapid to the engine. The principal concern of the pilot under icingcoaling in the float-type carburetor is caused by the absorp- conditions is not the possibility of detonation from the heat at

tion of heat from the air during vaporization of the fuel, and cruise power, but rather to keep the engine running no matter

also due in part to the high air velocity causing a low pressure how much heat is required. in known or suspected icing condi-

area through the carburetor ventunl. As a result of the latter tions, follow the instructions in the airplane Pilot’s Operatingtwo influences, the temperature in the mixing chamber of the Handbook. If the airplane does have an induction air or car-

carburetor may drop as much as 600 F below the temperature buretor air temperature gage, the thinking pilot who anticipatesof the incoming air. If this air contains a large amount of the possibility of induction ice can prevent it by maintainingmoisture, the cooling process can cause precipitation in the form heat during cruise and letdown. Any aircraft without an induc-of ice, generally in the vicinity of the "buaerfly" or throttle tion air gage must use either the full heat or full cold position.plate, and may build up to such an extent that a drop in power as an unknown amount ofpartial heat can actually cause induc-

output could result. If not corrected, ice accumulation may cause tion ice in the float-type carburetor, particularly where there

complete engine stoppage, is moisture in cIystal form in the incoming air that would or-

Now the thinking pilot will anticipate possible icing and dinarily pass through the induction system without any problem.utilize heat before the ice forms. However, should he fail to Partial heat melts these crystals and they form carburetor ice

anticipate icing with the float type carburetor and ice begins in the venturii when they come in contact with the cold metal

to form. he must definitely use the full heat position initially of the throttle plate. At a temperature of 200 F or below, any

in order to be sure of eliminating the ice. Using full heat will moisture in the air is frozen and heat should not be used. Par-

cause a loss of power and possible engine roughness. Heated tial heat may be possible with an induction temperature gage.

air directed into the induction system will melt the ice which which means less power loss.

STANDARDIZATION OF USE OF HEAT type of system.It is necessary to care_fully differentiate between the methods All Lycoming pressure carburetors have automatic mixture

of applying heat to the various flat opposed piston engines in controls. On the ground, any application of heat will affect theinduction icing conditions. Most light airplanes with float-type AMC unit so as to make it temporarily unpredictable in its ef-

carburetors do not have a carburetor air temperature gage, and feet on the carburetor. If for some reason the pilot used heat

therefore must use the heat position only in the full on, or full on the ground (i. e. checking the heat system), he must walt

off positions. and with the mixture leaned to compensate forat least two minutes before takeoff in order to avoid an erratic

the richer fuel/air ratio mixture with carburetor heat,fuel flow because of the effect of the heat on the AMC unit.

Don’t forget to check operation ofmanual alternate air control,\Because flight instructors and other experienced pilots fly before entering icing flight conditions. If alternate air is used,

various models of manufacturers’ airplanes and engines, it would remember that heat means some loss ofpower and a richer mi.u-be helpful to standardize the instruction of the use of heat in ture. Do something to get the power back increase powerthe landing configuration on aircraft using the float-type car- 2 inches manifold pressure over former setting,and lean mi.u-buretor. Textron Lycoming has no objection to the consistent ture with a manual mixture control.standardized use ofcarburetor heat in the landing configuration.

CONCLUSION

THE GO-AROUND Now that the operator understands how ice forms in the

Whenever carburetor heat is used in the landing configura- fuel metering device, and how the engine reacts when heat is

tion, and a go-around takes place (either unexpected or touch- applied, he can cope with an icing problem without panicand-go), there are some important phases of operation for the because he knows what is happening in his powerplant.

pilot to remember. We don’t insist on throttle first, nor heat

off first. However, if throttle is first, it must be a smooth ap-plication. A straight-arm of the throttle generally results in the

carburetor failing to respond, and no power. Cold Weather TipsIf the pilot forgets to remove carburetor heat on a go-

around, loss of power may become critical at low altitude and First, let’s make it clear that we are speaking of normal

low airspeed, In addition, on the higher performance cold weather operation experienced at temperatures to -250 F.

powerplant, there is the danger of detonation and/or engineFor tips on operating below -250 F., we’ll let the people who

damage using full heat and takeoff power on the go-around. operate in those temperatures give us the word.

A good place to start would be to realize that we are allOTHER TYPES OF INDUCTION ICING. stuck with three cold weather starting penalities. They are:

Thus far our discussion has limited itself to the float type 1. The lower the temperature, the more cranking energycarburetor which can incur ice in VFR flight conditions if there required.is the right combination of moisture, temperature and fuel mix- 2. The lower the temperature, the more reluctant the fuel/airture. In the case of fuel injection and pressure carburetors, it mixture is to ignite.is the IFR type flight condition which generally causes induc-

tion system icing. The fuel injected engine does not have the3. The lower the temperature, the lower the battery output.

threat of icing at the venturii; but other parts of the induction Now that we are aware of these penalties, let’s not imposesystem can gather ice such as bends in the system, the impact other unnecessary penalties upon the engine through neglect or

tubes, or on the air filter. lack ofknowledge. Therefore, before cold weather sets in, have

The pilot of a turbocharged powerplant should not be toothe spark plugs and magneto points inspected for serviceability

concerned with induction system icing except in extreme con-and proper gapping. Check for proper operation of carburetor

ditions because of the high temperature of the induction air whenheat controls, priming, exhaust, induction and ignition system.A defect in any one, or combination of several of the aforemen-

the compressor is running. However, slush/snow can be a tioned items, can be the difference between no start or good strut.blockage threat to the air filter if there is not easy availabilityto alternate air, impact ice at high altitude with some turbo-

This next cold weather tip is worthy of a separate little

charged engines may cause a loss of4 to 6 inches ofMP whensentence all of its own have the heating system checked for

going to the alternate air source,leaks. Remember, you can’t smell carbon monoxide.

The pressure carburetor is similar to the fuel injector inLet’s examine some tips, starting’with preflight inspection

that it is not very vulnerable to icing, other than that outlinedright through actual flight to landing.

in the previous paragraph. When a float-type carburetor is Guard against condensation in the fuel system. Simplestplaced next to a pressure carburetor for a visual inspection and precaution--keep fuel tanks full.

comparison, note that the float carburetor fuel jet is below the Drain the fuel sump religiously before the flight. Don’t at-

venturi and thronle butterfly, which means fuel is being squirted tempt to save fuel here. Moisture may collect at a low pointinto the worst possible place for icing the carburetor ven- in the system and a skimpy sump drain may only move theturi. On the other hand, the pressure carburetorjets are squirt- moisture to another point in the system.

ing fuel farther downstream beyond the venturi refrigeration At ground temperatures of 100 F and below, the enginechamber. which accounts for the less likelihood of icing in this and complete oil system should be preheated.

Once an board the aircraft, check the fuel selector valve Again, mostly for the novice, don’t run one set of fuel tanks

for freedom of movement. It may be frozen fast and you’d bet- nearly dry before switching tanks. Switch with plenty of fuel

ter find it out while still on the ground. remaining in the tanks first used. This is ’’money in the bank’’.

Assuming the engine has kicked off on the first attempt, should you find the selector valve frozen.

check for indication of oil pressure. Again, learn the Avoid power-off let downs. When possible, plan yourcharacteristics relative to response of oil pressure indications descents far enough away from your destination that a powerofyour aircraft-engine combination. On most single engine air- let down can be made. If a fairly rapid descent must be made.craft an almost immediate response is noted. On twin engine we suggest the aircraft be slowed and the gear and flap be

aircraft the response may be much slower. On some twins the lowered so that some power may be retained.

oil pressure may go up and during warm up may drop again Should a reduced power let down be necessary throughfor a short period of time then again rise to normal. All cases possible icing conditions, don’t hesitate to peak the exhaustmentioned may be normal, but the important thing is to know

temperature gauge ifone is installed. This will assure the greatestwhat to expect from your aircraft-engine combination.

possible engine heat for the power setting selected.After start, do not idle engine below 1000 RPM. It’s not

good practice to idle engines below 1000 RPM at any time. This

is particularly true during-cold weather to prevent lead foulingof spark plugs. (Exception Piper Pressurized Navajo). CoId Weather Operations

No take-offs should be made with carburetor heat on. The

only exception being, should outside temperature be so low that A note that came in the mail from a Fiver reader included

an increase in RPM is noted with the application of carburetor a suggestion which went something like tbis, "How about an

heat, region). article dealing more extensively with the cold start problem..."Now here’s a tip for the novice pilots. When setting up for A review of past Flyer issues indicates that this suggestion is

cruise configuration, be precise, read your instruments and a good one. It has been a long time since any cold weather con-

-~emembcr what you read. Example: Ifyou decide on 22 inches siderations have been addressed in the Fiver. and as the mail-

of manifold pressure, set it right on 22. If the RPM is to be ing list continues to grow, there are many’new readers to share

2350, make it 2350. Select an altitude;Trim the aircraft to hold our thoughts on this subject.that selected altitude. Note airspeed. Now if anything Most of the time, we think of starting any engine as a very

changes, barring turbulent air, it has to be a change in power. simple process. Just engage the starter and listen for the enginePerhaps it is carburetor or induction air icing. Suppose you pick- to start purring. Unfortunately, when the weather turns cold

ed up a bit of carburetor ice and the engine suffers a slight power it is not always that simple. When dealing with a reciprocatingloss. There will be a slight drop in manifold pressure, a loss aircraft engine, it may be essential to get a start on the first tryin airspeed. and the aircraft will want to lose altitude and if you in order to avoid icing over the spark plugs and making an im-

hold altitude you’ll find back pressure on the wheel is required. mediate start impossible. In order to achieve a start on the first

Therefore, even though you didn’t discover the power loss try, there are a number of factors to be considered. Those fac-

through instrument scanning, you’ll get a warning through the tars will be discussed in the following paragraphs."heavy" wheel or stick. Let’s start with the general health of the engine. When at-

During cruise, check your oil temperature. Should it be tempting a start under adverse conditions, it is imperative that

lower than normal (below 1650 Fl we recommend steps be taken the engine be well maintained and in excellent operating con-

to increase the temperature to normal. Install the oil cooler kit dition. Spark plugs and magneto points should be properly gap-supplied by the manufacturer. ped and ready to function effectively. In addition to the igni-

Remember, engines must breathe and in so doing, they take tion system, the proper functioning of other systems such as

in moisture. Normally the oil temperatures are high enough to the induction, priming, exhaust, and carburetor heat can have

evaporate this moisture. If oil temperatures are too low, the an effect on the starting and operation of the engine.moisture will collect in the crankcase and rocker box covers Although it might be good procedure to use an external

causing rust. We have drained many a wet sump engine that power source for starting during very cold weather, most ofcontained as much as a quart of water. Keep the operating us expect our battery to do the job. We should remember that

temperatures up, the battery is handicapped by cold weather. Particularly when

If flight is planned for bad weather, the preflight inspec- a single viscosity oil is being used, the colder the temperature.tion should include observation of the relief opening in the the more cranking energy required. Combine this with reduc-

engine breather tube so that any freezing of moisture at the end ed battery output at lower temperatures and it can be a serious

of the breather will not result in a loss of engine oil. (See ’’The handicap.Whistle Slot" in this book.) While on the subject of batteries, remember that freezinl

During flight in very low temperatures, exercise constant temperatures provide a perfect opportunity to destroy an alr-

speed props about every 30 minutes to help prevent congealing craft battery. The battery with a full charge survives nicely.

of oil in the prop dome, but one which is discharged will freeze. Once this happens, the

Should one engine of a twin, for any reason indicate the problem can only be remedied by replacing the battery, so It

prop must be feathered, don’t tarry too long with reduced poweris very worthwhile to take preventive measures. Shouldthe b3t-

in very cold weather. At reduced power, the oil may congeal tery be run down during an attempt to start, do not leave It;

making t’eathering an impossibility, get it charged immediately. And finally, be absolutely certain

that the master switch is always OFF while the aircraft is park- flies. When the correct number of primer strokes for eached between flights. If left on, the battery will discharge and temperature range has been established, the engine will usual-freeze. These rather miribr mistakes can be quite expensive. ly start very quickly. We may find that an engine starts easily

Oil is another factor to be considered in the cold weather when one stroke of the primer is used in the sixty degree range,

starting process. All oils are affected by temperature and tend two strokes in the fifty degree range, three strokes in the fortyto thicken as the temperature drops. The engine may be reluc- degree range, etc. This is an example of the trial and error we

tant to turn over when the oil is stiff; a summer weight oil is might use to establish the number ofprimer strokes to use under

not suitable in cold weather. It is also the condition which brings any particular temperature condition.

out the primary advantage of multi-viscosity oils. Because these While discussing the priming ofan engine, there have beenoils are thinner (lower viscosity), they allow the engine to be situations where primer lines become clogged. This makesturned over more easily. Because they flow more easily and engine starting difficult and negates any trial and error ex-

quickly, they also are available to lubricate the internal parts perimentation which may have been done. When maintenanceof the engine more quickly when it does start. Since the proper is done on an aircraft before the start of winter, it may be wiseoil viscosity is so imponant in all aspects of engine starting and to have those primer lines checked to insure that fuel will flow

operation, the recommendations of oil grade vs. temperature through them.

-range shown in Textron Lycoming Service Instruction No. 1014 The amount of fuel needed to achieve the correct fuellairshould be followed, mixture for starting a fuel injected engine is controlled by tim-

Preheat is another factor which must be considered prior ing rather than number ofprimer strokes. With the electric fuelto starting the engine. There are specific guidelines in Textron pump on, moving the mixture control to the rich position allows

Lycomingservice instructions which establish when preheat fuel to flow to the cylinders. For cold weather starting, it mayshould be used, but how much, or the method of preheat is be necessary to keep the mixture control in rich somewhat longergenerally left to the good judgement of the pilot or maintenance than in warm weather.

person doing the preheating. Use of the heated dip stick is not The fuel part of the fuel/air mixture may be the pan weiecommcnded by Textron Lycoming, although most other have the most control over during the engine start, but keepmethods are considered to be satisfactory. For most Lycoming in mind that the amount of throttle opening does have an effectmodels, preheat should be applied anytime temperatures are on the air which is pumped through the engine. Just as we com-below 10 degrees F. The exception to this rule is all 76 series pensate for cold/dense air by adding more fuel for stan, it maymodels; these engines should be preheated when temperatures also be appropriate to reduce the air part of the mixture whenare below 20 degrees F, It is recommended that these guidelines the temperature is very cold. For example, if the throttle is nor-be followed even when multi-viscosity oil is being used. In ad- mally set open one half inch for warm weather startine, it maydition to hard starting, failure to preheat the entire engine and be helpful to reduce this to one quarter inch in cold weather.oil supply system as recommended may result in minor amounts Again, it will require some experimentation to determine whatof abnormal wear to internal engine parts, and eventually to is needed to achieve the correct fuel/air mixture for any par-reduced engine performance and shortened TBO time. ticular aircraft at any temperature range.

Probably the most important factor in starting an engine When an engine does not start easily, it can be frustrating.is achieving a fuel/air mixture which is satisfactory for com- Of course this can occur at any time of the year and it is verybustion, Since the engine usually starts very easily, many pilots tempting to just keep grinding away with the starter in an at-

are unaware ofor ignore the change ofstarting procedure needed tempt to get it going. Should this happen to you, RELAX. Taketo successfully stan under varying temperature conditions. In care of that starter or it may fail. The general rule for starters

warm weather the air is less dense and therefore must be mix- is that they should not be operated for more than 10 to 12ed with a lesser amount of fuel than in cold weather. In addi- seconds; then a five minute cooling off period is required.tion to this, in warm weather the fuel will vaporize easily and Without this time limit for oper~ition and an adequate coolingmake staning easier. Simply stated, as temperatures go down offperiod, the starter will overheat and is likely to be damagedit becomes more and more important that we have a plan for or to fail completely.priming which will achieve the correct fueyair mixture. The previous paragraphs have addressed several issues

When priming a carbureted engine, the pilot’s plan must which relate primarily to cold weather starting.There are some

consider the temperature, the number of cylinders which have other cold weather items which should be considered in the

priming lines installed, and the number of strokes of the primer operation of the engine.which are needed to produce the correct fuellair mixture. The Water is one of the most likely contaminants of aviationprimer lines are ordered or installed by the airframe manufac- gasoline. The engine will not run on water, and although we

turer and not all aircraft are configured the same. Some air- may get away with small amounts of moisture in the fuel dur-craft have actually been produced with only one cylinder being ing warm weather, flight into freezing temperatures makes anyprimed and these engines are extremely hard to start in cold amount of moisture in the fuel system very critical. Even a tinyweather. The number of cylinders which are primed must be bubble of moisture may freeze in the fuel line and totally cut

considered since the total fuel delivered by the primer will be off the flow of fuel. Two steps should be taken to avoid thisdivided and sent to these cylinders. As the air becomes colder problem. First, avoid water contamination if possible. Keep fueland denser, the amount of prime used must be increased, but tanks full to prevent condensation and be sure fuel caps do not

the number of strokes to be used should be planned as a result allow leakage if the aircraft is parked outside in rain or snow.

of some trial and error experimentation for each aircraft a pilot Second, look for contamination before every nie;ht by drainingfuel tanks and sumps religiously.

Although carburetor ice is not necessarily a winter time tions are taken. Although many of the Pilot’s Operating Hand-

phenomena, a check of carburetor heat should be made during books cover the basic procedures for simulating emergencv

the engine run-up. Generally speaking, we can say that car- engine-out operation, there are gaps in the information on how

buretor heat should never be used for takeoff, but there is one to protect the engine during simulated procedures. Following

exception. This exception occurs when operating in temperatures are some questions which should fill in these gaps in informa-

so cold that application of carburetor heat produces a rise in tion for protecting the engine during this type of operation:RPM. Most pilots will never find themselves in circumstances i. Avoid practice feathering or simulated feathered enginewhich require use of carburetor heat for takeoff and climb; those during flight in very cold temperatures.who fly carbureted engines will almost certainly have occasion

2. To abruptly simulate engine out (feather or for zero thrust,to use carburetor heat during cruise or let down. Use of the full

first move mixture to idle cutoff to protect engine.hot or full cold position is recommended. An intermediate set-

ting should only be selected if the aircraft is equipped with a3. Low altitude slowly retard the throttle, (see following

carburetor air temperature (CAT) gage.article on NTSB warning).

Engine operating temperature is another item which is not A. DURING PRACTICE FEATHER

usually given enough consideration in cold weather. We usual- 1. Limit shutdown time to a minimum.

ly are very cautious about high oil temperature which we know a. Close cowl flap on feathered engine.is detrimental to good engine health, while a low oil temperature 2. Aircraft frequently used for training or sales demonstra-

is easier to accept. The desired oil temperature range for Lycom- tions should have unfeathering accumulators for easier

ing engines is from 160 degrees to 245 degrees F. If the air- in-flight starting.craft has a winterization kit, it should be installed when operating 3. During unfeathering, avoid strong surge in RPM. After

in outside air temperatures (OAT) which are below the 40 to starting, set RPM at cruise speed for warmup at low

45 degree range. If no winterization kit is supplied and the manifold pressure (about 15").engine is not equipped with a thermostatic by-pass valve, it may 4. Observe oil pressure at restart. Increase M. P. as enginebe necessary to improvise a means of blocking off a portion begins to warm up to aid process and do not use cruise

of the air flow to the oil cooler. Keeping the oil temperature power until CHT reaches 1500 F, or 650 C.about the minimum recommended temperature is a factor in

5. During flight on one engine, monitor good engineengine longevity. Low operating temperatures do not vaporize

temperatures.the moisture which collects in the oil as a result ofcombustion.

When minimum recommended oil temperatures are not main- B. ZERO THRUST SIMULATED ENGINE

tained, oil should be changed more frequently than the normal- OUT PROCEDURE

ly recommended 50 hour change cycle. This is necessary in i. After closing mixture or throttle, have pilot indicate dead

order to eliminate the moisture which collects and contaminates engine by moving that throttle to approximately 12 inches

the oil. M. P. zero thrust position.

And finally, power-off let downs should be avoided. This 2. Return mixture to rich position if used.

is especially applicable to cold weather operations when rapid 3. Set RPM on simulated dead engine at cruise speed.cylinder head cooling will be more pronounced. Plan ahead, 4. Close cowl flaps on zero thrust engine.reduce power gradually and maintain some power throughout 5. Monitor good engine temperatures.the descent. Also keep the fuel/air mixture leaned out duringthe descent. If an exhaust gas temperature gage is installed with

6. When simulated engine inoperative practice is completed,

a normally aspirated engine, keep it peaked to insure the greatestgradually return retarded throttle toward normal required

possible engine heat for the power setting selected; for a tur- power settings, and as CHT approaches green are, normal

power may be used.bocharged installation, lean to peak during descent unless other-

wise specified in the Pilot’s Operating Handbook or under con- EXPLANATION OF PROCEDURES

ditions where the limiting Turbine Inlet Temperature would beQUESTION Why use the mixture control first when

exceeded.practice feathering or simulating an engine-out condition?

Exposure to snow, frost and cold weather while flying re- ANSWER If the power is suddenly cut off the engine.quires the consideration of many factors, both airframe and such as simulated engine failure or for practice feathering dur-

engine related. This discussion deals strictly with issues relating ing flight, the mixture control should be cut first, leaving theto the engine. While there may be other issues, those items

throttle in normal open position until the engine has slowed downwhich are asked about most frequently have been discussed, because of lack of fuel. With the throttle open, it permits theSafer flying and longer engine life could result from careful con- cylinders to fill up with air with resulting normal compressionsideration of the material addressed. forces, which are sufficient to cushion the deceleration of the

engine.

QUESTION Why should the operator avoid rapid clo~-

Protecting The Engine During Simulated ing or opening of the throttle?

Emergency Procedure Operation ANSWER Rapid movement of the throttle will result

in detuning of the counterweights on the crankshaft. This is par-

In multi-engine aircraft, training procedures and sales ticularlv true of higher RPM and MP settings when the throttle

demonstrations can damage the engines unless certain precau-is moved rapidly. This sudden reversal of forces results in un

unnatural movement of the counterweights which detunes or the mixture to abruptly terminate power. By putting the mlx-weakens the metal considerably, setting up a potential failure ture control in idle cutoff position with the throale in a normalat any time thereafter.

open or operating position, the pilot merely cut off the fuel.QUESTION How about reviewing power sequence for but allowed the air to continue to fill the cylinders with resulting

the supercharged and turbocharged engines? normal compression forces, which are sufticient to cushion the

ANSWER During the excitement of emergency pro-deceleration of the engine and prevent the detuning of the

cedure flight operation, remember that to increase power:crankshaft counterweights and engine failure.

First increase props (enrich mixture if leaned) However, any practice on simulated engine-out condition

Second increase throttles at low altitudes should be best accomplished by a slow retarda-

To decrease power:tion of the throttle in accordance with the NTSB recommenda-

First decrease throttlestion. This careful technique will protect the engine, and at the

Second decrease propssame time provide for instant power if it is needed.

Importance Of TheNational Transportation Safety Board

Cylinder Head TemperatureWarning On Simulated Engine-Out

Maneuvers Although the smaller four cylinder engines of the low com-

pression, low horsepower variety do not generally use a cylinderhead temperature gage, the higher powered, more complex

In mid-1976, the NTSB issued an urgent warning to all powerplants require a cylinder head temperature gage in orderpilots simulating an engine-out condition on multi-engine to prevent unwitting abuse by the pilot. If head temperaturesairplanes, to eliminate actual engine shutdown and substitute are higher than normal during flight, it should not be ignoredinstead reduction of power at low altitudes such as in the traf- because there is some reason for it. It may be caused by hotfic pattern. The recommendation resulted from the NTSB in- ambient temperatures, a lean fuel metering device at higher thanvestigation of the fatal crash of a light twin in which a flight cruise power, bad baffles or leaking cowling, malfunctioninginstructor and an applicant for a multi-engine rating were kill- of the ignition system, or a mechanical problem may be develop-ed. The Board’s investigation revealed that some flight insuuc- ing in the engine.tors do use the fuel selector or the mixture control to shut down

an engine to test a multi-engine applicant. The NTSB observedAs a temporary measure in order to keep the remaining

that use of such procedures at traffic pattern altitudes may notflight safe, the pilot should attempt to reduce the head

permit instructors enough time to overcome possible errors ontemperatures by:

the pan of the applicant, i. Enriching the mixture

The recommendation by the NTSB means that all simulated2. Adjusting cowl flaps

engine-out operation at the lower altitudes will have to be ac- 3. Reducingpowercomplishcd by retarding the throttle and unless this is ex- 4. Any combination of the aboveccuted slowly and carefully engine failure can result.

We suggest that in order to help the mechanic diagnose theMany flight instructors down through the years used the problem, the pilot or some member of the crew should make

technique of abruptly cutting an engine with a multiengine can- a written record of the engine instrument readings during thedidate to test his emotional reaction and judgement with this above flight condition and present it to the maintenance people,extreme technique. Big radial piston engines with short, stub-

by crankshafts could tolerate the abrupt technique. However,flat apposed piston engines with their long crankshafts and at-

tached counterweights could not as readily take the abuse of More On Cylinder Head Temperaturesuddenly snapping a throttle shut, particularly at takeoff, or

climb power. Use of the laser technique would tend to detuneThe cylinder head temperature gage (CHT) helps the pilot

crankshaft counterweights and result in a nasty engine failure, protect his engine against the threat of excessive heat. MostGeneral Aviation aircraft take the CHT off the honest single

Since it was common technique by flight instructors to ter- cylinder of the four, six or eight cylinder powerplants deter-minate power abruptly in simulated engine-out procedure, we mined by extensive flight tests. Optional installations offerhad to protect the engine. As a result, we published in our readings from all cylinders. In Lycoming engines, all cylindersEngine Operator’s Manual, in Service Bulletin No. 245, and are drilled to accommodate a CHT bayonet type thermocouple.in the Flyer, the recommendation that if the power was abrupt-ly terminated, it must be accomplished with the mixture con-

Some operators in the field have been using a spark plug

trol. The student was to identify the dead engine by retardinggasket type installation in order to get cylinder head temperature

that throttle to about 12 inches MP to simulate zero thrust, orreadings. Textron Lycoming Engineering does not currently ap-

similar to having the prop feathered. At that point the instruc-prove this method ofdetermining CHT. Not only is the method

tar could return the mixture to an engine operating condition.less accurate than the recommended thermocouple type, but the

temperature readings differ noticeably from the approvedIn our publications we then explained the reason for using installations.

Minimum in-flight CHT should be 1500 F (650 C) and general aviation engine instruments are not precision laborator~

maximum in most direct drive normally aspirated Lycoming types, so crosscheck, and/or give yourself an extra margm for

engines is 5000 F (2600 C); but with some of our higher powered safety.more complex engines having a limit of 4750 F (2450 C).Although these are minimum and maximum limits, the pilotshould operate his or her engine at more reasonable tempe~-atures Engine Starting Suggestionsin order to achieve the expected overhaul life of the powerplant.In our sixty years ofbuilding engines, the engines have benefited

during continuous operation by keeping CHT below 4350 FExtra precautions should be taken when starting high per-

(2240 C) in order to achieve best life and wear of the powerplant.formance engines in cold weather, after changing oil, or after

In general, it would be normal during all year operations, inthe engine has not flown within a week. On the initial start.

climb and cruise to see head temperatures in the range of 3500 closely observe engine oil pressure. Ifoil pressure does not rise

F to 4350 F.to minimum idling range within 30 seconds after start, shut the

engine down and investigate.If an engine has bayonet probes in all cylinders, it is not

unusual to see variations in CHT readings on fuel injectedi. Damage to crankshaft bearings is possible if oil pressure

engines of 1000 F betweerlcylinders, and as much as 1500 Fis not within minimums as described above, and potential

on engines with float-type carburetors. With the-latter, an im- engine failure can result.

portant cause of the variation is the kind of distribution of fuel 2. Cold, fast starts also result in badly scuffed piston skirts

and air to the individual cylinders. Other influences on CHT and rings and scored cylinder walls with ultimately broken

are such items as cylinder baffles, cowling, cowling flaps, loca- piston rings and malfunctioning engines.tion of engine accessories, and, of course, manual control of 3. Complete engine preheating is recommended at ambientfuel mixture, temperatures of plus 100 F and below, because below this

Operators frequently ask about the difference between the temperature oil is like tar. Preheating for the 0-320-11

CHT and EGT (exhaust gas temperature) systems, and their and other "76 series" engines is recommended at 200 F

meaning to the pilot during operation of the engine or engines. and below.

The EGT probe is installed in a differentlocation from the CHT, 4. After start, do not exceed recommended RPM in the idleor about four inches from the cylinder head down the exhaust

range initially until oil pressure is definitely withinstack. Although the EGT has some troubleshooting ability, it minimums.is primarily a fuel management instrument. On the other hand,the CHT is an engine instrument designed to protect the

powerplant against its enemy, excessive heat.

More Suggestions On Engine Starts

An important part of the engine starting procedure is the

Interpreting Your Engine Instruments priming technique involved. Of course, the pilot’s operatinghandbook will specify the steps in starting a specific model

The present day piston engine instruments used in the engine. However, some of the pilot handbooks may not explain

typical general aviation airplane are not precision laboratory why certain procedures are used in the starting process.

instruments. We exclude the turbine and jet powered aircraft Priming can be best accomplished with an engine primingfrom this discussion and will consider only piston engines, system, as opposed to use of the throttle. The primer pumpsrecognizing that the more expensive pressurized twin engine extra fuel directly into the cylinder intake port or inductionmodels may also be exceptions. system. Some float-type and pressure carburetors also provide

Nevertheless, the purpose of this briefpresentation is a prac- a supplemental source of priming. Lycoming engines of more

tical approach to interpreting the readings of your engine in- than 118 HP have a throttle pump which can be used for prim-struments in accomplishing a safe and efficient flight. If, for ing under moderate ambient temperature conditions while turn-

example, you were to observe an irregular reading of one engine ing the engine with the starter.

instrument, it calls for a cross-check on all other instruments, Pilots should, however, be advised that excessive throttleand not relying on one instrument as a basis for a decision af- priming can cause flooding of the carburetor and airbox, and

fccting flight, result in a fire in the induction system or on the outside where

Since the engine is dependent on fuel, we consider the the fuel drains overboard. If the operator floods the engine bygasoline gage as a related engine instmment. If pilots are go- pumping the throttle and has a fire, it is possible to handle such

ing to attempt to stretch their flight range close to limits, they a frre in the early stages by continuing to turn the engine with

should be aware of the errors in the gages vs, the actual useable the starter, thereby sucking the fire back into the engine. Fur-

fuel. Some modern single engine aircraft have had the gas gage thermore, if there is any fire on the outside of the engine, If

show several gallons remaining, when in reality the tank was the engine starts there is a good chance it will blow out the es-

empty. Others have indicated a specific number of gallons when ternal fire.

filled, but actually the tank held several gallons less than Flooding of the engine without a fire, the operator shouldindicated,

open the throttle full and close the mixture; (see Opemtor’~Therefore, in planning for each flight, remember that Handbook on mixture) and turn the engine over several times

with the starter to clear it: then begin again with a normal start it would be safer to know that on the ground rather than in theroutine, air when the fuel boost pump is turned "off’.

Most Lycoming fuel injected engines are simply primed When in doubt, do the safest thing and use the fuel boostby turning the fuel boost pump on, opening the mixture briefly pump with Lycoming engines. Don’t be "stingy" with the boostto full rich, and cracking the throttle. Any pump- pump. In most cases they last the overhaul life of the engine.ing of the throttle is ineffective until the engine begins to fire, and are then exchanged or overhauled themselves. AS A

REMINDER The airframe Pilot’s Operating Handbook is

the authority if boost pump information is spelled out in it.

Use Of Fuel Boost Pumps With

Textron Lycoming Engines How To Avoid Broken

As an engine manufacturer, we are frequently asked about Piston Rings And Cracked Cylindersthe proper use of the fuel boost pump with our powerplants.Although we can’t pretend-to be an expert on the fuel boost A number ofmulti-engine pilots have contacted us over theirpump itself, we have some positive recommendations concern- concern for the effect on their powerplants of in-flight instruc-ing its use with our engines. Where a boost pump is provided tions by air traffic controllers. These pilots frequently fly inby the airframe manufacturer, and the airframe Pilot’s Operating and out ofhigh density airports where they are consistently askedHandbook has a limited treatment of the use of the fuel boost to make fast descents by ATC. Our check of the service records

pump, perhaps this discussion can provide the necessary fuel at the factory reveals that there has been a surge in the numberboost pump information for the pilot in order to operate his or of complaints of excessively worn piston ring grooves accom-

her engine as safely as possible. panied by broken rings, cracked cylinder heads, and warpedIt is necessary to supply the engine with a steady, uninter- exhaust valves in both engines of these multiengine aircraft, par-

ruptcd flow of fuel for all operating conditions. Entrapped air, ticularly those which are pressurized.temperature changes, pressure drops, agitation in the fuel lines Unless the pilot takes certain precautions, fast descents car-

and other factors affect the release of air and vapor from the rying high cruise RPM and low manifold pressure cause; brokenfuel system. Under some circumstances where an engine piston rings from ring flutter, and also cause cracked cylindersmounted fuel pump is provided, it may not be able to pump at the spark plug and valve ports, and warped exhaust valvesa continuous fuel supply free of excessive vapor. due to sudden cooling.

An effective continuous fuel supply is provided by use of In order to prevent engine problems of this type, we recom-

the fuel boost pump. As a general recommendation, the fuel mend the pilot maintain at least 15" MP or higher and set the

boost pump should be useawith Lycoming engines in all con- RPM at the lowest cruise position which should prevent ringditions where there is any possibility of excessive vapor for- fluner. Letdown speed should not exceed high cruise speed or

mation, or when a temporary cessation of fuel flow would in- approximately 1000 ft. per minute rate ofdescent. During close-

troduce undesirable hazards. The conditions under which Tex- in letdown, the aircraft can be "dirtied" by dropping the geartron Lycoming recommends operation of the fuel boost pump and some flaps, or both. This will prevent high airspeed and

are as follows: sudden cooling, and yet provide a good rate of descent.

i, Everytakeoff. However, any technique that prevents sudden cooling duringdescent will be helpful.

2. Climb after takeoff unless Pilot’s Operating Handbook

says it is not necessary.Those aircraft used to tow gliders and drop parachutists

should use similar precautions to prevent sudden cooling.3. When switching fuel selectors from one separate fuel tank

to another, the fuel boost pump should be "On" in the new

tank until the operator is assured there will be no inter-

ruption of the fuel flow. Avoid Sudden Cooling of Your Engine4. Every landing approach.5. Any time the fuel pressure is fluctuating and the engine is

Pilots must avoid fast letdowns with little or no power alongaffected by the fluctuation, with rich mixtures which cause sudden cooling and a number

of engine problems. The Lycoming Flyer has published a6. Hot weather, hot engine ground operation where fuel vapor number ofarticles over the years, recommending good operating

problems cause erratic engine operation. techniques to prevent sudden cooling of the engines.7. Some General Aviation aircraft require the use of the fuel Investigation of bent pushrods in our engines reveals that

boost pump during high altitude flight. This will be spell- sudden cooling during operation can cause this problem.ed out in the Pilot’s Operating Handbook.Engineering was able to produce like conditions that result in

8. If the engine mounted fuel pump fails. the exhaust valves sticking, which in turn causes bent pushrods.If the fuel boost pump is used during ground operation, Spark plug fouling is another of the problems brought on

don’t fail to check the condition ofthethe engine mounred fuel pump by sudden cooling during operation which we have written aboutbefore takeoff by turning the boost Dump off briefly, and then in past issues.. In order to avoid plug fouling, we have recom-back ’’on" for takeoff. If the engine mounted pump has failed, mended maintaining the mixture at the leaned cruise condition

during descent with a gradual richening of the mixture, carry- The second line ofdefense against dirt and abrasives is the

ing some power, and at a sensible airspeed in order to maintain full now oil filter which is standard with most Lycoming enginesthe most efficient engine temperatures possible. now being produced. Older engines were manufactured with

In another related article from the Flyer, we noted that Air a pressure screen, but may be convened to a full flow filter for

Traffic Control had advised pilots to expedite their descent in more effective cleaning of the oil. Textron Lycoming Service

Publication SSP-885-1 provides information and instructionssome instances, which resulted in sudden cooling and engine

needed for this conversion.problems. Aircraft used to tow gliders or drop parachutists have

also been vulnerable to the effects of sudden cooling after their Another contributor to a variety of engine problems, in-

drops and the descent to the airport. Investigation of a number eluding valve sticking, is frequent, long periodse of inactivity.

of these engines at the factory revealed broken piston rings, An engine should be flown regularly to stay in tiptop condi-

cracked cylinders at the spark plug and valve ports, and warped tion. The oil in the sump collects residue from combustion such

exhaust valves due to sudden cooling. as moisture, acid, and lead sludge. Flying the aircraft tends to

heat the oil enough to vaporize the moisture and help eliminateThe operating techniques recommended in the previous ar-

some of these contaminants, but an engine which is not flowntide, "How To Avoid Broken Piston Rings and Cracked

will collect moisture, acids and gums which may contribute toCylinders", are completely applicable to the items discussed

corrosion and to valve train problems. In addition to frequenthere. Whatever the circumstances, pilots must plan their flight

flight, these contaminants are also eliminated from the engineoperations so that the potential damage caused by sudden engine

by changing the oil. Textron Lycoming Service Bulletin No.cooling can be avoided.

480 dated January 18, 1988 recommends:

a. 50-hour interval oil change and filter replacement fur

all engines using a full-flow fitration system.

Operational and Maintenance b. 25-hour interval oil change and screen cleaning for ail

engines employing a pressure screen system.Procedures To Avoid Sticking Valves

c. A total of four months maximum between oil changesfor either of the systems discussed under a. and b.

As many Flyer readers know, an application for warrantyon any Lycoming reciprocating engine or engine part Reports from aircraft owners continue to indicate that trouble-

automatically places that item within the Service Information free operation through TBO is most often obtained with engines

Report (SIR) system. This computerized system, along with the subjected to frequent oil change intervals. Absurd as it may

record of telephone calls and correspondence from aviation seem, an engine which does not fly regularly should have the

maintenance facilities around the world provide the capability oil changed at more frequent flight time intervals than one which

to monitor trends and point out problem areas as they develop. does fly regularly.

These indicators show that there has been a trend, over the past Preventing a buildup of contaminants is just as importanttwo years, to an increase in the incidence of exhaust valve stick- as eliminating those that do form. Avoiding lone: periods of

ing. Therefore it seems very appropriate to provide our readers ground operation is a vital step since moisture forms readily

with some insight into this problem along with methods to help while the engine is running, but will not vaporize when the oil

avoid it, is not heated to normal operating temperatures. Ground run-

ning also involves a slightly rich mixture which contributes toFirst, consider that the properly timed sequence of valve

the formation of lead sludge in the oh. During flight, the depositopening and closing is essential to efficient and reliable engine of lead sludge in the oil can be minimized by proper leaning.operation. Also consider that the size tolel-ance between the con-

Although some excess fuel is required for engine coolingtinuously moving valve stem and its stationary valve guide is

during high power operation, proper leaning at cruise powerextremely critical. Even if the valve to guide clearance chosen

settings will promote complete burning of the fuel and,for use in an engine were perfect, the amount of clearance can

therefore, a minimum of lead sludge deposited in the oil. Thisbe affected and changed during the course of engine operation. is important since lead sludge is not filtered out, but is re-

In other words, a sticking or broken valve may not be the faultmoved by changing the oil. The airfI-ame manufacturers recom-

of the engine. It is possible to promote valve sticking, and theremendations and limitations for leaning should be observed, but

are many actions which can be taken to reduce or eliminate the it may be beneficial to be aware that when permitted by thepossibility of this phenomena. These actions will affect engine Pilot’s Operating Handbook, leaning to peak EGT at cruise

cooling, fuel management, and internal engine cleanliness.power settings will produce complete burning of the fuel/cilr

Engine cleanliness is a primary consideration which is af- mixture for best economy and reduction of combustion related

fected by many maintenance and operational procedures. Prop- contaminants.

er filter maintenance is one such item. The induction air filter Having touched on fuel management and maintenance items

is the first line of defense in keeping dirt and abrasives from required to keep an engine clean internally, the final factor af-

entering the engine. To prevent dirt from entering the engine, fecting potential valve sticking is engine operating temperature.the filter must form a good seal with the filter holder, and the Some operating procedures already discussed also have an ef-

induction system should be free of air leaks. The air filter should feet on engine temperature. Prolonged engine ground run-up

be cleaned or changed on a regular basis. In extremely dusty at high power settings, for example, can cause

conditions, a Biter change could be necessary as frequently as overheating or hot spots since cooling air flow is not

every few hours of operation. adequate when the aircraft is stationary.

Since proper engine operating temperatures fall within a also beneficial to continue the engine cooling process after lan-minimum and maximum range, it is important to consider all ding by insuring that several minutes ofengine operation at 800aspects. Baffles designedto direct cooling air over the cylinders to 1200 RPM are allowed before shut down. At large airportsmust be maintained in good condition. If these baffles deteriorate this is usually accomplished by the time taxi to the parking area

or are installed so that cooling air is not adequately contained is completed. At airports where clearing the runway puts theand directed, hot spots which promote a lead or carbon buildup aircraft in the parking area, a short period of additional opera-may occur. During hot weather in particular, those baffles or tion in the 800 to 1200 RPM range prior to engine shut downducts which direct cooling air through the oil cooler must also will allow temperatures to stabilize.be maintained in good condition. A logical question after this long series of things to do and

The pilot, as well as maintenance personnel, will play an things not to do might be this, "Is there any way to tell if a

important role in insuring that engine operating temperatures valve is sticking before serious damage occurs?" There are

do not promote valve sticking. As mentioned earlier, avoiding sometimes warning signs which should be investigated.ground running far in excess of the time necessary for engine Although there may be other causes, an intermittent hesitationwarm up should be avoided. Also to be avoided is continuous or miss in the engine may be an indication that carbon or other

operation at very low aircraft speeds which do not generate the similar contaminants have built up inside the valve guide caus-

most efficient flow of cooling air over the engine. This lack ing the valve stem to drag instead ofmoving freely. These con-

of effective cooling air may cause some areas of the engine to taminants should be removed by reaming the guide to its originalbe excessively hot and therefore have an effect on any con- size which should fall between .4995 and .5005 inch. The pro-taminants which may be in the oil. Essentially the oil becomes cedure to be used when reaming to remove valve guide deposit’’cookcd" and the formation of deposits is promoted. The ex- buildup is found in Textron Lycoming Service Instruction 1425.haust valve guide area is the most likely to be affected by these Known as "the old rope trick" to many A&P mechanics, this

deposits and a stuck or sticking valve may result. valve guide reaming procedure restores valve stem to guide run-

The other end of the spectrum controllable by the pilot is ning clearance and can be accomplished without removing the

excessively rapid cool down of an engine which has been run- engine from the aircraft.

ning at normal operating temperatures. Lycoming engines are To summarize, procedures to reduce valve sticking will also

made with various metals which expand and contract at different reduce the probability of additional engine damage which mayrates when exposed to heat or cold. Engineering tests have cause loss ofpower and the need for costly repairs. These pro-demonstrated that valves will stick when a large amount ofvery cedures may be reduced to relatively simple terms: The

cold air is directed over an engine which has been quickly throt- maintenance and operational procedures necessary to avoidtied back after operating at normal running temperatures. This sticking valves are those which keep the engine clean internal-is a good example for pilots. It is poor technique to "chop" ly and which cause it to run within proper operating temperaturethe power from cruise or higher power settings to idle and then ranges. The items discussed above should serve as a guide for

start a rapid let down which develops excessive cooling air flow A&P mechanics and for pilots.over the engine. It is always best to reduce power in increments

so that engine temperature changes will occur gradually. It is

Z

~cl"-

n’hen indications ofvalve slickine are nepleclcd. a bent pwhrod and damaped shroud tube mas´•

result. In the picture oba´•e. note the sa~ere bend in the normnlls´• straight shroud tube.

Sticking Valves Do Not Neglect vice Instruction 1425 provides recommendations to reduce the

The Warning Signs possibility of valve sticking. In particular, Part iII of the in-

struction gives a procedure for reaming valve guides which can

An article in Flyer No. 40 provided operational and be accomplished without removing the engine from the aircraftmaintenance techniques to help avoid sticking valves. The ar- or the cylinders from the engine.tide prompted several individuals to relay items from their per-sonal knowledge and experience. This information provides a

worthwhile addition to the data printed previously. It could be

very helpful and is passed along for that reason. Tips From The DangerOne of the regional service managers here at the Lycom-

ing factory indicated that his experience over the years includ- These are some of the more common questions asked at

ed working on engines with sticking valves. He commented that our service hanger:the engine will almost always provide a warning by running

QUESTION Do your new, remanufactured or overhaul-very rough at start up. As the engine warms up it may then

smooth out after a few seconds and run normally, but the in- ed engines require a "slow" flying or break-in period?

itial roughness is a warning that preventive maintenance action ANSWER--Definitely not. Fly them as you would a highis required, time engine. In fact, so-called "slow" flying may have harm-

Just a few days after these comments were made, a con-ful effects. The rings may not seat properly resulting in higher

versation with an aircraft owner confirmed that the regionalthan normal oil consumption.

manager’s comments were right on target. This is the story QUESTION At what rate of oil consumption does con-

which thcaircraft owner related. tinued operation of the engine become a hazard?

An aircraft had been purchased recently and the owner flew ANSWER--Generally speaking, when the oil consumptionit to altitude in the vicinity ofhis home airport to satisfy himself reaches one quart per hour, corrective action should be taken.

af the aircraft capability to fly over mountainous terrain during However, maximum permissible for each particular engine is

a planned vacation trip. Content that the aircraft and engine were listed in the engine operator’s manual.

capable of meeting his requirementsrthe vacation trip wasQUESTION What is the chief danger of operating an

undertaken. All went smoothly on the first 300 mile leg of theengine with high oil consumption?

trip which ended with a planned overnight stop.ANSWER Oil soaked carbon forms at a fast rate. At

When the engine was started the next day, it was very, very the same time, the presence of oil in the combustion chamberrough, but smoothed out and ran normally after a short time,

has the effect of lowering the octane rating of the fuel. OperatingWith the engine running smoothly, the vacation trip continued

temperatures go up. We have now set up conditions invitingto its destination. The aircraft was then tied down and not

operated until it was time for the return trip a period ofaboutdefonation and/or pre-ignition.

one week. QUESTION If I can’t get aviation fuel, may I use

automotive fuel if octane rating is equal or higher?As the engine was started for the return trip, it again gave

indications that a valve was momentarily sticking it ranANSWER No. There are 4 or 5 good reasons and all

very rough for several seconds, but then smoothed out. With important. They can be summed up in three words potentialthe engine running smoothly again, the return trip was started, engine failure.

After one to two hours of flight at altitude, over mountainous QUESTION What is the most common cause of

terrain. the engine ran very rough again for a short period of premature engine wear?

time, and then smoothed out. The pilot decided to land at theANSWER Dirt entering the engine through the car-

nearest airport, buretor or injector due to worn out air filter, torn induction hosesExamination of the engine revealed a considerable amount or broken air boxes.

of oil leakage. The cause a valve which had stuck solidlyQUESTION Does the spacer between the propeller and

and caused the pushrod to bend. This bending ruptured thethe engine currently becoming popular serve any purpose other

pushrod shroud tube and allowed oil to escape. This is a classicthan streamlining the nacelle?

example of the damage which sticking valves can cause.

ANSWER Yes. In many cases, moving the propellerThe lesson to be learned is quite simple. Do not neglect forward, which increases the clearance between propeller andthe warning signs. Perhaps the experience related here will allow

cowl, increases propeller efficiency and reduces nacelleothers to recognize a rough running engine at start up as a possi- vibration.ble indication of sticking valves. The next step is to take im-

mediate action to prevent damage. QUESTION In some cases, we note a minor discreIaan-

Although there may be an occasional exception, it is almost cy between the engine operator’s manual and the airplane Pilot’s

always ;tn exhaust valve which sticks. To prevent further valve Operating Handbook. Which one should be followed?

~tickinp: and to reduce the possiblitity of damage, all exhaust ANSWER The airframe Pilot’s Operating Handbook.

valve guides should be cleaned of any carbon, varnish, or other For various reasons. after the engine is installed in the airframe.

contamination buildup. This is accomplished by reaming the operational techniques may be altered or certain restrictions mav

guides to their original size as specified in Textron Lycoming be placed on the engine. A simple example would be a placardPublication SSP 1776. Table of Limits. Textron Lycoming Ser- restricting continuous operation in a certain RPM range.

QUESTION I fly an aircraft equipped with a fixed pitch The Pilot And Turbochargingpropeller. During cruise I’m told to keep increasing the RPMas my cruising altitude is increased. Since I fly pretty high, in What should the General Aviation pilot know about tur-order to hold 65% power, I find the RPM is mostly at 2550 bocharging the flat opposed piston engines, and how could heto 2600. Won’t this high RPM reduce the engine life? accumulate this information? He could read a number of the

ANSWER No. The higher RPM won’t harm the engine helpful articles published in aviation magazines during recent

or reduce service life. Remember, you are increasing the RPM years and get some information. In addition to this source, the

only to hold the same power you had at a lower altitude at say,pilot could get demonstration flights in the various equipment

2350 RPM. using turbocharging. Then to really complete his backgroundthe pilot could talk with the engineers responsible for tur-

QUESTION Is there really any difference between good bocharging the flat opposed piston engines and he would in allautomotive oil and aviation oil? probability have a pretty good basic understanding of

ANSWER Yes indeed there is! Don’t ever use auto- turbocharging.motive oil in your aircraft engine. Believe it or not, we still Perhaps we can save the interested reader or pilot a por-encounter engines that have burned holes in pistons due to the tion of the time and expense required to acquire this knowledgeuse ofautomotive oils which~ave an ash deposit causing preigni- by sharing our experience in the above areas. Although opera-tion. It seems awfully hard to convince people ~ho have had tion of the varied turbocbarged powerplants is relatively sim-great success with the oil used in their car that it may not be pie, nevertheless the pilot can stay out of trouble and also realizeused in their aircraft engine. more efficient use of this type equipment through a sound basic

NOTE~- Since we have had several questions on fuels and knowledge of the How, What, and Why of turbochargnng.oils, it might be well to mention that we canltthink ofa quickerway to void your engine warranty than by using anything other

Why Turbocharge?than the recommended FAA approved aviation fuels and oils. Before explaining the various turbocharging systems in the

QUESTION What are some common causes ofexcessive field and their operation, let us examine some of the reasons

oil consumption other than the burning o_f oil due to high engine for turbocharging the flat opposed piston engines up throughtime? 450 HP, and the accompanying advantages from doing so.

ANSWER Building up of crankcase pressure due to Experience has taught us that flying high and fast is most

"blow-by" caused by ring wear may result in oil being blown desirable on cross country flights, but only in the past few yearsout of the breather. The same thing can result from broken piston has the industry produced a small, lightweight, and inexpen-rings. Oil may be pumped overboard due to a faulty vacuum

sive turbocharger to make this possible, and at the same time

pump or faulty automotive type fuel pump. utilizing standard production engines.

QUESTION My dealer advised me to use straight Turbocharging has also given impetus toward continued ad-

mineral oil in my new engine until it’s "broken in". How dovancement and growth in general aviation by bringing on

I know when it’s "broken in"? economical cabin pressurization in general aviation aircraft.

ANSWER When oil consumption has stabilized. Exam-It has made it possible to climb above most of the

pie: After continued checking ofoil consumption you have deter-undesirable flying weather instead of banging through the poor

mined the engine is consistently using one quart in a knownvisibilities, bumpy air, icing, and slower speeds of the altitudes

number of hours.below 10,000 feet. The rare loss of an engine in a twin willnot necessarily result in the airplane being forced to descend

QUESTION What is normal oil consumption for my into the weather, but will mean merely slower flight while stillIO-320-B1A? maintaining the desired, safe altitude.

ANSWER The answer cannot be given in any specific With such great flexibility in choice of altitude, it will benumber of hours per quart. Normal oil consumption rate can possible to take better advantage of favorable winds, or avoidingbe anywhere from a quart in 5 hours to a quart in 20 hours. turbulance.

Our larger engines may be considered normal with a consump- Much safer flight is now possible over high mountains fortion of a quart in 4 hours to a quart in 12 hours. general aviation aircraft.

QUESTION I have problems with lead fouling of spark The turbocharged engine allows the pilot to maintain suf-plugs. What can I, as a pilot, do about it? ficient cruise power at high altitudes where there is less drag

ANSWER Several things. See that you have the correctwhich means faster true airspeeds and increased range with fuel

spark plugs that are recommended by the engine manufacturer’s economy. At the same time the powerplant has flexibility and

charts, not oddballs recommended by some well-meaning friend. can be flown at a low altitude without gulping fuel like a

Avoid prolonged idling on the ground. Avoid power off thirsty turbine.

descents. Lean out at cruise; even on short cross-country flights. The turbocharged powerplant is a blessing at high altitudeRotate plugs from bottom to top every 50 hours or 25 if airports. The normally aspirated engine may be mar~inal from

necessary, these fields, but turbocharging takes it out of this category.

When attached to the standard powerplant, the Nrbochargerdoes not take an~ horsepower from the engine to operate. it is

relatively simple mechanically, and some models can pressurize pressures may go as high as 45 Hg. However, the powerplantthe cabin, too, must be built to withstand the added stress. As an example of

The pilot who may have been considering the expensive this, the Lycoming TIG-541 model engine, which is a Ground

turbine powered aircraft with its more limited utility might Boosted powerplant permitting 38 to 43 of MP for takeoff,

reconsider in favor of the more practical, economical tur-has incorporated inconel exhaust valves with ni-resist guides

bocharged piston powered plane. which protect against the hotter exhaust temperatures, a largerand stronger crankshaft, lower compression ratio to protect the

Thus turbocharging has made another very important con-combustion chamber, and oil squirts in the crankcase which

tribution to the successful progress of general aviation by ex-direct a stream of oil at the pistons to help cool these critical

panding its utility, and the modern general aviation aircraft hasareas.

achieved success largely because of its utility.As our turbocharged aircraft is flown higher, the com-

What Is Turbocharging? presser wheel must run faster to compensate for the thinner air.

One problem in compressing air is that it gets hotter. Therefore,

At the risk of insulting the intelligence and experience level the higher we fly the faster the compressor must turn which

of some readers, we should nevertheless review for anyone in- produces a hotter charge to the cylinders, ususally reflected in

terested in the basic principle involved in turbocharging and higher cylinder head temperatures. The engine does not give

answer the question What is turt~charging? out the same horsepower for the same manifold pressure set-

ting where the air is not compressed. So don’t be confused bySome 50 years ago, a smart engineer thought of using the

the requirement to wry a moder;itely higher manifold pressureexhaust gases of the reciprocating engine for some practical pur-

at altitude on some models, for this compensates for the powerpose. The normally aspirated (unsupercharged) engines of that

lost from heat by compressing the air. The pilot can also under-day were inefficient at altitude and therefore altitude flight was

stand how important is the use of the correct fuel in a Groundnot very practical because the aircraft engine couldn’t pump Boosted powerplant. Detonation and probably engine failureenough of the thinner air to maintain sufficient power. would result from the use of a fuel with a lower than minimum

Our intelligent engineer merely directed the flow of the required aviation octane rating.powerplant’s exhaust gases over a turbine wheel attached to a

compressor wheel by a common shaft and had these two wheels Automatic vs, Manual Controlscontained within separate housings. As the exhaust gases from

the engine pass through the turbine housing it causes the tur- Control of the turbine speed in the various rurbochagersbine wheel to rotate. The compressor wheel (fan or blower) be- used in General Aviation is by means of the waste gate, which

ing mounted on tile same shaft rotates with the turbine and draws utilizes the same principles as a flood gate damning up water,

in outside air, compresses it (packs it or makes thin air dense), When the turbocharger wastegate is closed, the full force of

and delivers it to the cylinders. Thus the turbocharger can com- the exhaust gas is directed over the turbine wheel. Turbine speedpensate lup to a point) for the thin air at altitude simply by com- in the varying manufacturers’ models is controlled by either

pressing the intake air and making it dense, such as it is close manually or automatically adjusting the opening or closing of

to sea level, and thereby giving the engine the oxygen it needs the wastegate.for proper and efficient combustion. So you can see that the Early versions of a typical manually controlled wastegatetypical general aviation turbocharger on the market today can unit have separate controls for each engine, which the pilotsupply sea level dense air land maintain sea level horsepower) operates in the cockpit. Although we will discuss operation inat least to 16,000 feet and higher, depending on the type of

a later paragraph, it should be emphasized that the careless or

equipment. This leads us to the variations in turbocharging uneducated pilot can easily overboost his engine with the manualwhich the general aviation pilot ought to understand before he

system which can result in engine failure.

attempts to operate any of them.Pilot workload is reduced with a turbocharger which utilizes

an automatically controlled waste gate unit. The automatic con-Ground Boosting vs. Altitude Turbocharging

troller adjusts for temperature or pressure or both, dependingon the various applications, and permits the turbocharger to be

Altitude turbocharging (sometimes called normalizing) iscontrolled by normal throttle movements. The automatic con-

accomplished by use of a turbocharger that will maintain thetrol feature is normally set at the factory and should not be

sea level horsepower of an engine at higher altitudes. Thus a

tampered with in the field.250 HP engine for example would still put out 250 HP at full

power to altitudes of 16,000 to 20,000 feet, depending on theConversion Kit vs. Factory Mating of

type of turbocharging equipment. This method of turbocharg-ing does not take more from an engine than for what it was Turbocharger and Engineoriginally designed if operated properly.

Conversion kits in the field utilizing turbochargers haveGround boosting is another application of turbocharging

where more than the standard 29 inches of manifold pressuregenerally been quite successful. In order to be legal, the com-

are used in flight. This method of Nrbocharging increases thebination must have a Supplemental Type Certification issued

horsepower output of the engine without increasing the size orby the FAA. However, engine manufacturers have a lon~ stand-

weight, and also improves the altitude performance. in the ing policy that anything attached to the engine other thr;n it was

certified for at the factory eliminates the engine warranty ifvarious aircraft using Ground Boosting, takeoff manifold

malfunctioning takes place as a result of whatever was subse-

quently hung on the engine. Likewise, it would probably be less tie, and at this point the pilot would actuate the turbo controlspractical to attach a turbqcharger to an old or high time engine. g~adually so that climb power (at full rich mixture) can be main-Only kits for altitude Nrbocharging engines (both automatic and tained until cruise altitude is reached. At cruise refer to themanual) have been used as conversions in the field, because manufacturer’s chart to set up desired cruise power. Lycomingit would not be safe or practical to attempt a conversion to permits leaning by reference to an exhaust gas temperature gageground boosting except that done by the factory, or TIT.

Engine manufacturers have been providing a mated tur- Remember that cylinder head temperatures may averagebocharged engine package for both rotary and fixed wing air- at least 300 F higher than normally observed in the lowercraft for many years. If the engine manufacturer certifies such altitudes when flying above 10,000 feet with turbo on. Duringa power package, the full warranty will go along with it. The let down be careful to avoid overboosting. The pilot must be

ground boosted engine will have been beefed up for this addi- especially alert here so that reductions in power by turbo con-

tional power requirement. trol are made first.

The interested pilot may also want to know that the tur- The pilot cannot be careless with this system. We have in-bochargcr can be used with either a carburetor or fuel injection, vestigated cases where the operator failed to check on the tur-

bocharger before takeoff from a sea level airport and learnedOperation the hard way during takeoff that they were fully actuated. Before

he could control the power, the manifold pressure had gone toBoth the mechanic and the pilot must know how to operate 60 inches, which resulted in failure of both engines.

the specific turbocharged system on his aircraft; so this article

is not intended as a substitute for the Engine or AirplaneTherefore, although the system is simple, carelessness or

Manuals, because the treatment here is more general. But wea lack of knowledge concerning it can create serious trouble.

can augment those basic references with explanations from the

pilot’s point of view. The Automatically Controlled Systems

Probably the most practical consideration of operation There are important differences in the AiResearchwould be to treat the automatic and manual systems separate- automatically controlled system from that of the manually con-ly. However, before we dojust that, there are a few basic han-

trolled Rajay system.dling or operational requirements that apply to both systems.

Those engine owners with the Automatic Ground Boostedi. The throttle or throttles must be operated smoothly or the

feature should bfnow that the turbocharger is on at all timesengines will surge, which is hard on the turbocharger and

whenever the engine is operating.the engine.Although this particular system automatically protects2. Power sequence is very important with the turbocharged against overboost at all normal RPM and MP settings, it is possi-engine. ble to overboost a turbocharged engine nevertheless. Any sud-

To increase power (enrich mixture) den straight-arming of the throtles, particularly on cold engines,Increase RPM, then MP can cause an overboost condition which would exceed the red

To decrease power line. But overboost can also take place even though the red line

Decrease NP, then RPM MP has not been exceeded where the pilot may have a low RPM

and very high MP. An example of this has been observed where3. High altitude flights mean higher turbine speeds and

hotter cylinder head temperatures. Observe thesethe pilot has let down at low RPM, then on the final approachexecuted a go-around without first advancing RPM. Thus he

temperatures and stay within the limits prescribed for best

engine life,could be pulling maximum manifold pressure (to red line) at

low RPM which would be a definite overboost condition, with4. Cruise control at altitude is in accordance with the specific resulting heavy detonation and undersirable compressor surge.

instructions in the airplane Pilot’s Operating Handbook.The engine manufacturers have service bulletins and ser-

5. Turbocharged powerplants require 100 octane aviation vice instructions for reference if this should happen. A severe

grade fuel as a minimum. overboost could require a major overhaul of the engine and

replacement of the crankshaft.The Manually Controlled Turbocharger

Of course the nice feature of the automatic system for the

The pilot operating this system would take off with the tur-busy pilot during climb is that once the throttles are set, there

bocharger inoperative if the field elevation was below 4 to 5,000is a minimum ofadjustment required. Cruise handling is similar

feet density altitude. Takeoff from fields with elevations aboveto the other systems described earlier. During let down there

5,000 feet requires presetting the turbocharging before landingis no worry about high MP because the pilot merely retards his

or takeoff wherever possible. This should be learned by meansthrottles and the automatic system does the work for him.

of a demonstration from the checkout pilot. Where the tur- Since the turbocharger is operating during takeoff, all

bochargcr is operating at takeoff, mixture should be full rich takeoffs at any altitude require full rich mixture because the tur-

rcgardleu of field elevation. bocharger provides full rated horsepower, and full rich mix-

During the climb, somewhere between four and five thou- ture is required for that amount of power.

rand feet density altitude, the engine will have run out of throt-

Manually Controlled Mechanical Interconnect connections for security, lubricant leakage or air leakage. There

Turbocharger Systemare the usual 50 and 100 hour inspections which are brief in

what they recommend. Mechanics should not tinker with the

system unless they have been specifically schooled. A very in-Tcxtron Lycoming developed a simple mechanical control

portant requirement is the necessity to avoid dropping any looseturbocharger system, primarily for use in single engine installa-

items in the induction system. They will be sucked up and gotions. It consists of a mechanical interconnect between the ex-

through the turbine wheel damaging it and also possibly damae-haust waste gate valve and carburetor or fuel injector butter-

ing the engine as well. This could become very costly.fly, which is operated by the pilot’s throttle control. The rela-

tionship of the waste gate position to butterfly position is such Any overboosting should be entered in the log book by the

that at ground level, the rated manifold pressure and power oc-pilot. The mechanic must then refer to the manufacturer’s ser-

cur at less than full throttle. This is done so that the throttlevice publication for the necessary action to take. When the

engine is exchanged or overhauled, the turbocharger should alsocan be advanced by the pilot during climb to maintain rated

be exchanged or overhauled.manifold pressure if desired or permitted in the particular in-

stallation. To guard against dangerous overboost from inadver-Summary

tent excessive throttle opening, a pop-off type relief valve is

installed between the turbocharger and carbureto~ (or fuel in-One of the most exciting and certainly most promising of

jcctor), which will open to protect the engine, as manifoldthe new innovations in general aviation is the turbocharger for

pressure exceeds the approved limit.the flat opposed piston engines. Combining cabin pressuriza-

The pilot should carefnlly read the Pilot’s Operating Hand- tion and engine turbocharging from the same compressor in-book on this equipment, and also get a good check out by a eluded as part of the engine package, provides simplicity, which

competent pilot qualified in the aircraft. Pilot technique cau- leads to low cost and light weight. The helicopter people alsotions against sudden movements of the throttle, and recommends tell us that the turbocharged piston engine revolutionized theinStead slow deliberate movements. At takeoff, before releas- helicopter industry, particularly for use in mountainous areas.

ing brakes, advance the throttle smoothly to 30 inches manifold Altitude test flights and field experience have indicated excellent

pressure, and then pause to allow the tullbocharger to build up fuel economy and range with the accompanying higher true

RPM; release the brakes and carefully open the throttle to take-airspeeds.

off manifold pressure. During climb at a fixed throttle condi-

tion, manifold pressure will decrease at the rate ofapproximatelyWe recognize that the limit for the opposed engine will be

one inch for each thousand feet. The throttle may be advanced approximately 450 HP, and anything larger will be covered by

to restore the desired manifold pressure.the turbo-prop or pure jets. The turbocharger added to the pistonengine provides a great economy package and adds to the already

At cruise, manual leaning is accomplished by adjusting therecognized utility of these general aviation aircraft.

mixture in small amounts while monitoring the EGT gage,

allowing sufficient time between adjustments for the ExhaustIn closing, we observe that the turbocharger has been quite

Gas Temperature to stabilize. Leaning to Best Power Mixture compatible with our piston engines. We tried to answer the ques-

is accomplished by carefully finding peak EGT and thention: Why turbocharge? What is Turbocharging? and, How do

enriching until EGT decreases 1250 F. Best Power Mixture mayyou operate it? There is no substitute for a good checkout by

be utilized at high cruise power where more than 75% poweran experienced pilot; and for a sound basic knowledge be sure

is used, or with climb power, but never at take offpower. Best to read the airplane Pilot’s Operating Handbook. Give the

economy mixture is peak EGT. If the engine roughens at peak powerpiant and turbo the maintenance they require and the

EGT, enrich the mixture slightly. Peak EGT will be different careful operation they deserve, and they will give you perfor-

far varied power settings, therefore when changing power, the mance with a long and satisfactory life.

pilot must go back to rich and find a new peak for the different

setting.The pilot should be alert to the reaction of the manifold

Turbochargingpressure in this type engine when leaning at cruise power. At

a fixed RPM and throttle setting, the manifold pressure will in- A Brief Refreshercrease as the mixture is leaned to Best Power, and decrease when

further leaned to Best Economy. The recommended procedure Turbocharging has been a part of everyday operations for

is that at the completion of the leaning procedure, if the manifold some pilots and some A P mechanics for many years. The

pressure is more than one inch from the beginning MP value, science ofadding a turbocharger to an aircraft engine and mak-

it is recommended that the mixture be returned to full rich and ing that system provide us with a big bonus in operating capabili-the MP adjusted accordingly so that the leaning procedure pro- ty was well established when a series of articles on the subjectduces the desired manifold pressure. appeared in the Lycoming Flyer back in 1967. At that time.

turbocharging was found primarily in the more sophisticatedMaintenance twin engine aircraft, and as a result, exposure to turbochareing

was limited to a relatively small number ofpilots and mechanies.Maintenance for all the turbo systems covered here is

There are several factors which have caused an increaserelatively simple. The daily pre-flight merely calls for a visual

in the number of persons who must now know more and moreinspection prior to the first flight, of the turbo mountings and

about the peculiarities of the various turbocharger systems. First, are directed over the turbine, both wheels will turn faster andthe sophisticated twins have become very popular with many the density of the air supplied to the engine by the compressorbusinesses, which in recent years have found it beneficial to will increase allowing the engine to produce more power. Theseuse company aircraft for business travel. In addition, airline two wheels mounted on a shaft are enclosed within housingsderegulation has promoted the growth of many commuter which separate and contain the two functionsjust discussed; thisairlines and charter operations where an efficient, piston- is the turbocharger.powered, turbocharged aircraft has proved to be the proper Although the turbocharger is sometimes used to obtain an

machine for the job. More recently, the popularity and advan- increase of rated horsepower from a particular engine at sea

tages of turbocharging have caused it to be used in a growing level (the engine is described as ’ground boosted’), its primarynumber of single engine aircraft. With this rapid growth in function in many aircmft applications is to provide the capabilitynumber of turbocharged aircraft, many pilots and mechanics of maintaining sea level power to a predetermined, critical

are being exposed to turbocharging for the first time. As a result, altitude. At this altitude the turbocharger will be operating at

its maximum capability and engine power will deteriorate as

altitude is increased above the critical altitude.RJJY Since the speed at which a turbocharger must operate is

dependent upon the power desired from the engine and also uponthe density of the air at the altitude at which the aircraft is fly-

Nra~vr ~HurLing, it is necessary to provide the pilot with the capability of

adjusting turbocharger speed. This is accomplished by control-

ling the amount of exhaust gas which is directed to the turbineside of the turbocharger. In those cases where air of increased

density is not needed from the turbocharger Oow altitude or low

power required), a wastegate in the exhaust system is allowed

*v~ccrto remain open and the exhaust gas is vented around the tur-

bine wheel and through the wastegate to the atmosphere, ver’

much like the normally aspirated engine. As the demand foGdense air increases, the wastegate can be closed to a positionwhich will force the proper amount of exhaust gas into the tur-

cMnruac fbine and therefore speed up the compressor to meet the current

r~K /HLCT demand. Adjusting turbocharger speed to meet changing powerc´•nr~r´•raA f;mrl requirements is a matter of providing necessary controls over

OA~XHAyJT the flow of exhaust gas.

Control of the factory installed turbochargers is accom-

some of the things which have been written about turbocharg- plished by two basic methods. These are manual control or

ing in the past should now be repeated for the benefit of allautomatic control. Manual control is also divided into two types.

concerned. The simplest form of manual control is the fixed bleed

This refresher information will be a non-technical explana-system which does not incorporate a wastegate, but which allowssome exhaust gas to continuously escape through an orifice of

tion of what turbocharging does for the reciprocating engine, predetermined size. Size of the orifice establishes the criticalAs you know, the aircraft engine derives its power from the

altitude of the engine. The remainder of the exhaust gas is usedburning ofa mixture of fuel and air. Assuming that this fueyairmixture retains a constant ratio, the amount of power the engine

to turn the turbocharger mechanism anytime the engine is run-

develops will be directly proportional to the total mass of airning. In this system, engine power is adjusted by the positionof the throttle plate in the carburetor or fuel injector and the

pumped through the engine. Climbing to altitude in an aircraftamount of exhaust gas available to turn the turbocharger is a

equipped with a normally aspirated engine provides a very result of the power developed at that particular throttle setting.realistic example; as the air becomes less and less dense with

altitude, the engine is capable of producing less and less powerA second manual system is a throttle/wastegate intercon-

nect in which the positioning of the cockpit throttle control ac-as indicated by the decreasing rate of climb and eventually the

total inability to climb higher.tuates both the throttle plate and the turbocharger wastegate.The design of this mechanism causes a programmed movement

In simple terms, the turbocharger provides an air pump of the throttle plate and wastegate; the throttle plate starts towhich allows us to supply the engine with dense air not only move toward the full open position before movement of theat sea level, but also when operating in the thin air at altitude. wastegate affects any change in the exhaust bleed which willThe pump used in a turbocharger may be described more ac- cause turbocharger speed to increase. At the fully advanced

curately as a centrifugal air compressor which is mounted on positon of the throttle control, the throttle plate is at full opena shaft. To power the compressor, the hot exhaust gases which and the wastegate is closed to its maximum design limit.are discharged as wasted energy in a normally aspirated engine A pressure relief valve is normally included in the factoryare now harnessed by directing them through a turbine wheel developed system of each manually controlled turbocharger in-which might be described as a very sophisticated windmill. The stallation. The purpose of this valve is protection of the engmlturbine wheel is mounted on the same shaft as the air compressor in case.of an unintentional overactivation of the throttle loverso that during operation the compressor and turbine will turn boost) by the pilot. With a manually controlled turbochagerat the same speed. Therefore, as more exhaust gases (energy) system, the pilot is the controller, and must limit throttle move-

ment to keep manifold pressure within the limit specified for how they can create an unsafe flight condition. As an example.the engine. For takeoff, this requires very smooth application in most instances the moderate engine power loss that occurs

of the throttle until manifold pressure indicates about two in- from attempting a takeoff at sea level where an absent-runded

ches below the maximum for which the engine is rated. As the pilot has left the carburetor heat in full hot position from the

turbocharger speed builds up, the manifold pressure will increase previous landing, may cause a scare, bur not necessarily an ae-

slightly to the maximum limit. As engine power deteriorates cident. But move the situation to a 5000 feet plus (densltv

during climb, the piler slowly advances the throttle to maintain altitude) small airport, again forget there is full carburetor heat,

the desired manifold pressure until the full throttle position is add a rich carburetor condition, and the sum total of these com-

reached at the critical altitude. bined power thieves add up to a takeoff or g~around accident.

The automatic systems used to control turbocharger opera-Similarly, a review of accidents over the years tends to prove

tion utilize devices which sense differences of air pressure atin the majority of cases that it has rarely been one factor respon-sible for a crash, but rather one small item, added to another

various points in the induction system, and utilize any changesto adjust the oil pressure which controls the position of the

wastegate. Not all of these systems are exactly the same and,

thtrefore, it is very imponant that the piiot understand exactly Iwhat manifold pressures he should expect when full throttle is

TIGO-541 have controller systems which are set to provide red~LI

applied for takeoff. Engines such as the Lycoming TIG-541 and

line manifold pressures when the throttle is full open for takeoff. 8

Other engines, most of those in the Lycoming TIG-540 series, autilize a density controller which will maintain a set power out-

put at full throttle regardless of variations in altitude and in

temperatures above or below standard; as a result, manifold

pressures at full throttle may indicate several inches above or

below that specified for standard day conditions.

One final item which should be stressed during this brief

review of turbocharging. Those pilots trying a turbocharged in-

stallation for the first time should be aware of thronle sensitivitysmall factor, added to a third; all of these small items finally

and the need for very smooth throttle movements. In case of

the manual systems, the turbocharger requires time to follow add up to a total beyond the ability of the pilot to cope with

throttle movement since it may operate at speeds in excess of in the combined situation. This is how accidents tend to hap-

80,000 RPM. The automatic control systems experience this pen. So let’s identify as many of these power thieves as space

same phenomena and, in addition, all elements of the control permits in order to make flight as safe as we can.

system must stabilize following any movement of the throttle. PREVENT POWER LOSS ON TAKEOFF WITH

An anicle on turbocharging which was printed in the 1960’s DIRECT DRIVE ENGINES IN COLD WEATHER

gave this advice, "Move the throttle controls SLOWLY andIn cool or cold weather, pilots should take extra care prior

WAIT."to attempting to takeoff with a cold engine and cold oil, and

This advice is also good when leaning the mixture since thereby prevent a temporary power loss during a critical panthe mixture setting has a great effect on engine operating of the takeoff. Cold or heavy oil can and quite often does affect

temperatures. The operating temperatures of a Nrbocharged normal operation of the hydraulic lifters. Remember that avla-

engine will be somewhat higher than those of a similar normal- tion lubricants are heavier when cold than the commonly used

ly aspirated engine because the intake air is heated as it is com- automotive engine oils and require a little more time in warm-

pressed; this is particularly true at the higher altitudes where up to obtain normal now in order to function properlythe compressor must work very hard to supply dense air to the throughout the air cooled aircraft engine.engine. Cylinder head temperatures will average 300 F higher

To prevent possible power loss, a proper warm-up shouldat altitude, and smooth, steady operation of the mixture con-

be conducted. The engine is ususally warm enough for pre-flightrrol will insure that turbine inlet temperature (TIT) limitations

ground check in above freezing temperaturts after 2 to 3 minutesare not exceeded.

running at 1000 to 1200 RPM. Below freezing temperatures.This brief review of various aspects of the turbocharged the warm-up period should be longer. With turbocharged

engine is primarily from a pilot’s point of view, powerplants, cold oil and cold engines require a longer warm-

up period to assure proper controller operation and preventmanifold pressure overboost.

Thieves Of Aircraft Engine Power After the above recommended warm-up period in cool or

cold weather, including magneto and runup check, if the oil

and how to cope with them. pressure is consistently over maximum red line, have a

knowledgeable mechanic adjust oil pressure so that it does not

It appears that some General Aviation pilots are not really exceed red lint at rakeoff or climb powers, and yet it is within

aware of the number of detrimental influences on their aircraft the recommended green are area at cruise. Cold weather tends

engines which can be identified as thieves of engine power, and to require a longer warmup period.

Another cause of the power loss under these temperature It is possible to compensate for the horsepower loss due to heatand flight conditions has_been the use ofa heavier weight viscosi- by means ofthe latter technique if throttle or RPM are available.ty of oil than recommended for the ambient temperature flightcondition. A heavier weight oil than recommended in cool or EFFE(3TS ON POWER AT A HIGHcold weather will tend to prevent the normal operation of the AL?TI~UDE AIRPORT ON A HOT DAYhydraulic lifters and thereby cause a loss of power. Safe flight at a high altitude airport (5,000 ft. density altitude

Thus. to prevent power loss on takeoff with direct drive and above) on a warm weather day must consider theengines, select the proper weight oil for your engine for cold aerodynamic loss of efficiency on the airplane and propellerweather operation. Make a careful run-up prior to takeoff with under these conditions, and the power loss effect on the engine.cold oil and a cold engine and observe engine instruments. Ex- A good "rule of thumb" for the pilot to remember is fortend your warmup period in cold weather until oil pressure is each thousand feet above sea level, the takeoff run increaseswithin recommended limits, or consult a mechanic concerning approximately 25 percent. In the case of normally aspirateda compromise adjustment. If in doubt about power output, a engines (not tmbocharged or supercharged), at an altitude ofbrief smooth full throttle check is recommended. 10,000 feet, about one-half of available engine horsepower is

lost.CARBURETOR HEAT OR ALTERNATE ATRHEAT AS POWER THIEVES We can create a practical fight problem for the pilot who

In the opening paragraph, carburetor heat was used as anis faced with a high elevation field takeoff. At Denver, Col-

example of a cause of power loss, but many pilots aren’t sure

orado where the field elevation indicated on the airplanethey understand the reason for it. During flight test, and in the

altimeter is 5000 ft., the pilot should consult the density altitudechart for takeoff. He must know that the published performancetest cell, we have been able to measure fairly accurately a loss

of as much as r596 of engine power when full alternate air orcriteria ofan aircraft is generally based on standard a~nospheric

carburetor heat have been applied. As a specific explanation,conditions (temperatlue 590 F, pressure 29.92 inches of mer-

there is a small power loss when we use heat because the pilotcury at sea level). In checking the density chart and applying

has switched from the direct, colder ram air to an indirect car-the ambient temperatun of a summer day of 800 F, the careful

burcror heat muff, or a similar indirect source ofwarm air withpilot will note that the density altitude is actually 7500 ft., and

an alternate warm air source from inside the cowling. This ac-

the takeoff distance at this density altitude will be 2.3 times the

counts for an average 3A power drop because of the loss ofsea level takeoff roll shown in his Pilot’s Operating Handbook.

ram air. The major portion of the engine power loss is caused If the same pilot flew to Laramie, Wyoming for the next

by the carbuntor heat or alternate air heat. Aircraft engines are landing and subsequent takeoff he might meet these typicalchecked for their horsepower output in a test cell or in flight flight conditions:

with a pncision torquemeter at a corrected standard temperature The field elevation is 7,276 ft., and with an ambientof 590 F. Engineering has provided a simple rule of thumb for temperatun of 600 F, his actual density altitude will be 9.300the effect of heat on power, i. e. for every 100 F ofheat above ft., with a takeoff roll 2.9 times the sea level takeoff. Furthtr-the standard 590 F, there is a 1 4% power loss. Since the average more, the pilot must remember-the higher the ambienthear source on an engine provides at least 1000 F ofheat above temperatue indicates, the higher the density altitude becomes.standard. this heat condition causes an avenge power loss of At this elevation, the pilot ofnormally aspirated aircraft engines109E. Our measurable total power loss at ´•sea level, standard should consider takeoffs in tbe cool temperatures of early morn-conditions is alnady up to 13%. ing or evening hours, rather than during the hot hours of the dar.

When warm air is used by the pilot, the mixture becomes Summing up the specific flight conditionjust discussed, thericher and the engine may roughen with a~iother slight power pilot must remember--when the temperature becomes higherloss as a result. In addition, the higher the altitude with its less than standard (590 Fl, the density of the air is reduced anddense air, the gnater the enriching effect because the fuel meter-

ing device will become richer at altitude and the engine lessaerodynamically affects overall airplane performance. The

horsepower output of the engine Is decreased because its fucl-efficient. Thus, there will be another small, difficult to measure, air mixture intake is reduced. The propeller develops less thrustpower loss to be added to the 1396 loss already accumulated. because the blades are less efficient. The wings develop less

Most float-type carburetors react very sluggishly or ineffi- lift, because the less dense atmosphere exerts less force on theciently on a straight-arm throttle technique during a touch-and- wings as airfoils. As a result, the takeoff distance is incnasedgo landing or an aborted landing with full carburetor heat. In and the climb performance reduced.some cases, the float-type carbuntor has refused to accept the In order to cope with high elevation airport takeoffs withthrottle when the abrupt straight-arm technique was used, normally aspirated engines, whenever the density altitude is

We should also remind the pilot that when he uses car- 5,000 ft. or higher, the pilot must compensate on the groundburetor heat or alternate air heat at cruise power that he should before takeoff. With a diner drive engine and a fixed pitch pro-adjust his mixtnn lean, otherwise he will have a rich mixture. peller, run the engine up to takeoff RPM and lean the mixtureIf the heat causes an undesirable power loss at cruise, and the until a maximum RPM is noted; leave mixture at that positionpilot has throttle available, hemay bring the manifold pressure and accomplish the takeoff. If the eneine has a governor, run

up at least to the power reading he had befon application of it up to takeoff RPM and then lean ~ntii the engine smoothsheat: and if additional power is needed and available, he may out and gives the indication of maximum power. At 5,000 ft.add a maximum of two inches of MP, or 100 RPM (f~ted pitch density-altitude or higher, the available horsepower has beenprop) above the previous power. and then adjust the mixture. reduced so that leaning as described will not damage a healthy

Engine. If an EGT system is available, lean to 1000 F on the engines the leakage can be detected by observing fuel dyerich side of peak EGT on a direct drive normally aspirated evidence at the leakage area. Any time this condition is

Lycoming engine, discovered, it must be remedied before the aircraft is flown

All turbocharged or supercharged engines must use full rich again.for takeoff at any elevation airport. This includes either manual- In those engines using a carburetor, we have observed

ly operated turbos or the automatic type. power loss effects from wont air boxes where the carburetor

heat flapper valve in the air box remains partly open. WhenIGNITION SYSTEM POWER ROBBERS the outside air temperature is above 590 F, this malfunction can

There are several possibilities whereby the ignition system create a sneaky power loss, particularly at higher than cruise

can be the cause of power loss in the engine. We have, for ex- power.

ample, measured a power loss ofapproximately 3 4% with a singleBLOW-BY AND COMPRESSION LOSS

dead magneto or running on one mag. Ln fixed wing aircraft,if the pilot lost a magneto in flight it might not be a serious Another power loss condition is that of blow-by or oil

situation to complete the flight safely provided other power rob- blowing by the piston rings and getting into the combustion

bets didn’t begin to add to the problem. But in the case of the chamber in more than desirable amounts. It occurs with broken

rotor wing aircraft it could be serious during takeoff, hover or or worn piston rings, scored cylinder walls, and bell-mouthed

landing because there are the regular unusual inro~ds on powerexhaust valve guides. Oil in the combustion chamber tends to

such as operation of the tail rotor, the cooling fan, the foul spark plugs and reduce their efficiency. It also lowers the

generator or alternator, the transmission, and also power loss octane rating of the fuel and tends to cause a loss of power,

from any excessive rotor blade trim tab position beyond the particularly at takeoff or climb. If the engine is not close to its

manufactu~rers recommendation. Therefore, magneto normal overhaul life, then a top overhaul would be in order if

maintenance really is a critical item on ro~jr wing aircraft. more than one cylinder showed this condition.

Other power loss influences in the ignition system include Power loss from valve leakage may not be noticeable in

wlorn or fouled spark plugs which tend to provide a weak spark, flight to the pilot. If an exhaust valve becomes burned and

Likewise, deteriorated magneto points will have some powerdeteriorated at the edge of the head, it may cause an engine miss

loss influence. We have also learned thsdifficult way that old, in flight. But leaking intake valves are difficult to detect duringworn or cracked (insulation) ignition harnesses can cause a loss flight. The latter either get irregularly seated and cause a com-

of power, particularly at altitude. If this is suspected, it can be pression loss, or they can also cause a loss if they get Nlipedchecked by means of a harness tester. from pre-ignition. A good differential compression check will

pick up most of these discrepancies except for some occasionsWe know that magneto timing, either early or late, has a

of broken rings. However, any oil in the combustion chamberdetrimental influence on power. Sound maintenance can

from broken rings would, in addition, call for a visual inspec-eliminate these problems. But coming back to spark plugs, thetion with a boroscope or a gooseneck light.

correct plug is most important for efficient engine operation,and Textron Lycoming Service Instruction 1042 is the official SUMMARY:

reference source. Maintenance must also be careful that long We can’t list all the many power robbing factors here, butreach plugs are used only in those cylinders designated by an

we have tried to list the important ones, along with recommen-

area of yellow paint in the fin area between the spark plug anddations on how to cope with them. Again we want to remind

rocker box. Cylinders designed for short reach plugs may be all concerned of the dangerous difference between an engineeither grey, blue or unpainted in this area. If the wrong length problem where both spark plugs fail to fire in a cylinder, whichplug is used in the cylinder, it will cause a loss of power and

is immediately obvious as compared with the small power lossperhaps pre-ignition or detonation.

problem which is not as obvious. The power thieves take powerChampion Spark Plug Company published a bulletin f~ve away in small quantities per cylinder until several of them hap-

years ago warning that one dirty cigarette or contaminated plug pen to occur at the same time, reaching serious proportions and

barrel can rob an aircraft engine of two horsepower every a definite unsafe flight condition. Be aware--don’t become a

takeoff. When dirt and moisture are allowed to accumulate on victim of power thieves!the harness terminal (cigarene) or spark plug barrel insulator,connector well flashover can occur resulting in plug misfire.

The high voltage current will take the easy path to ground ratherWet Air Effect On Engine Power

than spark between the firing-end electrode gap. Cigarettes,harness terminals, seals, and spark plug barrels should be kept

The FAA has published a pamphlet entitled "Wet Air",clean and dry. When cigarettes are clean, do not touch them

which enlightens the pilot concerning this potential danger toas the moisture on fingers is enough to contaminate them again.

engine power. Scientists state that we can dismiss any ap-Replacing these parts and pieces at reasonable periods is inex-preciable effect of dampness in the air on the efficiency of the

pensive insurance against the power thieves. When the latterwing in lifting and the propeller in thrusting. But (they statel.

are at work, sharp performance and economy are lost.the effect ofwater vapor or high humidity on engine power out-

INDUCTION SYSTEM LEAKS put can be significant, and should be taken into consideration

If the intake pipes are loose at either end, leakage will take when planning takeoffs in muggy or high humidity weather.

place which tends to lean the mixture and cause a power loss. The pamphlet explains the power loss by pointing out the

It could be critical in the takeoff or climb power ranges. In most fact that with water vapor present there is less air entenng the

engine. Secondly, this creates an excessive enrichment because Throttle Jockeying Bad Techniquethe fuel amount is the same, but the amount of air is less. Fur-

thermore, the water vapor slows the burning which slightly af- Does Throttle Jockeying, i. e., rapid movement of throttlefccts power, but offers no cooling value to the engine, from low to high power settings, have an affect on spark plug

FAA recommends a rough rule of thumb is to keep high operations? It certainly does and here’s how.

moisture content in mind, and suggests the pilot consult his air- The deposits formed on spark plugs during extended idlecraft owner’s handbook for takeoff distances, and add another or low power settings are electrically conductive to some ex-

10 percent for the possible effects of engine power loss due to tent. However, sudden elevations of temperatures cause themwater vapor on a muggy day. The pilot can easily identify a to change chemically through stages to increasingly higher elec-high water vapor condition by the muggy, hot, sticky feeling trically conductive compounds. Misfiring then can occur if thein this kind of weather. The higher the ambient temperature, gaps become bridged or the material covers a sufficient area

the greater the water vapor content in the air; i. e. at 960 of the insulator nose.

F, the water vapor content will be eight times as great as at 420 Low temperature carbon deposits formed on spark plugsF. The writeup also states that the effect ofwater vapor on super- during idle or low power can normally be removed by perform-charged piston and fuel injection engines is subsanh’allv the same ing a proper engine "burn-out". This is accomplished by slowlyas the effect on other piston engines. "Fuel injection systems opening the throttle until full power is achieved. Should misfiremeter fuel on the basis of a given volume of gas entering the

occur during power application, decrease power slightly untilcombustion chamber, whether the gas is air or water vapor, just all plugs fire consistently for approximately 15 to 30 seconds,as the carburetor does. It cannot discriminate between com-

bustibles and non-combustibles."and again slowly open the throttle until full power capabilityhas been achieved.

Pilots be alert to the effect of wet air arrthe performanceof your engine. DISCOURAGE THROTTLE JOCKEYING AND GET

BETTER PLUG AND ENGINE PERFORMANCE!

(Courtesy of Champion Spark Plug)

Frequency Of Flight And Its

Effect On The Engine A Daily Engine Prefiight Checklist

We have firm evidence that engines not flown frequently I. FUEL look for signs of fuel dye which means leaks,

may not achieve the normal expected overhaul life. Engines check amount of fuel, drain for water.

flown only occasionally deteriorate much more rapidly than 2. OIL check for leaks, check oil level.

those which fly consistently. Pilots have asked What really 3. EXHAUST SYSTEM check for white stains which are

happens to an engine when it’s flown only one or two times exhaust leaks at the cylinder head or cracks in stacks, checkper month? An aircraft engine flown this infrequently tends to condition of heat muffs for cracks or leaks.accumulate rust and corrosion internally. This rust and corro- 4. COWLING AND BAFFLES check for cracks in cowl-sion is often found when an engine is torn down. Some operators ing and baffles, check for proper position ofbaffles, secureare running the engines on the ground in an attempt to prevent cowling fasteners.rust between infrequent flights. This may harm rather than helpthe engine if the oil temperature is not brought up to approx-

5. AIR FILTER good tight fit, good condition.

imately 1650 F, because water and acids from combustion will 6. ANYTHING LOOSE OR UNATTACHED wires or

accumulate in the engine oil. The one best way to get oil lines, fuel pump, bird’s nests, rags, etc.

temperature to 1650 F is fly the aircraft, for during flight the The average pilot is not sure what he is looking for whenoil gets hot enough to vaporize the water and most acids and he lifts the cowling to do a daily preflight. He can easilyeliminate them from the oil. If the engine is merely ground run, memorize the six items just listed, which will serve as a helpfulthe water accumulated in the oil will gradually turn to acid, guide.which is also undesirable. Prolonged ground running in an at-

tempt to bring oil temperature up is not recommended because

of inadequate cooling which may result in hot spots in the

cylinders, or baked and deteriorated ignition harness, and brit-

tie oil seals causing oil leaks. If the engine can’t be flown, then SPECIAL NOTEmerely pull it through by hand or briefly turn the engine with

the starter to coat the critical parts with oil. If the engine is flownin each issue of the Flyer we have listed all the

so infrequently that it does not accumulate the operating hoursLycoming Service Bulletins, Service Instruc-

which recommend an oil change (25 hours for a perssure screentions, and Service Letters which have been printed

system and 50 hours for a full-flow filter system), then the oilsince the previous Flyer. Concerned operators should

should be changed at four month intervals to eliminate waterretain this listing for their reference and utilize it

and acids, consistently.

Spark Plug Fouling 9. Swap top and bottom spark plugs every 25 to 50 hours.

Top plugs scavenge better than bottom.

Spark plug fouling in ~our aircraft engine may be a prob- 10. After flight or ground operations and before shut down.Iem. It is desirable to reduce the problem as much as

go to 1800 RPM for 15 to 20 seconds, reduce to 1200 RPM,possible. Textron Lycoming Service Letter L192 provides in- then shut engine off immediately with mixture control."formation which may be very helpful in reducing spark plugfouling. To aid our readers, the entire text of Service Letter

L192 is printed here: Test Your Knowledge On Engines"In many cases spark plug fouling resulting from the Check your knowledge of aircraft engines with the ques-

tetraethyl lead (TEL) in aviation fuels can be reduced or tions below.

eliminated by proper operation techniques. A. Multiple Choice. Circle the one best answer.

The problem of lead fouling arises when low engine i. In comparison to fuel injection systems, float-type car-

operating temperatures coupled with a rich mixture prevent the buretor systems are generally considered to becomplete vaporization of the TEL. Under these conditions, lead

(a) equally susceptible to icing as a fuel injection unit.deposits can form in the combustion chamber and may adhere

to the spark plug electrodes, causing misfiring. By establishing (b) less susceptible to icing than a fuel injection unit.

and maintaining proper engine operating temperatures, the TEL (c) susceptible to icing only when visible moisture is

can be kept properly vaporized and pass out the exhaust system. present.

For operators experiencing lead fouling, the following (d) more susceptible to icing that a fuel injection unit.

operating recommendations are made: 2. The basic purpose ofadjusting the fuel/air mixture control

at altitude is toi. By use of the spark plug recommendation charts, be cer-

(a) increase the fuel/air ratio for flying at altitude.tain the proper plugs are installed. Do not simply replacethe same part number of those removed. A previous (b) decrease the fuel flow in order to compensate for

mechanic may have installed the wrong plugs. Reference decreased air denisty.

Service Instruction No. 1042. (c) increase the amount of fuel in the mixture to com-

2. Do not accept an over rich carburetor or fuel injector atpensate for the decrease in pressure and density of

the air.idle or off idle engine speeds. Have a mechanic adjustmixture. (6) decrease the amount of fUel in the mixture in order

to compensate for increased air density.3. After a flooded start, slowly run the engine to high power

to burn off harmful lead deposits, then return the engine3. if the engine of an airplane is permitted to idle for a long

to normal power.period of time while on the ground,

(a) a hydraulic lock may develop in one or more4. When parked for any reason, avoid closed throttle idle.

cylinders.Set engine at 1200 RPM. The fuel contains a lead scaveng-

ing agent but it only functions with a spark plug nose core(b) the lean mixture may cause the engine to miss or quit.

tcmperamre at 8000 F or higher. To have a minimum of (c) the result may be an excessively high oil pressure.

8000 F nose core temperature you must have a minimum (d) the spark plugs may become fouled.

of 1200 engine RPM. Also, the engine will run cooler and 4. Assume that on your runup at an airport where the eleva-smoother and the alternator/generator will have more out- tion is 6,000 feet MSL, you note a slight engine roughnessput at 1200 RPM. (Taxlmg is exempt. Use the minimum that is not significantly affected by the magneto check but

required RPM.) grows worse during the carburetor heat check. Under these

5. Use normal recommended leaning technique at cruise condi- circumstances, which of the following would be your most

tions regardless of altitude and re-lean the mixture with logical initial action?

application of alternate air or carburetor heat. If aircraft (a) check to see that the mixture control is in the full rich

is used as a trainer, schedule cross country operation position.whenever possible. (b) reduce manifold pressure to control detonation.

6. Avoid fast, low power let down from altitude whenever (c) check the results obtained with a leaner setting of the

possible. Plan ahead. Descend with power. (Avoid over mixture control.

rich conditions.) (d) taxi back to the flight line for a maintenance check.

7. Avoid closed throttle landing approaches whenever pos- 5. With regard to the use of aviation gasoline, which state-

sible. Use a slight amount ofpower. Remember carburetors ment is true?

and fuel injectors are set slightly rich at closed throttle. (a) use of a lower-than-specified grade of fuel may result

8. Keep engine operating temperature in the normal operatingin a reduced power output but is usually less harmful

range. Too many people think the lower the temperaturesthan higher rated fuel.

the better. Keep cylinder head temperatures in normal (b) use of the next higher-than-specified grade of fuel

operating range by use of normal power and proper iean- is permissible if the specificed grade of fuel is not

ing and use oil cooler baffles to keep oil temperature upavailable.

in winter.

(c) use of the next lower-than-specified grade of fuel is greater with full power or maximum power available

permissible if_the specified grade of fuel is not for climb.

available. (c) Using less than 10096 power for takeoff and cruising(d) use of a higher-than-specified grade of fuel usually at 755% power or below.

results in lower-than-normal cylinder head (d) Running the engine at 1200 RPM for at least twentytemperatures. minutes before the first take off of the day.

6. If the grade of fuel used in an aircraft engine is lower than 12. The full flow oil filter is very useful in keeping an enginespecified for the engine, it will most likely cause clean, but it will not filter out-

(a) an increase in power which could overstress internal (a) Water

engine components. (b) Acids66) detonation.

(9) Leadsludge(9) lower cylinder head temperan~res. (d) Alloftheabove

(d) a non-uniform mixture of fuel and air in the cylinders.13. For aircraft with an EGT gage, a good "rule of

7. Which statement is true regarding aircraft engines that are thumb" for most general aviation engines at cruise is to

equipped with a fuel injection system instead of a lean to-carburetor?

(a) 500 on lean side of peak EGT.(a) vapor locks during ground operations on hot days are

less apt to occur with fuel injection. (b) PeakEGT.

(b) a disadvantage of fuel injection is the difficulty (c) 500 on rich side of peak EGT.

experienced in cold weather starting. (d) 1000 on rich side of peak EGT.

(c) slow throttle response is one of the disadvantages of 14. With high relative humidity carburetor icing may be ex-

fuel injection, pected within which of the following rangcs--

(d) fuel injection provides better fuel management and fuel (a). 320to590F

distribution to the engine. (b) 00to150F

8. The presence of carburetor ice, in an airplane equipped with 69) 200to90oF

a fixed-pitch propeller, can be verified by applying car- (d) 00to590Fburetor heat and noting

15. An aircraft engine which develops less and less power from(a) a decrease in RPM and then a gradual increase in

the point of takeoff to the service ceding is said to be-RPM.

(b) a decrease in RPM and then a constant RPM(a) Supercharged

indication. Normally aspirated

(c) an immediate increase in RPM with no further change (9) Turbocharged

in RPM. (d) Supercritical

(d) an increase in RPM and then a gradual decrease in 16. If full carburetor heat is used during cruise for the preven-RPM. tion of carburetor ice, some of the 1596 of power loss

9, If the engine oil temperature and cylinder head temperature incurred may be regained by-

gauges have exceeded their normal operating range, (a) Enriching the mixture.

you may have been (b) Squaring the power setting.(a) operating with higher-than-normal oil pressure. (c) Applying one pump of the primer every 15 minutes.

(b) using fuel that has a higher-than-specified fuel rating. (d) Leaning the mixture.

(C) operating with too much power and with the mixture 17. The final authority regarding operation of the general avia-set too lean. tion aircraft engine is

(d) operating with the mixture set too rich. (a) Engine operator’s manual provided by the engine10. What change occurs in the fueyair mixture when carburetor manufacturer.

heat is applied? (b) Pilot’s operating handbook provided by the airframe

(a) the fuel/air mixture becomes leaner, manufacturer.

66) the fuel/air mixture becomes richer. (c) Aviation circulars distributed by the FAA.

(C) no change occurs in the fuel/air mixture. (d) Your local fixed base operator.

(d) a decrease in RPM results from the lean mixture. 18. Use of partial heat to prevent carburetor icing is recom-

11. For maximum engine life and trouble-free operation, engine mended only if the aircraft has-

break-in during the first 25 to 50 hours of engine opera- (a) A carburetor air temperature gage CAT.

tion should be accomplished by: (b) A cylinder head temperature gage CHT.

(a) Limiting takeoff power to five minutes per flight and(c) An exhaust gas temperature gage EGT.

using 65% power maximum for cruise.(d) An outside air temperature gage OAT.

(b) Runnmg the engine continuously at 75% power or

B. Supply the best answer to the following essay questions: 8. Damage to an engine from leaning takes place at higher1. Explain why aerobatics or inverted flight should not be than recommended cruise power as detonation where an

attempted unless the engine has been modified for this typeaircraft does not have the necessary engine instruments to

flying. indicate the powerplant is being abused.

2. List two purposes of engine oil. 9. Requires proper leaning for safest, efficient performanceat takeoff.

3. What are the two FAA approved oils for general aviation?

4. When operating at the manufacturers’ recommended cruise 10. Two types of induction ice:

power, at what altitudes may leaning be accomplished? (a) impact ice typically on the air filter.

5, Of what significance is the 5,000 ft. density altitude (b) Refrigeration ice forms in the float-type carburetor.

reference point for normally aspirated engines?6. What causes engine roughness when leaning an engine us-

ing a float-type carburetor at recommended cruise power?7. The Exhaust Gas Temperature (EGT) system is more

Lest We Forgetprecise as a fuel management instrument with which of the The Engine Will Not Run Without Airfollowing?(a) Float-type carburetor. The gasoline engine operates on a fuel/air mixture which

(b) Fuel injection. is ignited by the spark plugs. Engines do not run when any of

8. How can damage to an engine take place as a result of these elements are missing. Pilots ~ow positively that they must

leaning? refuel the aircraft on a regular basis if they want to fly without

incident, but the possibility of losing the air part of the fuel/air9. What important consideration by the pilot for his engine mixture is not always considered and understood as well as it_

must take place with a normally aspirated engine at airports should be. Perhaps the personal experience ofseveral individualswhere the density altitude is 5,000 feet or higher?

can be used to help FIyer readers avoid an accident caused by10, List two types of induction ice.

_

lack of air for their engine.Remember that any material which reduces or cuts off the

ANSWERS TO QUESTIONS flow of air in the induction system has the potential to cause

A, MULTIPLE CHOICE RESPONSE a loss ofpower. A material failure of the air filter is one prob-

i. d 10i blem which is reported all too often. The filter is very necessary

2. b 11. bto keep dirt out of the engine; it must be inspected frequently

3. d 12.- dand should be changed on some regular schedule. A filter which

4. 13.is several years old and has filtered the air during hundreds of

5. b 14.hours ofoperation may be tired. One pilot reported that on turn

6. b 15. b up of the engine before takeoff, he could not get the static RPM

7. d 16. dwhich his engine and fixed pitch propeller should have produced.

8. a 17. bHe wisely elected to return to the line and have the engine in-

9. c 18. spected. The air filter had pulled loose from its supporting frame

and was lodged in the intake system where it was cutting off‘

B. ESSAY RESPONSEthe air supply.

If this incident had occurred in flight, the engine would1 Loss ofengine oil out the breather can cause engine damage

or failure. possibly not have been producing enough power to maintain

altitude. Depending on the particular airframe, there are some

2. (a) Lubricate moving parts. options which might be utilized to regain some of the lost power.

(b) Aid internal cooling of the engine. An alternate air system or carburetor heat system is designed

3. (a) Straight mineral, into the induction system primarily to combat induction icing,but use of these systems may possibly help when intake air is

(b) Ashless Dispersant.blocked by other foreign materials. In some cases, just leaning

4, At any altitude. the mixture may help to regain a little of the lost power.5. It is a climb reference point for normally aspirated power- Several years ago there was a reported loss of engine power

plants. Climb from sea level through 5,000 ft. (some in heavy rain. In that case, a paper air filter was being used.Cessna’s may use 3,000 ft.) should be full rich. Continued When saturated with water, the paper filter element becameclimb beyond (3,000 ft.) 5,000 ft. should use some lean- swollen so that airflow was impeded. In this case, the use ofing to improve engine efficiency. carburetor heat to bypass the filter and releaning to achieve a

5. The roughness is not detonation at recommended cruise better fuel/air mixture were successful tactics which kept the

power, The leanest cylinder in the less than perfect distribu- aircraft flying until a safe, on airport landing could be made.

tion pattern is cutting out. Operation in the roughness area We should keep in mind that it is not the ingestion of water

is not acceptable, through the engine which causes a serious loss of power; It is

7. Ib) fuel injection. the reduced airflow.

Some pilots of aircraft which utilize a fuel injected engine Next, it is imperative that the pilot recognize carburetorbelieve that this engine_makes them immune to induction ic- ice when it forms during flight. The loss of power which oc-

ing. This is not so. As an example, the pilot of a fuel injected curs will cause a reduction of RPM when flying with a fixedsingle reported flying at 11,000 feet in light drizzle. The pitch propeller and a loss of manifold pressure when a con-

temperature was slightly above freezing and water readily ran trollable pitch propeller is used. In either case, a loss of altitudeoff the windscreen. Although this would seem to be a no prob- or airspeed will occur. It is a good idea to consider carburetorIcm situation, the engine started to lose power. After considera- ice as the cause of any small unexplained power loss duringtion of the available options, the manual alternate air system cruise flight.was activated. The engine immediately regained the lost power Once a power loss is noticed by the pilot, immediate ac-and flight was continued to the home base destination. After tion should´•be taken to eliminate ice which has already formedlanding, the aircraft was taken into the hanger for examination. in the carburetor and to prevent further ice formation. This isIt was found that the air filter was covered with a layer of ice accomplished by applying full carburetor heat which will cause

which had cut off the airflow. This is not an isolated or unusual a further loss of power and, possibly, engine roughness. Thecase. When water is near freezing, movement of the water additional power loss is caused by the heated air which is be-molecules may sometimes cause instantaneous freezing. This ing directed into the induction system. Heated air makes theglazing over of the air filter is a I~nown phenomena which pilots mixture richer and also melts the ice which goes through theshould be expect and be ready to cope with. Again, bypassing engine as water. The throttle may be advanced and the mixturethe blockage by use of alternate air proved to be a successful may be leaned to help get some of the lost power back, but im-tatic for this pilot, mediately after the application of carburetor heat the pilot must

The most subtle and insidious of the airflow blockage be patient and keep the airplane flying until the ice has com-

po~sibilmes is probably carburetor ice. Unfortunately, there are pletely melted and normal power returns. How long this will

many pilots who are not fully aware of what carburetor ice cantake depends on the severity of the icing, but the pilot should

do or what to do about it when it does occur. An indication expect a delay of30 seconds to several minutes. Under the cir-

of this are statements made by pilots involved in power loss cumstances, this period of time will always seem longer than

accidents who have said that they tried carburetor heat, found it really is.

it did not work, and then returned the control to the cold posi- Although carburetor heat is not recommended for takeoff

tion. Carburetor heat does not provide instant relief when ap- and climb, It may be used continuously to prevent the forma-

plied after ice has formed in the carburetor. Once heat is ap- tion of carburetor ice during flight at cruis power. It is also ap-

plied, it should be left on until power returns. propriate to use full carburetor heat, if needed, to prevent ic-

Every pilot who flies an aircraft powered by a carbureteding when operating at low power for instrument approaches or

engine should be thoroughly educated about carburetor ice. Theyfor flight in the traffic pattern. An intermediate position of the

should know that undermoist conditions (a relative humiditycarburetor heat control should only be used in aircraft which

of 50% to 6096 is moist enough), carburetor ice can form withhave a carburetor air temperature (CAT) gage; with no CAT

any air temperature from 200 to 900F. It is most likely in the gage, only full cold or full hot should be selected.

300 to M)O range. Temperatures in the carburetor can drop 600 A review of the material discussed in this article should

to 700F as a result of fuel vaporization and the carburetor ven- help pilots to cope with reduction of engine power when it is

turi effect. It also happens that carburetor ice forms more readily caused by loss of intake air for combustion. A thoroughwhen the engine is operated at the lower power settings. It will understanding of the air intake system and the knowledge to

form while taxiing and this makes it very important to check complently deal with induction icing are essential to safe flightengine power before takeoff and to remove the ice if necessary,

in general aviation aircraft. Pilots are encouraged to enhance

Care should be taken to avoid dust or dirty conditions when the safety of their flying by knowning what to expect and what

utilizing carburetor heat on the ground. steps to take when the air flow to the engine is cut off for anyreason.

PAINTENANCE

INSPECTIONS

FAR 91.169 establishes minimum requirements pertainingMechanic’s Creed to annual and 100-hour inspections. Not only does the FAA re-

quire these inspections, but they stipulate that the owner/operatorUPON MY HONOR I swear that I shall hold in must maintain the airworthiness of the aircraft and engine dur-

sacred trust the rights and privileges conferred upon ing the time between the required inspections by having anyme as a certified mechanic. Knowing full well that the airworthiness defects corrected. Although maintenance re-

safety and lives of others are dependent upon my skill quirements will vary for different types of aircraft, the FAA

and judgment, I shall never knowingly subject others states that experience shows most aircraft will need some typeto risks which I would not be willing to assume for ofpreventive maintenance every 25 hours flying time, and minor

myself, or for those dear to me, maintenance at least every 100 hours.

IN DISCHARGING this trust, I pledge myself ANNUAL INSPECTION

never to undertake work or approve work which I feel

to be beyond the limits of my l(nowledge; nor shallThis inspection must be performed within the preceding 12

I allow any non-certified superior to persuade me tocalendar months, by either a certified A P mechanic holding

approve aircraft or equipment as airworthy against myan inspection authorization, an appropriately rated certified

better judgment; nor shall I permit my judgment torepair station, or the manufacturer of the aircraft.

be influenced by money or other personal gain; nor100-HOUR INSPECI?ONshall I pass as airworthy aircraft or equipment about

which I am in doubt, either as a result of direct in- An aircraft used to carry passengers for hire, or for flightspection or uncertainty regarding the ability of others instruction for hire, must be inspected within each 100 hourswho have worked on it to accomplish their work of time in service by either a certified A P mechanic, an ap-satisfactorily. propriately rated certificated repair station, or the manufacturer.

The annual inspection is acceptable as a 100´•hour inspection,butI REALIZE the grave responsibility which is mine the reverse is not true.

as a certified airman, to exercise my judgement on the

airworthiness of aircraft and equipment. I, therefore, DAILY AND PREFLIGHT INSPECTION

pledge unyielding adherence to these precepts for the

advancement of aviation and for the dignity of myThe owner/operator may conduct a daily inspection, if so

vocation, desired, but the pilot must perform a satisfactory preaieht in-

spection before flight (FAR 91.5).

AIRWORTHINESS DIRECTNES

Airworthiness Directives, commonly referred to as "AD

The Basics Of Maintenance In Notes’’, provide aircraft owners with information of unsafe con-

ditions. The AD’s specify the aircraft or component found toGeneral Aviation be unsafe by the FAA, and the conditions, limitations, or in-

spections, if any, under which the aircraft may continue to beEven the "pros" of our industry admit they need to be operated.

reminded from time to time of the basics of General Aviation

maintenance. Therefore to review, the term maintenance means The Federal Aviation Regulation require a presentationthe inspection, overhaul, repair, upkeep, and preservation of showing the current status of applicable airworthiness directives,an aircraft and engine, including the replacement of parts, ac- including the method of compliance, and the signature and cer-

cording to the FAA. The owner/operator is responsible for the tificate number of the mechanic or repair agency who compliedproper maintenance ofhis aircraft and engine. The pilot in com- with the AD.mand of an airplane is responsible for:

i. Maintaining his airplane in an airworthy condition. It is the aircraft owner/operator’s mandatory responsibili-ty to assure compliance with ail pertinent AD notes. This in-

2. Having a Registration Certificate and a valid Airworthi- eludes those AD’s of a recurrent or repetive nature; for exam-

ness Certificate appropriately displayed in his aircraft pie, an AD may require a certain inspection every 100 hours.during all operations. This means that the particular inspection shall be made and

3. Having available in the aircraft an FAA approved flightrecorded every 100 hours of flight time.

manual, or operational limitations.MANUFACTURER’S SERVICE BULLETINS

4. Assuring that maintenance is properly recorded in the

aircraft records. The FAA states that whenever an aircraft or enginemanufacturer determines, through service experience, that his

5. Keeping abreast of current regulations concerning the product may be improved by some modification, or that the ser-

operation and maintenance of his airplane and engine. vice life of his product may be extended by some particular

maintenance or repair, he may issue a service bulletin. The lat- Ask About Reference Publicationster will tell what the troubl~is and how to remedy it. The ser- Before Your Engine Is Taken Apartvice bulletin is technically not mandatory unless compliance is

made mandatory by an FAA Airworthiness Directive; however, People who fly should be concerned about the reliabilitywhere the service bulletin has a time limit requirement for com- of the aircraft they fly and the engine which powers that air-

pliance it virtually becomes mandatory. craft. One key to reliability is regular maintenance by a

In addition to service bulletins, Textron Lycoming also knowledgeable A P mechanic. "Knowledgeabie" does not

publishes service instructions and service letters. A service in- necessarily mean the mechanic must have every detail ofevery

struction is product information with which Lycoming definitely job locked in his (or her) memory. It does mean that the in-

recommends compliance. The service letter at Lycoming is prod- dividual should have relevant information readily available and

uct information which can be optional to the pilot/owner. be able to refer to it as needed.

What has been stated above is not just good common sense,

PREVENTIVE MAINTENANCE it is the law. Aviation mechanics are licensed (certified in avia-

Preventive maintenance means simple or minor preserva-tion terms) under Part 65 of the Code of Federal Air Regula-tions (FAR). FAR 65.81 (b) states: "A certificated mechanic

tion operations and the replacement ofsmall standard parts not

involving complex assembly operations. The holder of a pilot may not exercise the privileges ofhis certificate and rating unless

he understands the current instructions of the manufacturer, andcertificate issued under PAR 61 may perform preventivemaintenance on any aircraft owned or operated by him that is

the maintenance manuals, for the specific operation concern-

not used in air carrier service or air taxi. All other maintenance,ed." Is it possible for anyone to understand current instructions

or maintenance manuals if they are not available for reference’!repairs, rebuilding or alternations must be performed by per-

sons authorized to do so by the FAA. The point which a concerned pilot owner should be think-

ing about is this--does my A P mechanic or maintenance shopExcept as noted under "Preventive Maintenance", all

have appropriate maintenance publications available forrcp~airs and alterations are classed as either Major or Minor.

reference? While many maintenance activities do maintain a

Major repairs or alterations must be approved and returned togood reference library, others certainly do not. This can be easi-

service by an appropriately rated certified repair facility, anly determined from the questions which are asked of Lycom-

A P mechanic holding an inspection Authorization, or aing service representatives who continuously respond to phone

representative of the FAA. Minor repairs and alterations may calls for help. While the service personnel are available to pro-be returned to service by an appropriately rated certified

vide help when troubleshooting does not readily reveal theA P mechanic or repair facility,

source of, or solution to, a problem, their time is being wasted

when they are asked to dig out information for a mechanic whoPROGRESSIVE MAINTENANCE

has not made the effort to acquire required reference materials.

This is a continuous maintenance progam whereby the re- Without these reference materials, the quality of maintenance

quired FAA and manufacturer inspections are accomplished dur- is open to question.ing the most convenient time, while keeping the aircraft in a How can publications which apply to Lycomingstate of continuous airworthiness. reciprocating engines be obtained--and which ones are need-

Several General Aviation airframe manufacturers have ed? Starting with the last question, an Operator’s Manual should

established sound Progressive Maintenance programs with FAA have enough information to satisfy the needs of the engine owner

approval. Owners and operators are reminded that certain FAA or pilot. For the maintenance person, what is needed depends

requirements must be met before a Progressive Maintenance on the depth of maintenance to be performed and the particular

program can be used. These requirements are contained in the engine models to be maintained. Once these items have been

Federal Aviation regulations, Part 43, "Maintenance, Preven- determined, the latest revision of Textron Lycoming Service

tive Maintenance, Rebuilding and Alteration", and Part 91, Letter No. L114 is a guide to all service publications which are

"General Operating and Flight Rules". available for sale. It lists Lycoming Parts Catalogs and Overhaul

Manuals which provide much of the information needed for ma-

The Progressive Maintenance program has had more ap- jor work on Lycoming reciprocating aircraft engines. Sptcializ-peal where planes for hire are involved (i. e., commuter, air ed procedures and amplifying information are provided from

taxi, flight instruction), rather than the private owner. time to time in the form of bulletins, letters, and instructions.

These publications serve as supplements to the OverhaulAIRCRAFT FLIGHT TEST AFTER Manual. Without these publications to provide the latest data

REPAIR OR ALTERATION published by the manufacturer, the A P mechanic may not

be reminded of a required inspection, or may be unaware ofThe FAA reminds us that whenever a repair or alteration

a new and helpful maintenance technique.has been made to your aircraft or engine, the person author-

ized to return the aircraft to service should decide if a flight Service Bulletins are manufacturer publications which could

test is necessary. If the decision is affirmative, the aircraft must possibly affect safety of flight. Therefore, a bulletin is con-

be flight tested after repair or alteration before it may be used sidered by the manufacturer to be mandatory. In some cases,

to carry passengers in accordance with FAR 91.167. The test a bulletin will become the subject of an FAA Airworthiness

pilot must log the findings of the test flight in the aircraft or Directive (AD). The AD gets broad distribution to aircraft

engine record, or maintenance record, owners and is mandatory by law. Therefore. a subject which

is covered by both a bulletin and an AD is much more likely overhauled engines, some small particles of metallic shavingsto receive attention, might be found, but these are not dangerous. The oil filter does

Other more routine items of maintenance also requires anot remove water, acids, or lead sludge of combustion from

reference. When changing spark plugs, for example, a copy of the oil.

Lycoming Service Instruction No. 1042 provides a listing of The oil filter is even more important to the high compres-recommended and approved spark plugs for each engine model. sion or higher power engine. Some of the aircraft manufacturers

Use of this reference will insure that the correct plugs are used. have had good success in the small, lower compression, four

cylinder engines without using a full flow filter. GenerailvThere is a message here which aircraft owners should con-

sider. Qaulity of maintenance cannot always be detennined speaking, these engines are also able to achieve their expectedbeforehand, but the chances for good quality will cenainly be

overhaul life; as long as oil is consistently changed, and opera-

better when adequate reference materials are available. The ideation and maintenance is accomplished in accordance with the

ofsimply asking what reference materials are available in yourairframe and engine manufacturers recommendations.

mechanics reference library would seem to be a good one. It Pilots and mechanics should know what weight, type, and

will encourage the mechanic or maintenance activity to acquire brand ofoil is being used in the engine being serviced. At each

and use appropriate reference materials and it may help aircraft oil change, this specific information should be recorded in the

owners to determine the quality of maintenance they will engine logbook. Except as a temporary measure in an emergcn-

receive. cy, different oils should not be mixed. Consistent indiscriminate

mixing of oil has created a high oil consumption problem, or

clogged oil control rings and oil screens.

Oil consumption is a very important engine health trendThe Oil And Your Efngine to monitor. The operator and maintenance people should know

the- general history of oil consumption during the life of the

There are two basic types of FAA approved aviation oils engine. It is typical of an engine during seating of new pistonused in general aviation aircraft piston engines. rings that oil consumption may be erratic or high; but after the

i. Straight mineral rings are seated, generally within the first 25 to 50 hours, oil

consumption should level off below the maximum limits2. Ashless dispersant (AD)

established by the manufacturer. Later, during the life of theMost of these engines use straight mineral oil for "break- engine if there is a noticeable increase ofoil consumption within

in" purposes with a new, remanufactured, or overhauled engine; a 25 hour period, this could be a possible danger signal andthen the operators switch~to AD after "break-in" has been ac- calls for an investigation. The oil screens and filter should be

complished, (exceptions are our TO-360-C-F, TIO-360-C, carefully observed for signs ofmetal. Maintenance personnelTIO-541, and TIGO-541qowerplants which require only AD should take a compression check of the cylinders, using dif-oil). Those engines using straight mineral oil beyond the nor- ferential pressure equipment, and also look inside the cylindersmal break-in period, and later switched to AD, must watch their with a boroscope or gooseneck light to detect any unusualoil screens after each flight until clots ofsludge no longer appear. conditions.

Since modern FAA approved Ashless Dispersant oils

already include additives which make them superior to straightmineral oil, the use of additional oil additives has not been con- More About Oil And Yoursidered necessary to good engine health and none were ap- Aircraft Engineproved. The exception to this general policy is spelled out in

Textron Lycoming Service Bulletins 446 and 471 and in Ser-

vice Instruction 1409. These publications approve the use ofWe received such a favorable response to an article on oil

in Flyer No. 14 titled ’’The Oil and Your Engine’’, that an ex-I~ycoming pan number LW-16702, an anti-scuffing, anti-wear

oil additive, for all Lycoming reciprocating engines, and re-pansion ofthe subject might also be of interest. In the previous

quire its use in certain engine models. These models are the article, we listed the two basic types of oil used in general avia-

0-320-11, 0-360-E, LO-360-E, TO-360-E, LTO-360-E,tion aircraft piston engines as straight mineral and ashless

TIO-541, and TIGO-541. dispersant (AD). We also stressed the importance of clean oil

in achieving good engine life; and oil consumption as an in-Clean engine oil is essential to long engine life, and the dication ofengine health was another important item discussed.

full;now oil filter is an added improvement over older methods

of filtration. Generally, service experience has shown that the Continuing our consideration of the oil and the aircraft

use of external oil filters can increase the time between oil engine, the primary purpose of a lubricant is to reduce friction

changes provided filter elements are replaced at each oil change.between moving parts. Another additional responsibility of the

However, operation in dusty areas, cold climates, and whereoil is to help cool the engine. As it circulates through the engine,

infrequent flights with long idle periods are encountered, willthe oil absorbs heat from the parts. Pistons and cylinder walls

require proportionately more frequent oil changes despite useare especially dependent on the oil for cooling. In addition to

of the oil filter. The oil and oil filter element should be routinely reducing friction, the oil acts as a cushion between metal pans.

replaced after each fifty hours of engine operation, and it shouldThe oil also aids in forming a seal between the piston and the

be cut open in order to examine the material trapped in the filter cylinder wall to prevent leakage of gases from the combustion

for evidence of internal engine damage. In new or recentlychamber. Oils likewise help reduce wear by picking up foreignpanicles and carrying them to a filter where they are removed.

Using a direct drive, wet sump Lycoming powerplant as ed, when the outside temperature is 100 F or lower, preheat

an example, we can describe the basic lubrication system of these of the Lycoming engine is recommended before attempting to

less complex aircraft enginesrA more detailed description may start the engine, or damage to the powerplant may result. Tex-

be found in the Overhaul Manual. In a wet sump engine the tron Lycoming does not approve the use ofoil dilution for cold

oil is contained in the engine sump as opposed to a dry sump weather operation of its engines. It is extremely important that

powerplant where the oil is in an external oil tank located only oil in the grade recommended by Lycoming be used.

perhaps in the wheel well or the rear of the aircraft engine To simplify the selection ofoils, they are classified under

nacelle. In a dry sump engine, the oil is drawn from the oil tank an SAE (Society of Automotive Engineers) system, which

and pumped throughout the engine by the pressure section of divides all oils into groups as follows:

the oil pump, and then returned to the oil tank by the scavenge

section of the oil pump. The other basic parts of the oil system Commercial Commercial Army NavyAviation No. SAE No. Spec. No.

are very similar to those used in the direct drive, wet sump65 30 1065

Lycaming powerplants.80 40 1080

In the wet sump engine, the oil pump draws oil from the100 so 1100

rear of the sump through the suction screen and sends it to the

oil pressure screen. A bypass valve in some models is located If you are looking for a can of 30 weight aviation oil and

between the pressure side of the oil sump and the oil screen. it has the number 65 on it, then it is 30 and also 1065 under

It permits unfiltered oil to bypass the screen and enter the engine the Army Navy Spec. If it has a more complete designationwhen the oil filter is clogged, or during a cold start. The spring with theletter "W" added, then 30W indicates the viscosity

loading on the bypass valve allows the valve to open before the (grade) of oil, it does not indicate quality or other essential

oil pressure collapses the screen, or in the case of cold con- characteristics. At this time (1973) any FAA approved avia-

gealed oil, it provides a low-resistance path around the screen. tion oil on the market does a good job and without usingIt is felt that dirty oil in an engine is better than no lubrication

any additives by the owners in the field.

at all. Most oil systems offer as optional or standard, a ther-Before we conclude our discussion, we want to remind our

moshtIc by pass valve in this same location which also con-readers of a couple of miscellaneous but important related items.

tains a pressure relief feature to bypass the cooler in case it isOn multi-engine aircraft each engine is supplied with oil from

clogged. As the name implies, this unit regulates the temperature its own complete and independent system. Another reminder

of the oil by either running it through the oil cooler if it ex-_ every engine has a breather which can be considered a part

ceeds a pre-set temperature, or bypassing the oil cooler if theof the oil system. If that engine does not have special provi-

oil temperature is lower than the thermostatic by-pass setting. sions for aerobatic flight and is flown inverted, the oil will be

Continuing its travel, the oil next encounters a pressure lost out the breather and a serious engine failure can result. We

relief valve. The latter regulates the engine oil pressure by allow- definitely recommend that engines not built for aerobatic flighting excessive oil to return to the sump. The oil continues its should not be flown inverted.

travel through drilled passageways throughout the system andIn summing up this brief supplement consideration of oil

finally returns by gravity to the oil sump where it begins theand your engine, it was not intended as instruction as detailed

journey all over again. as the knowledge required to be a mechanic. But we think you

Thus the principal units in the typical wet sump engine are will agree that the Typical Pilot should know more about his

a sump of sufficient size to contain the necessary amount aircraft engine than Mr. Typical Driver knows about his

of oil, an engine oil pump, oil cooler and by pass valve, pressure automobile engine the penalty for not knowing the basics

screen and by pass valve, pressure regulating valve, oil pressure is greater in aviation.

and temperature instruments in the cockpit, an oil sump drain,

a filler neck to put oil in the engine, a dipstick to measure the

amount of oil, and a suction oil screen. The full flow oil filter

is optional on the small four cylinder powerplants, but recom- Safety Tip-Sealant Usemended for higher powered engines.

We need screens and filters in the oil system to keep the Textron Lycoming Service Instruction No. 1125 specifiesoil clean as it circulates through the engine. If the oil is con- POB No. 4 Perfect Seal and silk thread as the generally used

taminated, it carries that contamination as it circulates. We also items for sealing finished parting surfaces which do not employneed an ail cooler for most engines so that the oil temperature gaskets. Two other products RTV-102 or LOC-TITE 515 ap-

may be kept within prescribed limits and the oil is able to per- plied as a very thin film, may be used as alternate materials

form its function efficiently. Of course, there is more to an oil for sealing crankcase parting surfaces. Other sealants have not

system than this briefdescription. But for the operator who need been tested and approved for this purpose and NONE are ap-

not be a mechanic, this basic information can be helpful, proved for other uses in the assembly of Lycoming engines.

The oil companies tell us the basics about their product. Improper use of these and other sealing compounds can create

Viscosity of oil is resistance to flow. An oil which flows slowly serious problems. As an example, a red colored sealant was used

has a high viscosity. If oil flows freely, it has a low viscosity. by a mechanic to hold the pressure screen gasket in place. As

Unfanunately, viscosity of oil is affected by high or low the material solidified, pieces broke loose and eventually blocked

temperatures. At below freezing temperatures some high viscosi- the engine’s small oil passages causing oil starvation and engine

ty oils become virtually solid. which makes circulation and failure. The bottom line: Use only approved materials fo;np-lubrication impossible. But no matter what viscosity oil is us- proved purposes.

Maintaining Oil Levels of Multi-Viscosity Oils

Wet Sump Engines Multi-viscosity oils are one of the newest items in the field

ofaviation products. Many aircraft owners and mechanics haveIn order to avoid confusion over wet sump engines, we are been asking about the use of these new oils which cover a broad

listing examples of them for clarification so that operators, line band ofviscosity levels. Both the 15W-50 and 20W-50 oils are

crews and maintenance personnel can properly check oil. The approved by the latest revision to Lycoming Service Insuuc-

following aircraft and engine models carry a capacity of six tion 1014. These aviation grade, ashless dispersant (AD) oils

quarts of oil: are approved for all temperature operation. They should proveto be very beneficial in those aircraft which are operated in a

Alrcrm Model Engine Model wide range of temperatures and in those situations where a

Cessna Slryhawk 172N d32~H2AD scheduled oil change does not seem to coincide with a drastic

change in seasonal temperatures.Ce~rna 152 0-235-L2C

Piper Tomahawk 0-235-L2C

Becch Sldppcr 0-235-I~C Tips For Changing Your

Piper Scminole (Twin) 0-360~E1A6D Spin-On Oil FilterGrumman American Q235-C2C

Trainer Many of the aircraft engines produced today are equipped

In addition to the above aircraft, there are others in lesserwith full flow, spin-on oil filters. For long engine life, it is

numbers using these and other engine models with a~six quartnecessary to change both the oil and the filter at regular inter-

oil capacity. In order to be sure what an engine requires, con-vals. The information we receive indicates that problems are

suit the Pilot’s Operating Handbook.sometimes encountered because proper proceduns an not

followed when changing the spin-on filter. Therefore, it is ap-One problem reported to us concerning the six quart capaci- propriate to provide a few tips from a cumnt service instruction.

ty engines has been that of over-filling the engine with oil. ByThe hardware which adapts many Lycoming engines for

referring to the Pilot’s Operating handbook the pilot will not

confuse his engine with those wet sump powerplants which haveuse of the spin-on oil biter includes an oil filter adapter (Lycom-

a capacity of eight quarts of oil. ing Part Number 15047) and a converter kit (Lycoming Part

Number LW-13904). Not all engines use the oil filter adapterThe Pilot’s Operating Handbook for the Cessna models 152, because the accessory housing on some models is machined to

and 172N Skyhawk have the following information concern- take a converter kit and a spin-on biter. The kit includes a con-

ing the engine oil: vener plate which has a gasket permanently glued to the plate;

"Capacity of Engine Sump--6 quarts. Do not operate onthis gasket seals the plate on the side which faces the engine.

less than 4 quarts. To minimize loss of oil through breather,If the spin-on filter seats too tightly against the opposite side

fill to 5 quart level for normal flights of less than 3 hours. Forof the plate when it is installed, the convener plate gasket may

extended flight, N1 to 6 quarts. These quantities refer to oil dipbe slightly damaged when the oil filter is subsequently remov-

stick level readings. During oil and oil filter changes, one ad-ed. This damage could result in oil leakage.

ditional quart is required when the filter is changed." To prevent damage to the converter plate gasket, the oil

biter gasket should be lubricated with a thin coating of Dow-The Pilot’s Operating Handbook for the Piper PA-44-180

Coming Compound @C-4) before the filter is installed. TheSeminole states as follows concerning oil requirements: filter should then be installed andhand tightened until the seating

"The oil capacity of the Lycoming engines is 6 quarts per surface makes contact with the lubricated gasket. The ftlter

engine with a minimum safe quantity of 2 quarts per engine, should then be Nmed with a torque wrench until a torque of

It is necessary that oil be maintained at full (6 quarts) for max- 18-20 foot pounds is reached. The 20 foot pound maximum tor-

imum endurance flights." que should not be exceeded.

The phrase "a minimum safe quantity of 2 quarts per The oil filter element should normally be replaced each 50

engine" should be explained. If the operator checked oil after hours ofengine operation. Before discarding the element of the

a flight and found less than 2 quarts in the engine, it is quite full-flow filter assembly, an examination of the Ntcr element

probable that engine damage has resulted. should by accomplished. The full now, spin-on filter may be

opened by use of Champion tool CT-470. The element is thenPilots and mechanics should not confuse the models just removed from the filter and tilter material is cut from the end

discussed with other Lycoming four cylinder wet sump engines,caps. Carefully unfold the element and examine the material

which hold a maximum of 8 quarts of oil. There is no change trapped in the filter. In new or newly overhauled engines somein our recommendations when checking oil for the latter. Dur-

small particles of metallic shavings might be found, but theseing normal routine flying, oil levels are best maintained at the

are generally of no consequence and should not be confused5 to 7 quart level.

with particles produced by impacting, abrasion or pressure.Don’t forget when in doubt consult the Pilot’s Operating Evidence of excessive metal contamination found in the filter

Handbook. element justifies further examination to determine the cause.

After the filter element has been replaced and properly a test cell is not available. The Lycoming overhaul manuals for

torqued, the lock wire must be replaced and the engine run to fixed wing powerplants allow it with certain qualifications. But

check for oil leaks, the "Overhaul Manual (for) Lycoming Helicopter Engines"

Textron Lycoming Service Publication SSP-885-1 provideslimits its recommendation to the following statement:

information about the installation of engine mounted oil filters. "After the completion of assembly of the engine after

overhaul, it is recommended that the engine be mounted upon

a test stand for its initial or run-in operation."

For fixed wing aircraft, this advice applies. LycomingUnderstanding Engine Color Codes

recommends that a test cell be used for run-in of engines after

overhaul. In the event that a test cell is not available, it is per-Hundreds of Lycoming engines leave the factory monthly missible to mount the engine in the airframe for the run-in pro-

and are marked with a variety of colors on each cylinder. Theseviding the requirements of Textron Lycoming Service Instruc-

colors have a definite meaning and provide valuable informa- tion 1427 are carefully observed.tion about the engine. Questions concerning these colors and

their meanings have been asked by many owners and

maintenance personnel.

In the past, color coding of cylinders was confined to col-

ored bands around the base of each cylinder. Today, new Engine Test After Overhaul

methods of painting (enameling) engines, and a need for quick, With the engine installed in a Fixed Wing Aricrafteasy engine identification were instrumental in changing color

code location. (A reprint of Service Instruction 1427)

The factory color code, a large painted stripe, is now locatedIdeally, a newly overhauled aircraft engine should be tested

on the cylinder head between the push rods from the spark plugin a test cell where operating conditions can be closely

bi5ss to bottom of the cylinder head. Additional color codingmonitored. Where a test cell is not available, the engine should

has been added to identify cylinders requiring long reach sparkstill be tested on a test stand with a club propeller and a cooling

plugs versus short reach spark plugs. Location of spark plugshroud. However, it is not always convenient to test an engine

identification color code is between the spark plug boss andin even this manner.

rocker box.Ifa test cell or a test stand is not available, an engine should

COLOR CODE FOR CYLINDER IDENTIFICATION be properly tested after it has been installed in the aircraft.

Location Between push rods on cylinder head, or band The following procedure provides a guideline for testing

around base of cylinder barrel.a newly overhauled engine that is mounted in the aircraft. In~

Engine grey or unpainted Standard steel cylinder barrels. formation on the "ground run after top overhaul or cylinder

Orange stripe Chrome plated cylinder barrels, change with new rings" and the "flight test after top overhaul

or cylinder change with new rings" procedures are publishedBlue stripe Nitride hardened cylinder barrels.

in Lycoming operators’ manuals and Service Instruction No.

*Grcen stripe Steel cylinder 0.010 oversize. 1124B.

"Yellow stripe Steel cylinder 0.020 oversize.PREPARATION FOR TEST

"Color code applicable only to engines overhauled in the

field, i. Pre-oil the engine in accordance with Service Instruction

No. 1241.Lycoming does not sell oversize cylinders.

2. It is particularly important that the cylinder head temperatureCOLOR CODE FOR SPARK PLUG IDENTIFICATION

gage, oil temperature gage, manifold pressure gage, and

Location Fin area between spark plug and rocker box. tachometer be calibrated prior to testmg.

Engine grey or unpainted Short reach spark plugs. 3. Engine accessories, such as the fuel pump, fuel metering

Yellow Long reach spark plugs, unit, and magnetos, should be overhauled or replaced with

new units before testing engine. This applies to over-Caution Use only approved spark plugs for all models

hauled engines only.of Lycoming engines. See Service Instruction No. 1042 for ap

proved spark plugs. CAUTION

Check that all vent and breather lines are

properly installed and secured as described

in the airframe maintenance manual.

Test Procedure For The 4. Install airframe and intercylinder baffles and cowlin_r.

Overhauled Engine 5. For optimum cooling during ground testing, a test club

should be used. Where this is not possible, however, the

The factory is always being asked by people in the field regular flight propeller can be substituted but cylinder head

ifa newly overhauled engine can be run-in in the airplane when temperature must be monitored closely.

GROUND TEST CAUTION

i. Face the aircraft in_to the wind. Avoid low-manifold pressure during high engine2. Start the engine and observe the oil pressure gage. If ade- speeds (under 15" Hg). and rapid changes in engine

quate pressure is not indicated within 30 seconds, shut the speeds with engines that have dynamic counterweight

engine down and determine the cause. Operate the engine assemblies. These conditions can detune, or damage,at 1000 RPM until the oil temperature has stabilized or

the dampers, rollers, and bushings in the counterweights.reached 1400F. After warm up, the oil pressure should not 6. Descend at low cruise power, while closely monitoring thebe less than the minimum pressure specified in the ap- engine instruments. Avoid long descents at low manifold

plicable operator’s manual. pressure. Do not re~duce altitude too rapidly or engine3. Check magneto drop-off as described in the latest revision temperatlre may drop too quickly.

of Service Instruction No. 1132. 7. Afterlandingandshutdown, checkforleaksatfueland oil

4. Continue operation at 100011200 rpm for 15 minutes. fittings and at engine and accessory parting surfaces. Com-

Insure that cylinder head temperature, oil temperature and pute fuel and oil consumption and compare to the limitsoil pressure are within the limits specified in the operator’s given in operator’s manual. If consumption exceeds figuresmanual. Shut the engine down and allow it to cool if shown in maoual, determine the cause before releasing air-

necessary to complete this portion of the test. If any cI-aft for service.

malfunction is noted, determine the cause and make the 8. Remove oil suction screen and oil pressure screen or oilnecessary correction before continuing with this test, filter to check again for contamination.

5. Start the engine again and monitor oil pressure. IncreaseNOTE

enginl speed to 1500 rpm for a 5minute period. Cycle pro-peller pitch and perform feathering ch~-dkas applicable per To seat the piston rings in a newly overhauled engine,airframe manufacturer’s recommendation, cruise the aircraft at 6596 to 7546 power for the first

6. Run engine to full-static airframe-recommended power for 50-hours, or until oil consumption stabilizes.

a period of no more than 10 seconds.

7. After operating the engine at full-power, allow it to cool

down moderately. Check idle mixture adjustment prior to

shutdown. The Compression Check As8. Inspect the engine for oil leaks.

A Maintenance Aid9. Remove the oil suction screen and the oil pressure screen

or oil filter to determine any contamination. If no con-

tamination is evidemi-the aircraft is ready for flight testing.Those of us who visit many maintenance organizations in

General Aviation can’t help noticing that the compression checkNOTE is used quite universally as a maintenance aid. It was also used

Compile a log of all pertinent data accumulated for many years by the military and airline maintenance people

during both the ground testing and flight testing. on their reciprocating engines. Despite universal use, little, if

anything, was available in writing as a reference concerningFLIGHT TEST

its application to General Aviation powerplants. Therefore, this

WARNING provides an ideal situation for misuse or abuse of this

ENGINE TEST CLUBS MUST BE REPLACEDmaintenance check method.

WITH APPROVED FLIGHT PROPELLERS Since almost everybody is using the compression check in

BEFORE FLYING AIRCRAFT. one form or another as a method of determining the condition

of the combustion chamber in our flat opposed engines, it mighti, Start the engine and perform a normal preflight n~n-up be helpful if we, as an engine manufacturer, share our ex-

in accordance with the engine operator’s manual. perience on this equipment with all concerned.2, Take off at airframe-recommended take-off power, while

WHY A COMPRESSION CHECK?monitoring RPM, fi~el flow, oil pressure, oil temperature,and cylinder head temperatures. A compression test can be made any time faulty compres-

3. As soon as possible, reduce to climb power specified insion is suspected, and should be made if the pilot notices a loss

operator’s manual. Assume a shallow climb angle to aofpower in flight, finds high oil consumption, or observes soft

suitable cruise altitude. Adjust mixture per pilot’s operating spots when hand pulling the prop. It is also considered pan of

handbook, the 100-hour engine inspection and the annual inspection. But

most experienced maintenance personnel feel that the compres-4. After establishing cruise altitude, reduce power to approx- sion check is best used to chart a trend over a period of flightimately 752 and continue flight for 2 hours. For the hours. A gradual deterioration of charted compression takensecond hour, alternate power settings between 65% and during routine maintenance checks would be a sound basis for751 power per operator’s manual, further investigation and possible cylinder removal. This

5. Increase engine power to maximum airframe-recommended maintenance attempt to reduce the possibility of engine failureand maintain for 30 minutes, provided engine and aircraft is generally called preventive maintenance.are performing within operating manual specifications.

HQW IS IT ACCOMPLISHED? rotate engine with the starter and recheck compression.

As all maintenance people know, there are two basic 9. Caution. Take all necessary precautions against accidental

equipments in use, (1) the direct compression (Old automotive firing of the engines.

type), and (2) the differential, using an input of 80 Ibs. of air.DIRECT COMPRESSION CHECK

Of these two, the differential is considered best in that it is a

more precise method of locating specific areas of trouble, it is This automotive type general compression check reveals

simple to use, and it is better than the direct method for locating actual pressure because the engine is turned over during the

combustion chamber problems in an early stage of their check, but it provides only momentary pressure, and flaws are

development, not easily detected; furthermore there are many related factors

to consider using this equipment. Therefore, it might be helpfulIt has been our experience that either method of compres-

to review the basic procedure involved in the direct compres-sion investigation can be handled in such a way as to give almost

sion check as a first consideration.any reading. This does not infer that there are necessarily

i. Check the engine as soon as possible after shutdown (hotdishonest mechanics, but it is an attempt to advise operatorsthat cylinders should not be pulled indiscriminately, based on engine check is best).

a single set of readings. Mechanics make honest errors, equip- 2. Take all standard precautions against accidental firing of

ment becomes inaccurate, and since there is little or no stan- the engines, and place a guard in front of the propeller.dardized information for reference purposes, it is relatively easy 3. Remove the most accessible spark plug from each cylinder.to incur unnecessary maintenance charges.

4. Attach an external power source if available.

Therefore. suppose we list some key points to observe con-5. Rotate the engine crankshaft a minimum of 16 revolutions

ccming direct and differential compression checks, review somewith the starter to expel any excess oil or loose carbon in

cross checks which should be made when low compressionreadings are observed, and state a brief logical conclusion.

the cylinder.

6. Install the compression tester correctly in the spark plugDIFFERENTIAL COMPRESSION TEST bushing of each cylinder in turn.

We will attempt to repeat the operating instructions which 7. Turn the engine with the starter through the compressionaccompany the equipment. This should be read and followed stroke a minimum of three times and record the compres-

carefully for best results. The following recommendations will sion reading.supplement the instructions accompanying the equipment:

8. If any cylinder shows a noticeably low reading, recheck

i. A standard 80 Ibs. of input air is recommended. More after turning engine over again several revolutions.

pressure makes it difficult to hold the prop.At this point we should comment on the "related factors"

2. A loss in excess of 25 percent of the 80 Ibs., or a reading mentioned earlier which must be considered when using thisof 60/80 is the recommended maximum allowable loss.

equipment. Readings will be low or not valid if either the engine3, The engine should have been run up to normal operating or the weather is cold, the starter weak, or the battery is low

temperatures immediately preceding the compression check. when not using an external power source. Ina multi-engine air-

In other words, we recommend a hot engine check, craft, ifan external power source isn’t used, by the time a check

4. The differential compression equipment must be kept clean is made on the second engine, the battery is usually weaker.

and should be checked regularly for accuracy. Check equip- We find that the slower turning rate will result in lower readings.

ment with the shutoff valve closed and regulated pressure Many small airplanes do not have a ready means of connecting

at 80 psi. (the cylinder pressure gage must indicate 80 psi an external power source.

plus or minus 2 psi) and hold this reading for at least 5 The principal difficulty with this method of compressionseconds. Home made equipment should be carefully check lies in its vague standard, making it difficult to decide

calibrated, whether to remove a cylinder when this is the only equipment

5. Combustion chambers with five piston rings tend to seal used to check the condition of the combustion chamber. Our

better than 3 or 4 piston rings, with the result that the dif- experience dictates that when a problem does show up with a

ferential does not consistently show excessive wear or direct compression check it is too far gone to utilize preventive

breakage where 5 piston rings are involved. maintenance. On the other hand, heavy reliance on this instru-

ment has resulted on occasion in maintenance cost increase due6, If erratic readings are observed on the equipment, inspect

to unnecessary removal of cylinders.compressor system for water or dirt.

All of this brings us down to the controversial question:7. If low readings result. do not remove the cylinders without

What are healthy direct compressionreadings, and what are

a re-check after running up the engine at least three minutes,possible unhealthy readings? Our experience reveals that it is

and refer to the cross checks listed later herein.consistency of the readings of all cylinders in an engine which

8, If valves show continual leakage after recheck, remove is the important factor. By that we mean all cylinders shouldn’t

rocker box cover and place a fiber drift on the rocker armvary more than approximately 15 Ibs. from each other. On the

immediately over the valve stem and tap the drift several other hand, if one or two cylinders are noticeably lower than

times with a one or two-pound hammer. When tapping the majority of remaining cylinders (more than 15 Ibs. lower).valves thusly, rotate the prop so that the piston will not be then we should be suspicious and carry out any of the cross

an top dead center. This is necessary in some engines to checks we will outline.

prevent the valve from striking the head of the piston. Then

If the above is not necessarily a desirably clear cut descrip Spark Plugs Ition, it is because of the vague nature of the equipment. Its bestcharacteristics or useis as a crosscheck reference. Therefore, Key To Smooth Engine Operationall of these "related factors" mentioned earlier tend to point Hot and Cold Plugsout that this direct compression equipment is not a particularlyreliable means of accurately checking the combustion chamber (Courtesy: Chtunpion Spark Plug)condition.

CROSS CHECKING IS IMPORTANT Today, the term ’’hot and cold" is commonplace in generalRather than rely on one source of information concerning aviation especially when related to engine spark plugs.

the condition of the combustion chamber, it is wise to make With the introduction of high compression, and highcross checks, particularly when the compression readings are horsepower engines, a need for improved spark plugs was emi-questionable. Therefore, we would like to recommend the

following before removing a cylinder,nent. Spark plugs used in low compression, low horsepowerengines were not compatible with the new, more sophisticated

i, Consider using the direct compression check first and then powerplants. The non-compatibility factor of existing plugs withfollow with the differential. The direct tends to blow out new engines resulted in development of spark plugs capable ofloose deposits, it lubricates the piston rings, and serves as operating efficiently at high compression ratios and high powera general cross check on the differential equipment and settings.readings.

Many aircraft operators have come in direct or indirect con-2. Remember that spark plugs tell a story. Carefully checkthe spark plugs removed from any cylinder with a low

tact with the term "hot and cold" during the course of conver-

reading, sation with other pilots or mechanics. Its meaning and relation-

ship to engine operation was sometimes rather vague. What do3. Use at least a goose-neck light or preferably a borbscopeand carefully check the top of the piston and cylinder walls.

we mean by "hot and cold’’ spark plugs? What is the relation-

ship between an engine and spark plugs? How important is it4. consider the health history of the engine. Has it had

previous difficulty of this nature?to smooth engine operation? There are but a few questions we

will try to answer in this article.5. Has the pilot observed any loss ofpower in the engine dur-

ing flight or during runup? Both spark plug and engine manufacturer working together

6. How has the engine been maintained and operated duringdetermine the proper type spark plug suitable for each engine

its life? If the maintenance and care have been proper andmodel. These plugs can be either fine wire or massive electrode

consistent there is less likelihood of trouble. type. Before being released for production, each new type plup

7. The supervisor of maintenance should evaluate the knownis checked in the laboratory and under actual flight conditions.

factors such as those discussed here and make a recom-They are tested through a wide range of operating conditions

mendation to the pilot. and at different power settings, and only after both engine and

CONCLUSION spark plug manufacturer are completely satisfied with test data

are plugs released for production. To eliminate any possibilityWhatever your opinion of the compression check as a oferror in spark plug selection both manufacturers provide sparkmaintenance aid, it is probable that no pilot or mechanic would plug charts as a guide for proper plug selection. Final authori-care to omit it during a 100-hour or annual inspection. On the

other hand, since most everyone seems to use it on the flat op-ty concerning proper plugs for a specific engine is the enginemanufacturer. When selecting spark plugs, be sure to also cun-

posed engines, we ought to share our experiences with its

application to our powerplants. This has indicated that the dif-sider the spark plugs’ heat range.

ferential is the best of the two equipments currently is use, and Operating temperature of the spark plug insulator core nose

particularly so when the readings are charted as a trend overis one factor which governs formation of troublesome combus-

a number of routine inspections. It is a good tool for preven- tion deposits. To help overcome this problem, selection ofsparktive maintenance and aiding in avoiding in-flight failures. Cross plugs with the proper heat range should be made. Spark plugschecking is good procedure rather than relying on one source are susceptible to carbon deposits when the operatingof information concerning the condition of the combustion temperature of the core nose insulator is at or below 8000 F,chamber, but an increase of just 1000 F is sufficient to eliminate forma-

tion of these deposits. Also, lead deposits form because thebromide scavenger contained in tetrethyl lead is non-active at

Oil and Filter Change Recommendations low temperatures. At 9000 F temperature, the bromide scavengeris fUlly activated, disposing of lead deposits with combustion

It has often been said that regular doses of clean, fresh oil gases during exhaust cycle. In this case, an increase ofjust 100U

provide the least expensive maintenance an owner can give an F was sufficient to make the difference between a smooth and

engine, Textron Lycoming Service Bulletin No. 480 makes these rough running engine. To eliminate or keep this problem at a

specific recommendations: minimum, avoid prolonged idling at low RPM, avoid power-A. Fifty hour interval oil change and filter replacement for off let downs and after flooded starts run engine at medium RPM

all engines using a full-flow oil filtration system. before taxiing.B. Twenty-five hour interval oil change and screen clean-

ing for all engines employing a pressure screen system.Deposits formed between 10000 F and 13000 F are low In

C. A total of four months maximum between changes forvolume and electrical conductivity and are least apt to cause

both systems listed under "A" and ’’B". spark plug fouling. This is the reason for selecting a plug that

will operate within the aforemention temperature range at all Cross-firing in the magneto distributor can also produce

power settings. spark plug insulator failure and piston distress.

Now let’s get back to the term "hot and cold" as related The bottom ofthe insulator well around the contact cap loca-

to engine spark plugs. Normally, a hot plug is used in a cold tion should be inspected for the presence of black contamina-

engine low horsepower, and a cold plug in a hot engine tion on the walls and also at the contact cap. Black soot-like

high horsepower, in actuality, these terms refer to the plugs deposits usually indicate that the insulation of the ignition lead

ability to transfer heat from its firing end to the engine cylinder has been exposed to temperatures above normal.

head. To avoid spark plug overheating where combustion

chamber or cylinder head temperatures are relatively high, a Damage From Excessive Temperaturescold plug is recommended such as in a high compressionengine. A cold-running plug has the ability to transfer heat more Overheating of the spark plug barrel, sometimes caused by

readily. A hot-running plug has a much slower rate of heat damaged cylinder baffles or missing cooling air blast tubes, may

transfer and is used to avoid fouling when combustion chamber seriously deteriorate the ignition leads. Any overheating of the

and cylinder head temperatures are relatively iow. spark plug barrel by a defective baffle or exhaust gas leakageat the exhaust pipe mounting flange can generate temperatures

From our discussion, it is clear to see that there is morein the insulator tip sufficient to cause preignition and piston

tospark plugs thanjust buyinga set and installing them in your distress.engine. Be sure you know what type of spark plugsTo use with

your engine. Also, good spark plug service and maintenance Interpreting Color of Insulator Tip Depositsis as important as proper plug selection. Take care in selecting

The firing end of the spark plug should be inspected forand maintaining your plugs, it can result in many additional

color of the deposits, cracked insulator tips and gap size. Thehours of smadth engine operation. Additional spark plug in-

electrodes should be inspected for signs of foreign object damageformation is always available from the engii~ or spark plug

and the massive type also for copper run-out.manufacturers and other service organizations.

Spark plug tables are available by writing to Product Sup The normal color of the deposits usually is brownish grey

port Department, Textron Lycoming, Williamsport, PA 17701; or gray tinted slightly with red. These colors are most prevalent,

Champion Spark Plug Company, Aviation Department, Toledo, but there may be a different color combination which would

Ohio 43661; or SGL Auburn Spark Plug Company, 89 York be normal for the type of operation the spark plugs have been

Street, Auburn, New York 13021. exposed to.

Dull and smooth black deposits on the insulator tip usually

indicate that the spark plug is lead carbon fouled. This type ofspark plug fouling is caused by incomplete combustion; it usual-

Spark Plugs If ly results from improper ground operation when the engine is

Key To Smooth Engine Operation cold, and is more prevalent when the atmosphere is cold and

very humid. It can also happen in a cylinder with weak com-

pression, an engine with a defective primer solenoid or in a(Editor’s Note: The following article is published with the

cylinder that is using excessive amounts of oil. In many in-permission of AC Spark Plug Division.)

stances, if both spark plugs are affected, the deposits will not

Aircraft spark plugs removed from engines, especially if bum off under normal engine bum-out procedure, makingengine malfunctioning has been reported, should be closely in- replacement of spark plugs necessary.

spccted for abnormal indication or conditions because theseBlack, with some glaze or irregular formation and of suf-

analyses could help in determining the source of the reportedficient amounts to short out the spark plugs, usually indicates

malfunction. Spark plugs tell a story.prolonged ground operation with a very rich carburetor setting,

Terminal End and Lead Connectorsfollowed by a sudden increase in power output. This causes a

rapid increase of the insulator tip temperature and prevents theIn "all-weathcr’’ or "’k 20" terminal type, the insulator

deposit formation from being vaporized. This type of spark plugsleeve has an exposed edge or end, which should be inspected fouling is more prevalent in float equipped aircraft.for evidence of carbon tracks. These will appear as heavy lead

pencil lines across the entire width of the end of the insulator Orange-yellow and glaze appearing deposits on the insulator

sleeve and indicate that the ignition lead connector, which was tip usually indicate that the spark plugs have been exposed to

attached to the spark plug, may be defective. This permits elec- higher than normal temperatures as it happens when detona-

trical discharge to the metal part of the spark plug shield. tion is experienced.

The misfiring of the spark plug, induced by the defective An ash-grey colored surface or chalk-white surface on the

connector, will be noticed during take-off and climb engine insulator tip, and the exposed metal parts, indicates that the spark

operations, or at high altitudes, and may not be encountered plug was exposed to very high combustion chamber

during ground operation or with new spark plugs. temperatures, usually caused by severe detonation or preigni-tion. The free end of the side electrodes on fine wire spark plugs

Short leads preventing a positive contact between the con-will be of a bluish-gray color and free of any accumulation of

tact spring and the contact gap in the spark plug may cause thedeposits. In massive type spark plugs. evidence of copper run-

engine to misfire during take-off and climb operation and, inout could be visible.

extreme cases during low power, especially with lean mixtures.

The cylinders from which spark plugs with the above con-

ditions were found should be inspected with the aid of a

boroscope. It may be desirable to replace the cylinder, especiallys e6~

if backfiring was reported by the flight crew. The reason for

this precautionary action is that if the engine was operated under

some detonation conditions, but not to the extent that it caused

a complete piston failure, the piston rings could be broken and

a piston failure requiring a complete engine change may show

up at a later date.

A black-colored deposit on the spark plug gasket and the

gasket flange indicates that the spark plug was insufficiently tor-

qucd, allowing combustion chamber gases to leak past the spark

’I´•plug threads. In aircraft engines using helicoil inserts, it mayalso cause a helicoil burnout.

Cylinders in which spark plugs with cracked insulator tips ~4

have been found should be thoroughly inspected for damagedue to abnormal combustion chamber conditions, even thoughthe ceramic separation could have been caused by improper in-

LIstallation procedures, improper method used to check or reset

the gapior from being dropped. The electrode gap size should

be inspected for uniformity and the electrodes for sign of distor- By comparing the two spark plugs in this picture, you can

tion and nicks, see the results of overtorquing at the distorted end of the left

Besides cracked insulator and lead carbon fouling, spark spark plug. Since this distortion may make the spark plugplugs may also be made inoperative by ice or oil bridging of unuseable, great care should be taken to tighten the connector

the electrodes; and if both spark plugs are affected in the same in accordance with the manufacturer’s instructions.

cylinder, it usually requires replacement. Spark plugs with fine

wire electrodes are less suspectible to this form of maIfnnction

due to the smaller surfaces available to collect the moisture or

oil.Why Rotate Spark Plugs

Electrode Gaps The Positive and The NegativeThe size of the electrode gap has a very definite effect on

spark plug service life and also on the performance ofthe engine. The policy of rotating spark plugs from top to bottom has

Insufficient gap size will not only cause misfiring during idle, been practiced by mechanics and pilots for many years. It is

but will also misfrre during cruise power with lean fuel/air mix- common knowledge in the industry that the bottom plugs are

ture. This intermittent misfiring during cruise lowers the always the dirty ones and the top plugs are the clean ones. By

temperature of the insulator tip to such an extent that lead periodically switching the plugs from top to bottom, you get

deposits forming on the insulators may not vaporize suff~cient- a self-cleaning action from the engine whereby the dirty plug

ly to keep the tips clean. placed in the top is cleaned, while the clean plug replaced in

the bottom gradually becomes dirty. Based on this cleaning ac-

tion. a rotational time period must be established.

Due to the ever-increasing cost of aircraft maintenance and

Is Your Spark Plug Connector Overtorqued? a desire to get the maximum service life from your spark plugs,the following information is offered on the effects of constant

This is a brief summary of the Champion Spark Plug in- polarity and how to rotate plugs to get maximum service life.

struction for connecting the spark plug to the connector:The polarity of an electrical spark, either positive or

Terminal sleeves should be handled only with clean, dry negative, and its effects on spark plug electrode erosion has longhands. Before installation, wipe off the connector with a clean, been known, but has had little effect on spark plug life in the

lint-free cloth moistened in methylethylketone, acetone, wood relatively low performance engines of the past. However, in

alchohol, naptha or clean unleaded gasoline. Make certain that the later, high performance, normally aspirated and turho-

the inside of the spark plug shielding barrel is clean and dry. charged engines where cylinder temperature and pressure are

Then, without touching the connector or spring with the fingers, much higher, the adverse effects ofconstant polarity are becom-

insert the assembly in a straight line with the spark plug. Screw ing more prevalent. As you can see in the picture compann%the connector nut into place finger tight then tighten an spark plug wear, when a spark plug is installed in a cylinderadditional turn with the proper wrench. Damaged threads that is fired negative and is allowed to remain there for a loneor cracked shielding barrels mav result ifthe connector nuts period of time, more erosion occurs on the center electrode than

are riRh~ened excessive!v. Avoid excessive side load while on the ground electrode, and when a spark plup, is fired poatlve.tightening more erosion occurs on the ground electrode than on the center

electrode. From this we can see that a periodic exchange of spark generally considered to be ’’shelf’ life. All hose manufactured

plugs fired positive with those fired negative will result in even for aircraft use is marked indicating the quarter year in which

wear and longer spark plugservice life, it was manufactured. The listing "4488" means the hose was

manufactured in the fourth quarter of 1988. Maintenance per-sonnel should not use hoses with a high "shelf’ life age.

IPARK PLVO FIRED NEGATIVE SPARI( PLVG FIREDPOSITIYETo eliminate relatively short "shelf’ life limits. Textron

Lycoming is phasing in Teflon hoses with silicone coated fire

sleeves. These are the only hoses which are available as nplace-ment in the field, and they will be found on most engines which

are shipped from the factory.

Service Instruction No. 1247 lists the fuel and oil hoses

used by Textron Lycoming. It also explains how the number-

ing system defines hose size. This instruction should be usedAWERSE *WERSE

DENTER ELECTRODE GROUnO ELECTRODE as a reference anytime hoses are to be replaced.WEAR WEAR

To get a polarity change, as well as switching the plugsAir Filter Maintenance

from top to bottom, the following rotational sequence is sug-

gested. First, when removing the spark plugs from the engine,keep them in magneto sets. After the plugs have been serviced (Somethiug the pilot should Pfso ImoH)

and are ready to be reinstalled in the engine, make the follow-

ing plug exchange. For six cylinder engines, switch the plugs Dust or some form of dirt is frequently the principal factor

from the odd number cylinders with the plugs from the evenin premature piston ring and cylinder wear. If a worn or poor-

numbered cylinders. For example, switch 1 with 2, 3 with 4, ly fit air filter allows as much as a tablespoon of abrasive dirt

5 with 6, or 1 with 6, 2 with 5, and 3 with 4. On four cylinder material into the cylinders, it will cause wear to the extent that

engines, you mud switch 1 with 4 and 2 with 3. During the an overhaul will be required. Evidence of dust or other dirt

following operating period, each plug will be fired at reversematerial in the induction system beyond the air filter is indicative

polarity to the former operating period. This will result in evenof inadequate filter care, or a damaged filter.

spark plug wear and longer service life. This rotational pro- To prevent undesirable combustion chamber wear, follow

cedure works equally well on all four and six cylinder Lycom- the instructions outlined in the Aircraft and Engine Manuals on

ing engines except four cylinder engines equipped with the filter maintenance procedures. They will stress such recommen-

single-unit dual magneto. This is a constant polarity magneto dations as inspecting the entire air induction system to

and the only benefit to be gained by rotating the plugs is the preclude the introduction of unfiltered air between the filter and

reduction of lead deposit built-up on the spark plugs when a fuel injector or carburetor. The manual also recommends in-

rotational time period is established and followed. Another ex- specting the carburetor heat door, or the alternate air door, to

ception occurs on a few four cylinder engines where one ensure that they are operating correctly and sealing properly.magneto will fire all of the top spark plugs and the other magneto Any accumulation of dirt and dust in or near the entrance of

will fire all of the bottom spark plugs. If the plugs are rotated the alternate air door or carburetor heat door, will be drawn

as previously recommended, a polarity change will result but into the engine if the above doors are opened. Subsequently,since the plugs do not get moved from top to bottom, no self- aircraft parked or stored in dusty areas should have the unfiltered

cleaning action by the engine will occur. This may result in the section of the induction system ahead of the air door examined

necessity to clean the bottom plugs at regular intervals as these and cleaned, if dirty, before use.

are always the dirtiest. For those engines with magnetos which

fire all top or bottom spark plugs the choice of rotating plugsto change polarity or to obtain bottom to top cleaning action

must be made by the aircraft owner or the A P mechanic.

Checking And Adjusting Dry Tappet

Clearance On Lycoming Engines

Engine Hoses Any time work is done on the valve train of an engine, such

as grinding valves or seats, replacing valves or valve rockers.

As airplanes and engines attain age, there appears to be a or any other component of the valve operating mechanism. the

need to re-emphasize the inspection or replacement of engine dry tappet clearance should be checked and adjusted to insure

hoses or Lines carrying fuel, oil, or hydraulic fluid. The hose that the correct tappet clearance is maintained. Any time tap-manufacturers definitely recommend the replacement ofall such pet clearance is allowed to vary too far from prescribed limits,

hoses at every engine change even though they look good. the engine will not operate properly. For example, if clearances

Age limit of rubber-steel or fiber banded hose has general- are too small, burned valves or compression loss may result:

ly been established at four years. This limit of four years is and if clearances are too great, the engine will become noisy.

In both cases, the engine ~hanical haust valves on all engines except the TIG-541 and TIGO-W 1failure may be the result. series powerplants; the latter should be .040 to .105. If clearance

The following is a b;iefdescription ofprocedures to check falls within these limits, no adjustment is necessary. It not, then

and adjust the dry tappet clearance. After observing all safety adjust to within limits in the following manner: If clearance is

precautions, rotate the engine until the piston is on top dead too great remove the push rod and install a longer one. If

center (TDC) of the cylinder to be checked. (1) Remove the clearance is too small install a shorter push rod and recheck

rocker box cover, and also remove rocker shaft covers on angle to be sure clearance is within limits.

head cylinders, valve rockers, thrust washer tangle head on- To determine a short push rod from a long one, check the

ly), push rods, and shroud tubes. (2) Then remove hydraulic part number on the end of the push rod. The lowest numberunit from the tappet body. On TIG-541 and TIGO-541 engines is the shortest rod, and the highest number is the longest rod.

remove the unit with fixture ST-233. On all other engines use On older type push rods, machined grooves will be found on

special tool Part No. 64941, that can be purchased from Lycom- one side of the push rod, three grooves represent the short rod,

ing, or fabricate a puller from a piece of wire. NO MAGNET and no grooves represent the long rods. Consult Lycoming Ser-

PLEASE. (3) Disassemble the hydraulic unit and flush out all vice instruction No. 1060, and applicable parts catalog.oil from the unit. Also, remove all oil from the tappet body.(4) Re-assemble hydraulic unit and install in the tappet body.

Importance Of The Correct Cylinder

LBase Nut Tightening Procedure

,1 The need to constantly stress the comet cylinder base nut

tightening procedure seems apparent. Operators in the field are

occasionally having engine problems and malfunctioning after

~fltreinstalling cylinders, and not tightening the cylinder base nuts

~iLucorrectly. The latter tends to cause crankshaft bearing shifting,

Icrankcase frening, or broken cylinder studs, and possible enginefailure.

´•´•Cz I-: II -~i´•"

Again we remind all operators in the field that we called

j-´•´•i this problem to your attention in Flyer No. 15, published in

1972, and repeated the information again in 1973 in the KeyReprints. In order to properly reinstall cylinders, consult Tex-

.~,´•´•Ctron Lycoming Service Instruction No. 1029.

Q

Maintenance people should ensure that torque wrenches

I have been correctly calibrated before accomplishing cylinder´•i base nut tightening. After reinstalling cylinders, a ground run

r~ JIP: of the engine should be accomplished as outlined in the Lycom-i: ,,-´•´•la ing "Engine Operator’s Manual", followed by a shutdown and

inspection. Then the engine should be test flown normally, and

ij.;´•´•-´• following the flight, a good inspection of the engine should be

r;´•r~

u-

made before returning the aircraft to routine use.

CAUTION: Be sure and keep hydraulic units as one Fuel Injector Nozzies Haveassembly because mixing hydraulic unit parts may result in

changing the leak down rate of the unit and may cause a roughBeen Improved

operating engine. Reports from operators of fuel injected engines and from

CAUTION: After cleaning the hydraulic unit and tappet Lycoming service representatives provide some insights into the

body, and unit is installed in the engine, do not turn the prop subject of clogged fuel injector nozzles. By providing our

because this will pump oil into the hydraulic unit and result in readers with information from these sources, it may help some

an inaccurate dry tappet clearance check. (5) Next, replace the of them to recognize and treat a similar problem in their own

shroud tubes using new seals. (6) Install push rods, valve aircraft.

rockers, and thrust washer on angle head cylinders only. (7) A recent letter from the owner of a twin engine aircraft withTo check dry tappet clearance, depress hydraulic unit by press- Lycoming 10-540 engines indicated that after 900 hours ofing on the push rod end of the rocker, and measuring the operation the engines had performed flawlessly except for minorclearance between the valve stem and heel of the rockers by problems involving the fuel injection system. This particularusing a feeler gage, aircraft was equipped with an exhaust gas temperature (EGT)

On engines using rotators on the valves, the clearance is probe at each cylinder so the cylinder causing a problem couldmeasured between the rotator and the heel of the rocker. In both be pinpointed by using the EGT analyzer. Here is a descriptioncases, the clearance should be .028 to .080 on intake and ex- of how this problem was observed by this owner.

From time to time there would be erratic combustion on two-piece fuel injector nozzle assembly.one cylinder which would either raise the exhaust gas

temperature as shown on the analyzer lan indication of a lean

mixture on that one cylinder) or in some rare cases the individual

cylinder would become inoperative. Thorough cleaning of the Unauthorized Additions To Your

nozzle and line had little effect, but simply replacing the noz- Engine Can Cause Troublezle and line caused the cylinder to operate normally and broughtexhaust temperatures back into line; EGT was again respon- Some accidents and forced landings have been reported to

sive to mixture control, us which have been caused by adding certain equipment to the

The basic problem boils down to almost microscopic pieces engines out in the field. In most instances, the equipment add-

of dirt that get into the fuel nozzle. These bits and pieces are ed to the engine has not been approved by the airframe manufac-

extremely hard to dislodge and they may severely restrict fuel turer or the engine manufacturer. Here are two of many ex-

flow to the individual cylinder. Cleaning the line and nozzle amples reported to us:

does not always remove the dirt and correct the problem, One owner added a magnetic pickup to the engine oil drain

although on the surface it would appear that it should. plug which restricted oil flow to the oil suction screen, causingWhen fuel flow is only partially blocked by dirt in the in- oil starvation to the engine, and resulted in failure.

jector nozzle, the exhaust gas temperature will rise´•and not re- Another owner installed an oil quick-drain plug on thespend to mixture control until idle cut off is reached. The reason engine sump of a plane with a retractable landing gear. Whenfor this is that the blockage now becomes the primary restric- the gear was retracted, it ~ocked the protruding plug off, allow-tion and is independent of mixture control position. ing the oil to escape and resulted in engine failure.

In those aircraft which do not have an EGT probe on each Operators in the field desiring to add any part to the enginecylinder. erratic combustion or engine surging which may be should first consult with the engine and airframe manufacturer.an indication of clogged or dirty fuel injector nozzles may Any addition or change of engine parts also calls for a careful

possibly be checked by noting the fuel flow gage. Those fuel ground run and inspection of the area of the engine after shut-flow gages which actually measure pressure will have an in- down. Then the engine should be flown and the engine in-dicator calibrated to show gallons or pounds of flow per hour. struments carefUlly observed during the test flight. After theWith this type of instrument, a clogged nozzle will cause a latter, the engine should again be inspected for oil or fuel leaks,pressure increase and. therefore, an unusually high fuel flow etc., before flying with passengers. The Engine Operator’sindication, Direct flow meters do not react in this manner. To Manual has a ground run checklist and a flight test record for

pinpoint the individual nozzle or noules which are clogged, such occasions.it will be necessary for a mechanic to flow check all lines into

The Textron Lycoming standard warranty statement sum-containers of equal size. Fuel flow in each line should be equal, marizes our discussion in the following all inclusive statement:so a line with clogged nozzT~ may be identified by a smaller

amount of fuel which flows into its container during the flow Textron Lycoming reserves the right to deny any warran-

check period, ty claim if it reasonably determines that the engine or part has

been subjected to accident or used, adjusted, altered, handled,As indicated earlier. fuel injector nozzles have traditional-

maintained or stored other than as directed in your operator’sly been difficult to clean. Under no circumstances should the

manual.fuel injector nozzie be probed with a sharp instrument. The proper method of cleaning described in Textron Lycoming Service

Instruction 1275B includes washing the nozzle thoroughly with

acetone and blowing it out with compressed air. Also, as in-

dicated earlier, there have been times when cleaning did not A Simple Check Of

return the fuel flow to normal and the only recourse was replace- Internal Engine Timingment of the nozzle and line.

The difficult job of cleaning fuel injector nozzles has been The A&P mechanic is often called upon to troubleshoot an

made easier with the recent introduction of the "two-piece air engine problem relating to low power. There are many causes

bleed injector nozzle." These nozzles are now being installed for this kind ofcomplaint. This anicle will discuss one possibili-in production engines and are available as replacements for the ty which should be considered if this problem occurs after an

nozzles which were used previously. They are physically and engine has been overhauled or disassembled for other reasons.

fuctionally interchangeable with the corresponding old style First, let us consider the symptoms. In case of an enginenozzle. fined with a fixed pitch propeller, the static RPM may be several

The minor fuel flow problems cited by the aircraft owner hundred RPM below what is specifred for this engine/airframein the first few paragraphs of this article were experienced with combination. For an engine with constant speed propeller which

old style fuel injector nozzles. The new two-piece injector nozzle has the governor and propeller blade angle set properly, it is

has an advantage; it can be taken apart for easy cleaning. This possible that both static RPM and/or performance mav be low.

feature should make trouble shooting and repair of dirt related The cause of these symptoms in an engine which has recently

fuel flow restrictions much easier. See Textron Lycoming Ser- been disassembled may be the result of improper timing bet-

vice Instruction 1414 or Bendix Service Bulletin No. RS-77, ween the crankshaft and the camshaft. Misalignment by one or

Revision i, for more details on installation and cleaning of the two gear teeth may have occurred during engine assembly.

If these symptoms exist and if improper timing is suspected, having unlike part numbers.it is not necessary to dis_assemble the engine to check the inter- This can be a little confusing and we have had reports fromnal engine timing between crankshaft and camshaft. The pro- mechanics who assembled an engine using two different sizecedure for accomplishing this check will be detailed below for rollers (two different part numbers) in the same counterweight.those A&P mechanics who have not been exposed to this method Fortunately, in the cases we are aware of, the error was cor-

before. rected before assembly of the engine continued.

First, insure that magneto and electrical switches are in the To help in clearing up this possible source of confusion,OFF position. Next, remove the cowling so that rocker box it should be remembered that each counterweight is installed

covers and spa~k plugs are accessible. Then rotate the engine with two identical rollers. The rollers will have the same panso the piston in number one cylinder is positioned at top dead number and be the same size. The next counterweight on thecenter on the compression stroke. The number one cylinder of same crankshaft may use rollers of a different size and panLycoming engines is the right front cylinder except for the 541 number, but these two rollers will also be identical.models which have number one cylinder at the left front posi- For more details on the assembly of crankshafttion. For all Lycoming direct drive engine models, the top dead

counterveights, see the latest revision of Service Instructioncenter position of number one piston can be vertified by observ- 1012.ing that the mark indicating the #1 TDC position on the rear

side of the starter ring gear is exactly aligned with the split line

of the crankcase at the top of the engine. As the last step of

preparation, remove the rocker box cover from number two Maintenance Suggestions From Thecylinder.

Engine timing is checked by first observing the number twoLycoming Service Hanger, I

cylinder valve rocker arms. Both valves should be closed or

nearly closed. The next step is to move the propeller slightly Spark plugs are an important engine accessory. Perhaps it’s

-in one direction. Rocker arm motion should be seen as one valvebecause they do such an important job so well, yet are often

taken for granted. This little fellow has character. For the alert,starts to open. STOP. Now rotate the engine back to the original

knowledgeable mechanic, Mr. Plug is ever willing to reveal itsposition with the #1 TDC mark again aligned with the split in

secrets pertaining to the health of the engine’s fuel system, oilthe crankcase halves. Both valves should again be closed or near-

consumption, combustion chamber and even the engine treat-ly closed. Now move the propeller slightly in the direction op-

ment given by the pilot. At the Textron Lycoming Serviceposite from the first movement. Rocker arm motion should again

Hanger, we have come to lean heavily on Mr. Plug’s abilitybe seen as the other valve starts to open. If the two valves started

to open as described with only a small amount of engine move-to "tell a story". Actually, he’s our ace troubleshooter.

mcnt in each direction, the engine timing is correct. To make it possible for Mr. Plug to do even a better jab,

For some individuals it may be simpler to rock the pro-we are listing some "do’s and don’ts". These tidbits are directed

at both the mechanic and pilot.peller slightly with a back and forth motion while observingthat first one valve and then the other will start to open. Ifmove- The massive electrode type are the least expensive to buyment in either direction exceeds twenty degrees of engine rota- and do a fine job. The fine wire platinum plug is more expen-

tion before motion of the rocker arm occurs, the crankshaft to sive but gives longer life, is less prone to frosting over duringcamshaft timing is not correct, cold starts and appears to be less susceptible to lead fouling.

If the observed rocker arm movement indicates that inter- The more expensive fine wire iridium plug has all the qualities

nal engine timing is correct, then this is not the cause of theof the platinum plug, plus the fact that the iridium material resists

low power being investigated. On the other hand, ifboth rockerlead salts errosion to a much greater degree than platinum. This

arms do not move from engine rotation within the parametersresults in longer plug life. So make your choice.

discussed earlier, the internal engine timing is not correct. This DON’T reuse spark plug gaskets.indicates a probable error during engine assembly and it can DO use the recommended torque when installing plugs.only be corrected by opening the engine and realigning the

crankshaft and camshaft gears. Instructions for accomplishingDON’T be a throttle jockey. For years we have been

this task will be found in the appropriate overhaul ri~anual. preaching that engines don’t like sudden throttle movement.

Well, the spark plugs don’t like it either.

DO after a successful flooded start, slowly apply highpower to burn off harmful plug deposits.

Installation of DON’T close throttle idle any engine. Fuel contains a

Counterweight Rollers lead scavenging agent that is effective only when the plup, nose

core temperature is 9000 F or more. To attain this temperature.

you need a minimum of 1200 RPM, (TIGO-541 is an exccp-Textran Lycoming Service Instruction 1012D provides in-tion). Besides, the engine’s fuel system is slightly rich atformation on the location and assembly procedure forclosed throttle idle. This ends up with Mr. Plug having a sooty

counterweights on each Lycoming crankshaft equipped withface.

cnunterweiphts. The illustrations in this service instruction show

that some crankshafts may have two or more counterweights DON’T fly with worn or dirty air filters or holes in In-

of the same part number attached to the crankshaft with rollers duction hoses and air boxes, for this :ts the fastest wav of wenr-

ing out engines. Mr. Plug doesn’t like it either. One of his worst The lack of printed matter on this suqiect may be due to

enemies is silicon (a fancy name for dirt), the difficulty in adequately describing types and amounts ot

DON’T you mechanics attempt to clean lead depositsmetal. It’s like asking for a precise measurement and _rettln_r

the answer, "why it’s twenty five thousandths plus a little bit".from plugs with an abrasive type cleaner tan excellent way to

Therefore, what follows are meant to be general guidehnes. but

keep the plug manufacturer on overtime filling replacementeach case must be considered as an Individual one, Textron

orders), Use the vibrator type cleaner sold by the plug manufac-Lycoming does nor consider this discussion a technical bulletin.

turers. Then. sparingly use the air powered abrasive.but merely a source of generally helpful mformatlon.

DO properly lean your engine in flight as recommend-GENERAL INFORMATION

ed by the Pilot’s Operating Handbook. and Lycoming Service

Instruction No. 1094. In addition to being helpful to the engine 1. DON’T PANIC on small amounts of shiny flakes or small

in many ways, it also helps the plugs run cleaner, more eff!- amounts of short hair-like bits of ma_gnetic matenal.

ciently and longer. Experience has shown that far too many engmes are

DO-you mechanics be a little more careful in gap setting pulled unnecessarily.

of massive electrode plugs. The top and the bottom of the ground 2. DON’T PANIC if it’s a low time engine. A few bits of

electrode should be parallel with the center electrode. metal is not too uncommon in the oil screen or Alters on

new or remanufactured engines.DON’T reuse obviously worn plugs, regardless of how

they bomb check, Mon than 50Z of the ground electrode erod- 3. DON’T PANIC. Again if it’s a low time engine, it ma)

ed awav; the center electrode shaped like a footballs the center be a replacement for one that had previously suffered a

core oi the ground electrode badly dimpled? If the answer is srmcrural failure. The metal may have just been dislodped

yes, replace. from some hiding place in the oil cooler, oil lines or oil tank.

DO use anti-seize compound when reinstalling plu~. r4. Item 3 brings up the importance of properly cleaning all

Caution: only sparingly on the first three threads. Here is not items transferred from a failed engine to a replacement

a case of twice as much being twice as good. engine. On dry sump engines. don’t overlook cleaning of

the oil tank. Oil coolers and oil lines should be cleaned byDON’T accept dirty and stained cigarettes: the~ may

a proven method or replaced.cause misfirt.

5. In some rare cases where the pleated cylindrical type oil

DON’T use any spark plug that has been dropped. Onescreen is used, the screen itself mav be making metal.

manufacturer says "lf you drop it once, drop it Mice TheClosely inspect the end of the internal relief valve ball. If

second time in the trash barrel." the ball is deformed, this is probably the culprit. Replace

DON’T reuse any plug with cracked porcelain, the screen assembly.

rcpardless of how it may have been working or how it bomb 6. In cases where metal shows up and its origin is unknown.

checked. It will cause serious preignition. the metal may be forwarded to the Lycoming factory for

DON’T shrug off oily spark plugs. New, topped, or ma- inspection. The processing can be expedited by callinr the

jorcd engines with some oil in the plugs is normal because rin_gs factory Product Suppon Department when maiiine marenal.

haven’t seated. High time engine oily plugs means rings are

wearing out. One oily plug with others dry, means a problem EXAMPLES:

in the cviinder with the oily plug. (The bottom-plugs are always Several pieces of shiny flake-like, non-maenetic. or several

first to tell the story), short hair-like pieces of magnetic material: place aircraft

DON’T clean plugs with a powered wire wheel. This back in service and again check oil screen or filter in 75

is known as "a slow death on a fast wheel". hours.

DON’T you mechanics determine replacement spar~e 2. As in Item 1. but larger amount, such as 45-60 small pieces,

plugs by referring to model number on old plug in the engine. clean screen, drain oil and refill. Run engine on ground

The man ahead of you may have installed the wrong model. for 20-30 minutes. Inspect screen. If clean, fly aircraft for

Use the manufactunr’s chart on all plug replacements: also con- 1 to 2 hours and again inspect screen. if clean, inspect

suit Lycoming Service Instruction No. 1042, "Factory Ap screen after 10 hours of flipht time.

proved Spark Plugs". NOTE: In cases one and two, we are determining whether

the small amount of metal was a ’’one shot and done deal’’

(not entirely uncommon).

3. Chunks of metal ranging in size of broken lead pencil point

Maintenance Suggestions From The or geater. Remove suction (sump) screen as large pieces

of metal may have fallen into the sump. In any event,

Lycoming Service Hanger, II ground aircraft and conduct investipation. A mixture of

magnetic and non-magnetic in this case oft-times means

The telephone is always a good indication of the type of valve or rine and piston failure. Removing bottom spark

information needed in the field. Therefore, for this issue, we’ll plugs ususally reveals the offending cylinder.

attempt a logical approach to the proper action to be taken when4. Non-magnetic plating averaging approximately 5:," In

metal shows up in the oil screen or oil filter cartridge. diameter. may have copperish tint. Quantity found ’ii

teaspoonful or more; ground aircraft and investigate. If

origin can’t be determined, mail metal to Lycomingfactory for analysis, attention Product Support.

IMPORTANT5, Same as Item 4, but may be slightly larger in size and minus

copperish tint. On dinct drive engines, propeller action may Before installing this replacemenl cngme. all a~rcraft

be impaired. Ground aircraft. If origin can’t be deter- oil system components. oil coolers. hnes and supp)~

mined, mail material to Lycoming attention Product tanks, where used. must be thoroughtly cleaned for contarmna-

Support. 6on. Textron Lycormng will nor be held responsible for con-

6, Non-magnetic metal brass or copperish colored. Resemblestamination u, this newly installed engine.

coarse sand in consistency. Quantity of f& teaspoonful or PRODUCT SUPPORT DEPARTMENT

more; ground aircraft, if origin can’t be determined, mailTEXTRON LYCOMING WIUIAMSPORT PLANTmetal to Lycoming attention Product Support.

7. Anytime metal in the amount of’h teaspoonful or more,~Viliiamsport. PA 17701

it is usually grounds for engine removal. An exceptionshould be where problem is confined to one cylinderassembly (rings, valves, piston, cylinder). In this case,

if the entire engine does not appear to be contaminated, the

offending cylinder assembly kit may be replaced. After cor-

rective action is completed, conduct the routine ground SAFETY NOTESrunning and screen’ inspection as previousiy described in

Item 2. In an attempt to reduce the cost of flying, some

operators have nsorted to methods of operation which8. Ifany singleorseveralpieces ofmetal largerthanpreviously

are considered to be unsafe. Textron Lycoming makesmentioned an found, magnetic or non-magnetic, groundaircraft. Iforigin can’t be determined, a call may be made

the following recommendations ngarding these

practices:to the Lycoming Product Support Department. A gooddescription of the metal may result in placing its origin. i. Do not advance timing set timing in accordance

When phoning Lycoming or when returning metal n- with the En~ne Operator’s Manual for the specificmoved from engines, supply the complete engine model engine model.

designation, serial number, history of engine, oil

temperatures, oil pressures, and any odd behavior of the2. Do not use a hotter spark plug for low power

engine on ground or flight opeI-dtion,cruise unless it is approved for the specificengine as listed in Lycoming Service instruction

No. 1042.NOTE: Metal samples for analysis can only by acceptedif the engine from which the sample is taken is a new, 3. Do not abbreviate the warmup of a turbochargedremanufacturcd, or overhauled engine from the Lycoming engine follow the instructions of the manual

factory. Engines overhauled by other facilities may have penaining to oil temperatures, otherwise an over-

pans which cannot be identified by analysis at Lycoming. boost or erratic power condition will result.

POSTSCRIPT 4. Do not use automotive oils in aircraft enginesthey will cause engine damage or possible failure.

As an important postscript to "Maintenance SuggestionsFrom The Service Hanger" column, factory personnel have 5. Do nor use automotive fuel in aviation engmes.

become concerned over unnecessary engine removals because Quality of automotive fuel varies widely and

metal was found in the new or remanufactured replacement additives may result in deterioration of fuel system

engine after a prior malfunctioning removal. These unfortunate I components. The engine manufacturers contend

engine removals were largely caused by maintenance person- that use of auto fuel in an aircraft induces

nel failing to thoroughly flush and clean all aircraft oil system unnecessary risk.

components. As a result, the factory Product Support Depart-ment now sends the following tag with every service engineleaving our factory:

Engine Suggestions For Operators

OIL FILTERS

Clean engine oil is essential to long engine life. Generally.service experience has shown that the use of the external fullflow filters can increase the time between oil changes providedthat the filter elements are replaced at each oil change. Under

normal operating circumstances the oil should be changed every50 hours, and the oil filter element should be replaced after each

50 hours of engine operation, and the filter element cut open Recommendation Regarding Use

in order to examine the materi_al trapped in the filter for evidence Of Incorrect Fuelof internal engine condition. However, operation in dusty areas

or cold climates may require more frequent oil changes despiteThere has been an increase in the number of incidents In

the use of an oil fliter. An engine which sits for long periodsthe past two years of the accidental use of the wrong fuel

between flights should have an oil change at four month inter-particularly turbine fuel. Turbocharged piston engines with the

vals regardless of the limited flight time accumulated. The filterterm "Turbocharged’’ painted on the engine nacelle have been

cannot filter water and acids which may accumulate in the oil.interpreted by refueling crews to require turbine fuel. We must

remind the pilot-in-command again, as we have over the years,OIL CONSUMPTION

he or she must be responsible for the proper fuel in the aircraft

Oil consumption is a very important trend to monitor in tanks at refueling.an engine. The operator and maintenance people should know

Turbine fuel, or a mixture of turbine and aviation gasoline,the general history of oil consumption during the life of the

.has proven to be a particularly ruinous fuel for piston engines.engine. It is typical of an engine during seating of new piston As a result, if the engine has been operated with this unspecifiedrings that oil consumption may be erratic or high; but after the

fuel, qualified maintenance personnel must make a detailed in-

rings are seated, generally within the first 25 to 50 hours, oilspection of the engine with particular attention to the combus-

consumption should level off below the maximum limitstion chambers. If detonation has been severe enough, further

established by the manufacturer. Later, during the life of thedamage will occur to crank pins and main beanngs,

engine, if there is a noticeable increase ofoil consumption withincounterveights and valve train components. In view of possi-

a 25-hour period tone quart or more per hr.), this could be able damage, disassembly and inspection of the engine parts is

danger signal and calls for an investigation, the only safe recommendation that can be made after the engineThe oil screens and filter should be carefiilly observed for has been operated with improper fuels. If it has been determin-

signs of metal, and maintenande personnel should take a com- ed that the engine has been run on unspecified fuel, do not con-

pression check of the cylinders, preferably using differential tinue to operate it unless it has been inspected and cenified to

pressure equipment, and also look inside the cylinders with a be airworthy by competent maintenance personnel.boroscope or gooseneck light to detect any unusual condition.

Textron Lycoming Service Bulletin No. 398 is the latest

THE AIR FILTER reference concerning Lycoming engines which have been

The induction air filter is a very important element in the operated with unspecified fuel.

life of an aircraft engine. With the modern high performancepowerplant, the operator must keep dirt and abrasives out of

the engine if it is to attain the expected life and trouble-free

hours. Although this is ~maintenance responsibility, theRecommendations For Aircraft Or

pilot/owner should be aware that excessive wear and earlyfailures of reciprocating engine parts is due, in many instances, Engine Struck By Lightningto contaminates introduced through or around the air filter. The

aircraft manufacturer’s instructions for maintenance of the airTextron Lycoming Service Bulletin No. 401 makes recom-

filter must be closely followed. When operating in very dusty mendations to operators any time an aircraft has been struckor sandy conditions, it may be necessary to service the filters

by lightning. It points out that damage to an aircraft, which has

daily or every few hours in accordance with the airframebeen struck by lightning, is often confined to a specific area

manufacturer’s recommendations. of the structure. In such instances where the engine and its ac-

cessories, controls, fuel or exhaust systems are involved, it is

necessary to evaluate and repair the damage before the aircraft

is flown again.

Top Overhaul The Service Bulletin explains that although the path of the

lightning may appear to have been around the external hous-

We are frequently asked the question should my engine ings of the engine components, it is nevertheless impossible to

have a top overhaul at some point between major overhauls? assess the internal damage that might have occurred by heat dur-

Our reply to that question is top overhauls should only be ing the lightning discharge. Therefore, in the event the engine

done when needed on the diagnosis of a competent mechanic, has been damaged by lightning, disassemble and inspect the

It is unfonunate that too many people are spending money component parts. Heat generated by the arcing effect of the clec-

needlessly on a top overhaul. trical discharge can cause irrepairable damage to the hardened

surfaces ofball bearings, crankshaft bearing surfaces, camshaftWith proper operation, good maintenance, and frequent

lobes, gear teeth and other parts that are surface hard-night. today’s engines should reach their expected TBO without

ened. These pans should not be reused if discoloration, cracksa top overhaul along the way,

or other indication of damage by lightning is evident.

Keep Your Direct Drive Engine page or a hard ground strike has caused subsequent en_glnefailures. Some faiclures resulted from an overstressed crankshaftStarter Clean To Avoid Troublegear dowel which ultimately sheared. When this part breaks,all power is lost.

Too many starters used on our direct drive engines are be-

ing returned to us at the factory reported as malfunctioning, but In other cases, stoppage or ground strikes have resulted In

investigation here revealed the problem to be dirt. The loca- over-stressed connecting rod bolts which failed soon thereafter.

tion of the starting motor on many aircraft engines subjects the When a rod bolt fails, it allows the connecting rod to get loose

Bendix Drive of the starter to contamination from dust, dirt and and flail inside of the engine causing a nasty failure with a

moisture because the drive housing is open and the engine con-serious fire potential.

stantly circulates air around the starting motor. After a prop strike or sudden stoppage, the pilot and a com-

Typical indications of a dirty Bendix Drive are: petent A P mechanic must decide what to do after a careful

inspection of the engine; and the incident must be entered ini, Sluggish operation operator has to make several attempts the engine logbook. If a decision is made to disassemble the

before the starting motor will crank the engine. engine, it will require a skilled mechanic who knows what to2. Noisy operation a grinding noise when the starter is look for in the affected engine. When in doubt, do the safest

energized, thing, consult Textron Lycoming Service Letter No. 163.

3, Failure to engage.Whenever any of the above complaints are received, the

starting motor should be removed immediately and the Bendix

Drive cleaned and lubricated. Oil should never be used because Some Tips On The Lycoming 0-235 Engineoil in thatrocation collects dust and dirt, becoming gummy and

causing the Bendix Drive to stick. Little things are sometimes forgotten. For that reason, a

In most cases it will be necessary to partially disassemblereminder is sometimes necessary. In the case of the Textron

the starting motor in order to service the Bendix Drive. TheLycoming 0-235 engine, it is a little different from most other

latter should he removed from the motor shaft to insure thoroughLycoming models. Other models are equipped with hydraulic

cleaning and lubricating. Clean the arw in front of the Bendix tappets which do not require frequent adjustment. Occ~sional-

Drive pinion before removing the drive from the shaft.ly there is a report of an 0-235 which is running rough or not

producing normal power. Investigation often reveals that theDo not use carburetor cleaner or any cleaning solution that solid tappets of the 0-235 need adjustment. The L~comingcould damage the rubber block inside the Bendix Drive. Use Operator’s Manual states that valve rocker clearance should be

only clean petroleum base cleaners such as kerosene or varsol. checked, and reset if necessary, at each 100-hour inspection.Thoroughly clean the Bendix Drive to remove all dirt and We find that since this engine model is a little different, this

contamination from the sc~rewshaft threads and control nut. If inspection item is often overlooked. This reminder may helpthe drive is exceptionally dirty, the drive pinion cup can be operators of the 0-235 engine to keep it running smoothly.removed to insure a thorough cleaning job. Do not attempt to A second problem sometimes reported with the 0-235remove the control nut, engine also is the result of it being just a little different from

After the Bendix Drive has been thoroughly cleaned and other Lycoming models. Some 0-235 engines which use a full

blown dry with compressed air, lubricate the screwshaft threads flow oil filter have had very low oil pressure at idle after beingand rachet with a silicone spray. Lubricate the motor shaft with overhauled. The oil pressure would then increase as power was

the same silicone lubricant before installing the drive assembly increased and decrease as power was reduced. This inconslsten-

on the shall. cy from the normal oil pressure indications was traced to im-

For more details on the above, refer to Prestolite Service proper installation of the oil filter adapter. Textron Lvcomlnce

Publications ASM-7 (revised 3-15-75). Also refer to TextronService Publication SSP-885-1 provides instructions for this

installation.Lycoming Service Instruction No. 1278.

These instructions specify that for the 0-235 engine only,

a plare--lycoming Part Number LW-12999--is to be installedbetween the accessory housing and the oil filter adapter. The

plate is sandwiched between two gaskets--lycoming Part

Propeller Ground Strike or SuddenNumber LW-12795. The plate is designed with a hole that

meters the amount of oil flow and prevents an excessive flow

Stoppage Can Be Dangerous of oil to the idler pear. When this plate is not installed as re-

quired, it results in the oil pressure discrepancy discussed eclrller

As an engine manufacturer, we are often asked to guide Anyone who has occasion to install the oil filter kit after

pilots and mechanics concerning what to do about an engine overhaul--or at any other time--should follow the

after sudden stoppage, or a ground strike by the propeller. Tex- carefully and should consider that the 0-235 installation is ~llpht-tron Lycoming Service Letter No. 163 states our position con- ly different from other Lycomin_e models.

eerninf this problem, This important publication points out there The preceding paragraphs seem to plctun the 0-’35 ~nrlnr

mav be hidden internal engine damage from such an incident. as an eccentric problem creator which it certainly is nut. ~V’henFu;thermore. the unseen damage to an en_elne by sudden stop- the engine is malntalned and operated In accordance with

manufacturer instructions. it is so reliable that in 1986 many ed with the letter S. The S indicates a "slrvict: part" which

m~dels became eligible for an increase in TBO. Textran Lycom- will alwavs have a median weight. Use of a connect~ng rod

ing Service Letter No, L213 grves the details which owners of stamprd;Hith an S will insure that the weight match between

an 0-235 engine may want to examine more closely. Starting rods is always within the tolerance allowed by the Lycomlnce

in June of 1986, all new, remanufactured, and factory overhaul- specification for that particulnr part number.

ed 0-235 engines which have compression ratios of 8.5: 1 or If a piston is to be replaced, it is strongly recommended

8.1:1 are built with a new increased strength piston, Part that the powerplant mechanic refer to Lycominl Service Instruc-

Number LW-18729. This part change. together with past ser- tion No. 1243. This service instruction shows that certain pistonvice history, will allow Textron Lycoming to increase the

part numbers are designed to fall within a specified standard

recommended TBO from 2000 hours to 2400 hours, weight range. Any genuine Lycoming piston with that pmt

For those individuals who own an 0-235 with 8.5:1 or 8.1:1 number will be a satisfactory replacement, although the H´•elchts

compression ratio, a TBO Errension Kit is available. The kit of each piston should be compared before installation.includes four new pistons and all other parts necessary for the Other pistons are marked as A or B wrights and are used

change. It should be noted that the TBO extension may only in matched sets when an engine is built. When these pistonsbe applied to those engines which contain 100% GENUINE must be replaced as a partial set, "service part" pistons are

Lyeomine pans, provided by Textron Lycoming. These will be marked with AS

Those 0-235 models with a compression ratio of 6.75:1 or BS and are restricted to a very narrow weight range whtch

are immediately eligible for a 2400-hour TBO if they contain falls between the A and B weights. Use of these pistons as

1004 GENUINE Lycoming pans. For those owners who have replacements will insure that the entire set, both old and new.

maintained their engine reliability and durability by using only fall within overall weight limit tolerances set by Testron

~ycominp parts, this notification of increased TBO is good Lycoming.news, Connecting rods and pistons are one more example of the

need for appropriate reference materials when working on

Lycoming engines. Overhaul Manuals, Parts Catalogs, or ser-

vice instructions are the source for those details we cannot r~-

Notes on Replacing rain in memory.

Connecting Rods or Pistons

An anicle an Engine Balance explained that certain engine Maintenance Tipparts are organized in matched sets, by weight, before they are

installed in an engine being built at the Lycoming factory. Oc-Fuel injector nozzles are occasionally blocked by

casionally, it may be necessary to replace one of these partsmicroscopic pieces of brass, rubber or other foreign matenals.

during the operational life of the engine. When this happens,Particularly with the older style, one piece nozzle, cleanm_e the

mechanics in the field should know that Lycoming parts whichnozzle and line may not remove these tiny bits and pieces which

are matched by weight when an engine is built should only becan serverely restrict fuel flow. Standard procedure after any

replaced with pans which fall within design specifications forcleanine or maintenance of fuel injector nozzles should Includr:

service (replacement) pans,a flow check to determine that all noules flow a smooth, stead~´•

Staning with connecting rods, the system of marking stream with no fluctuation. The amount oftlow from each nozzl;~pfcifies that each part will be marked with one of these let- should also prove to be the same when the fuel is viewed after

ters: A, B, S, D, or E. Connecting rods with the same identify-a flow check. A fluctuation of fuel flow or variation in the flow

ing letter are installed when the engine is new: if only one orto each cylinder may require a nozzle change or noule and lint:

two rods are to be replaced in the field, they must be those mark- change to achieve satisfactory engine operation.

LYCOMING MODEL CODE FOR

RECIPROCATING ENGINES

Each Lycoming reciprocating engine has a model designation. The designation is made

up of a prefix which is a series of letters, a three-digit number, and a suffix which

combines letters and numbers. The letters and numbers in this model code have

meaning. Most people who fly or work on general aviation aircraft are curious about

the meaning of the code, but only a small number thoroughly understand it. Perhapsthe explanation and examples provided here will promote a better understanding of what

the engine model designations do mean.

EXAMPLES: TO 360 CIA6D

IO 540 AA1AS

IO 360 A3B6D

PREFIX DISPLACEMENT SUFFIX

L Left Hand Rotation Crankshaft Cubic Inches* A or AA Power Section Rating

T -Turbocharged (exhaustgasdriven) *Note (541)- A 3 Nose Section

I Fuel Injected displacement B Accessory Section

G Geared (reduction gear) ending in "1" 6 Counterveight Application

S Supercharged (mechanical) indicates a D Dual Magneto

V Vertical Helicopter specific engine (Subsequent changes to models

H Horizontal Helicopter model which are reflected in the suffix.)

A --Aerobatic incorporates

AE Aerobatic Engine integral

O Opposed Cylinders accessory drive.

With the information above and a few The three-digit number always provides fourth place in the suff~x will usually be a

explanatory details, the Lycoming engine an indication of engine size in terms ofap- number to indicate a specific counterweightcode is not difficult to understand. Starting proximate cubic inches of displacement. application. Depending; upon the need for

with the prefix section, an O will be found Engines currently in production at Lycom- a counterweight number, a D mav be used

in the engine designation of all flat op- ing Williamr;part have di~placemcntvalues aS either the 4rh or 5th chancier. The D

posed cylinder engines. In addition to the of235, 320, 360, 435, 480, 540, and 720indicates that the engine uses a dual

O, a combination of the other letters may cubic inches.magneto contained in a single housing.

To determine the minor differences in anbe used to further describe the engine. The The suffix of the reciprocating engine engine model which are reflected in theO alone indicates a carbureted engine, but code is a little more complex and the dif- model code suffix, it is necessary to con-

an IO will show that the engine is fuel in- ferences signified by each letter or number suit the engine specification. Mast aircraft

jected. A further example is the TIGO are not readily apparent. The first owners or pilots will have no need for this

prefix. Broken down, this says that the .characters of the suffix will always apply type ofdetail. Those who are curious about

engine is TT) Nrbocharged, O fuel injected, to the parts of the engine indicated in the an engine can get a good idea of its size and

lGj geared (which means the prop will run examples; in some cases, such as the character by simply applying the model

at a lower speed than the crankshaft) and, IO-540-AA1A5. two characters are used to code information which has been presentedfinally. the (0) for opposed cylinders, designate one section of the engine. The in this brief outline.

Lycoming FLYERissue No. 49 December. 198’)

Ibllshed by: Williamsport Plant Willlamsport. PA 17701

THE UNFORTUNATE CHOICE EDITOR’S COLUMN

There ore many who look for an aircraft engine on the open market. While there By ~en W. Johnson

is nothing wrong wi;h this approach to acquiring a needed powerplant, it sometimes Dear Friends:results in a purchase which is an unfortunate choice. Perhaps a little information on This is m~ "Goodbve" issue afterthe possible pitfalls may help to reduce the number of bad choices. exactly ten’vears as~ editor of the

Individuals working on home built aircraft are particularly susceptible to this L,Tomlng FI,er. As I move into retirr-

type of error. At Lvcoming. there have been many calls from people who grabbed an,,,t .t the end of 1989. it is evident

I´•neinr which seemed to he an exceptionally good deal only to find that this that there ha\´•e been many things that

"pnpine of their dreams" woultl not fit into the aircraft they are building. helped to make the Fl~er and I~r)´•Cooniider the circumstances which lead to these problems. The person looking Reprints what the!, Lire.

lilr all engine is usually building an aircraft from his own plans or from a kit supplied First, the many vears as a Naval a~ ia-

t,v it kit manufacturrr. tor did much to prepare me for my roleIn the latter case. a particular engine model is often recommended. Finding

as editor. Second. my predecessor, blr.lhill mutlel engine available, and for sale on the open market, may be virtuallly J,, Diblin. had alreadv established the

imy,oskible. Lycoming requires an exchange engine core of the same model for any Fl~rr and Reprints as publicationsovc´•rhauled or remanufactured engine ordered. Since the home builder is starting with an eucellellt reputation. He alsoCrtrnl scratch. there is no core to exchange. This means a new engine is the only left volumes of written illformation fromreilclilv available option: for many, this option is prohibitively expensive. which 1 acquired much of my know-

As the airframe hegtns to lake shape, obtaining a suitable engine may be reason ledge of the flat. opposed cylinderli,r kc,me concern and anxiety. When a Lvcomine 0-320. 0-360, or other engine with

Lvcominp engine. Third. the compnn~Ill’l’n,l’’iil~e horsel’ower rattng is round: there is a temptation to buy now and ask

_ first A~ro and now Testron haslater. This could be a serious mistake. paid the bills while giving me freedom

*I’I1(´• article "Low Time Engine hlav Not Mean Quality and Value’’ whichto write what seemed to be most apyru-

ul’l"’u".’l in Fher No. 48 explained that old engines with low time are frequently priate for L!c´•omin~ engine owners.

c~ll´•c´•tc´•rl L,v int;nlal rust and corrosion. Any engine which is not used frequently But. it has been vou. the readers, whoslllll~ltl I,c´• preserved. The condition or the engine is just one of the items to he

have really helpetf the cause.

when acquiring a power plant in the resale market. There have been numerous questions()tJlrr n,istakes often involve the engine model. Unfortunately there are those ..d comme,,ts From readers which

who I,~´•lic´•vr Illat all Lvcomine 0-320 engine models are alike and that all Lvcoming pointed the direction fur articles which()-3(,() c´•nFillr Inotlels are also ven~ similar. The Lvcoming certificated aircraft later provrcl I~rllrlicial for all. The

(ItlFillll li~l hlll)Wk 58 0~320 motlels ~ntl 51 0-360 models. While these engines may ,,j,, thrust of Ille Fiver hits beenI,r´• hil~lililT II1 tllilllV resl)ects. it is the differences which are likely to cause installa- simple pro~ide information Hhic´•i~~ioll I""’t,lc´•~lls atltl H.JliCII SIIould I,e well understood before an engine is purchased. will help readers to get the best possible

What are tllesr differences which may cause installation problems’! The engine service from their Lvcoming enpille.n,oullch hllOUI~1 l,e considered. Older engine models were built with conical mounts ,,d t,.,,k, Il!in~ safer.which make illstallation somewhat easier. hut which do not dampen engine vibration It has I,eetl a Illeadure to speak wtthu~ well. With very Few exceptions, engines certified during the 19705 and 1980s FI,´•er readers. L,oth by telephollrhave dvnaFocal mounts. and 1,1 persoll. The illvitations I have

Although tile type of engine mount is not likely to be a serious problem, the received to visit many of vour ur~anizil-sllill’C of the stlml’´• the location of the cad,uretor. or an engine mounted oil filter mav tions are greatl~ Jpprrrioled.rc´•.sule in ilirfranle interference which makes installation of a particular engine model Finally. tile Illallv letters rec.etvecjtlinir´•ul~ or iml,ossil,le. Some aircraft. For example. do not llave enough space r,,,, readers all over the world fromI~(´•1Wrl´•ll tile engitle alltl the fire wall for an engine mounted oil filter. In the case of Australia to %il~ll,a[,wr alld lust abolltutr c´•np;illr with it hingle unit dual magneto. there is nothing which can be done since r\´•ervwherr rl~r ha\e provjtlecl muc´•lltile is a required part of the engine design. All Lycoming engines with two praise for tile c´•oml,llnlr,l-irl(liviclunl can l,e conligurell to operate without an oil filter. Shoultl a,l oil

tarv letters Irrolll ~ou. the Fl,er readers.Illtc´•r u,ld the sl,ac´•e needecl to remove it l,r the only problem in adapting this tyl,e of have pn,,itl~´•tl .snliaCac´•tioll ilntl Ill(.t~ll-

c.~llzirlr to an airframe. tile filter anti adapter ran he removed and an oil pressure live for the editor. I thank vot! I;,rsc´•rc´•c´•n Ilou,sin~ c´•an l,e installetl il,steatl. Shoultl this step be necessary. the rec´•om-

,Ilc´•~ltlr´•tl oil cllrlllFc. i~ltrn´•nl is rt´•tlurrd to ~5 hours. A second option would i,l~olve

rt´•movine the filter fronl its stalldartl loc´•ation atld mounting it remotely.

I~npint´• to lirpwall is Ilot t~lr o~llv area \\here s~,ac´•e nlav be limited. Tile sump is

ollcrr in,sizr anti ~ll!l,r to rneet tJle re(luirements for a particular airframe.

I:or tllat T(‘ilh()ll tile Il~,nlrl,uiltlrr rnav fitltl tl,at ~onle engine motlels will not fit tJlr

una*Gu~ El, oN 1’4(;E 6~

TEXTRON LYCOMING LIGHTWEIGHT STARTER

CYLINDER BARREL SURFACES AVAILABLE FROM LYCO~IING

There are pilots a_nd technicians who remember when the TBO’s for general Aircraft weight and balance is a criti-

aviation piston engines were much shorter than thev are today. In the 1950’s and cal factor in aircraft design. The weightcurly 1960’s, normal overhaul at 800 hours of operation was the recommendation for of the engine and accessories in the

most Lycoming engines. An engine examined and found to be in good condition nose of the aircraft must be balanced by

mibht he extended for 200 hours on two occasions. This made 12M) hours the some equivalent amount in the b~ck of

maximum TBO for even for the simplest direct drive engine, the aircraft. Because of this, aircraft

Today, 1800 or 2000 hour TBO’s are recommended for many Lycoming builders both individual and c´•ompa-

engines, There are a variety of reasons for these significant increases in recom- nies often find it desirable to reduce

mended TBO. This discussion will be directed at the methods used to reduce the weight of the engine and accesao-

cylinder barrel wear and the reasons why Lycoming prefers the nitriding process. ries. This is not an easy task since most

The first Lycoming opposed cylinder engines with a design similar to today’s items attached to the engine are consid-

models were certificated in the early 1940’s. These early engines were designed with ered to be necessary.

low compression, were relatively low in horsepower, and were built with plain steel To assist aircraft builders with weight

cylinder barrels, reduction, Lvcoming has developed and

certified the Lycoming light weight stnr-As higher horsepower engines were developed, compression ratios were

increuked. The higher compression ratios caused increased cylinder wear, To com- ter which weighs less than 11%

bat this increased wear, and to provide a desired improvement in recommended POU"dS. Use of these new starters will

TUU, harder cylinder wall surfaces were needed. reduce weight approximately 5’/r to 6’/,.

The plating of cylinder walls with chromium to obtain a harder wearing surface p"U"dS depending upon the model

was an invention of the 1930’s. As larger and more powerful engines were devel- being replaced.

oprd, the use of chrome plating became standard in the manufacture of Lycomingrvlinders. Cast iron rings were used in a variety of combinations to keep oil

consumption within specifications. The increased cylinder lire did contribute to

longer TaO’s than could be obtained with plain steel barrels.

In spite of the good results in terms of cylinder wear, the use of chrome platingcreated many manufacturing and quality problems. Any cylinder barrel surface must

l,r capable of trapping and retaining enough oil to provide good lubrication between

piston rings end cylinder wall. Chrome is not oil wettable, and therefore, each

c)rrome plated cylinder barrel had to receive a secondary treatment which could

create a channel chrome surface which was porous enough to hold the needed

lubricating oil. For Lycoming this was not a cost effective program.

Obtaining a quality product consistently is also very unlikely when chrome

plating cylinder walls. The plating process is very sensitive. Absolute cleanliness is

,lecessnry. Even a tiny speck of dirt mav cause a spot where the chrome does not STARTERSadhere to the cylinder wall. Inspection ofthe cylinder barrel may not reveal this naw Th,., Lvrumlne Jtnrlrr u c,n

until slier tile engine has been run. Ih~ le/I clnd Ihe Pr~slol,lr slnrler rs; on Ihr

After the engine has been run, it may be too late. Should a tiny piece of ehronle riFrhl.

r,rcl away from the cylinder wall and be dispensed through the engine, this very hard

~nutc?riul will contaminate the engine causing bearing surfaces to wear quick". The I" mo"t cases, the Lycoming light

rC’huIt could be a very short TBO. weight starter is a direct replacement

Lycoming had years of experience with chrome, and as a result, the need for afO’ fhe standard Prestolite starter pres-

Il~ltr?r process was very evident. The development of the nitride hardened steel allov entry used on most LvcominF direct

was a great step forward. Manufacturin~ is simpler, and the compdrive engines. Some engines with altrr-

homogenous surface results in consistent high quality in the final product. Nitrided ""~O’S mou"ted on the left side nlav nut

cvlintlrr~ also produce excellent oil consumption results when the engine is properly accommodate the lightweight starter.

Lrokol in,The pad used to attach the starter to the

What ih nitriding’! It is the addition of nitrogen to the surface of an alloy steel engine is the same, and the electrical

I"udu’ine B hard, wear resistent surface. The introduction of nitrogen into the wiring connections are also duplicated.

hU~(´•C luvers of allov steel is brought about bp subjecting the prdcticallv nnisherfI" Some cases the alternator allorhinp

I’L"I" 10 ill) atmosphere of ammonia gas. The process requires special heat treatinglink map require modification bv himplvadding a spacer, but this is a verv minur

hlnlac´•rh wllic´•h are air tight and capable of holding the parts at high temperature.

At a hc!at level of 975 degrees rahrenheit, the ammonia gas nowing into the furnacr adjustment.

ih l,roken down into its elements, hvdroSen alld nitrokell. This is the source of the The pinion Fears on starters For

wl,ic´•h llenetrates tile surface of;he sleet. To produce a satisfactory nitrided LYcoming engines come in 1~14 pitchand ]0/12 pitch. To utilize the 1%/1~

~urfut.e, tile ~,mc.ess must be continuously operatetl for up to 80 hours.

I’rotluc´•tjon of nitritled cvlintlerbarrels began at Lycoming in 1960. The service I’ifch, the starter ring gear will havr

149 teeth. A ring pear with 1’’’’ teethrc´•c´•ortl of tJlc.be nitritled cvlinders has been excellent. Only a few small, low power

c´•ngi~lr´•h are l,uilt with plain steel barrels todav. The vast majority of Lvcomin~Will accept the 10/12 pitch pinion gear.

c~ngineh have nitritlrd I,arrels when they leave the Carton’. Some favorable character-The light weight starters are currenl-

Iv available in both 12 and 2´•1 volt motl-iMfi(’k of I,arrels are:

els wit)t 12/14 pitch pinion gear~. II I.s

i. c´•vlillder wall wear the harder a surface the more cliflicult to e?tpec´•ted that 10/1:’ pitch lipllt weightwear down.

(COATINUEI, ON PAC;E 71

EXHAUST SYSTEM MAINTENANCE The third type of exhaust flange rence. A close visual check at each

PAY NOW OR PAY LATER gasket available from Lycoming has periodic inspection and prompt atten-

V-shaped spiral wound layers of stain- tion to correct any defect which mav be

It is unfortunate that the exhaust less steel and asbestos. These gaskets found will usually be enough to avoid

systems attached to aircraft engines are are available for all Lycoming engines the need for more expensive repairs.

one of the most overlooked and ignored using the 2 or 3-hole gasket design. Exhaust systems with slipjoints

parts of the aircraft. Almost all aircraft This design provides a resilient action present another problem. The joints are

with normally aspirated engines have that automatically adjusts for mechani- necessary because the pipes must

an exhaust system supplied by the air- cal compression, internal pressure var- move. Vibration, along with heating

frame manufacturer. Engines which are iations, and temperature changes. The and cooling of the system which causes

turbocharged by Lycoming will also spiral wound exhaust flange gasket has expansion and contraction make it

have most of the exhaust system sup- superior sealing qualities and, unless essential that the system be designed so

plied by Lycoming. an exhaust leak is evident, may be that it has flexibility. Exhaust residue

Lycoming technical representa- reused when the exhaust manifold is and heat may eventually cause slip-

tivcs get many calls about exhaust sys- loosened or removed. New gaskets joints to seize. Because a slipjoint

tem problems. It makes no difference should always be used when the engine which has seized can be expected to

who supplied the system. There are sev- is overhauled, cause breakage of the exhaust system

eral areas where discrepancies may All exhaust flange gaskets which pipes, regular maintenance to keep

occur loose baffles in the muffler, were originally designed with asbestos these joints free is a must. Mouse hlilk

exhaust leaks at the exhaust flange as one of the basic materials are now or a similar lubricant should be applied

Rasket, and slipjoints which do not slip. manufactured to a new standard. to the slipjoint at regular intervals to

Exhaust gas leakage at the exhaust Although the part number may be the prevent seizing of the pipes.

flange gasket will cause erosion of the same, asbestos has been replaced with Maintenance of an exhaust system

aluminum cylinder head material, and an alternate material. with siipjoints is a pay now or pay later

a frozen slipjoint will cause cracks in At each periodic inspection, the situation. If the preventive maintenance

the exhaust pipe system. Loose baffles exhaust system should be checked to is not accomplished, it will mean bu~-

in the muffler may result in a loss of insure that exhaust gases are not leak- ing new parts for the exhaust system.

power. These problems can be minim- ing at the exhaust flange. A leak can be Paying for a new exhaust system is not

ized by regular exhaust system mainte- identified by the powdery residue which the worst part. A broken pipe could

nance at each periodic inspection, will be evident around the place where allow hot exhaust gases to escape into

The muffler should be checked the leak is occurring. This residue may the engine compartment where there is

carefully each time the exhaust system range from white to light brown in color. the potential for fire which would fur-

is inspected or anytime a loss of power A leak at the exhaust flange gasket ther damage the aircraft and present a

is evident. Baffles which have come is often caused by improper torquing. serious hazard for pilot and passengers.

loose tend to lodge at various places Too little torque and the connnection Maintenance on this type of

inside the muffler. When the exhaust loosens. Too much torque and the exhaust system requires that it he taken

outlet is blocked, a power loss will gasket will bow slightly again allow- apart if the slipjoint will not move.

occur due to the excessive back pres- ing exhaust gases to leak. If left uncor- Should a slipjoint be frozen, Mouse

sure created in the exhaust system, rected, erosion of the aluminum cylin- Milk or a good penetrating oil should be

Attempting to look into the muffler may der head material will occur quite used to free it up. Then each joint must

reveal baffling which is loose, but usu- quickly. A loss of material amounting to be cleaned of all exhaust residue and

ally this is not something that can be only a few thousandths of an inch could thoroughly examined to insure that

determined visually. A sharp bump on be enough to make the cylinder unus- there are no cracks or damage that

the muffler with the palm of the hand able. Therefore, correcting the problem would prevent free movement. Before

while listening for any rattling sound quickly is essential. reassembling the exhaust system, the

may produce better results than look- If the aluminum cylinder head slipjoint surfaces should be coated with

ing. II. loose ba~fling is found, the muf- material has already s;oded as the high temperature lubricant such as

fler should be replaced with a new or result of an exhaust gas leak, repair is Fel-Pro C5A or equivalent.

overhauled unit before the next flight, sometimes possible. This cannot be Exhaust system maintenance prob-

Another important part of the done by hand. Studs must be removed ably should not be considered as com-

exhaust system is the exhaust flange and the damaged surface refinished by ple;e unless it has included a review of

gasket. Three different types are avail- use of a milling operation. No more airframe and engine manufacturer bul-

able from Lycoming. The manufactur- than twenty thousandths of an inch may letins which may apply. From time to

ing standard is the copper/asbestos be removed. Should it be necessary to time product improvements are made

gasket or the beaded gasket. Where the remove more than twenty thousandths available. A prior review of service bul-

beaded exhaust flange type gaskets are of an inch to obtain a true surface, the letins would allow these to be ineorpor-

ubed, they must be assembled (two each cylinder should be replaced. ated when the regular periodic muinte-

per exhaust port flange) with their Where erosion of the cylinder nance is being done.

beads interlocking. The flat side of the head has not occurred, replacing the The point of this entire discussi(,n

gasket must face toward the cylinder exhaust flange gasket with a new one is to point out the need for regular

head, and the raised or bead side, will usually eliminate the leak. Insuring inspections and preventive exhaust sv~-

toward the exhaust stack. After initial that the correct torque is applied during tem maintennnce. Prevention is alwa\´•h

installation, exhaust nange nuts should installation of the gasket is necessary to less expensive and less hazardous than

be carefully retorqued after the first 25 avoid future problems. waiting for serious problems to occur.

Ilours of engine operation. These stan- Fortunately, an exhaust leak at the

dilrd gaskets should not be reused. exhaust flange is not a frequent occur-

THE "SAME ENGINE" MYTH

Questions which frequently are

asked of Lycoming sales personnel,engineers and technicallepresentativesindicate that there is a myth regardingI~ycuming piston engines. This mythseems to be prevalent among aircraft

owners and aviation writers. In the

minds of these individuals, each

engine series is essentiallythe same. For example, all 360 cubic

inch displacement engines are inher-

ently the some except for differences in

fuel metering or turbocharging. The

idea that these engines are the same is~i´•

false. A few specific examples may help

to put this myth to rest.

Lycoming builds 0-320 engineswhich produce 150HP or 160HP. The TEXTRON LYCOh´•IING T1O-540-J2BD

150 HP 0-320-E series engines operate Th, TW‘en~mepirrurpd on Ihe next pc~e ic A’OT n cierr3~ri q/the thr 11; nlnlo prrlc´•s

at a compression ratio of 7.0:1. The en~ine pictur~cl abulr. "The 5A~IE EIYGINE’ M,´•th" nrticle on Ihes~yapt´•s hns morr clt´•lalL. I ~The

0-320-D series has high compression pictur~s are nol Ihe strme sccrle)

pistons which raise the compressionratio to 8.5:1 and increase rated output

to 1GOHP. Those who believe that the gested that by putting 10.0:1 compres- AF1A and the ~a\aJo ?;eries rnFlnrb

pihtons are the only difference in these sion ratio pistons in an 10-360 engine, are: small main I,earinp instead of large

engines will be disappointed when they it could be the same as the main l,earing. 8.0:1 comprrssion ratlu

plan to upgrade their 0-320-E to the HIO-360-D1A. These are some charac- rather than 7.3:1. interc´•uuled and nol~-

hiaher horsepower by simply changing teristics of the HIO-360-D1A helicopter intercooled. presaurized Slirl; mapnt´•tus

pis~l,ns. Many models in the 0-320-E engine which can be compared with the versus BendisiTChl nlapnetos, and an

,s~´•ries were designed for the purpose of data on the 10-360 listed in the previ- R~.45AD1 fuel i~ljector in place of the

kc´•el)ing the cost down. Thousands of ous paragraph. To start, the HIO has K~AIOADI inirctor. Thrrr are aomr

these low compression engines were conical rather than dynafocal mounts. other differences. I,ut those comyerl-

built with plain steel cylinder barrels The main bearing is a thick wall bear- sons listed shoul(l convince even

in´•~cnd of the nitrided barrels used in ing instead of the thin wall, high crush tile most skeptical that these engines

the CJI-320-D series engines. They also bearing used in the 10-360. Other dif- are vastly different.

had two narrow bearings instead of one ferences include: crankshaft designed By making comparisons of various

long front main bearing. The engines for small crankpins, high speed cam- parts and accessories used in engine

w~´•rr certified at 150HP and were not shaft, rear mounted RSA7AAI fuel models which some individuals have

intended to withstand the additional injector, large intake valves, and tor- considered to be much the same, it is

.slres.s of higher horsepower. sional vibration damper magneto possible to illustrate the differences.

Because of the similarity in designa- drives. Although some L~coming models art´•

tion, it would be easy to believe that the Finallv. l,oth the Navajo engines and closely related, this cannot he

().361J-A1A and the IO-360-A1A are the new turl,oc´•har~ed Lycoming used in assumed. A of the engineering

the hnmu engine except that the first the Illoonev TLS are equul,l,eed with dif- parts list for each engine model by a

I´•~lginu h:i a curburetor and the second ferential a;ld density controllers which knowledgeable individual is the onl\

a fuel injection system. Here are some autonlatic´•all~ set tile maximum allow- sure way of establishing similarities and

fcu~urcs of each engine for comparison. al,le horsel,;,wt´•r when the throttle is differences. For those who ma, have

The 0-3(j0-A1A has a bottom mounted aclvancc´•rl hlttv for takeoff. Some who been taken in by the mvth that 811

uprlruft carburetor, parallel valves, have not taken the time to compare L~eoming engines of a particular diu-

8.5:1 compression ratio, and produces these engitles Ila\r jumped to tl,e r´•on- placemeent are much the same.

IHI)HI’. The 1O-360-A1A features a c´•lusion that tile which vou are now armed with a better knnn-

Irorizontill front mounted fuel injector, I,owers the Moollrv TLS is sinll,lv a ledge of this subject.

angle valves. 8.7:1 compression ratio, c~erated Navajo rll~illr. This c´•onclusioll

;Irrd is rated at 200HP. The IO-360-A1A c´•oulcl harcllv I,r nl~,re inacc´•urate. The

ill~r, these design items Illost ol,viou~ cliCfrrenc.r. e\.e!~ to the

ilre not included in the 0-360: c´•oml,lelr Ilo~ic´•r. (´•n11 I,e srr~l look-

I~jhlOll I1OZZ1l´•5, stronger crank- illi: at tile roc´•lrr I,o\ co\rrs. TilePERRIISSION TO KEI’HINT

.shult. tollRur and groove connectill,P l’l()-540-AFlr\ i~ rated at 2701-11’ a,lcl

rclrls witll hlTC1CII bolts. tuned intake Ilax clowtl rs)lilu~t c´•vlill-

hySt(~l)l. lll1d rotator tyl,u intake valves. cft´•rs. l’llt´• Nil~ajl, srrirh liatl tilrrC2l, loll:: Illr (()llt"\t ol lll1()rlll~lllOll

’I:llc´•rc´• ilrc´• ilcr~ually few rl,~i,leh at 325HP. alld

c´•~r´•l´•l’l I~lr Lha 300 c´•ubic illl´•ll disl,l;l~´•e- c´•rc´•tlrt i?.

111(’t1t.

’I’lrcn´•;lre i,ldividualx \\hu havct.u´•l!p- dilrrrrllcc´•b rrhl,rc´•li\´•rl!~ in tile ’70Ht~

ENGINE ACCESSORY TBO

Do engine accessories have a speci-fied TBO’ This question has been

asked by Flyer readers on several occa-

sions. Except for early throw-away ver-

sions of Slick magnetos (4000 and 5100

series) which were produced during the

1970s, accessories are not assigned a

specific number of hours which they are

expected to operate.

bIay we assume then, that the TBO

for accessories is the same as the

engine on which they are used’ For

many accessories this is not a bad

assumption. An Air Research Industri-

al Division Service Letter states that

."iturbochargers, controllers, wastegate

:t´• valves, and pressure relief valves man-

ufactured by AirResearch should be

overhauled when their service time

reaches the TBO of the engine. A com-

municaticln from the Romec Division elf

Lear Siegler also indicates that Romec

TEXTRON LYCOMING TIO-540-AF1A fuel pump overhaul should coincide

with overhaul of the engine on which It

MAGNETOS NEED TLC cloth if necessary, (c) lubricate felt is used. According to manufacturer

located at the breaker points and at the documents, fuel system products such

It would seem to be self-evident that distributor gear bearing, an (d) time as injectors and flow dividers from Ben-

magnetos err: a critical element in the magnetos in accordance with instruc- dix, and hIarvel-Schebler or Facet cilr-

reliable and efficient operation of the tions in the operatois manual. buretors are to be overhauled at the

reciprocating aircraft engine. A review The magneto manufacturers also time of engine overhaul. In the case of

of the Tcxtron Lvcoming Index for ser- make recommendations for inspection the carburetors. Facet does state that

vice bulletins, instructions, and letters and maintenance of their products. The service m~v be required prior to the

reveals that both the magneto and latest revision of Slick Service Bulletin engine TBO.

engine manufacturer have printed 2-80 says that 5200 and 6200 series Magnetos are a particularly cntlc~l

Ilumemus recommendations for the magnetos now being produced should accessor?l. Bendis Engine Products bul-

maintenance and inspection of magne- be inspected externally every 100 hours letin SB586A recommends maFlleto

fUh. and internally every 500 hours. The overhaul at the time of engine overhaul.

A,s il,l esaml,le, Textron Lycomine 500 hour inspection would include such This statement is qualified by stating

~l´•rvic´•e 183A was written in items as contact points, carbon brush, that magneto overhaul is recommended

LS)57 nlorr tllrtn 50 years ago and impulse coupling and other components at four-year intervals regardless of the

ih still all il(´•tiVr l,lll,lication. This I,ulle- subject to wear. Based on the inspec- time accumulated on the engine.

li,i hllllph that faulty engine perCor- tion, these components should be Unison Industries. the manufacturer

tlli~ll(’c’. ~)lln11 I)iStOllS illl(l engine Tail- replaced as necessary. blagneto rotor of Slick magnetos, requires that the cur-

un’s were tracrrl to inll,rol,rrlv timed shaft bearings must be replaced every rent 4"0016%00 series magnetos be

ianit;l,n;lntl illaclerluate ig,litioll insl,er- 1000 hours. inspected externally every 100 hour.s

tioll. Sl,lllr n,aintenunce personnel have These standard maintenance sched- and internall\ every 500 hours. Should

illhl’L’’’f~’l ipllitiUI1 tinljllg without using ules are supplemented by a series of the inspections find discrepancies

~I timil,F light to inrlicate I,reaker poillt service bulletins from the magneto man- which require it, the magnetos are to be

1.,I’L’"il~g. This is all error in ~ec´•hnirlue ufacturer. Bulletins usually require completely overhauled. In an~´• case.

killc’e it lilllille liSllt is IleCeSSaTY 10 inspections or hardware changes in total time in service mav not exceed the

Ilc´•llir\e rPcluirrtl arc´•urac´•v. addition to the routine maintenance manufacturer’s TBO for the engine on

Il~aintcnance items for special atten- items mentioned earlier. which the maeneto is installed.

tiol~ is the subject of Textron Lvcoming To summarize, magneto inspection The manufacturers of other aecessv-

S~´•rvir´•e instruction 1080A which is and maintenance should be a part of ries such as propellers, governors, I~rll-

claterl January, 1978. This instruction every regularly scheduled inspection. tion harness, starters. anti al~rmnlura

warns that inellicicnt engine operation, To insure engine reliability, this main- mar have specified TBOs for their prucl-

loss DC power, and detona- tenance must be conscientiousl) ucts, but no written ducumrnlntion

ti~,rl dcvclul,ing into pre-ignition could accomplished. Perhaps the best advice regarding these item,s Hab a~illlable

all I,e the result of lark of maglleto for the powerplant mechanic is to when this article was prepared. linlc.sh

Illclin~cnurlee. These maintenance research and follow the manufacturers’ there is notillcatlon frolll the milllurar´•-

iu´•tioll.s are rcc´•onlnlc~ldcd: (al check instructions at every periodic inspec- turer. it will be nt´•ces,zan. to c´•onsldrr

I,i. nlile~lrto breaker points. Ih) tion. accrssorv olc´•rhaul as a~l "aa nc´•etled"

(´•II(´•I´•I\ fr,r I)il in bPeaker c´•onl- requirement.

I’ullll,~´•rll anrl wills dr! with a clei!~l

ENGINE OVERBOOST SERVICE BULLETINS, LE?TERS, INSTRUCTIONS

PUBLISHED FROM JUNE 30, 1989 TO NOVEMBER 30, 1989Many Lycoming turbocharged

engines are equipped with density con- The service publications listed below are those which have been issued most

trollers. These engines are used in air- recently. We strongly recommend that a complete set of these publications be

craft such as the Piper Aztec, Piper maintained by all maintenance organizations which work on Lycoming reciprocating

Navajo series, the Lake Renegade, the aircraft engines. A subscription may be obtained through any Textron Lycoming

Aerospatiale Trinidad TC, and the Moo- distributor or directly from the Textron Lycoming FVilliamsport Product Support

ney TLS. Department. Call or write for a copy of Textron Lycoming Service Letter No. L114

The purpose of the density controller which provides a listing of available publications, prices, and ordering instructions.

is to aid the pilot. When the throttle is

fully advanced, the controller should SERVICE BULLETINS

assume responsibility for obtaining 486 Inspection of SINGLE BELT Driven Ring Gear Support Assemblies

rated horsepower from the engine. Note All new, remanufactured and overhauled engines shipped from

two very important items: (1) Should Textron Lycoming from January i, 1988 until June 12, 1989.

assume responsibility is based on the487 Fuel pump vent restriction TIO-540-AE2A engines with serial num-

controller being adjusted as described bers up to and including L9064-61A.in the latest revision ofTextron Lycom-ing Service Instruction 1187 and, (2) 488 Propeller governor line support All four cylinder engines with rear

Rated horsepower does not mean a spe-mounted governor.

cific manifold pressure. 490A Installation of intake and exhaust valve guides T10/LT10-550-

It is unfortunate that pilots who ny V2AD, -W2A engine.these aircraft do not always understand

SERVICE INSTRUCTIONSwhat the density controller is designedto do. This may also apply to some A 1187G Turbocharger density controller adjustment TIO-530-Ali\, -A1B,

P technicians. Let’s take an example. -A2A, -A2B, -A2C, -C1A, -F2BD, -J2B, -JZBD, -N2BD, -AAli\D,

Cold weather has just arrived with fury -ABIAD, -AF1A; LTIO-540-F2BD, -J2B, -JZBD, -N;?BD

and Mr. Pilot goes out to fly. On takeoff 1445 Precision Airmotive Service Bylletin No. PRS-91 Testron

he notes that the manifold pressure is Lycoming HIO-360-D1A engines.two or three inches below the red line

144~ Possible ruptured pressure regulator diaphragm in AN fuel pump.manifold pressure on the gage. Back on

All Textron Lycoming engines equipped with AN type fuel pumps.the around he tells his favorite A P

that he is not getting enough manifold SERVICE LETTERS

pressure at takeoff. When the A P

rtnds nothing wrong with the engine, he 114AC Reciprocating engine and accessory maintenance publications.

adjusts the controller so that the needle 214A Discontinuance of reconditioned camshaft exchange program.

on the manifold pressure gage goes to 227 Listing of parts catalogs and applicable revisions or special service

red line when the throttle is fully publications.advanced. Both of these individuals are

in error, and each time the throttle is

fully advanced, the engine is beingoverboosted. the engine is being forced THE UNFORTUNATE CHOICE Continued

to produce more power than its typecertificate allows, plane being built because of interference. As if this were not enough to be concerned

Generally speaking, overboost is bad about, the carburetor or fuel injector location must also be considered. These fuel

for the engine. It may cause exhaust metering devices are frequelltly mounted under the engine in an up-draft confipur~-

ciystem leaks. Internal engine damage tion, but there are also front and rear mounted configura~ions. Some enRinr models

from preignition or the excessive loads are equipped with horizontal carburetors. All of these variations in model may have

put on internal engine parts may also an effect on engine/airframe fit.

occur. But, you say, as a pilot I will Another error in choice which occurs all too frequently is the purchase of an

take my ehnnees with a controller which engine originally designed for a high wing aircraft when the builder has a low H’infi

causes the engine to produce more pow- design under construction. The low wing needs a fuel pump, but the high wing

cr than it is rated for. It may come in usually delivers fuel to the carburetor by gravity. in most cases a fuel pump cannot

handy if an engine should fail and I am be added to the engine because the drive mechanism was not built in during engine

faced with a Single engine situation on manufacture and the accessory housing was not machined to allow mounting of a fuel

the twin I fly. Keep in mind that aircraft pump.

performance is only assured when all As a result of contacts with individuals who have made engine I~u"´•hnses fur

parameters are the same as when the their aircraft, we know that the variations in engine configuration outlined in thl,s

aircraft was test nown for certification, article have resulted in problems. The purpose of bringing these issuea to the

The available rudder may not be adequ- attention of Flrer readers is to help them avoid making the same mistakes others

ate to handle additional power on one have made. Ifa particular engine model has been recommended by a kit manufactur-

engine. That extra power with too little er, it is best to search out that model. Although similar, other engine models may nut

rudtler might be enough to cause the meet vour needs. When buying a used engine in the open market, do not make illl

uirc´•rart to roll inverted. Too much pow- unfortunate choice get it right the first time.

cr may l,r´• just as l,atl as too little.

(CONTINUEI) ON L’AGI~ 7)

TEXTRON LYCOMING CYLINDER BARREL SURFACES Continued

RECIPROCATING ENGINE 2. Natural choked barrels providing improved piston ring life due to a resulting

TROUBLESHOOTING SCHOOL straight cylinder wall when engine is hot or operating, and a belter Job of

sealing.Texlron Lycoming Williamsport 3. Nitriding permits use of chrome plated piston rings which are more wear

offers a four-day, Monday through resistent and quite compatible with hardened steel.

Thursday, troubleshooting course for4. Nitriding provides a hardened surface with an increased fatigue strength.

aircraft mechanics. Emphasis is on the5. Nitrided barrels also have the ability to resist softening when heated during

diagnosis and correction of problems inengine operation.

various piston engine parts or accesso- The main advantage of chrome over nitriding comes into play when used

rics such as turhocharger systems, mag- cylinders are to be overhauled. Worn cylinder barrels which are out of sen.ice Jlmita

nelus and fuel injectors. k tour of thecan be coaled with enough chrome to bring them back to their ori~inal ~pecification.

Williamsport Plant is included.The problem with this is that the up-to-specification cylinder barrel will be matched

The course is offered at no charge, with used cylinder head. The steel barrel with its chrome coat mav now be ready to

but each individual attending will beperform through another full TBO, but it is very unlikely that the cylinder head will

responsible for travel, meals and lodg~ survive for that period of time.

ine. Transportation between localTypically, cylinder barrels which are worn bevond service limits have worked

motels and the school will be provided through more than one TBO. The aluminum head which is the other major cumyo-

if required. nent of the cylinder will also have heen in use for this period. Running at %-IUC)

Although the schedule for 1990 isRPM, that head is exposed to 72.000 firing impulses ever´• hour. Over a period of

not cuntplete as this notice is written, 2000 hours, this is over 140 million impulses or quick thermal changes. The agingclasses are normally scheduled about

process is also affected by the continuous heating and cooling each time the ellFinetwice each month. For further informa-

i~ started and shut down. Assuming average flight lengths of two hours, this is 100()

lion on specific class dates and to thermal cycles during the life of a 2000 hour TBO ell~ine. The longer an enptne

resPrve a space in a future class, con-runs, the more susceptible the cylinder head is to rrac´•kin~. Cylinder heads which

tact:are cracked are often repaired b; welding, a proc´•ess which Lvcoming has found to

Don Stahl be of limited value. While the overhauled cylinder nlav look good, and the chrome

Instructor/Training Center barrel may provide an excellent wearing su;fac´•e. the unknown quality of the over-

Textron Lycoming Williamsport hauled cylinder head is typically the weakest structural part of the cylinder. This

h52 OLiver Street could be the place where cylinder prol,lemu occur before the engine has again

Williamspurt. PA 17701 reached TBO. In this case, the quality of the cylinder barrel coating is of little

Phone: (717)327-7338/7308 co"se9uence.

Lvcoming has adopted a policy of shipping all engines from the factun (ne\´•.

reman;factured. and overhauled) with brand new cvlindew. By doing this, the

factorv en~ine has the best cylinder quality it is possible to provide.ivcoming cylinder kits are available through all distributors. Each kil c~untalnk

ENGINE OVERBOOSTa brand new cylinder assembly and all the parts needed to assemble the rvlindrr oll

Continued the engine. Currently selling at reduced prices, these high quality genuine L~c´•onl-

ing cylinder kits are an exceptional value, and at the same time eliminate all lhr

back to the density controller. What

,should the pilot expect and how should 9uesf’o"s relative to the value of chrome plating and reworkin~ of

To summarize, the improved hardness of cylinder barrel surfaces is all Illl~,or-the controller be set’ The A P

tant Tactor in the increase in recommended engine TBO. For Lvcoming. the

mrchunic must have the tools specifiedprocess has manv advantages. These include manufacturink elr~ciencv and c´•onaiL~-

in the luteht revision of service instruc-lent quality. Although this article has focused primarily on methods of ob~alninF

lion 11117. and must follow the proce- cylinder barrel hardness for good wear characteristics. it is the entire cylinder which

durcs outlined. The engine must be atmust be considered when making a decision about the cylinders to be used for

normill operatin~ temperature. Induc-engine overhaul or for replacement of a single cylinder for any reason.

lion air temperature is then checked

;Ipainbt manifold pressure utilizing the

curves in the service instruction. The

c´•untroller should only be adjusted if FO’ Ihe pilot. expect lower than red DID YOU KNOW’)

this ih necessary to h;ing the manifold line manifold pressure readings for all

takeoffs. Once it is set correctly. the The diaphragm style fuel pump~ uhed

I""""U"r within the limits shown on theon many Lycominp engines are penenll-densitv controller will insure that vou

(:I1Nwq;cn the conlrollc´•r is set properly, pet rated en~ine power for take ofT. IV k"O"" as AC Fuel pumpa. Since Ihc~

Once the function of the density con-have I,een used on Lvcominp enFules.

the pilot shoultl not expect the manifoldtroller is urlderstood. it truly is an aid to the’ ha\´•~ I,oth an i\C I,ilrt numt,er and

i""""" needle to settle on the mani-a Lvcomin~ I,art numl,er. Todal. Ihe~r

fol(l pressure limit marked on the gaee.the pilot. In addition to supplying rated

Air ccml,rrature is a major filrtor in the I’O"e’- it goes one E´•tep further. It will pUmpS "’e I"O’1U’f of Teutron LZcc,nl-

umountof power produced. Since the also prevent engine overboost. ing. T~lrv 51111 carry an r\C and a

Lvcominp I,art numl,er. The AC Ilum-

tlc´•~lsity controller is sensing tempera- l,er is rrtainecl for reference I,ur),o.seh.

ture, as well as pressure, it will demandThe Fiver I,rovider: prorluc´•1 in- hut the Lvcominp nunll,t´•r sl,l,ulcl b~

mr,rr manifold I,ressure in hot weatherf~rmnlion. In/ormed pilotb anti ’Isetl whrll a ~unll, i:, to I,r or~lerrd Irc,m

anti IChS ill cold weather. In either case. Lvcomin~.mec´•hanic´•~ rontril,utr to sn/eat, c´•cluivelu~lt amount of I,ower will I,e

~,rodurPd. 11?´•inp.

Doifrioht.Do it new,

Don’t settle for salvage: recondi-tioned cylinders that may, or maynot reach TBO. Reconditioned is,after all, used.

Our experience has shown thatwhen the engine is operated by-the-book and normal maintenance is

performed, factory-new cylinderswill typically last beyondTBO.Lycoming cylinder kits come withnitrided barrel", aluminum head,intake and exhaust valves, piston,rings, springs, valve seats, keys,gaskets, seals. Everything youneed, all brand-new and warranteedfor one full year, regardless of thenumber of hours flown. Partsand labor.

If reconditioned cylinders were

as good as new cylinders, they’dcome with the same kind of war-

ranty. And, they don’t.The price for new lycoming kits?

Your customers will be delightfullysurprised at how competitive we are.

~B Call your local distributor today, andi-

I see for yourself.

’t. salvage anymore.

There’s no reason to settle for

Li ~C i~:l Lycoming´•s;LI´• ´•e

Texlron Lycom;ng SUD.; diary ot Torrron Ire1C~r,

652 Obver Street Wlliiamsport PA 17701

Your Lycomlng dlstnbutorPI 4) i.

~3C10 TPZlrOh Lycom~og Certln low-com~ress an mcde(s

ACCESSORY TBO Continued MOBIL AV 1 OIL LIGHTWEIGHT STARTER

An "as needed" accessory overhaul APPROVED FOR USE IN Continued

may be the result of normal wear and LYCOMING AIRCRAFT ENGINES starters will be available early in 1990.

tear. Exposure to unusual conditionsIndividuals building an aircraft ma~

Textron Lycoming Service Instruction find it convenient to plan for use of thecould also bring about the need for

No. 1014 states that the company which light weight starter when cnlculatinf:accessory overhaul. Conditions such as produces a lubricating oil is responsible weight and balance. Although theselightning strike, engine overspeed, or for insuring that the oil conforms to

,,,,t,,t,, are capable of.rudden stoppage are examples of condi-

MILL-22851. The results of extensive replacing the mounting and startingtionci which could have a very detrimen-testing done by MOBIL were presented to capability of the standard starter now in

tal effect on engine accessories.Lycoming engineers for evaluation. The

use on many certified aircraft which areShould on accessory require overhaul

tests indicated that Mobil AV 1, a fully Lvcoming powered, this mav not bebefore the engine reaches its recom- synthetic oil, exceeded the requirements done without careful consideration ofmended TBO, a very careful logbook of MIL-L22851. Based on the testing by the effect on aircraft weight andrecord should be kept. This will provide MOBIL and evaluation of the results by balance. Because of the weight differ-information on which to base a decision

Lycoming, Mobil AV 1 Oil is approvedence, weight and balance must be

at engine overhaul time. A new or over- by Lycoming for use in Lycoming aircraft recalculated and proper FAA approvalhauled accessory which has had only engines, obtained. After recalculating weightlimited service on an engine which is Although this fully synthetic oil ..d balance, the filing of Form 337due for overhaul would probably not be received Lycoming approval in Decem- with the FAA ma~ be adequate furrepaired at the same time as the engine. ber, 1989, compliance with Lycoming approval, but this change in certitica-

An accessory which continues to pro- service publications is required, and may tion data must not be overlooked.vide satisfactory service for the life of qualify certain aspects of the approval. F,, those who may need a lightthe engine or for a long period before For example, service instructions 1015 weight starter, the!: can be orderedthe engine reaches TBO should be over- and 1392 set specific temperatures below through any Lvcoming distributor. Thehauled or replaced at the same time the which the engine should be preheated, 12V model with l~l´•I´• pitch mav beengine is overhauled. Not only will this regardless of the type of oil used. Service identified by use of this part numberLI´• more convenient and less expensive bulletin 480 recommends oil and filter 31A21198. The 2-tV model with tllrover the long term, it will usually assure replacement at 50 hour intervals. pinion gear pitch has this parta relatively long period of

Engines which do not have filters should number 31B210~. Port numbt´•rrmaintenance-free operation with the have the pressure screen cleaned at 25 for light weight starters with 10/12 pitchnewly overhauled engine. hour intervals and oil changed at the pinion gears will be assigned when

From this discussion it becomessame time. In any case, a maximum of these models are available.

clear that TBO is not a well defined four months between oil changes should

period for most engine accessories.not be exceeded.

(vcerhlul will usually be accomplished N,,,tter what oil is used, Lycomingon an "as needed" basis and it is not considers compliance with all service

LYCO~IING "FLYER"unusual for this need to occur prior to publications dealing with lubricating oilsthe requirement for an engine overhaul,

to be important in achieving lone engine December 1989Unlehs an accessory has only a very life. In particular, the oil change inter-brief period of operation before the vals specified in Lycomin~ Service Bulle- ISSUE NO. 49I,np;inu is overhauled, overhauling the tin 480 are necessary to avoid a build up

accessory at the time of engine overhaul of contaminants which result from com- Editor ii. W. Johnsonih a reasonable course of action. bustion.

~t

Wllliamsport Plant PAIDTFJ´•xtron LycomlngfSubsldlary of Textron Inc

652 Qllver Street P*rml~ ~o lb3

Wllllamsport. PA 17701 U.S.A.

7171323´•S181

ADDRESS CORRECTION REQUESTED

49

Iiave You Moved’

If kO, I,lense brncl your

olti arlcl new atldrc´•ss.

LYCOMING

issue No. 50 Published by Textron LycomingLycomingApril, 1991 Williamsport, PA 17701

I I

Synfhefi~ Oil Approved Flying In Clean Air

Although fi~lly synthetic oils are not an entirely new development, Will your flying be affected byapproving one for use in a Lycoming air cooled, piston, aircraft engine is the Federal Clean Air Act! Most

new. When Lycoming aircraft engines were first produced, mineral oils of us who fly have had no

were the only product available for the lubrication and cooling of warning that our hobby and

engines. Until recently, only mineral oils had across the board approval possibly our livelihood may soon

for use in Lycoming aircraft engines. be subject, to change. Take heed,A brief look at history will provide some insight into the oil use and it is not just the handwriting on

approval process. During the many years before the arrival of jet en- the wall, it is now written in the

gines, the U.S. military used piston engines. The oil to be used in these law of the land. The changesengines was required to meet standards set by the military in written which are forthcoming are those

specifications MILSPECS. Because the standards for oil set by the aimed at eliminating all lead and

military were completely appropriate for the engines produced by lead additives from motor fuels.

Lycoming, those specifications were adopted, and have been the guide- The law also applies to theline used throughout the years. engines which use these fuels.

Mineral oils did change as oil companies attempted to make Before we become involved in

improvements in their products. Additives were mixed with mineral where aviation fuels are headed,oils to create viscosities which could be used across a wide range of lets review where they have been

temperatures. Other additives helped to keep dirt suspended in the oil and where they are now. In

so that it could be trapped by a filter or drained out when the oil was years past, aviation gasoline was

changed rather than become a deposit of sludge in the bottom of the split into five octane gradesengine. These improved oils for use in aircraft engines are known as 80, 91, 100, 108, and 115. As U.S.Ashless IXispersant (AD) oils. Because these oils continued to meet the airlines and the U.S. militaryMILSPECS, they were given automatic approval for use in Lycoming uansitioned from piston enginesengines. to turbines, the consumption ofPlease rum to Page 2 Column 2

aviation gasoline decreased to

I I u less than one half of 1% of the

Rocker Arm Id~ntificafion gasoline market. As the market

volume of aviation gasolineRecently there have been the rocker arm by its part num- became less and less, octane

questions about rocker arm ber. The calls to our Technical levels were consolidated into two

identification. In many cases, the Representatives make it apparent primary grades 80 octane (.5rocker arm for the intake valve is that some A&P mechanics do not mt/gal lead) and 100 octane ~4different from the rocker arm for know where to look for the part mt/gal lead). For many refiner-

the exhaust valve. The two parts number. The caller will provide ies, the very low volume made

may look very much alike, but the raised number on the side of even two aviation fuel gradesthey must be identified in order the fin when asked for the part difficult to justify. In the middle

to tell which is used with the number. This very easy to find 1970s, a final consolidation

exhaust and which is used with and read number is a forging occurred. The result was 100 Low

the intake, number (see picture). One Lead aviation gasoline (2 mWgalFirst it is necessary to identify forging may be used to make lead).

Please tunz lo Page 7, Column Please lurn to Page 3. Column I

Textron Lycoming Throughout the years, Lycoming engines have been used in many

Reciprocafing Engine areas of the world where the climate is much less temperate than thatwhich we experience in Pennsylvania, the location of the LycomingSchool Schedule factory. Before the advent of multi-viscosity oils, extremely coldclimates caused oils to become so viscous they would not flow withinThis four-day course is pro- the engine, and therefore could not lubricate. To overcome thisvided by Textron Lycoming on a problem, a synthetic lubricant called Anderol 471 was developed inno charge basis. Personnel the 1960s. This oil flowed easily in very cold climates, but because itattending will be responsible for had a detrimental effect on seals and gaskets in the oil system, itthe cost of meals and lodging. A received limited approval from Lycoming as a ’Special Purpose"tour of the Textron Lycoming lubricant to be used where mineral oils could not be used effectively.Williamsport Plant will be in-This early synthetic oil was used on a limited basis and has not beeneluded in the course. To sched-available to aircraft owners in recent years.ule for one of the four-day

classes listed below, call DonaldOver the past 15 or 20 years, several synthetic and semi-synthetic

E. Stahl, Liaison Training Instruc-Oils have reached the marketplace. The semi-synthetic oils generally

tor, at 717-327-7127were produced to achieve viscosities which could be used over a fairly

July 8,9,10,11 22,23,24,25wide range of temperatures. Being mineral oil based, the semi-synthet-

hugusr 5,6,7,8 19,20,21,22ics usually met MILSPEC standards and were automatically approved

September 9,10,11,12 23,24,25,26fo’ USe in Lycoming engines. On the other hand, the full synthetic

October lubricants did not meet the MILSPECS and were not approved.7,8,9,10 21,22,23,24November 4,5,6,7 18,19,20,21

This was not to say that the synthetic oils were inferior. TheyDecember 2,3,4,5 simply did not meet the guideline standards used by Lycoming. To

receive Lycoming approval, a full scale testing program was needed todetermine the effect of any new oil on a Lycoming engine over itsentire recommended Time Between Overhaul (TBO). Mobii Oil re-Safety Tip cently completed extensive testing of Mobil AVI, a fully syntheticaviation engine oil.

Xt is extremely jmpastanr Mobil AV1 development goes back to 1978. This product was Erstto check the pressurescreen, suction screen, and

tested under laboratory conditions. Flight resting began in 1980 and

the oil filter at each oilabout 100,000 hours of in-the-field flying have been accomplished.

change. Utilize LycomingThe results of this testing and experience provided the data needed by

Special To61 SSP 885-I toLycoming Williamsport to approve AV1 for use in all Lycoming piston

open the spin on filter canengines. In addition to the data, Lycoming engineers looked at the

so that the filter material history of an HIO-360-D1A engine operated by the Las Vegas Police

can be examined for metal Department. It was one of the first engines in the field to be operatedas required by the 50-hour exclusively with Mobil AVI. Installed in a Schweizer helicopter which

Inspection check list tn thethe police used as a trainer, this engine was often run in outside air

Lycoming Engine Operator’s temperatures over 100 degrees Fahrenheit. The engine was operatedManual. Also look for metal

fo’ 280 hours over the recommended 1500 hour TBO. The engine tear

in the screens. Metal will down was accomplished at the Lycoming plane and revelled a verynever be found in the filter clean engine with little or no sign of wear on the crankshaft or cam-

or screens if the individual shaft. Also, all rings were free and all valve guides were free of

changing the oil does not deposits.look for it. Should metal be Based on the data available, and the observed condition of thefound, it will be necessary HIO-360 engine at tear down, Textron Lycoming will issue Serviceto examine the interior of Letter No. L229 as the approval for use of Mobil AVI in Lycomingthe engine more closely, engines. Because water, acids, and lead sludge will accumulate insideMetal which has contami- the engine, the oil change recommendations of Service Bulletin No.nated the engine and which 480 apply to Mobil AVI as well as to the AD oils which will continueis not found during the to be used in many engines. These recommendations are:

regular oil changes could A. 50-hour interval oil change and frlter replacement for all en-lead to catastrophic engine gines using a full-flow filtration system.failure.

Please rum to Page 7, Column I2´•April 1991

FLYE~I

At the time of the consolida- automotive fuel tended to pro- will be searching for the data

tion to a single fuel grade, mote valve seat wear. Solving every Lycoming engine owner

approximately 65% of the general this problem required the use of and operator will need. Our

aviation fleet was powered by better metals. Today’s aircraft purpose is to help you get the

low compression engines which engines already use improved best possible performance and

were built to operate on 80 materials in these areas so it is longevity from the Lycomingoctane fuel. As a result of using unlikely that removal of lead engine you own now or those

the higher leaded 100 octane LL from the fuel will result in a wear you may own in the future.

fuel, these engines were subject problem.to some lead fouling not experi- Many of the high performanceenced previously. Engine manu- Lycoming engines operatingfacturers vied to counteract these today may not need 100 octane

problems by coming out with fuel to obtain rated takeoff and Recalled Fornew engine models with higher climb performance due to the Temporary Dut~:ycompression ratios; these engines richer mixtures used for coolingcould digest the higher leaded during these operations. If EDITOR’S COLUMN

100LL more iasily. Some opera- unleaded fuel with a maximum For many, many years the Flyertars turned to the use of auto 93 octane rating is adopted, has been a means by which

fuel. Although some characteris- changes in cruise leaning proce- Lycoming has communicated

ties of auto fuel were quite dures will be necessary because with thousands of customers

different from aviation gasoline, of reduced detonation margins. around the world. An excellent

the lead content and octane level With a change in cruise perfor- rapport, has been established bywere similar to the original 80 mance and in leaning limits, Pilot providing information about

octane aviation gasoline. What Operating Handbooks and engine maintenance, operation,has been discussed to this point Engine Operating Manuals would and safety. Because this is 2 wayis history. Ndw it is time to look require changes. to help Lycoming engine owners

to the future. There are two This discussion of new fuel get the best possible service from

specific amendments to the and engine requirements should their Lycoming engines, and to

Federal Clean Air Act which may indicate to every reader that promote flying safety, there is a

affect general aviation flyers. there are many questions to be suong desire to continue pub-First, after 1332 no aircraft answered before the proposed lishing the Flyer on a regularengines requiring leaded aviation regulations which interpret this basis.

gasoline may be produced or law become effective. Texvon To accomplish the resumptionsold. Second, after 1995 the law Lycoming Williamsport has of publication after a short

prohibits the sale of any motor initiated a program to develop period of delay since issue No.

gasoline which contains lead or the data which will help to 49, I have been recalled to work

lead additives. answer these questions. A on issue No. 50. Although this is

It is quite likely that the recipe quantity of unleaded aviation strictly work to be accomplishedfor aviation gasoline will not gasoline has been obtained and on a part time basis, I am happychange except for the removal of detonation and endurance to again be able to write and edit

the lead. This will have the effect testing is scheduled over the next materials which will be of helpof changing 100 octane Low Lead several months. Based on the to so many Flyerreaders.fuel to a No Lead aviation gaso- results of these initial tests, the You will note that the format

line of approximately 93 to 94 program will be directed toward and appearance of the Flyerhaveoctane. There are at least two those areas where it may be changed to provide a more

areas of uncertainty to be ex- possible to find solutions to the modern look. The information

plored before 100LL disappears potential problems presented by presented is intended to be the

from the market place. What the use of unleaded fuel. same ’this is what you need to

effect will no lead have on A change to unleaded fuel will know" data as in the past. Should

today’s engines and how will affect the way we operate our you have questions which could

those engines tolerate the re- engines and the performance possibly be the subject for futureduced octane level, which may be expected of them. articles, please communicate

The removal of lead from Texuon Lycoming Wiliiamsport them to us. Ken W. Johnson

LYCOMING FLYER 3

I

Safotu Tipl Birth of an AD

Aircraft owners should The Airworthiness Directive, or what is is usually referred to in

understand that Textron aviation language as simply an AD, is an amendment to Federal Air

Lycoming considers compli- Regulation Part 39. Once issued, AD’s have the force of law and theyance with Service Bulletins remain in force until superseded or revoked. The AD is written againstto be MANDATORY. If your

all types of aeronautical products to mandate safety in the use of

helicopter or, fixed wingthose products. Unfortunately an AD often requires inspections and

aircraft is powered by awork which would not be necessary if manufacturer recommendations

piston engine the we’e followed as they should be. This article is a case study which

requirements of Service indicates the importance of publications in proper maintenance. It alsoBulletin Na, 388A should shows that at least one AD would not have been necessary if all

not be overlooked. For aircraft owners and maintenance personnel had been utilizing the

helicopters, the inspections i"formation provided in publications made available by Lycoming.should occur at 300 hour As we look back about ten years to the beginning of this case, let

intervals, For fixed wing us hope that what is written here will be a lesson in safety for aircraft

aircraft, inspections begin atOw"e’S. Over the years the Lycomlng Flyer ha’s stressed many times

the mid-point of engine that use of manufacturer publications is absolutely essential to mainte-

service life as recommended "a"ce practices which lead to safe flying.in LycominS Service! ~Cetter When an aircraft or engine part develops an unexpected problem201. There are two pur-

during its period of field use, and the manufacturer becomes aware of

poses for this critical that problem, there are several publications which can be used to

inspection procedure. The communicate this information to maintenance facilities. Which publi-first is to determine if wear

cation is used depends upon the urgency of the situation. A Lycominghas caused excessive Service Bulletin is printed in red, and always indicates a high degreeexhaust valve guide ctear´• of urgency. The information and procedures provided in a bullerinance. Excessive valve guide must be observed for safety reasons, and therefore are considered byclearance may eventually the manufacturer to be mandatory. Service Instructions and Service

cause the exhaust valve toLetters give maintenance information with somewhat lower levels of

break The second purpose urgency. The Service Letter is the least urgent of the three. Althoughofthe inspection is to

there are many good maintenance facilities, it is unfortunate that theredetermine if there has been a’e those which either do not have the necessary publications avail-a lead or carbon bundup in able or do not take the information provided seriously. Althoughthe exhaust valve guide owners are ultimately responsible for the airworthiness of their air-

which has resulted in craft, some choose to save a few dollars, and risk their lives until an

insufficient valve to guideAD makes a recommended procedure or part mandatory. When an AD

clearance. Too little clear- covering a particular product has been issued, most owners take

ancr! between the valve action to comply.stem and guide may result To begin this review of events, we go back to May of 1982 whenin a sticking valve. These Lycoming Service Bulletin No. 240K was issued. This bulletin deals withkinds of failure are prevent-

the parts of a Lycoming engine which are to be replaced at overhaul.able if aircraft owners will Where a product improvement is to be incorporated, it is often recom-

require that SE 388A be mended that it be done at overhaul. In the case of four-cylinder enginescompiled with at the appro-

With a rear mounted governor, this publication clearly stared that the

priate inspection intervals, aluminum elbow which connects the propeller governor oil line at theand that an appropriate log f’o"t of the crankcase should be replaced with a steel elbow at over-

book entry attest to compl-haUI. Engines have been found in service today which were overhauled

ance with the Service in the field and which still have the aluminum elbow. This is an indica-Bulletin. tion that someone was not aware of the bulletin or simply chose not to

comply. They reused the old aluminum elbow.The subject of this propeller governor oil line was addressed

How should you operate again in Part II of Service Instruction No. 1435 which was issued inyour aircraft? The Pilot’s April of 1986. As a product improvement, the line was to comeOperating Handbook is the equipped with a steel nut which would join the steel elbow previouslyfinal authority! discussed. The instruction also has a drawing which shows where the

a´•April 1991

FLYER

line is attached to the engine and that it is to be supported with Cam and Tappefclamps. Failure to support the line as shown can lead to a chafed or

broken line, oil loss, and possible engine failure. It has become Wearevident that many individuals working on these engines do not have

The lobes of the camshaft andthe information provided in this service instruction, or do not under-stand the need to correctly clamp and support this type of line. These

the tappets which they continu-

examples of poor maintenance practice have been found in the courseally operate against have always

of accident investigations.been subject to wear. Someone

Accident investigators were finding that some Lycoming enginesrecently stated that in recent

years there has been an unac-with rear mounted governors had indeed failed from oil starvation; the

oil had been lost because of a break in the propeller governor oil iine.ceptable rise in the occurrence of

spalling tappets and worn camInvestigation also revealed that the breaks were occurring in engines lobes. Is this a factual statement!where the propeller governor oil line was not supported as recom-

Perhaps it may help if we take amended by Lycoming. In all cases, one or both of the Textronlook at one or two of the causes

Lycoming supplied governor oil line clamps and/or supports, whichof wear on these parts. From this

had been installed at the pliant, were missing. Maintenance recordswe may reach a conclusion about

indicate very poot attention to detail in several of these cases. in onewhy this statement could possi-

case the steel line failed and was replaced, but the supporting clamps bly be true today.were still not installed. In another case, a broken clamp was removed

Corrosion is a known cause offrom the line, but it was not replaced. The accidents which resulted

tapper and earn lobe wear. Thefrom these poor maintenance practices are ones which could have

engines of aircraft that are notbeen prevented. flown regularly may be extremelyIn the interest of safety, it was necessary to get the attention of

vulnerable to corrosion. 7JQhenthose who were not following good maintenance practice. Utilizing the film of oil drains from thethe publication which would show the most urgency, Lycoming issued

interior parts of the engine afterService Bulletin No, 488 in September of 1989. Entitled’Propeller it has been run, those partsGovernor Line Support", Service Bulletin No. 488 required an inspec- become prey to the chemicaltion of the Propeller Governor Oil Line on all four-cylinder engines changes which are caused bywith rear mounted governor within the next 25 hours of operation, moisture, acids, and oxygen.and at overhaul.

Tappets from engines whichThe engine failures which have resulted from improper mainte- have not been operated for long

nance of the propeller governor oil line are unfortunate reminders of periods have been closelythe importance of compliance with manufacturers publications. Be- examined. Under a microscope,cause there were too many who failed to follow these instructions it is not unusual to find micro-voluntarily, it became necessary for the FAA to issue Airworthiness scopic pits on the face of theDirective 90-04-06 in February of 1930. The AD is the law and should

tapper. This is the beginning ofbe complied with. It requires an inspection of the propeller governor trouble. Starting with these veryoil line within 25 hours of operation. Any damage found, or improper tiny pits, tiny particles of rustinstallation of the support clamps, even if no damage is found, would also affect the cam lobes. Oncerequire that the line be changed. It also requirP~ that aluminum fittings started, the process is not likelyused in the installation of the line be removed from service and to stop until the wear reaches a

replaced with the steel fittings which Lycoming has been recommend- point where these parts are

ing for years, doing an unacceptable job.For the information of those concerned, FAR 91.163 places the Some people might question

primary responsibility for maintaining the airworthiness of an aircraft, the assertion that engines can

including compliance with Airworthiness Directives, upon the owner attract unusually large amounts

or operator. In addition, FAR 91.173 also requires aircraft owners and of moisture. Brief operatingoperators to maintain records which include the current status of periods, low en~ine oil operatingapplicable ADs. In spite of those requirements, and more than a year temperatures, and condensationafter AD 90-04-06 was issued, accident investigators have recently all contribute. It might be veryfound an aircraft in which there was no compliance with this AD. It is surprising to take an enginealso interesting to note that this aircraft had its annual inspection in which has flown 15 to 25 hoursthe interim, over the course of four to six

For those individuals complying with AD 90-04-06, the information months and drain the oil into a

Please lurn ro Page 8, Column I Please turn to Page 6, Column r

LYCOMING FLYER 5

I I

clear container. The amount of Service Bullefins, Letfers, Insfructionswater which settles to the bottom

is likely to be more than one Published from Decem~ber 5 1989would eKpect. Also remember tg Feb~uary 18, 1991that combustion causes acids to

collect in the oil. When these are The service publications listed below are those which have been

not removed by regular oil issued most recently. We strongly recommend that a complete set of

changes, the acids as well as the these publications be maintained by all maintenance organizationsmoisture will promote the growth which work on Lycoming reciprocating aircraft engines. A subscriptionof microscopic pitting which may be obtained through any Textron Lycoming distributor or directlyeventually leads to excessively from the Textron Lycoming Product Support Departmant. Call or write

worn tappets and cam lobes. for a copy of Textron Lycoming Service Letter No. L114 which pro-Another factor in the unaccept- vides a listing of available publications, prices, and ordering instruc-

able rise of tappet spalling in tions.

general aviation engines may be

the product which is put into Sent~ce Bulletkzs

many of those engines at over-369H Engine Inspection After Overspeed or Overboost All

haul. To reduce the costs ofTextron Lycoming piston engines.

overhaul, there is an increasing411B Adapter Kit for Magneto Isolation Drive Certain 0-3tj0-tendency to put reground cam-

shafts and tappets into these A3A, A4A, A4J, and IO-360-B4A engines. See Bulletin for

engines. Although camshafts mayserial numbers and ship dates.

be reground, there is a very strict 4758 Crankshaft Gear Modification and Assembly Procedures

limit on the amount of grinding All Textron Lycoming Direct Drive Piston Aircraft Engineswhich can be tolerated. Grind except: O-320-H, 0-360-E, LO-360-E, TO-360-E, LTO-360-E,too much and the hardened and nO-541 series engines.

surface of the cam lobe is gone. 488A and Propeller Governor Line Support All Textron LycomingAfter this kind of grinding, the Supple- four-cylinder engines with rear mounted governor.

cam may look great, but it will ment 1 Corrects part number in Piper Aircraft Corporation note

be wearing on the soft metal on Page 2 of 2.

which was once protected by a 489A Oil Sump Baffle Assembly Inspection All Textronhardened surface. Textron Lycoming six cylinder fuel injected engines which incorpo-Lycoming does not recommend rate Baffle Assembly P/N LW-13383.the use of reground tappets 491A Inspection of Exhaust Transition Bolts TIO-540-AE2Aunder any circumstances, but

engines installed in Piper Malibu Mirage Aircraft. Seemany engines overhauled in the

bulletin for serial numbers to which Part I and Part II apply.held today come back to the

492 Redesigned V-BAnd Couplings for Tailpipe Installationowner with reground tappets and

camshaft. In some cases at least,All n0-540-AE2A engines with serial numbers up to L-9156-61A and also L-9158-61A and L3159-61A.

these items ate nothing more

than good looking junk. 494 Installation of Restricted Fuel Pump Vent Fitrings TIO-

Because of the high percentage 540-C1A, -EIA, -G1A, -HIA, -AA1AD, -ABIAD, -AFIA series

of refurbished used parts which with serial numbers to and including L-9244-61/61A.

go into many overhauls, and the 495 Reprint of Precision Airmotive Corporation Service Bulletin

many airplanes which sit for long MSA-1 Subject: Replacement of composit floats with

periods without being flown, metal floats. All Textron Lycoming piston aircraft enginesthere could be more tappet employing Marvel-Schebler carburetors.

spalling today than in the past. 496 Reprint of Lear Romec Service Bulletin 101SB019 Subject:These are some of the reasons Rotary Fuel Valve Diaphragm Replacementwhy the statement that there has All Textron Lycoming engine series with applicable fuelbeen an unacceptable rise in pump models and serial numbers listed in this publication.spalled tappets and worn cam 497 Installation of new, restricted Fuel Pump Vent Fittings in ANlobes in recent years might just Drive Fuel Pumps See bulletin for engine models affected

Please lum to Page 8, Column I and fittings to be used.

6´•April 1991

LYCOWEK)~

FLYERI

Seruke Instruct~ons several different part numbers.

10388 Propeller Flange Bushing Location All Textron Lycoming The part number is

direct drive engines. vibropeened on every rocker

1125B Alternate Crankcase Parting Surface Sealants All Textron arm. it is always in the same

Lycoming Opposed Cylinder Engines. location on top of the rocker

1334A Crankcase Tappet Bore Repair All Textron Lycoming arm, but with hours of operation

reciprocating aircraft engines. it may be difficult to read. The

Supple- Adjustment of the Linkage Rod between the Fuel Injector pab "Umber is pointed out in the

ment 1 and the Variable Pressure Controller TIO 540-AE2A. accompanying picture. It may be

to 3431 necessary to dean the area very

1442 Improved Oil Filter Bypass Valve All Textron Lycoming Be"fly with Scotch Brite. Should

piston engines with dual magneto accessory housing.the number still be difficult to

1447A Light Weight Starter Installation Instructions All Textron See, use a magnifying glass. It is

Lycoming direct drive piston engines except the 10-720 and important to identify the part

those engines with alternators or compressors mounted onnumber of both the intake and

the left side. exhaust rocker arms. These

14´•18 Installation of Tailpipes and Heater Muffler Covers n0-Should then be compared with

540-AE2A engine installed in Piper Malibu Mirage aircraft.the numbers in the Parts Catalog

1443for the appropriate engineinstallation of Rotomaster Turbocharger (46A21184) TO/model. In most cases this will

no-360-clA6D; TO-360-F1A6D.provide all the information which

1450 Alternate Connecting Rod Bolt and Torque Application is necessary. You will knowTextron Lycoming engines using Connecting Rod Assembly which is intake and which isP/N LW-11750 or Conncecting Rod Assembly P/N LW-13865.

exhaust from checking the actual1451 Alternator, Starter and Compressor Installation All TIO-

part numbers against the num-540-AE2A engines. bers specified in the Parts Cata-

11152 Reindexing of Prop Flange Bushings 0-360-C1G engines log.installed in Christen Husky aircraft with serial numbers up But suppose the numbers onto and including L-32584-36A. the valve rockers do not agree

with those shown in the PartsSeru~ce Letters

Catalog. Don’t panic. There is a

L201C Recommended Time Between Overhaul Periods AII possibility that the rocker armsTextron Lycoming Piston Aircraft Engines. taken from the engine may have

L228 Cracking of Cylinder-Head Exhaust Port All field recondi- been superseded by rocker arms

tioned, parallel-valve cylinder heads. with a different part number. The

superseding number is now

I I I shown in the Parts Catalog. If

this happens, it is time to callB. 25-hour interval oil change and screen cleaning for all engines

employing a pressure screen system.your Textron Lycoming distribu-

tor and ask if the part numbersC. A total of four months maximum between oil changes for both

on the rocker arms have beensystems listed under A and B.

superseded. By providing theWith the approval of synthetic Mobil AV1 for use in Lycoming

engine model and serial number,piston engines, it joins the line of mineral based AD oils which are

known to provide good lubrication and cooling results in Lycomingyou should be able to get assis-

tance with this matter, and alsoengines. Owners and operators of Lycoming engines may now choose

find which number is the intakeeither a mineral based or fully synthetic oil for use in their Lycomingand which is the exhaust.

engine.There is one further scenario

rl:ilwhich might be encountered. On

engines with parallel valves

which have been produced in

recent years, the intake and

exhaust rocker arms may be the

For01n0 number Put numberPleare rum to Page 8, Column

LYCOMING FLYER 7

in Supplement 1 to Service Instruction 1435 may be of interest. This same. They will have the same

supplement authorizes the use of a flexible hose in place of the part number. Should your engine

existing stainless steel tube assembly for the propeller governor oil be one of these, you will find

line on engines with rear mounted governors. It further states that that a rocker arm previously used

’Textron Lycoming teflon hoses with steel braiding and firesleeving only on the exhaust side is also

conforming to FAA TSO-C53A Type ’D’ specifications must be used being used for the intake. In this

for this installation." The supplement provides part numbers for case you can expect to find a

various hose lengths which may be needed and it also provides drip hole on the bottom of both

installation instructions, rocker arms.

There is a message in all of this. Use of manufacturer publications This discussion should helpis vital~co aircraft safety. Overhaul manuals, parts catalogs, and the those individuals who need helpservice letters, instructions, and bulletins provide the data needed to with identification of rocker

accomplish maintenance on an aircraft or engine. These Lycoming arms. Keep in mind that rocker

publications, their cost, and ordering instructions are found in the arms, like all other parts, should

latest version of Service Letter No. L114. Some shops which maintain be identified by utilizing the

aircraft do not have a publications library for reference. Others do not Parts Catalog and other service

use the reference materials. In still other cases, an owner may be publications which apply to the

advised of a manufacturer recommendation, and choose to ignore it engine model being worked on.

because of the cost. In the interest of safety, the person or shop doing Distinguishing between the

maintenance on an airplane should have and use the necessary refer- intake and exhaust rocker arm is

ence materials; owners should insist on it, and they should also accept just one problem which can be

recommendations which are made to enhance their flying safety, solved by using the proper

Attention to this detail of aircraft ownership may serve a two-fold reference publications.purpose: (1) saving your aircraft from damage and yourself from

embarrassment, and (2) possibly helping to eliminate the necessity for

the issuance of additional Airworthiness Directives. PERMISSION TO REPRINT

Permission to reprint from

the Lycoming gnnted, so

long ~s the eontca of infarrm~bn

rrnclins intia md Ippropriate c´•cdit

is given.be true. Ask about the parts time of overhaul than it is to pay

which are Being into your for replacing worn out parts

overhaul. It may be less expen- before your engine has reached

sive to pay for new parts at the its expected TBO.

April 1991 Issue No. 50

Editor: Ken W. Johnson

FIFbCiT~ LycomingWilliamsport Plant US POSTAGETextron LycominglSubsidiary of Textron Inc. PAID652 Oliver Street WILIVAMSPORT. PAWilliamsport, PA 17701 USA PERMIT NO. 163717/323-6181

ADDRESS CORRECTION REQUESTED

8 ´•April 1991 LYCOMING FLYER #50

LYCOMING

Ileue No. 51 Published by Textron LycomingLycomingNovember, 1991 Williamsport. PA 17701

_JII I II

~he Aviafion FueT OLlflook Oil Flow Screens,Recent Congressional Legislation aimed ar stiffening environmental Filter, Cooler, and

re~uiation has created a scramble for informatioil in the general Pressure Reliefaviation public. As usual, various interpretations of the printed word

and outright speculations have resulted in confusion. The flow of oil through a

What Happened? Lycoming reciprocating aircraft

Congress recently passed amendments to strengthen the 1970 engine is known to be a neces-

Clean Air Act. One of the amendments specifies that after 1992, no sary function during the opera-more off road engines requiring leaded gasoline may be sold. The key tion of the engine. Pilots are

issue here was exactly what type of vehicles would be covered by the often not at all concerned about

"off road" definition. Certainly chain saws, lawn tractors and dirt bikes how this function occurs, as longfell into this category, but what about aircraft? Critics pointed out that as the oil pressure and oil

in the original Clean Air Act, aircraft engines were treated separately temperature indicators show a

and distinctly from the off road category, and therefore were nor proper reading. A Sr P mechan-

intended to be covered under this requirement. The whole question ics, on the other hand, often

was resolved on September 4, 1991 when the EPA ruled that recipro- need to know how the systemeating aircraft engines are not included under the category entitled "off works and what parts control the

road", This means that, at least for the immediate future, reciprocating flow of oil during various phasesaircraft engines may still be operated utilizing a leaded aviation of operation. Because of the

gasoline, large number of calls concerningPlease tum I~ Page 2 Column 2

this subject which are received

I I LY by Lycoming Service Engineers,we can be sure that there are

Mow Moclf is Elfough? Inany n´•ho do not have a goodunderstanding of the oil system

How much oil does my engine shape of that sump will diff~r It is not surprising that many

need? When should the oil level with the various engine models.A g: p mechanics do not have a

be checked? Questions like these Because of this, the d;pstick to firm grasp on the operation ofcontinue to be asked of Textron be used must be calibrated for a the oil system. There is room forLycoming Service Engineers. particular engine model. Further,

a great deal of confusion sinceDepending upon the specific the dipstick is usually calibrated

there are two basic systems andengine model being discussed, for the aircraft model in which several variations on each ofthe answers to the questions may the engine is used. Most aircraft

these.not be exactly the same in all do nor sir exactly level, and the

Except for the screens, filter,cases, but there are some points aircraft attitude while at rest will

and oil cooler, the flow of oilwhich may help those who have affect the reading obtained on through the engine is completelyquestions like these. the dipstick. To get an accurate

pre-determined by the designedThe oil used in a wet sump reading, it is important that

engine running clearances andengine is stored in the sump inflation of the landing gear by the passages which are drilledwhich is attached to the bottom struts be exactly as specified, and

i, the crankcase and accessoryof the engine. The size and that the dipstick provided with

Please Iunt to Page 3, Column Please Iu171 ro Page 4, Column I

_

I

Do Engines Survive Without Lead?

The automotive industry has already been down the road of

Before you call or write the conversion to unleaded fuels. One of the problems which they en-

factory with any question about countered was with valve seat recession (wear of the valve seat) when

your engine, be prepared. If your using cnleaded fuel. This could also affect aircraft engines. Appar-question is about your engine, entry the lead acts as a lubricant between the valve and valve seat,

the engine serial number and the cushioning the impact of the valve on the valve seat. Their solution

complete model designarion are was to use a harder valve seat material. Today, this is nor an issue In

necessary. This is the absolute automobile engines. Lycoming reciprocating aircraft engines alreadyminimum of information needed

,,e high quality material for valve seats. A rest program conducted

to access any records Lycoming by the FAA Experimental Test Center, using unleaded fuel in a

may have. Any other data you Lycoming engine, showed no significant valve seat recession. The

can provide may also be helpful country of Sweden has operated its general aviation low compressionin answering your questions, engine fleet on unleaded aviation fuel for the past eight years with no

Hours on the engine, overhaul or adverse consequences. To confirm these results, Lycoming procured a

modification information, and sample of unleaded aviation gasoline. A series of comparative endur-

maintenance history are ex- ance rests were conducted to document wear characteristics. No

amples of items it would be well significant difference in valvelvalve seat wear was noted between

to have in hand before initiating engines run with leaded and unleaded aviation gasolines.a call to Textron Lycoming.

To summarize the unleaded issue:When your question deals with

spare or superseded parts, you Are aircraft engines included in the "off road" category!

should request help from EPA has ruled that aircraft engines are not included.

aftermarket sales. Maintenance Will present valve seats in Lycoming engines be acceptable for use

assistance is the responsibility of with unleaded aviation fuels anticipated for the future!

the Service Engineers. Being Test data indicate yes. When we must progress to unleaded

prepared before dialing will help fuels, existing valve and seat materials are satisfactory.

you to reach the proper party Any Other Fuel Issues?more quickly and to attain the

information you need more~iost definitely. The fuel specification for aviation gasoline, AST~I

efficiently. D-910, was developed many years ago for high performance engines

which, for the most parr, do not exist today. Aviation fuel utilizes the

cream of the petroleum barrel to meet its fairly simple formulation.

With the competitive situation which exists today with fuel stocks, the

cost of Avgas will continue to be substantially higher than Autogas.

AD ~lotes of Interest Ironically, energy and environmental concerns are now forcing rightercontrols on Autogas. The formulation process, additives, and vapor

AD 91-0b-07 and Textron pressure characteristics are being scrutinized and changed. The auro-

Lycoming Service Bulletins No. motive fuel of the future will be a different product than the fuel

434 and No. 437 address the which is available today.installation of new, restricted fuel Another recent amendment to the Clean Air Act prohibits the sale

pump vent fittings in turbo- of leaded motor gas after 1995. Although aviation fuel is not directly

charged engines with AN drive affected by this legislation, it will be the only leaded fuel type remain-

type fuel pumps. ing after enactment. It is easy to predict the refining and distribution

AD 31-14-22, Textron problems which will result when a high volume of unleaded fuel must

Lycoming Service Bulletin No. share the stage with a very low volume of leaded aviation fuel. Sepa-

~75A, and Service Letter No. ration of storage facilities, processing facilities, and transportationL163C address crankshaft gear systems will be required. In the long term, this factor will be unfavor-

modification and assembly able for both the availability and cost of aviation gasoline.

procedures. These proceduresWhat Should the General Aviation Industry do

are required during engineto Deal With Its Impending Future "FUEL CRISIS"?

overhaul, after prop strike or

other sudden stoppage, orThere is a definite need to develop a new aviation fuel specifica-

whenever crankshaft gear re- tion which will be more compatible with future motor fuel blends.

moval is required.

2´•November 1991

LYCOMING

FLYER

Keep in mind that future motor fuels will be substantiall)I changed in the engine for a particularareas which concern the aviation industry today, such as additives and aircraft model be used with that

vapor pressure. Regardless of claims, there have been and continue to aircraft. Even with everythingbe problems with the use of today’s Autogas in aircraft. The wider above just as specified, it is still

tolerance in vapor pressure and use of additives and alcohols in the difficult to get an accurate

composition of autogas have resulted in sudden operational and long- reading with some engine mod-

term material compatibility issues. Until these issues are resolved, els. With the O-540-J and L

autogas users will continue to evaluate the effect of these differences models, for example, the slow,

and changes on their engines and aircraft. deliberate insertion of the dip-As motor fuel stocks are better controlled, a new aviation fuel stick into the tube is helpful in

specification must be developed which is more compatible with the obtaining an accurate reading.new formulation practices, and yet still acceptable for our more While an engine is running,

stringent requirements. Aviation gasoline consumption represents less the oil is continuously beingthan one quarter of one percent of the total gasoline usage in the pumped through oil supplyUnited States. To exist in the 21st century, it is imperative that Avgas passages to all locations which

be more consistent with future motor fuel stocks. Economically or must be lubricated and cooled It

logistically, Avgas cannot continue to be a specialty product. will take several minutes for the

Textron Lycoming is participating with the General Aviation oil to drain back into the sump

Manufacturers’ Association (GAMA) on the ASTM J2 Fuel Committee to after engine shut down. There-

Please lurn to Paae 7, Column I fore it is a good idea to wait

several minutes (10 minutes will

I probably do) after shut down

before attempting to check the

Changing fhe 8il oil level.

What oil level is satisfactory for

It has been said that "changing A. 50-hour interval oil change flight! This is a question with

the oil is the least expensive and filter replacement for all many answers. It depends on the

method of maintaining an aircraft engines using a full-flow filtra- particular engine and the lengthengine." The reports received tion system. of night being planned. As

from Lycoming engine owners B. 25-hour interval oil change indicated earlier, each engineover the years have affirmed the and screen cleaning for all model is equipped with a sump

truth of this statement. Although engines employing a pressure designed for that engine as it Is

the addition of a filter in the oil screen system. used in a specific aircraft model.

system helps to reduce dirt C. A total of four months Many Lycoming four-cylinderwhich causes wear; water, acids, maximum between oil changes engines are equipped with an

and lead sludge still accumulate for either of the systems listed eight quart sump and six-cylinderin the oil. This contamination of under A and B. engines are often equipped with

the oil can lead to sticking valves The recommendations of SE a 12 quart sump. Owners of

and deterioration of tnetll 480 assume the aircraft is being these engines frequently maintain

surfaces inside the engine. To operated from a paved runway the oil level at one to two quartsavoid these problems, regular oil under normal operating condi- below the full mark. Unless these

changes which remove the tions. For operation from a dirt engines are known to be usingcontaminated oil are necessary. strip where conditions are dusty, excessive quantities of oil, these

The oil change recommendations or for aircraft used in Agricultural oil levels will probably be

of Service Bulletin No. 480 apply Applications, more frequent oil adequate for most normal flights.with any oil which is chosen for changes may be necessary. A second group of Lycoming

use; whether a mineral based AD An item often missed in the engines come equipped with

oil as defined in Textron routine of oil change mainte- smaller sumps. A number of four

Lycsming Service Instruction No. nance is the checking and cylinder models have a six-quart19~11, or a synthetic oil as ap- cleaning of the suction screen sump. Several six-cylinderproved by Textron Lycoming which is located in the sump. models have oil sumps which

Service Letter No. L229. The This should be done at each oil hold as little as eight quarts.recommendations stated in change, regardless of the changeTextron Lycoming Service Bulle- interval which has been selected. Please turn to Page 6, Column

tin No. 480 are:

LYCOMING FLYER 3

housing during engine manufac- system are reduced allowing the routed through the oil filterture. This flow of oil serves three by-pass valve to close and adapter, the filter, and then again

purposes. First, it lubricates, but forcing oil flow through the oil through the filter adapter, acces-

cooling the engine by carrying cooler. Although the By-pass sory housing and finally into the

away the heat generated by valve helps the engine to warm crankcase.

combustion is a second purpose up more quickly by routing cold The oil filter is another part ofwhich is often just as important. oil around the oil cooler, its the system where blockage could

Many engines, particularly those primary function is for system cause serious problems. For thiswhich are turbocharged, have oil safety; should the oil cooler reason an oil filter by-pass is

squirts in each cylinder which become plugged for any reason, built into the oil filter adapter, or

are designed to direct cooling oil system pressure will rise and the in the case of engines utilizing a

on the back side of the piston. differential pressure across the dual magneto, Into the accesslirv

And finally, the oil cleans the by-pass valve will again cause housing. These by-pass valves

engine by picking up dirt and the valve to open. This by-passes are a built-in safety feature which

depositing it in the screens or the oil cooler and prevents a activate as a result of excessive

filter, or by keeping that dirt in possible rupture of the cooler pressure in the oil filter. The oil

suspension until the oil is and loss of oil. filter by-pass is not adjustable.changed. Oil enters the crankcase of

The oil which has done its r-’ most Lycoming engines near the

lubricating, cooling, and cleaning top of the right rear cylindernows by gravity back to the oil where it passes through the

sump. From the sump, the oil pressure relief valve. There are

pump pulls oil through the three types of pressure relief

suction screen. This screen will valve. With either the short or

iilrer our large particles of ’i longdomevalve, pressure is

carbon, dirt, or metal. The pump 1 r--. adjusted by removing the domethen forces the oil through one and adding or deleting washersof the two basic systems. In each which are located under theof the two basic systems there is FC~i,: controlling spring. There is also a

a valve which forces the oil OilTillerrldopler third style pressure relief valve

through the oil cooler when the which may be adjusted with the

valve is seated, or allows the oil The Thermostatic Oil Cooler twist of a wrench or screw

to by-pass the cooler when the By-Pass Valve was designed to driver.

valve is open. Lycoming engines provide better control of the An individual looking for the

were originally equipped with a engine oil temperature while also pressure screen housing may not

By-Pass valve which was con- maintaining the safety ot the oil find exactly what he or she is

trolled by a spring. Referred to as system by by-passing oil around looking for since there are two

a spring and plunger type, it an oil cooler which is plugged possible variations. The housingfunctioned as a result of the for any reason. The thermostatic for the pressure screen may have

amount of pressure in the oil oil cooler by-pass valve may be one hole facing the rear of the

system. The spring controlled by- used on engines which use the engine. This housing is used on

pass system was superseded by a pressure screen system and on engines incorporating a springsystem controlled by a Thermo- engines which have a full flow and plunger to control oil flow,static Oil Cooler By-Pass which oil filter. For most engine models and the single hole will be used

reacts to oil temperature an oil filter also requires an oil for the oil temperature probe.changes, filter adapter. While the oil is Another style pressure screen

Operation of the spring con- cold, this system allows oil to housing has two holes facing the

trolled By-Pass system is the flow through the oil filter without rear of the engine. The small

result of thick oil which causes passing through the oil cooler. hole is used for the oil tempera-an increase in differential pres- As oil temperature rises to ture bulb connection, and a

sure across the by-pass valve and approximately 1.80 degrees Thermostatic Oil Cooler By-Passcauses the by-pass valve to be Fahrenheit, the valve closes and Valve is installed in the largeopen, thus by-passing the oil forces oil to pass through the oil hole.

cooler. As the oil warms up, oil cooler. The oil then returns to Even more attention to detail

viscosity and pressure in the the accessory housing where it is may be required when an oil

4´•November 1991

LYCOYINO

~LYER

filter is installed. The pressure A Review of Old Ir~ives Talesscreen housing must be removed

and the oil filter adapter installed Tale Number One "The most timefor an engine/allure to

in its place. With the oil filter occur is at thefirstpoLL~er reduction after takeof~ Ever~ individual who

adapter installed, either a spring pilots an aircraft has probably heard this statement at some time. Is it

controlled by-pass valve installed a true statement! We will venture a guess and say that perhaps it may

in the accessory housing just have been at some time in the distant past.above the adapter, or a thermo- Several years ago this question was asked of me and it led to

static by-pass valve installed in questioning some FA-~ employees and a number of other pilots about

the bottom of the adapter may be where the justification for this statement might be found. After several

used to control oil flow to the oil weeks of poking into this subject, it was finally necessary to conclude

cooler. Because of the better oil that we could find no justification that it was simply an "Old Wives

temperature control, use of the Tale."

thermostatic oil cooler by-pass A letter which recently came from a Flyer reader takes this one

valve is preferred by Textron step further. First it appears that there are many who continue to

repeat this tale. This caused our reader to delve into the subject a little

deeper perhaps a little more scientifically than I did. Our reader

studied a computer readout which had data on incidents of enginefailure over a recent three year period. Based on the material in that

report, this reader concluded that engine failures during takeoff are

quite rare, and that failures during cruise are far more common. This

does seem logical since the engines of fixed wing aircraft run a

majority of their operating life in the cruise power range.

Our reader also had a very believable theory about how this tale

may have gotten starred. He wrote, "I! seems likely to me that thisPressure Screen Zlouslngs

idea got started when twin engine flight instructors would simulate an

engine our during takeoff right about the time that the student put

Lycoming. For engines shipped his hand on the prop control to reduce power.... Gradually the idea

from the factory with an oil filter, was propagated that this was the most likely rime for an engine failure

and requiring an oil cooler in the when in reality it was a likely time for an instructor to simulate a

aircraft installation, it is standard failure."

procedure for Textron Lycoming From these two searches for justification with none beingto supply a thermostatic by-pass found in either case, I believe it is fair to conclude that ’the idea of an

valve. The hole in the accessory engine failure being most likely to occur at the first power reduction

housing which is provided for a after takeoff" is in fact an old wives tale. For the sake of safety, lets

spring controlled by-pass valve is stop repeating this false tale and start promoting the idea that we

capped with a plug. A hole on should be ready to deal with power failure at any time.

the top of the adapter is pro- A second Old Wives Tale which is still being promoted by some

vided for the oil temperature individuals involves the constant speed propeller and goes like this:

bulb. "The RPM in hundreds should not be exceeded by the manifoldpressureOne case of confusion over the in inches ofmercury. Referred to as a "squared power setting" (i.e.

possible variations of this instal- 2400 RPM x 24 inches of MP), it appears that this tale may be the

lation was documented in the result of a carry-over from some models of the old radial enginesNovember ’1390 issue of Light which were vulnerable to bearing wear at high power settings.Plane Maintenance. The owner of Changes in engine design along with improved metals and lubricants

a 1376 Cessna 172 could not permit changes in the operation of modern flat, opposed cylinderdetermine why oil temperature in power plants.his engine tended to be high Any piler who believes that squared power settings continue to be

during hot weather. Upon exami- necessary should be urged to read and understand the information in

nation, he found that the filter the Pilot’s Operating Handbook (POH). While there are limits to the

adapter had a plug installed power which should be raken from most engines, particularly those

instead of a Thermostatic By-Pass which are turbocharged, the combinations of RPM and MP listed in the

Valve. This led to an article power charts of the POH have been flight rested and approved by the

entitled "The Case of the Missing Please rum to Page 7. Column I

Please ~um to Page 7, Column 3

LYCOMING FLYER ´•5

While these smaller sumps Service Bullefins, Letters, InstructIOnSprovide a very adequate oil

Published from March 1, 1991supply, there is less margin for

error. The pilot must be more to August 31, iS9idedicated to carefully checking

The service publications listed below are those which have beenoil levels and filling the sump as

issued most recently. We strongly recommend that a complete set ofneeded. For engines with these

these publications be maintained by all maintenance organizationssmaller sumps, one quart belowwhich work on Lycoming reciprocating engines. A subscription may be

the full mark may be adequateobtained through any Textron L~coming distributor or directly from

for a short night, however any the Textron Lycoming Product Support Department. Call or write far anight of extended duration

copy of Textron Lycoming Service Letter No. L114 which provides ashould bcgir? with the oil level at

the: full mark.listing of available publications, prices, and ordering instructions.

One problem which sometimesSen/ice Bulletins

occurs with engines having240L liandatory replacement of parts at normal overhaul All

smaller sumps is overfilling at theTextron Lycoming reciprocating aircraft engines.

time of oil change. The Pilot’s3691 Engine inspection after overspeed or overboost All

Operating Iiandbook should be

consulted to determine the oilTextron Lycoming piston engines.

456D Replacement of oil pump impellers with change of compli-sump capacity. When the filter is

ance time to "within 1CtO hours, next annual inspection orchanged, an additional amount of

overhaul, whichever comes first." Applies to 0-235, O-oil possibly as much as one

320, 10-320, LiO-320, 0-360, HO-360, 10-360, HIO-360, VO-quart will be required to bring

360, Ivo-36c, AIO-360, LIO-360, 0-540, and 10-540 withthe reading up to the full level.

This should be checked after thelimiting serial numbers and models as specified in this

bulletin. Note: AD 81-18-04 applies.engine has been run following

498 Reprint of Precision Airmotive Corporation Service Bulletinthe oil and filter change.

hlSA-~ 0-235, 0-230, 0-320 series engines.Finally, some Pilot’s Operating

439A Installation of one-piece exhaust pipe kit (05#21503)Handbooks may give a minimum

Ti0-540-S1AD.safe quantity in the discussion of

500 Reprint of Lear Romec Service Bulletin No. 3402 Alloil levels. These numbers, in

Textron Lycoming engine series with applicable fuel pumpsome cases as low as two quarts, models and serial numbers listed in this publication.must De taken in the proper 501A Recall of piston pin Fart No. L\1C’-14077 Iciodels and serialcontext. What this indicates is an

numbers of all engines affected and shipped from Textronoil level which might possibly be

Lycoming between June 18. 1391 and August 5, 1391 arefound after flight when a great

listed following the text of the bulletin.deal of oil has for some reason

been used or lost. As one mightService

expect, this minimum oil level1187G Supplement No. 1 provides curve No. 13495-A which re-

can be extremely attitude sensi-places curve No. 13435 on page 8 of 3. T0-5400AAli\

tive. I-Iowever, if the dipstickengines.

does: not show an amount below1343A Set screw for propeller governor idler shaft 0, IO, LIO,the minimum safe I~vel stated, it

AIO, AEIO-320 series; O, LO, IO, LIO, AIO, AEIO, TO, TIO-is unlikely that engine damage 360 series; O, 1O, AEIO, TIG, LTIO-540 series; 10-720 widehas resulted from the unusually

cylinder nange engines equipped with a front crankcaselow oil level. Obviously, no flightshould ever be initiated with

mounted prop governor.1448 Supplement No. 1 gives proper installation of crossover pipeonly a minimum safe quantity of

supporting hardware and hear shield TIO-540-AE2r\oil in the sump.

This brief discussion of "Howengines.

1453 Replacement of oil filter converter plate gasket AllMuch is Enough" may help those

aircraft owners who have hadTextron Lycoming dual magneto engines and T1O-541-E 8~

nGO-541 series engines.questions on this subject. But

Pleare turn to Page 8, Column I

6´•Novemberl991

FLYERI

1454 Parallel valve rocker arm installation All Testron Bypass Valve". Engines delivered

Lycoming engines incorporating parallel valves escept 0- to Ces,Ena for this model year

235 series, 0-290 series, 0-320-11 series, and O, LO, TO-360- were delivered with a pressure

E series. Note: Service Bulletin No. 477 and AD 17-10-06 screen housing and a springapply, controlled oil cooler by-pass

valve. \Slhen the aircraft manufac-

Sentice Letters turer provided an oil filter as an

L163C Recommendations regarding accidental engine stoppage, option, the adapter and filter

propeller strike, loss of propeller blade or tip Applies to were installed at the aircraft

all Textron Lycoming opposed series aircraft engines. manufacturer’s plant, but the

L229 The use of MOBIL AV 1 synthetic lubricating oil in Textron original spring controlled by-passLycoming reciprocating aircraft engines Applies to all valve was retained and installed

Textron Lycoming opposed cylinder aircraft engines. in the accessory housing. As

stated in Textron LycomingService Instruction 1008B, instal-

lation of a thermostatic oil coolerinitiate the development of a new fuel specification for an unleaded by-pass valve will provide betteraviation fuel. An initial fuel specification guideline has been devel- control of the engine oil tem-

(3ped by the GAMA fuels committee and will be presented to theperature. This aircraft owner did

American Society for Testing and Materials (ASTM). This proposed fuel achieve better control of his oilwill have the highest octane possible to minimize the need to modify temperature by modif)Iing his oil

engine models. For instance, if the minimum octane level of futuresystem to include a thermostatic

unleaded Avgas was 98 octane, very little would need to be done to by-pass valve instead of theaccomodate this fuel in existing installations. This work has just been spring controlled one.

initiated and will require several years until a final specification is There is one more possiblecompleted. Testing, certification, and production will further delay variation to the flow of oil whichintroduction of the new fuel at the pumps until the latter part of this

,,y b, found with a Lycomingdecade, engine. Some air frame manufac-

The EPA has positively stated that they do not have plans today to turers have utilized small engineeliminate the lead in aviation fuel. The present fuel, 100LL, should be models n´•ithout an oil cooler. Atavailable for general aviation use for at least the next decade. How- the request of these airframe

ever, it is time to act to protect the general aviation industry for the manufacturers, these engines are

decades to come. It is also important for general aviation to be socially not machined to accomodate an

responsible and share solutions for environmental and energy prob- oil cooler. Individuals wholems. acquire these engines for use in

In summary, there is reason for general aviation to be concerned their home built aircraft mayabout future availability of 100LL aviation gasoline. Some of this threat need an oil cooler to keepstems from environmental legislation and some from very real energy temperatures within operatingissues. If the industry acts promptly and effectively today, it will head limits. This can be accomplishedoff a crisis in the future. Textron Lycoming has initiated action to by utilizing an adapteraccomplish those tasks which must be done to meet near term require- Lvcoming part number 62418.ments and ensure long term availability of a compatible aviation Utilization of this adapter will

gasoline. As events unfold and this situation is clarified, Textron allow the engine to be used and

Lycoming will use every available means to keep customers informed. the oil to be cooled, but there

are limitations. An oil Filter

cannot be installed, and only the

airframe and powerplant engineers. For example, if the POI-I chart lists one-hole pressure screen housing

2200 RPM and 26 inches of MP as an approved power setting, pilots Ca" be used. This limits the

should not be apprehensive about using that setting if it meets their system to use of a spring con-

needs.trolled oil cooler by-pass valve

Isn’t it strange that some bits of information come to be believedwhich is installed in the adapter.

There are several bits ofby large segments of a population even when they are untrue! The

two issues discussed above are good examples. \Y’ill it ever be pos- Please ~urn to Page 8, Column 2

.sible to get all of our fellow pilots to reject the two false ideas out-

lined here? Let’s keep trying.LYCOMING FLYER 7

Safefy Tip’ information which may be Safety Tiphelpful to those who have now

If your field overhauled acquired a better understanding Textron Lycoming ServiceTextron Lycoming engine is of the Lycoming engine oil Bulletin No. 483A requiresequipped with parallel valve system. Lycoming Service Instruc- inspection of the oil suction

cylinder heads which have tion 1008B gives instructions for screen at each oil change.been reconditioned, it is installation of a Thermostatic Oil In those fuel injected six

subject to the inspection Cooler By-Pass Valve on engines cylinder engines whichrecommended in Service which have a pressure screen incorporate Oil Sump BaffleLetter No. L228. Field housing and no filter. Special Assembly P/N L’Vir-13383,inspections have revealed Service Publication (SSP) 885-1 reports from the field havethat the cylinder-head gives instruction for the installa- disclosed that in some

exhaust port area on some tion of engine mounted oil filter instances vertical deflectors

parallel-valve cylinders kits. And finally, a kit (Number on the Baffle Assembly havereconditioned in the field 05K21437) for a remotely been loose. if a rivet is

may be prone to cracking, mounted oil filter has been found in the suction screen

These fine cracks are developed. Instructions for the during the normal oildifficult to detect visually, installation of this kit are not change, the baffle assemblyand therefore a dye pen- complete as this article is being must be removed andctrant must be used. If written. replaced. In recently as-

cracking is evident, Textron The Service Engineers at the sembled engines, an im-

Lycoming advises replace- Lycoming factory receive many proved riveting procedure isment of die cylinder-head/ calls about the oil system and its used to eliminate the loosebarrel assembly. See Service many possible variario~s. The rivet possibility.Letter No. L228 for more material presented here is in-

detail about how to conduct tended to help answer many ofthe inspection. those questions.

----LYCOMING

FL~ERPERMISSION TO REPRINTalways remember, the Pilot’s Permission to reprint material from

Operating Handbook is the the Lycoming "FFyer’’s granted, so

authorized source of information lo"g Is the context of information

remains intact and appropriate creditabout your airplane. is given.

November 1991 Issue No. 51

Editor: Ken W. Johnson

LifiCi~:ILycomingBULK RATE

Wllliamaport PlantUS POSTAGE

Textron LycominglSubsidiary of Textron Inc.PAID

652 Oliver Street

Williamsport, PA 17701 Us’A WIILIAMSPORT. PA

717/323-6181 PERMIT h’O. 163

ADDRESS CORRECTION REQUESTED

1 1A 2

HO AHNINOAIRCRAFT TECHNICAL PUBLISHER

101 SOOTH HILL DRIVE

BRISBANE CA 94005

8´•November 1991 LYCOMING FLYER #51

LYCOMING

May,1991JLIJ:CILT.I:1 LycomingReciprocating Engine Division

Reeog%rizing and Treafing Carb~efor Ice #igh Time CylindersA recent incident at the local airport is just one reason for reviewing The aluminum alloy cylinder

this subject. The pilot of a light general aviation aircraft flying above the heads used or. air cooled aircraft

clouds reported a partial loss of engine power to the controlling FAA engines are subject to highfacility. After a brief period, a safe let down and landing were accom- stresses while operating. In

plished. The radio transmissions from the aircraft were monitored in the addition, they are heated and

facilities of the local FBO where they were heard by a Lycoming Field cooled with each engine start upService Engineer who is both a licer~sed mechanic end a licensed pilot. and shut down. Over long

When the pilot of the troubled aircraft came into the FBO facility, he periods of operation, these

was offered assistance in determining the cause of the power loss by the stresses can lead to fatigue and

Lycoming employee. The pilot bluntly indicated that he was not inter- eventually the cylinder head may

ested in any discussion or assistance. He also asserted that there was no develop cracks.

possibility that carburetor ice could have caused the problem because he Lycoming metallurgists argue

was flying above the clouds and not in them. that welding of cracks in alumi-

While many pilots are well versed on the insidious characteristics of num cylinder heads is not likelycarburetor ice, there are some who could use a thorough review of the to meet with long term success.

subject. One of the best sources of information is a study done by the Therefore, an overhauled cylin-National Transportation Safety Board. Much of the following data are der has little chance of being as

taken from that report. Some of the material will be verbatim, but other serviceable as a new cylinder.Even if there were no cracks at

Please rum to Page 2 Column 2the time of overhaul, metal

I IL I a L fatigue is still a ,Factor to be

considered. But how! There is no

~he CrankShaff Gear about the contents of Textron record of time in use required for

Lycoming Service Bulletin No. a cylinder assembly. An over-

At first glance this would 475A and AD 91-14-22. These hauled cylinder could have 4000,seem to be a pretty boring documents have been issued to 6000, 8000 hours or more when

subject. Who really needs to help assure safety of flight it is put on an overhauled en-

know about a crankshaft gear? through compliance with the gir.e. Even a cylinder from yourThe answer to that question procedures outlined therein. own engine with only one tnp to

would be "Any aircraft owner Service Bulletin No. 475A is TBO may not make it to TBO a

who depends upon his engine titled "Crankshaft Gear Modifica- second time.

to provide the power for flight." tion and Assembly Procedures." As a result of the scenario

Although the subject may seem The introductory paragraph outlined above, Lycoming has for

boring, a failed crankshaft gear should lend emphasis to the many years recommended new

will cause engine failure and need For compliance at each cylinders when engines are

that is when the excitement may specified time. That paragraph overhauled. To practice what is

reach levels which are undesir- states: "Damage to the crank- being preached, Lycoming uses

able, shah gear and the counterbored new cylinders on all enginesWhat is all this leading up to? recess in the rear of the crank- shipped from the Williamsport

A reminder to Flyer readers shaft, as well as badly worn or Plant, including factory over-

Please rum to Page 4, Column I Please rum to Page 2, Column I

hauls. It is less expensive to items will be condensed to keep the length of this article within reason-

install new cylinders during the able limits.

overhaul as compared to having During the five-year period from which this data is taken, there

the engine torn down once or were 360 general aviation accidents involving carburetor ice as a cause

twice for cylinder replacement factor. There were 40 fatalities, and 160 persons were injured, 40 of

before it reaches the recom- them seriously. The number of persons exposed to death or injury in

mended TBO as an overhauled these accidents was 636; ´•i7 aircraft were destroyed and 313 were

engine. The added reliability substantially damaged.must also be considered. "Carburetor ice", as used in the report, meant ice at any location in

With all the above a matter of the induction system of aircraft equipped with reciprocating engines.

record, there are still aircraft The term is uaditional. It is used in aircraft accident records, even

owners who write to ask for an though many reciprocating engine installations have fuel injectors rather

honest opinion regarding "the than carburetors.

risks of serious cracks in high- The report noted that carburetor ice normally does not remain in

time cylinders." One such letter evidence for very long after an accident occurs. Thus, there may have

stated, "...we owners all know been additional accidents during chat five year period which were nor so

that Lycoming would prefer to appraised because of the lack of evidence at the time of the investiga-

sell us new cylinders at overhaul tion.

time." This is true, because Unlike mechanical failure, over which the pilot has little in- flight

experience tells us that new control, carburetor icing accidents can be prevented by the pilot in

~ylinders are in the owners best virtually all cases. Increased pilot awareness and proper, timely action

interest for the long run. can reduce the number of accidents caused by carburetor ice. To aid in

Per all those doubters who improving awareness and to suggest the proper procedures to be taken,

have read to this point, it is not the NTSB study covers many of the details which pilots should know.

necessary to take the word of It is important for pilots to knowthe three categories of carburetor

anyone at Lycoming on this ice, and the manner in which each is formed. These categories aics-’’

subject. The following material impact ice, fuel ice, and throttle ice.

was written by Richard L. According to the NTSB report, impact ice is formed by the impinge-

Collins, long time editor of ment of moisture-laden air at temperatures between IS degrees F, and 32

Flying Magazine and currently a degrees F. onto the elements of the induction system which are at

contributor to AOPA Pilot temperatures below approximately 32 degrees F. Under these conditions,

Magazine.´•The material written ice builds up on such components as the air scoop, hear valve, carbure-

by Mr. Collins seems to confirm tor screen, throttle, and carburetor metering elements. Pilots should be

the stand which Lycoming has particularly alert to such icing when they are operating in snow, sleet,

taken the more hours of rain, or clouds. The ambient temperature at which impact ice can be

operation on a cylinder, the expected is about 25 degrees F. when the supercooled moisture is still in

more likely it is to crack. The a semi-liquid state.

following material is reprin’ted Ftlel ice forms at and downstream from the point at which fuel is

from PLYING, March, 1337. introduced, when and if any entrained moisture reaches a freezing

Copyright 1387, CBS Magazines, temperature as a result of cooling of the mixture by fuel vaporiza-

from "Qn Top" by Dick Collins. tion. This cooling process takes place in the aircraft induction systemwhen the heat necessary for fuel vaporization is taken from the

Cylindrical Objects surrounding air. Then, because the cool air can hold less water

"It’s amazing how long it can vapo’l the excess is precipitated in the form of condensation, which

take to catch on to basic me- then freezes. When any structure, such as an adapter elbow, lies in

chanical truths. This realization the path of the water, ice accretion develops on that structure. If no

was sparked by a conversation anti-icing action is taken, the ice buildup can increase until the

with Jack Riley, Jr., principal in obstruction throttles the engine.RAM Aircraft. The subject was Visible moisture in the air is not necessary for fuel icing, only air of

the overhaul of the TSIO-520 high humidity is required. This fact, coupled with the fact that fuel icing

engine in my airplane. Riley was can occur at high ambient temperatures, may make it difficult for a pilot

surprised that the engine had to believe that ice is forming unless he is fully aware of the fuel Icing

been overhauled twice (both process. It can occur in no more than scattered clouds, or even In bngh~times at TBO) and had not had sunshine, as often happens in Florida.

Please lunt ~o Page 3, Column 3

2´•MAY1992

LICiOMl~i

FLYER

The usual range of ambient temperatures at which fuel icing may new cylinders. Then he launched

be expected is 40 degrees F. to 80 degrees F., although the upper into a dissertation on how the

limit may extend to as high as 100 degrees F. The minimum relative metal in cylinders wears out with

humidity generally necessary for fuel icing is 50%, with the icing operating time. The engine loghazard increasing as the humidity level increases. Fuel ice is not a revealed how right he was. On

problem in systems designed to inject the fuel at any location be- the first run of the engine from

yond which the passage surfaces are maintained above freezing. new, there were no cylinder

Thus injection of fuel directly into each cylinder obviously ~iill problems. On the second run,

preclude the possibility of such icing. with the original cylindersThrottle ice is formed at, or near, a partly closed throttle (butterfly) chromed, there was one incident

when water vapor in the induction air condenses and freezes due to the of cylinder cracking Cbetween a

expansion cooling and lower pressure as t~e air pasbes the restriction spark plug and the fuel injectionimposed by the throttle. This temperature drop normally does not line). On the third run of the

exceed 5 degrees F. When the’ambient temperature is above 37 degrees engine, still using the originalF, then the pilot need not be concerned with throttle icing as long as cylinders, there were four inci-

only air passes the throttle, such as in a fuel injection installation with dents of cylinder crackingthe fuel introduced downstream from the throttle. three between a plug and the

When there is a fuel-air mixture at the throttle, however, any ice injector and the fourth a largeformation would be attributable to water vapor freezing from the cumu- crack that finally led to a little

lative effects of the fuel ice and throttle ice phenomena. Icing at the chunk coming out of the inside

throttle then can occur at ambient temperatures much higher than 37 of the cylinder. If I had sprung

degrees F. Throttle ice is not a problem in some fuel systems which are for new cylinders on the second

designed so that the throttle is located in a warmed region. For example, overhaul I would have saved a

Lycoming designed turbocharger systems place the fuel metering device lot of money, because changingdownstream of the compressor which places it in a warm area. a cylinder isn’t exactly inexpen-

Any one or a combination of these ice-forming situations may cause sive. That knowledge coupledloss of power by restriction of induction flow and interference with an with the fact that there was

appropriate fuel-air ratio. One reason it can be important to use carbure- another cylinder with 4000 hours,tor heat as an anti-icer rather than a deicer lies in the "vicious circle" and Lhe rest had an vndeter-

aspect, especially in fast-forming conditions and when the ice buildup mined amount of time on them

might not be diagnosed at an early stage. An uncorrected carburetor ice (because they were recondi-

condition can mean less power, and thus reduced carburetor heat which tioned cylinders and no record is

may result in the formation of more ice. It is certainly only prudent to kept of total time on individual

guard against a buildup of carburetor ice before deicing capability is parts) added some urgency to

lost, the matter of getting the engineThe results of tests conducted on light aircraft utilizing a float to RAIM for another overhaul and

type carburetor may provide a better concept of when ice formation new cylinders. There is simply a

might be expected. Serious Icing occurred up to carburetor air rime when some parts wear out.

tenlpcratures of 62 degrees F. and relative humidity of 80% or more TJnril Riley told me that cylindersat high-cruise power settings. At low-cruise power settings, ice wear out, I had never heard of

formed at carburetor air temperatures as high as 63 degrees F. with this. Bur they do. and I’11 never

relative humidity as low as 60"/o. These tests clearly indicate that again waste overhaul money on

carburetor ice may form while the engine is operating at cruise cylinders that have more than

power. The tests also indicated that the possibility of ice forming in two TI)O runs on them. And I’11

the carburetor is much greater under glide-power conditions. With never buy a reconditioned

this lower power serring, ice formed at temperatures as high as 93 cylinder that has an undeter-

degrees F, and with relative humidity as low as 30%. mined amount ot rime on it

Carburetor air heaters in small aircraft are usually of the exhaust

pipe cuff type. The exhaust-heated air is directed into the carburetor air

duct as desired, so that with full carburetor hear the normal air duct is

essentially closed off at the carburetor heat valve location. The I;lyer provides productUnder certain conditions, partial carburetor heat may be wO’Se than infornlarion Inf!,rnted pilots

none at all. For example, the fuel/air mixture temperature might be at 20 ,,d mechanics contributu re,

degrees F, with no hear applied.’l‘his normally would be less conducive safe flyingPlease lunt to Page 4, Column 2

LYCOMING FLYER 3

broken gear alignment dowels 22 and jervice Bulletin 475A these two publications to be

are the result of improper have been completed. extremely important. They

assembly techniques or the In the interest of flight safety, should be considered equally

reuse of worn or damaged parts both Textron Lycoming and the important by mechanics, pilots,

during reassembly. Since a FAA consider compliance with and aircraft owners.

Failure of the gear or the gear

attaching parts would result in

complete engine stoppage, the

proper inspection and reassem-

bly of these parts is very impor-tant, The procedures to ice forming than a temperature brought to 30 degrees F. by use of

dcscribed...are mandatory." partial heat. Full heat could be expected to raise the temperature out of

THIS BULLETIN AND THE AD the icing range entirely. With smaller engine installations where there is

WHICH MAKES COMPLIANCE no instrumentation to determine the temperature of carburetor air or

MANDATORY apply to all fuel/air mixture, the general rule should be to apply full heat whenever

Lyeoming direct drive piston carburetor heat is to be used. The use of full carburetor heat will reduce

aircraft engines except the O- the amount of power available and can raise cylinder head tempera-

320-H, 0-360-E, LO-360-E, TO- tures. Since carburetor heat is rarely required under high power condi-

369-E, LTO-360-E, and TIG-541 tions, it is generally recommended that the carburetor heat be set st the

series engines. The time of cold position for all high power operations such takeoff, climb, or go

compliance is normally during arounds.

overhaul, BUT ANY PROP With larger, higher output engines, the installation usually includes

STRIKE OR SUDDEN STOPPAGE temperature instrumentation which the pilot should use as a reference in

ALSO REQUIRES COIMPLIANCE. controlling all engine temperatures, including that of che fuel/air mix-

The loss of a prop or prop rip is ture. L:se of induction temperature instrumentation serves to assist in the

included in the definition of anti-icing effort, and also aids In protecting the engine fiom possiblesudden stoppage. Also, the overheat damage.bulletin and AD are to be Carburetor ice should be considered immediately as the possible

complied with any time crank- cause of a power loss. With a fixed pitch propeller a power loss is

shaft gear removal or gear train indicated by a reduction of engine speed. When there is a manifold

repair is required, pressure gage installed, a reduction in manifold pressure would show

For the majority of aircraft up along with the engine speed reduction. With a constant speed

owners, the requirements of AD propeller installation, however, only the manifold pressure would be

31-14- 22 will only come into decreased.

play when their engine is over- Engine roughness may also be an indication of an iced carburetor.

hauled or when they exchange it is not a good indicator because in some casts the roughness mighttheir run out en~ine for a newly not appear until the engine is close to complete stoppage.

overhauled one. In either case The susceptibility to induction system icing varies greatly among the:

the engine being installed in the various aircraft models. For example, an engine installation emploving a

aircraft should have had its neat-type carburetor and having fuel introduced upstream from the

crankshafr and crankshaft gear throttle valve would be the most susceptible to carburetor icing. At the

inspected in accordance with the opposite end would be an installation with direct cylinder fuel iniection.

step by step instructions which However, the induction system might still be subject to impact icing.

make up Service Bulletin 475A. Consider use of the following procedures to help avoid carburetor

NeFv parts may be required icing troubles:

based on the inspection, but as 1. Periodically check carburetor heat systems and controls for

a nllnlmum a new lockplare and proper condition and operation.bolt must be used in assembling 7. Start engine with carburetor heat control in the "cold" position

the Bear to the crankshait. IT the to avoid damage to the carburetor heat system.

lofibook entry rcquiri´•mrtnts of 3 :\s a preilighl item, check carburetor heat function by sclect-

SLI ´•i75A are completed by the Ing heat "on" and noting a power drop indtcatcd by a drop In

overhauler, you as an n~ncr can IT there is no drop In power, have the carburetor heat

actually check to be sure that s)´•stcm checked BEFOKI: I~LIGH’I’.

tile tasks required by nI) It the relative humidl~v Is above 500,i and the ambient

4´•MAY 1992

temperature is below 80 degrees F, use carburetor heat I~MME- Densify ConfrollerDIATELY BEFORE TAKEOFF to clear the system of ice which

may have formed during taxi. Return the selector to COLD Adjustmentbefore takeoff. In general, carburetor hear should not be used

during taxi because air is unfilrered in the "alternate" or Many Lycoming engine models

carburetor heat "on" position. are equipped with density

5, Conduct takeoff without carburetor hear unless EXTREhlE conrrollers. This is a listing oi

carburetor icing conditions are present and the use of carbure- those models to which Service

tor heat is approved in the Pilot’s Operating Handbook. If heat Instruction 1187G applies: TIO-

is used, insure that ample runway is available for the reduced 540-A1A, -A1B, -A2A, -A2B,-t\2C,

Bower condition and that the increased engine temperatures -CIA, -F2BD, -J2B, -J2BD, -N2BD,

willnot incur engine damage. -,4AIAD, -AB1AD, -Ar’lA; LnO-

6, Remain alert after takeoff for indications of carburetor icing, 540-F2BD, -J2B, -J2BD, -N2BD.

especially when the relative humidity is above 50%, or when To insure that these enginevisible moisture is present. models will develop the masl-

7. With supplemental instrumentation, such as a carburetor air mum power for which they are

temperature gage, partial carburetor heat should be used as certified, the density controller

necessary to maintain safe temperatures and forestall icing. must be adjusted as defined in

Without such instrumentation, use full heat intermittently if the latest version of Textron

considered necessary. Lycoming Service Instruction

8, If carburetor ice is suspected of causing a power loss, i;VIMEDI- 1187. The latest issue of this

ATELY APPLY FULL HEAT AND KEEP IT ON. Go not disturb instruction is 1187G dated Augustthe throttle initially, since throttle movement may kill the 18, 1989, and Supplement No. 1

engine if heavy icing is present. Watch for fUrther power loss to Service Instruction 1187G

to indicate effect of carburetor heat, then a rise in power as dated April 22, 1391. The supple-the ice melts. Once heat has been applied, BE PATIENT. DC) ment updates the instruction to

NOT EXPECT IMMEDIATE RESULTS AS IT WILL TAKE TIME include the TIO-540-AF1A en-

FOR THE ICE TO BE CLEARED FROM THE INDUCTION gine. Density controller settingsSYSTEM. for TVO-435 and TIVO-540

9. In case carburetor ice persists after a period of several minutes engines are covered in the

of full heat, gradually move throttle to full open position and Lycoming Engine Operator’sclimb aircraft at maximum rate to obtain the greatest amount Manual.

of carburetor heat. Cautiously adjust the mixture to the leanest Although all engines are

practicable setting. thoroughly tested after manufac-

10. Avoid flying in clouds as much as possible, but also remember ture, remanufacture, or overhaul

that carburetor ice can occur in clear air. at the Tex-tron Lycominl: Recipro-11. Consider that carburetor icing can occur with ambient tem- cation Engine Division, it is

perarure as high as 100 degrees F and´•humic~ity as low as 50%. impossible to duplicate the

12. PRIOR to reduced throttle operation, such as for a descent, individual installation chaiacteris-

apply full heat and leave on throughout the reduced throttle ties an engine will encounter in

sequence unless the Piler’s Operating Handbook indicates the aircraft; conslquently the

otherwise. Periodically open throttle during extended reduced density controller, which sovern´•

power operatio~´•1 so that enough engine heat will be produced the turbocharging, must be

to prevent icing. Be prepared to remove carburetor heat if a adjusted after the engine is

go-around is initiated. installed and before the aircraft Is

13. Return control to "cold" position immediately after landing to flown. Densir)´• controllers

avoid the use of unfiltered air. shipped as spare parts must also

Because the formation of carburetor ice in general aviation engines be checked and adjusted after

seems to be just as prevalent today as it was 20 or 30 years ago, it is installation and before the

imperative that each pilot have a good knowledge of the causes and the aircraft is flown Before anv

cures. With knowledge, carburetor Ice is a phenomenon which need not adjustment is made to the denslr)´•be a hazard to safe niKht.’l’hc: information which was presented in the controller, the accurac~)´• of rhr´•

I1"I’SU report on "<:arburelor Ice in ~;L´•neral Aviarlon* and which is manifold pressure gage shoulci

reprinted here is an effon to help make general aviation flying safer, be established.

Please ~unt to Page C~iumn i

LYCOMING FLYEA 5

L I

Log Book Entries Service Bulletins, Letters, instructions

The Federal Air RegulaIi~ns arePublished from September i, 1992

quirr speci8e in designating fo March 31, 1992those individuals and organiza-tions who are authorized to The service publications listed below are those which have been

approve aircraft, airframes, issued most recently. We strongly recommend that a complete set of

aircraft engines, propellers, these publications be maintained by all maintenance organizations

appliances or component parts which work on Lycoming reciprocating engines. A subscription may be

for return to service after mainte- obtained through any Textron Lycoming distributor or directly from

nance, preventive maintenance, the Texuon Lycoming Aftermarket Sales Department. Call or write for

rebuildiag, or alteration. These a copy oETextron Lycoming Service Letter No. L114 which provides a

include the holder of a mechanic listing of available publications, prices, and ordering instructions.

certificate, inspection authority,

repair station certificate, or the Service Bulletinr

manufacturer. 4560 Supplement No. 1 states that replacement of an oil pumpThe regulations also require body incorporatiag a pinned idler shah requires that Service

that those who are authorized to Instruction No. 1341 must also be complied with.

return an aircraft to service after 501B Recall of piston pin part no. LW-14077 Subject piston pinsmaintenance do so by supplying received and used between June 18, 1331 and August 5, 1931written details of the mainte- must be returned to Textron Lycoming Williamsport for

nance which was performed, exchange. Affected engine’ models and numbers are listed in

This information is to be an entry the bulletin.

in the maintenance record of the

equipment. The record will I I

contain this information:

1. A description (or reference Service 8ul~etins, Letters,to data acceptable to the oaTE

instructions ~AD NotesP,dministator) of work performed. i;, a ~h O/C~ -4, rJL~ Ancr

2. The d’dte of completion ofg

the work performed.r~lr

T~ C\L-- C;\ -3

3. The naine, certificate num-

ber, and kind of certificate held

by the person approving the Q,, rzcl c sh3~eu

-\\o c:-owork and returning the aircraft to auj~ ibce Sn, (.,f

service.

It is important’ that we under-

stand the intent of these require-3

ments. First, that only those who

have the necessary training and

skills will work on aircraft and

their components. Second, that

these maintenance recordsExbit~it I

provide a history of what has

been done to the equipment over the entries made in the aircraft certif~ing information includingits entire life, and engine logbooks are some- kind of certificate and certificate

To accomplish the spirit and times woefully inadequate. number. Except for the three

intent of the regulations, each Refer to Exhibit 1 as the items black circles in the lower rightaircraft is delivered with an in that log book entry are dis- corner of that black mark, the

airframe log book and an engine cussed. Note that this IS a cop)’ of log book entry was blacked out

log book. If the subsequent a logged entry which actually just as shown here

untrics In these documents applied to an airplan~- In ServiCL. item number one of the loggedcun~ain the appropriate derails, a ’I‘hc- \-crv first Item ~ilih we sec´• cntn´• declares that two cvlindcr~

very maintt´•narice I~ Ihc~ large black mar~ c,n the WCTL’ rcpir-1CCd From the data

hi~tor!r will rc´•sult. Unfortunately, io~i´•r right which obliterates the furnished, we do nc,t know why

6´•MAY~992

Ll(iVMIPl(i

FLYIERI

SEru~ce Instruct~ons cleaned, gapped and tested

1164A Oil Pump Application~ All direct drive Textron Lycoming would add to the history of this

engines except engines that incorporate an integral crankcase engine. Also there is no mention

and accessory housing assembly. of rotating the plugs from top to

124UC Valve Spring Replacement All Textron Lycoming aircraft bottom which is a fairly standard

engines, maintenance practice.

1304G Engine Nameplate Replacement All Textron Lycoming Perhaps items four, five and

aircraft engines. six are adequate to tell what was

1374B Slick Magnetos All four and six cylinder Textron Lycoming accomplished, but simply stating

engines equipped with Slick magnetos. "tach 346" does not give the

1443A Approved Slick magnetos on Textron Lycoming engines information needed for the

Engine model breakdown makes up the text of the instruc- aircraft and engine history. The

tion. total airframe hours and enginehours since new or since over-

Service Letters haul are needed for a complete

L114AD Reciprocating engine and accessory maintenance publications history.

Applies to all Textron Lycoming opposed cylinder aircraft Exhibit 2 is a second example

engines,of a log book entry which tells

L223A Revision A provides additional information about the use of lit’le or nothing about the main-

MOBIL AV 1 synthetic lubricating oil in Texrron Lycomingtenance of the aircraft. Again, the

reciprocating aircraft engines Applies to all’l’exuon certification information has been

Lycoming opposed cylinder aircraft engines.obliterated. The abbreviated

entry is extremely difficult to

read and leaves much to theL I I II imagination. What was accom-

plished prior to the engine

ENGINE LOG SERIAL No. ground run and flight!

TIMESimply stated, these examples

on´•re*UYII~ do not comply with the spirit andh,~lMln ´•.IIYICI-IIY´•I´•I rlou~lull

re. F\a, A 3intent of Federal Air Regulations.

\r’ /L\´•OS Ci/W They do not provide the data

c~J JPC needed to establish a mainte-

Po nance history of the aircraft and

engine which they represent.

Unfortunately. Lycoming p~rson-nel who have occasion to exam-

ine log books on a regular basis

are finding that entries such as

those shown in these exhibits areP´•9´• Toc~l ~II R´•C´•lr D´•t´• Mb´•t 8´•´•r tk´• E~ndorr´•m´•n

ot C´•rytlc~t´•d M´•gh´•nlc. ´•nd hi, R´•clng all too common. While there areBroupn~ Forw´•rd

eno C´•rtltk~1´• Num~´•r MUST b´• Shown.many excellent maintenance

organizations which do a very

Exb~liN 2good job of following up their

work with adequate records,they were replaced or which single viscosity, multi-viscosity, there are also those which do a

cylinders they were. Any me- or perhaps a synthetic oil! What poor job of maintaining a run-

chanic working on this engine in brand was it! Was the filter ning history of maintenance

the future will not be able to tell changed too? And was the performed.which cylinders were replaced suction screen removed, cleaned, Aircraft owners are ultimatelyon June 12, 15)30, This makes and checked for metal. This entry responsible for the airworthinessFuture trouble shooting difficult. leaves many unanswered ques- of their aircraft. Therefore It is

Item two would appear to tions. important that owners examine

mean that the oil was changed. Item three deals with spark the logbook entries ~´•ilch make?hcre is no intiication of what plugs.’l‘he condition of the plugs up the maintenance history ofkind of oil was used. Was it which required that they be

PleaJe ~unt to Pa~e S, Column ,1

LYCOMING FLYER 7

I

A characteristic of the adjustment, require reference to may prove to be lust as Impor-

controller which is nor ,nsl2r- the latest version of Service rant as the work on the alrcrait

stood by some operaron Is its Instruction No. 1187, or the or its components.

ability to adjust engine ~urput at appropriate Lycoming Enginefull throttle to obtain the rated Operator’s;Manual. Engine Nameplatepower of the engine reasrdless For installations which have

of air temperature. This is ion- had an intercooler added in the Replacementfusing because manifold plzssure field, it is required that the

Policyat full throttle will var~ with the owner/operator consult the

temperature of the air entering Pilot’s Operating HandbookA nameplate, to replace

the engine. Pilots should noc Supplement or hlainrenanceone that has been lost, n´•ill

jump to the conclusion rhar a Supplement for density controllerbe issued only upon wrlrten

problem exists when the?´• do nor set up instructions which arerequest, and when accamp~-

see the manifold pressure at red specific to the applicable Supple-nied by a document Irom the

line or do not see the s3me mental Type Certificate CSTC).FAA authorizing a replace-

manifold pressure with 23Ch This general requirement alsoment nameplate. Upon

takeoff, applies to all turbo systemreceipt of the FAA letter, your

It is required that densit\- modifications done by STC.

controller operation be chkcked written request, and a check

for $7.50, a new nameplatebefore an engine is flown tor the

will be issued. Requestsfirst time, and periodicaliy during

their aircraft each time mainte- should be sent to Testronthe life of the engine. This

nance is accomplished. Do the Lycoming Lusromer Service,relatively simple procedur~

entries tell what has been accom- Aftermarker Sales Depart-consists of measuring air rem-

ment, ~52 Oliver Street,plished so that it can be under-perature at the compressor stood when read at some future Williamsport, Pennsylvaniadischarge (induction sir rem-

1770i.rime! Remember that a goodperature) under operating condi-

record of maintenance performedtions, and comparing it with

indicated manifold pressure. ~nou*o

Then, if necessary, the jensity FLYERcontroller should be adiusted. PERMISSION TO REPRINT

Accurate determination of the Permission to reprint material fromPublished by

the Lycoming ’Flyer’is granted, soiextron iycomlngneed for an adjustment to the long as the contexl of information

Heciprocating Engine Division

density controller, and the remains intact and appropriate creditMny 1992 Issue No 52

instructions for making that is given. Editor: Ken W. Johnson

Reciprocating Engine Division, US POSTAGESubsidiary of Textron Inc. PAID652 Ollvel Street WILLIAMSPORT. PAWllllamspOrl PA 17701 US´•t

PERMIT NO 163717,323-6181

ADDRESS CORRECTION REOUESTED

1 1A E

HO ANNIHOAIRCRAFT TECHNICAL PUBLISHER101 SOUTH HILL DRIVEBRISBANE CA 94005

B MAY 1992 LYCOMING FLYER ff52

LYCOMIIVG

LycomingReciprocating Engine Division

Refieslter On Engine Break-in Fuel Information

Service Engineers at the Textron Lycoming Reciprocating Engine Flyer Number 51 discussed

Division get a surprising number of telephone calls asking about recent amendments to the Clean

engine break-in. Because aircraft owners who are having a replace- Air Act and the affect these

ment engine put into their aircraft are very interested in achieving the amendments were likely to have

maximum in service and performance from that engine, a review of on the availability of aviation

break-in planning and procedures is in order, gasoline. First and foremost,Textron Lycoming Service Instruction No. 1427A is entitled ’En- these amendments prohibit the

gine Test After Overhaul With Engine Installed in AircraR" In some sale of leaded motor gas after

ways this title is misleading because the procedures for break-in are 1995. Aviation gasoline will then

not limited to overhauled engines. Any Lycoming reciprocating engine be the only leaded fuel typeinstalled in a fixed wing aircraft as a replacement should be subjected remaining. Considering the veryto the break-in procedures recommended in this service instruction. low volume demand for aviation

The engine may be new, remanufactured, or overhauled. Even an gasoline as compared to the

engine which has had a cylinder replaced, or just had new rings large volume of unleaded auto

installed after the cylinder barrels were rehoned, should be broken in gas, the logistics will tend to

all over again. Service Instruction 1427 is being updated to also make leaded aviation gasolineinclude the break-in of engines installed in helicopters. costly, or perhaps not available

at all.Plearo hem to Pago 5 Column 2

Because of the circumstances

outlined above, there is a need

to develop 1 new aviation fuel

Does Your Nose Seal Leak? specification. The Textron

Lycoming Reciprocating EnginePerhaps the first step in dis- Before installation of a crank- Division is working with the

cussing this subject is to first get shaft oil seal, it is important to General Aviation Manufacturers’

the terminology correct. check the recess into which it fits Association on the ASTM J2 Fuel

Lycoming Service Instruction for proper size. Excessive wear Committee to initiate the devel-

1324A calls it a Crankshaft Oil which enlarges the crankcase opment of a new fuel specifica-Seal. Although almost everyone bore for any reason may cause tion for an unleaded aviation

knows exactly what you are the crankshaft oil seal to leak. An fuel.

talking about when the term under size crankshaft could As one of the first steps in

Nose Seal is used, correct termi- result in the same poor fit and ;1 developing this new specificationnology can be important, leak. This is usually caused by a for unleaded aviation gasoline,

Should this seal leak immedi- rusty or pitted surface which has Textron Lycoming has run

ately after installation, it is been polished excessively. premium grade unleaded auto-

possible that the seal was dam- Lycoming Service Instruction No. mobile gasoline in Lycomingaged during the installation 1111 specifies the maximum engines designed for a minimum

process, but a poor fit between under size grind or polish which of 91/96 octane aviation gaso-the crankcase and seal or the is allowable for the removal of line. At the service station pump,crankshaft and seal could also be rust or pits. It also prescribes the these automotive fuels am listed

responsible for the leak. Pleat~ hem to Pogo 4, Column I P~s´• turn to Pogo 2 Column I

at 94 octane. Results of the tests What is the objective of the engine break-in? To obtain a compres-proved to be less than satisfac- sion gas and oil seal between the cylinder walls and the piston ringstory because detonation occurred while also keeping friction to a minimum. This objective is achievedwhen the engine was leaned for by first ground running the engine as prescribed in the latest versioncruise operation, of Service Instruction 1427 and then continuing the break-in by run-

Of course there is 1 reason for ning the engine at high cruise power settings during all flights untilthese results. Aviation gasolines break-in is complete. These high power settings cause expansion ofare assigned both a lean and rich the piston rings so that excess oil will be scraped from the cylinderrating with the lower number walls. Under these conditions, the oil is not baked into a shiny glazebeing the lean rating. These on the cylinder walls and the rings and cylinders will form the sealoctane rating numbers are not which is desired.determined with the same test Engines which are shipped from the factory in Williamsport,methods as the octane rating Pennsylvania always arrive with an hour or more of running time innumbers found on the pump at the test cell. This applies to all engines, new, remanufactured, andyour local service station. The overhauled. This in-plant test run assures new owners that the engineauto fuel taring is found by meets all specifications for RPM, manifold pressure, fuel flow, oilaveraging the Research Number pressure, and the amount of power produced. Although this test run

(which is based on light duty starts the engine break-in, a thorough break-in sometimes takes as

operation and therefore tends to long as 50 hours. The initial engine testing in the aircraft will bebe quite high) and the Motor discussed here. Following this initial engine running, the new ownerNumber (which is usually quite should continue to utilize the recommended power settings for engineclose to an aviation lean rating). break-in until a satisfactory break-in is assured.This average provides the 93 or Before proceeding further, the subject of oil used for engine94 octane taring which is placed break-in should be discussed. Lubricating oils recommended for use Inon premium automobile fuel. Lycoming opposed cylinder engines are listed in Textron Lycoming

Aviation octane performance Service Instruction No.l0l4K along with general information regardingtests on these same premium 94 lubrication. The general rule for engine break-in is: Llse Straightoctane automobile fuels resulted Mineral Oil. There are a few engine models which are exceptions toin octane ratings in the high this rule. These are: TO-360-C, TO-360-F, TIO-360-C, TIO-541, andeighties when using the aviation T1GO-541. These engine models are to be serviced with ashlesslean test method. This is the dispersant oil for the entire life of the engine, including the break-inreason an aviation engine rated period.for a minimum of 91/96 octane Certain additional information applies to the break-in of thesefuel might not operate satisfac- engine models: 0-320-H, On0-360-E, TO/LTO-360-E. Although thetorily with these fuels when general rule of using straight mineral oil during break-in does applyleaned for cruise. for these engines, Service Instruction No.l0l4K also states that

If we do not consider the high Lycoming oil additive, Part Number LW16702, must be added to thevapor pressures or additives oil of these engines when the engine is installed in the airframe andwhich may make automobile

every 50 hours thereafter, or at every oil change.fuels less than satisfactory for use The factory produced engine, as stated earlier, will always have anin many aircraft fuel systems, initial test run. Installation of the engine in the airframe should be inthese premium automobile fuels accordance with standard shop practice. To avoid contamination of thedo have octane levels which

replacement engine, the oil cooler and lines should be cleaned andshould prevent detonation in flushed before they are installed. All vent and breather lines must beengines designed for 80 octane properly installed and secured as described in the airframe mainte-aviation gasoline,

nance manual. Airframe and intercylinder baffles must be installedThe most important result of along with the engine cowling to insure that optimum cooling is

these tests is the finding thatachieved, and that engine temperatures are maintained within speci-

premium automobile fuels, in fled operating limits during both ground and flight testing.spite of the octane level adver-

tised at the pump, are notAlthough all engines shipped from the Textron Lycoming factory

suitable for use In aviationhaYe been run in the test cell, an engine ground test in the aircraft as

described in Service Instruction No. 1427 will be beneficial for theseengines which were designed

engines as well as for those overhauled in the field with no test cellfor a minimum of 91/96available. On start up it is imperative that adequate oil pressure be

Please turn to Page 7, Column S shown on the gage within 30 seconds or the engine should immedI-2´•JANUARY1993

~LYER

ately be shut d,,,The engine should be run until it is completely 101360 TBO Mysterywarmed up so that several items can be checked before the aircraft is

released for flight. These items include a standard magneto check with The Lycoming IO-360-A was

the engine producing power, and a quick OFF and ON check at first produced in the 1960s. h´•iany

engine idle to insure that the magneto is not hot with the switch in the versions of this 200 horsepowerOFF position. Operation of the alternator, vacuum pump, and carbure- engine have been built over the

tor heat or alternate air system should be checked during this period years. These include the IO-360-

of ground operation. Cycling of the propeller for models with a c, IO-360-D, and the IO-360-J.controllable prop, 2 feather check if the engine is installed in a multi- Some of these models, such as

engine aircraft, and a brief run to full power determine the proper the LIe360-C1E6, have been

functioning of the engine/propeller combination. During this engine manufactured for use in twin

run up, the oil pressure should be carefully checked to determine if engine aircraft and rotate to the

any adjustment is necessary. After a period at idle for engine cool left rather than the right which is

down, idle mixture and idle speed are checked to see if adjustment standard. Although the 10-360

may be needed. After shut down, the engine should be inspected for has also been adapted for use in

oil leaks. Finally, the oil suction screen, and oil pressure screen or oil helicopters, the paragraphsfilter should be checked for contamination. If no contamination is which follow will deal only with

evident, the aircraft is ready for flight testing. those engines used in fixed wingThe flight test after installing a replacement engine should follow aircraft.

the procedures outlined here. They are taken from Service Instruction Because of its long history, the

No. 1427A. recommended TBO for some of

1. Start the engine and perform a normal preflight run-up in the older 10-360 engines which

accordance with the engine operator’s manual. are still operating seems to be a

2. Take off It airframe-recommended power, while monitoring mystery to their owners, and in

RPM, fuel flow, oil pressure, oil temperature, and cylinder head many cases to the A&P mechan-

temperatures. ics who are called upon to work

3. As soon as possible, reduce to climb power specified in the on these engines or provide

operator’s manual. Assume a shallow climb angle to a suitable cruise advice about their use. This is

altitude. Adjust mixture per pilot’s operating handbook. not surprising considering that

´•I. After establishing cruise altitude, reduce power to approxi- there have been a number of

mately 750m and continue flight for two hours. For the second hour, product improvements over the

alternate power settings berween 65% and 75% power per the years, and the recommended

operator’s manual. TBO has generally been in-

5. Increase engine power to maximum airframe-recommended and creased as these improvementsmaintain for 30 minutes, provided engine and aircraft Ire performing have been incorporated.within operating manual specifications. Let’s start at the beginning.

Early 10-360 engines utilized a

CAUTION stepped dowel to hold the

Avoid low-manifold pressure (under 15" Hg.) during high engine bearings in place. TBO for these

speeds. Also avoid rapid changes in engine speed with engines that engines was 1200 hours and is

have dynamic counterweight assemblies. These conditions can detune, Still 1200 hours for any engine

or damage, the dampers, rollers, and bushings in the counterweights. which has nor been modified as

6. Descend at low cruise power, while closely monitoring the required by Lycoming Service

engine instruments. Avoid long descents at row manifold pressure. Do Bulletin No. 326 or 326A. There

not reduce altitude too rapidly or the engine temperature may drop a’e probably very few engines

too quickly,which fall into this category, but

7. After landing and shutdown, check for leaks at fuel and oil fhere is the possibility that a few

nttings and at engine and accessory parting surfaces. Compute fuel engines overhauled in the field

and oil consumption and compare to the limits given in the operator’s may not have been updated and

manual. If consumption exceeds figures shown in manual, determine a’e Still in operation.Service Bulletin No. 326the cause before releasing the aircraft for service.

8. Remove oil suction screen and pressure screen or filter to check ’e9uired the stepped dowels to

again for contamination.be replaced with straight dowels

After the initial flight has been accomplished and the aircraft is i" all bearing saddles except the

Pleara tun? lo P~go 8, Column I Plear~ rum Io Pag´• 4, Column 3

LYCOMING FLYER 3

procedures for replating the ers know this is a possibility, and front main in the 10-360. Be-crankshaft flange and seal area. since they design with the cause the bearings requiredh~ieasurement of both the crank- intention of preventing engine larger holes to accommodate theshaft and the crankcase to insure related problems of this kind, larger straight dowels, dowelsthat they meet Table of Limit some means of preventing and bearings were replaced intolerances should be standard freeze-up of the crankcase complete sets following themaintenance procedure before breather is usually a part of the instructions printed in Serviceinstallation of a crankshaft oil aircraft design. The breather tube Bulletin No. 326. All new 10-360seal, may be insulated, it may be engines starting with serial

To avoid damage during designed so the end is located in number L7100-51A incorporatedinstallation, it is important go a hot area, it may be equipped the straight bearing dowels.follow the instructions provided with an electric heater, or it may Except for five engines whichin L~coming Service Instruction incorporate a hole, notch, or slot have serial numbers listed inNo. 1324A. This instruction gives which is often called a "whistle Service Bulletin No. 326A, allinformation on the two types of slot." Because of its simplicity, remanufactured engines whichseals which may be used in the whistle slot is often used and were shipped from theL~coming direct drive engines, is located in a warm area near Williamspore Plant after Januarythe part numbers of both the the engine where it will not 26, 1970 were updated. All IO-standard and the oversized seals, freeze. Aircraft operators should 360 engines with the larger-and the method of installing both know which method of prevent- straight bearing dowels were

types of seal. ing freeze-up is used and then then assigned a recommendedWhen a leak at the crankshaft insure that the configuration is TBO of 1400 hours.

oil seal develops after many maintained as specified by the A second product improvementhours of normal operation, it is airframe manufacturer. which affected TBO occurred inusually the result of other prob- Should leakage at the crank- 15)72. A redesigned camshaft waslems. The experienced Field shaft oil seal occur as a result of introduced. It featured aService Engineers at Lycoming oil slinger clearance which is too smoother cam profile that greatlyindicate that a leaking cranl;shaft tight, the problem can initially be improved the action of the valveoil seal is frequently caused by a identified by checking for exces- train which consequently in-restricted breather or an oil sive end clearance. This can be

slinger clearance that is too tight. done with a dial indicator.The leak might also be caused by Remove the prop and then pusha propeller defect which places the prop flange to the extreme appropriate clearance is thean abnormal side load on the ah position and zero the indica- result of excessive wear on thecrankshaft oil seal, tor. Then pull the prop flange Crankcase Thrust Face which will

To avoid the problem of oil full forward and read the travel allow oil to be pumped out pastleakage at the crankshaft oil seal on the indicator. Compare this the crankcase oil seal.because of an engine breather figure with the limits listed in the Overhaul time Is usually whenrestriction, examination of the Table of Limits for the appropri- the crankcase thrust face mightbreather tube to determine its ate engine model. receive needed repair. Shouldcondition is an excellent idea. If Should the end clearance the srankcase oil seal be leakingthe tube is in good condition, exceed the limits specified, the excessively, it may simply meanalso remember that the engine oil slinger clearance should then that overhaul time has arrivedexpels moisture through the be checked. First, remove the old early. Fortunately this is some-tube. Under freezing conditions nose seal and clean the work thing which does not happenthere is some possibility thas. the area. Again, push the crankshaft very often.moisture may freeze at the end to the rear of the engine. Insert a Crankcases with worn orof the tube and ice will build up .002 inch feeler gage about 3/16 damaged thrust face areas can beuntil the tube is completely inch wide between the oil slinger repaired by reworking the thrustrestricted. Should this happen, on the crankshaft and the crank- face area to permit installation ofpressure may build up in the case. Again, pull the crankshaft new thrust bearing washers.crankcase until something gives forward. If the .OOi inch feeler These bearings are available asusually the Crankshaft Oil gage is pinched tight, the re- repair items. Thrust bearingSeal. quired .002 to .007 inch clear- washers may be reused If they

Since the airframe manufactur- ance has been exceeded. Lack of do not show wear and if their4´•JANUARY1993

FLYER

creased the service life of the had both of the improvements quent requests about the recom-

exhaust valves. The redesigned discussed here aarger straight mended TBO for the 10-360camshafts were incorporated in bearing dowels and redesigned engine, it seemed appropriateall engines with these serial camshaft) would have 2 recom- that this detailed explanationnumbers or higher: L524-67A and mended TBO of 1600 hours. At start at the very beginning and

L3762-51A. For those who own that time, there were three attempt to clear up the reasons

10-360 or LIO-360 engines with possible recommended TBO for the many changes which have

serial numbers lower than these, times for these engines: 1200, occurred over the years. With

you could be the owner of a 1400, and 1600 hours. As time this information, owners of older

1400 hour TBO engine. If the passed, all engines engines should be able to review

camshaft was changed during remanufactured or overhauled It the logbook data on their en-

overhaul, and one of these the Lycoming factory incorpo- gines and determine if the

redesigned camshafts is now in rated these new features which changes outlined above have

the engine, the TBO recom- increased the recommended TBO been made. For those whose

mended In the current version of time to 1600 hours. Overhauls engines have all the recom-

Lycoming Service Letter No. 201 done in the field should also mended changes and those with

would apply. The TBO have incorporated these changes, engines which have higher serial

recommendation for aerobatic but to know for sure, the records numbers than those listed above,engines is qualified by Note 6 of for older engines overhauled in congratulations, you am the

Service Letter L201C. The part the field must be examined on owner of an engine which has

numbers for clmshafts with the an engine by engine basis. proven to be worthy ofa 2000

revised cam profile are: LW- The product improvements hour recommended TBO and

13222 (with separate cam gear), which were made to the 10-360, that’s not 2 mystery.LW-11754, LW-12311, and LW- 200 horsepower engine in the

12312 (with integral cam gear). early years made it an excellent

Lycoming Service Instruction engine which is still beingNo. 1009T was issued on October manufactured today. By tracking13, 1972, It stated that IO-360, engine performance and reliabil- I~ainfenance200 horsepower engines which ity records over the years, Nofice

Lycoming was again able to

recommend another increase in Textron Lycoming ServiceTBO time when Service Instruc- Bulletins 446 and 471 require the

thickness is sufficient to maintain tion No. 1009AE was issued on use of oil additive LW-16702 in

compliance with the crankshaft June 19, 1981. At that time all IO- certain Lycoming reciprocatingand crankcase end clearance 360 engines which had been engines. Textron Lycomingspecifications in the Lycoming upgraded to be eligible fora Service Instruction No. 1409Table of Limits. 1600 hour TBO were recom- recommends its use in all

Instructions for repairing the mended for a further increase to Lycoming reciprocating engines.crankcase thrust face are found 1800 hours. In the northern hemisphere we

in Lycoming Service Instruction The publication by which now have cold weather affectingNo. 1354B. This repair should Lycoming makes TBO recommen- many aspects of our flightbring the oil slinger clearance dations was changed to Service activity, so it may be an Pppro-back into tolerance and should Letter No. 201 in 1984. By priate time to consider the

cure the leaking crankcase oil continuing to observe the condi- benefits of using LW-16702. The

sell which would also have been tion of engines when torn down additive is carried to all parts of

repllced during the reassembly at TBO, wear characteristics and the engine by the oil and forms a

of the engine, reliability of the 10-360 engine protective film on all metal parts.The information provided in remained under evaluation. This This protective film is particularly

this brief article may help aircraft resulted in an additional increase helpful in reducing wear on cam

owners to prevent the possibility in the recommended TBO to lobes and tappets. Using LW-

of a leaking crankshaft oil seal 2000 hours when Service Letter 16702 or an oil which alreadyand to understand the serious No. 201C was issued on March 9, has the equivalent of LW-I6702nature of the repair required if 1990. included may save your enginethis seal is found to be leaking Because Lycoming Field from unnecessary wear duringexcessively. Service Engineers receive fre- cold weather starting.

LYCOMING FLYER 5

AD Notes of Interest Service Bulletins, Letfers, Instructions

AD 90-04-06 has been revised. Published from April i, 1992 toRevision one placed May 1, 1992

as the date by which compliance November ~5, ~992with the AD was to be com-

pleted. The AD and its revision The service publications listed below are those which have been

apply to any Textron Lycoming issued most recently. VQe strongly recommend that a complete set of

four cylinder piston engine these publications be maintained by all maintenance organizationsmanufactured prior to January 1, which work on Lycoming reciprocating engines. A subscription may

1930, and equipped with a rear be obtained through any Textron Lycoming distributor, or directlymounted propeller governor and from the Textron Lycoming Aftermarket Sales Department. Call or

external oil line. Any governor write for the most recent issue of Textron Lycoming Service Letter No.

oil line assembly having integral L114 which provides a listing of available publications, prices, and

aluminum connecting nuts must ordering insuuctions.

be replaced with a similar line

utilizing steel fittings. Engine Service Bulletins

case/governor aluminum fittings225B Replacement of valve rocker thrust washers All Textron

must also be replaced withLycoming angle head valve engines.

corresponding steel fittings. An240M Mandatory replacement of parts at normal overhaul All

optional method of complianceTexuon Lycoming reciprocating aircraft engines.

with this AD is the installation of342A Fuel line (stainless steel tube assembly) and support clamp

steel fittings and a fire resistant

flexible hose assembly. Although inspection and installation All fuel injected Texuon

Lycoming engines as indicated in fuel line and clampingthe time for compliance with this

diagrams.AD has passed, it is recom-

mended that owners of these 388B Procedure to determine exhaust valve and guide condition

engines review maintenance All Texvon Lycoming reciprocating aircraft engines.

records to insure that appropriate 425B Teledyne Continental Motors Service Bulletin No. 599D

lines and fittings are now in- All Textron Lycoming engines equipped with S-20, S-1200,

stalled in their aircraft, and D-2000 and D-3000 series magnetos having riveted impulse

examine the work to see if those couplings.lines are supported as specified 456B Replacement of sintered iron oil pump impellers Many

in the AD. Textron Lycoming Textron Lycoming reciprocating engine models are affected

Service Bulletin No. 488A and by this bulletin; serial numbers and other engine identifica-

Service Instruction No. 1435 with tion data are included in the bulletin.

Supplement 1 to each are appli- 495A Reprint of Precision Airmotive Corporation Service Bulletin

cable to this AD. No. MSA-I, Revision No. 1 All Textron Lycoming pistonAD 92-12-10 is applicable to aircraft engines employing Marrel-Schebler carburetors.

L~coming TIO-540-S1AD engines 498A Reprint of Precision Airmotive Corporation Service Bulletin

installed on Piper PA-32 series No. MSA-2, Revision No. 1 Textron Lycoming 0-235,aircraft. This AD required the 0-290, and 0-320 series engines.fist visual inspection of the fuel 501B Recall of piston pin part no. L~Jlr-14077 Attachment 1

injector fuel lines between the provides and issue date of November 15, 1991.fuel manifold and the fuel 502 Replacement of part number LW-13262 intake valves etched

injector nozzles within ten flight with date code K-L. Bulletin applies to some engines ofhours after its effective date. these models, TO, TIO-360-C1A6D; TO-360-F1A6D; (L) TIO-Lines which are not supported as 540-V2AD; TIO-541-E; TIGO-541-E. Specific serial numbers

specified in the AD or which and time of new intake valve installation are spelled out in

show signs of leakage or damage the bulletin.must be replaced. Follow up 503 Exhaust valve guide replacement on TIO-540-AP18 enginesinspection of these lines and

_ All TIO 540-AF1A engines up to and including number L-

replacement as necessary is 9293-61A except those which have exhaust valve guidesrequired at every 100 hour changed since April 1991.

Please htm to Page 7, Column I 504 Consolidated Fuel Systems Inc. mandatory service bulletin

6´•JANUARY1993

FLYERI: I

No. CF1-92, Revision 1- Carburetor flolt ldt CF66~-915 with Reciprocating EngineCF30-766 float, date stamped 1091 All Texuon Lycoming Mainfenance School0-235 series, 0-290 series, and 0-320 series engines

equipped with Marvel-Schebler, F~cet Aerospace, Precision ’Ihe Texuon Lycoming Recipro-

Airmotive MA-3, U~-3A, MA-3PA, MA-3SPA, MA-4SPA series eating Engine Division offers a

carburetors overhauled by Consolidated Fuel Sysrems Inc. or hlaintenance and Service Training

in the 8eld by referenced carburetor floats listed ;Ibove School in two forms. The first is

between November 1, 1991 and July 14, 1992. a four-day course held at the

507 Missing spotfaces on P/N 74218 Cylinder He~d Assembly Williamsporr/Lycoming Count~

All Textron Lycoming VO-435 and TVO-435 series engines. Airporr located in Montoursville,

Pennsylvania.The school schedule for

Seruice Instruct~onsJanuary through June of 1993 is:

1009A] Recommended Time Between Overhaul Periods All

Texuon Lycoming piston aircraft engines. January

1012P Supplement No. 1 states that counterweight assemblies with 25, 26, 27, 28

pan numbers LW-19225E, LW-19226E, and LW-19227E ue February 8, 9, 10, 11

nor to be used on the crankshaft of an engine equipped 22. 23, 24, 25

with reduction gears. Measurement and marking of some March 8, 9, 10, 11

counterweights will be required. 22, 23, 24, 25

lld3B Supplement No.2 replaces Supplement No.l. Changes April 12, 13, 34, 15

dimensional and tooling information for grinding of counter- 26, 27, 28, 29

weight bushings. May

11139 installation of new integral camshaft and gear assembly 17, 18, 19, 20

0-540, 10-540, and TIG-540 standard cylinder flange en- June 7, 8, 9, 10

gines. 21, 22, 23, 24

11139 Supplement No. 1 lists a new telephone number for Pacific A mobile Training School is

Aviation Pry. Ltd. as (61) 2-708-9200. also offered to provide Textron

1455 Installation of new fuel injection manifold kit Put No. Lycoming customers with mainte-

05K21433 TIO-360-C1A6D engines equipped with two nance and service training at

fuel manifold assemblies and TO-360-C1A6D engines con- their base of operation.verted to n0-360-C1A6D engines using SSP-584. More information on enroll-

1457 Textron Lycoming remote mount oil filter kit All 0-235 ment, tuition, transportation, and

series engines with the accessory housing machined for oil scheduling may be obtained by

cooler installation. All 320, 360, 540, and 10-720 direct drive calling Robert Ohnmeiss It (717)

series engines equipped with two individual mlgnetos. 327-7127 or by sending 1 fur to

1´•158 Soft connecting rod bolts All Textron Lycoming recipro- his attention a (717) 327-7100.

caring engines.Service I;etten

L230 A listing of and ordering instructions for Textron Lycoming

publications which are available on Microfiche. octane aviation fuel. Thue-

L231 An updated listing of variable absolute pressure controller fore, the Textron Lycomingcalibration values for AiResearch turbo control test set Pan Reciprocating Engine Division

Number 481070-1. strongly recommends that

owners of these enginesAn updated INDEX of Service Bulletins, instructions, and Letters, refrain from attempting to use

SSP-292, was issued in June 1992 and may be ordered from theany kind of automohIle fuel in

Tcxuon Lycoming Aftermarket Sales Department. Price is 52.00 per theit engines. What you read on

copy, the automotive fuel pump at

your local service station does

not equate to the same octane

PERMISSION TO REPRINT value found on the aviation fuelPermission to reprint material from

pump at your local FBO. Theinspection, annual inspection, the Lycoming granted, so

and engine overhaul. Textron long as the context of information difference might result in less

Lycoming Service Bulletin No. remains intact and appropriate credit than satisfactory engine perfor-is given mance when it is least expected.342A applies.

LYCOMING FLYER 7

nlelsed for flight, it is the responsibility of the owner/piler to con- Mainfenan~e Tiptinue the break-in procedure. To seat the rings properly, the engineshould be run at cruise settings between 65% and 750/6 power for 50 Murphy’s Law prevails. Twohours of operation or until oil consumption stabilizes. If the engine is damps which hold the curbo-

operated at low power settings during this break-in period, a condi- charger transition and tailpipe oftion commonly known as glazing of the cylinder walls may occur. the TIO-540-P2BD and nO-540-When this happens, the ring break-in stops, and excessive oil con- J2BD engines ~Piper Navajo 325sumption often occurs. Extensive glazing can only be corrected by and Piper Chieftain) have beenremoving the cylinders and rehoning the cylinder walls. Because this used in reverse locations byis an expensive procedure it is a good reason for accomplishing a individuals in the held Althoughcorrect and thorough break-in of the engine. these clamps Ire similar in size

Many questions which are being asked about engine break-in and appearance, they are not theshould be answered by the material in this article. To summarize, same. The result of reversingthese are the items which owners should keep in mind when a re- these two damps is transitionplacement engine is installed in their aircraft. (1) Follow the engine -exirnrsc- pipes which come

manufacturer’s recommendation regarding the oil to be used for break- loose. The confusion involvesin. (2) Run the engine at high cruise power levels for best piston ring/ Lycoming part numbers LW-

cylinder wall mating. (3) Continue-break-in operation fo~ 50 hours or 12093-6uld LW-12125-3. Partuntil oil consumption stabilizes, then switch to an Ashless Dispersmt number designedCAD) oil to keep the engine clean during its operating life. to be installed at the bottom of

the wastegate which is the

wastegate to nit pipe connec-

No~ice tioa Part number LW-12125-3should be installed to connect

CMC Aviation Limited would above should there be one the waste gate to the transition.like to know if any Lycoming available which is not beingdistributor or other maintenance used. Any organization havingorganization has 1 Turbo-Conuol such a test set which they would FLYERTest Set which is in excess to be willing to sell may contact htheir needs. This unit with Part M. Dastur, Managing Director ofNo. 481070 would be suitable for CMC Aviation, at Wilson Airport,testing controllers fitted to P.O. Box 44580, Nairobi, Kenya. Published byLycoming TIG-540 series engines. Textron LycomlngMr. Dastur may be reached by Reciprocating Engine Division

CMC Aviation would like to telephone in Kenya at 501221 or January 1993 Issue No. 53purchase 2 test set as described 501213. Editor: Ken W. Johnson

C~ ~C ir~ LycomingBUU( RATE

Reciprocating Engine Divisionl US POSTAGESubsidiary of Textron Inc. PAID652 Ollver StreetW1LamspoR.PA ~7701 U.S.A. WIIlIAMSPORT, PA

717/323´•6181 PERMTTNO.163ADDRESS CORRECTION REQUESfED

1 IA ZAIRCRAFT TECH PUBLISHERSfiS HARRIET ANNINO701 SOUTH HILL DRBRIS~ANE CA 94005

8´•JANUARY 1993 LYCOMING RYER #53