C208 Technical Lectures

8/11/2019 C208 Technical Lectures

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CESSNA 208B

GRAND CARAVAN

INDEX

1 AIRFRAME PAGE 2

2 FLIGHT CONTROLS PAGE 3

3 COCKPIT ARRANGEMENT PAGE 6

4 CABIN DOORS PAGE 8

5 WARNING SYSTEMS PAGE 9

6 LANDING GEAR AND BRAKE SYSTEM PAGE 13

7 TURBINE ENGINE THEORY PAGE 14

8 POWER PLANT PAGE 19

9 PROPELLER PAGE 36

1 FUEL SYSTEM PAGE 4

11 ELECTRICAL SYSTEM PAGE 45

12 LIGHTING PAGE 52

13 AIR CONDITIONING PAGE 54

14 O!YGEN PAGE 58

15 INSTRUMENTS PAGE 58

16 ICE AND RAIN PROTECTION PAGE 59

17 AUTOFLIGHT SYSTEM AND A"IONICS PAGE 61

18 LIMITATIONS PAGE 71

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1 AIRFRAME

GENERAL

The Cessna C208B Grand Caravan is an all-metal, high wing, single-engine aeroplane equippedwith a tricycle landing gear ! composite cargo pod is optional equipment

FUSELAGE

The "uselage length is #$ "eet $ inches %C208& and '1 "eet $ inches %C208B& The construction o" the"uselage is a conventional "ormed sheet metal (ul)head, stringer and s)in re"erred to as

semimonocoque *tringers are long metal strips which run the length o" the "uselage and are "astenedto the rings and (ul)heads The principle o" the monocoque design is that the s)in is designed tocarry the loads and stresses The circular shape is (eing maintained (y the use o" "rames andstringers +n addition, the stringers are designed to sti""en the s)in ongerons ta)e up the endloadings due to (ending

a.or components o" the structure are/

The "ront and rear carry-through spar and (ul)head The "ront carry-through spar and (ul)head

is an integral "ail-sa"e structure with "orgings at the top "or attaching the "ront wing spar and"orgings at the (ottom "or the attaching the wing strut

The rear carry-through spar and landing gear (ul)head The rear carry-through spar and landing

gear (ul)head is an integral "ail-sa"e structure with "orgings at the top "or attaching the rear wingspar and "orgings at the (ottom "or attaching the main landing gear trunnions

The "orward door post The "orward door post provides the load path "or trans"erring the loads

"rom the engine mount directly to the primary structure

ail-sa"e construction assures that the structure is designed and (uilt in such a way that should anystructural component "ail, the remaining structure is capa(le o" carrying certi"ied limit "light loads

WINGS

The wing span is 2 "eet 1 inch The eternally (raced wings are constructed o" a "ront and rearspars, "ormed sheet metal ri(s, dou(lers and stringers 3i(s maintain the aerodynamic shape o" thewing and trans"er loads to the s)in and spars The entire structure is covered with aluminium s)in

The primary wing spars, wing carry-through spars in the "uselage, wing struts and attaching structureare o" "ail-sa"e construction "or limit "light loads The "ront spar is equipped with wing-to-"uselageand wing-to-strut attach "ittings The rear spar is equipped with wing-to-"uselage attach "ittingsBoth wings contain an integral "uel tan) These tan)s are "ormed (y the "ront and rear spars, upperand lower s)ins and in(oard and out(oard closeout ri(s The in(oard tan) ends are located 18 inches"rom the wing root to "orm a 4dry (ay5 "or )eeping "uel away "rom the ca(in in an accident The

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wing is designed to accept impact out(oard o" the "uel tan) while minimising damage to the "uel tan)area

EMPENNAGE

The height is 1' "eet 10 inches The empennage consists o" a conventional vertical sta(iliser, rudder,hori6ontal sta(iliser and elevator The vertical sta(iliser consists o" a "orward and a"t spar, sheet metalri(s and rein"orcements, "our s)in panels, "ormed leading edge s)ins and a dorsal "in The hori6ontalsta(iliser is constructed o" a "orward and a"t spar, ri(s and sti""eners "our upper and "our lower s)in

panels and two le"t and right wrap around s)in panels which also "orm the leading edges

! pro(lem o" marginal nose-down elevator power was o(served in transitional out-o"-trim "lightevaluations This was alleviated (y a single row o" vorte generators "itted on top o" the hori6ontalsta(iliser .ust "orward o" the elevators They enhance nose down elevator and trim authority The

generators are intended to prevent "low separation over the elevators at slow speeds

CARGO POD

The pod attaches to the (ottom o" the "uselage with screws and can (e removed The pod is"a(ricated with a 7ome inner housing, a layer o" evlar and a "i(reglass outer layer

The pod has a load-carrying capacity o" 1090 pounds +t has ' separate compartments divided (yaluminium (ul)heads :ach compartment has a maimum "loor loading o" #0 l(s;sq"t Themaimum weight "or each compartment is as "ollows/

orward compartment 2#0 l(s

Centre compartment "wd #10 l(s

Centre compartment a"t 2$0 l(s

!"t compartment 280 l(s

:ach compartment has an individual loading door :ach door is secured in the closed position (y 2handles which latch the doors when rotated 90< to the hori6ontal position

2 FLIGHT CONTROLS

The "light controls consist o" a conventional aileron, elevator and rudder control sur"aces and a pairo" spoilers mounted a(ove the out(oard ends o" the "laps The "light control sur"aces are manuallyoperated through mechanical lin)ages !ll control ca(les are o" stainless steel construction

AILERONS

3ound-nose ailerons are o" conventional "ormed sheet metal ri(s and smooth aluminium s)inconstruction !ileron trimming is achieved (y a trimma(le servo ta( attached to the right aileron andconnected mechanically to a )no( located on the control pedestal The servo ta( on the le"t aileron

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provides reduced manoeuvring control wheel "orces ences in(oard on the ailerons on the modelC208 and C208! only, enhance lateral sta(ility

SPOILERS

=ue to the long wing and greater "uel load "urther out in the wings, spoilers are "itted to improvelateral control at low speeds (y disrupting li"t over the appropriate "lap The e""ect is more enhancedin a "lap down con"iguration This "eature, in turn, permits shorter length ailerons to accommodatethe etremely long-span wing "laps needed "or meeting the !!>s maimum stall speed limit o" ?1)nots

The spoilers are interconnected to the aileron system through a push-rod mounted on an arm on theaileron ovement "or the "irst < o" aileron travel is negligi(le @nce the aileron has (een de"lectedupward past the < point, spoiler travel is proportional to aileron travel The spoiler is "ully retracted

when the aileron is de"lected downward aimum de"lection angle is '0


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! rudder loc) loc)s the rudder in the neutral position :arlier serial models are equipped with arudder loc) which is operated (y a spring-loaded, pull-type T-handle located on the (ottom o" theinstrument panel to the right o" the control pedestal !n interloc) (etween the rudder loc) and the

"uel condition lever prevents loc)ing the rudder when the "uel condition lever is in any position otherthan CAT@ The handle is released "rom the loc)ed position (y rotating it 90< and allowing it toretract "orward to the unloc)ed position

ater serial models incorporate an eternal rudder gust loc) located on the le"t side o" the tail cone! "ail-sa"e connection automatically disengages the loc) when the elevator is de"lected upward a(outone-"ourth o" its travel "rom neutral Because o" the "ail-sa"e system, the elevator loc) should always

(e engaged prior to engaging the rudder loc) when securing the aircra"t a"ter shutdown The rudderloc) should (e disengaged (e"ore towing, starting the engine or moving the aircra"t on the ground inany manner

WING FLAP SYSTEM

The wing "laps are large span, single-slotted, semi-"owler type "laps The "laps span $0 o" the wing,increasing the area (y 1 The out(oard portions have ru((er leading edge vorte generators and atrailing edge lip

The "laps are driven (y an electric motor The wing "laps are etended or retracted (y positioning the+7G !D *::CT@3 :E:3 on the control pedestal to the desired position ! slotted panel

provides mechanical stops at 10< and 20< positions ! white tipped pointer provides "lap positionindication The system is protected (y the !D @T@3 circuit (rea)er on the circuit (rea)er

panel

STANDBY FLAP SYSTEM

! stand(y system can (e used to operate the "laps i" the primary system has a mal"unction +t consistso" the "ollowing/ a stand(y "lap motor, a guarded stand(y "lap motor switch and stand(y "lap motorup;down switch The guarded 7@3 position permits operation o" the "laps using the selector onthe control pedestal The *TBF position disa(les the dynamic (rea)ing o" the primary "lap motorwhen the stand(y "lap motor system is operated The AD;=@7 switch has a AD, centre-o"" and=@7 position

To operate the "laps with the stand(y system/

*elect the "lap lever to the desired position

i"t the guard and place the stand(y "lap motor switch in the *TBF position

!ctuate the stand(y "lap motor AD;=@7 switch momentarily to AD or =@7 as desired

@(serve the "lap position indicator to o(tain the desired position !s the stand(y "lap system has nolimit switches, actuation o" the AD;=@7 switch should (e terminated (e"ore the "laps reach "ull upor down travel, otherwise damage to the stand(y "lap motor mounts may result

Ase o" the stand(y "lap system should (e avoided with the autopilot engaged since it will cause thetrim to run in opposite direction to the autopilot inputs


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3 COCKPIT ARRANGEMENT

INSTRUMENT PANEL

The "light instruments layout is designed around the (asic 4T5 con"iguration +mmediately to thele"t o" the "light instruments are the cloc), propeller anti-ice ammeter, suction gage, volt;ammeter,volt;ammeter selector switch, propeller overspeed governor test switch, le"t air vent pull )no(, le"tair vent outlet and microphone and headset .ac)s

The lower le"t side o" the instrument panel contains a switch panel "or the switches necessary tooperate the aircra"t systems These include toggle switches "or the eterior and interior lights, de-ice and anti-ice systems

Below the "light instrument panel are the par)ing (ra)e, lighting switch panel and inertial separatorcontrol

!(ove the "light instrument panel are the annunciator panel, annunciator panel day;night switch,annunciator test switch and "ire detector test switch

!vionics equipment is placed vertically in dual stac)s approimately in the center and .ust to theright o" the instrument panel

ocated a(ove the avionics stac)s in the top center o" the instrument panel are the engineinstruments consisting o" the torque indicator, propeller 3D indicator, +TT indicator, 7g 3Dindicator, oil pressure;oil temperature gage, "uel "low indicator and le"t and right "uel quantityindicators

=irectly to the right o" the right "light instrument panel are the hour meter, right "resh air vent pull)no(, right "resh air vent outlet and microphone and headset .ac)s and map compartment

ocated (elow the avionics stac)s are the ca(in heat switch and control panel Drovisions "or airconditioning controls are also provided

CONTROL PEDESTAL

! control pedestal etending "rom the center o" the instrument panel to the "loor contains theemergency power lever, power lever, propeller control lever, "uel conditioning lever and wing "lapselector and position indicator ! quadrant "riction loc) is located on the right side o" the pedestal

The elevator trim control and position indicator is located on the le"t side o" the pedestal Theaileron and rudder trim controls and position indicators, the "uel shuto"" valve control and ca(inheat "irewall shuto"" valve control and a microphone are located on the lower end o" the pedestal

LEFT SIDEWALL SWITCH AND CIRCUIT BREAKER PANEL

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Control switches "or the engine, electrical system including circuit (rea)ers and avionics systemare located on a separate panel mounted on the le"t ca(in sidewall ad.acent to the pilot

O"ERHEAD PANEL

The le"t and right "uel tan) selectors, stand(y "lap motor switches, le"t and right vent air control)no(s, le"t and right vent air outlets are located on the overhead panel Drovisions "or an oygenshuto"" valve pressure gage are also provided

PILOT SEATS

The si-way ad.usta(le pilot>s seats may (e moved "orward or a"t, ad.usted "or height and the seatangle changed Dosition the seat (y pulling on the small T-handle under the center o" the seat

(ottom and slide the seat into position then release the handle and chec) that the seat is loc)edinto place

3aise or lower the seat (y rotating a large cran) under the "ront right corner o" the seat *eat (ac)angle is ad.usted (y rotating a small cran) under the "ront le"t corner o" the seat The seat (ottomangle will change as the seat (ac) angle changes

ater serial aircra"t seats are equipped with armrests which can (e moved to the side and raised toa position (eside the seat (ac) "or stowage

Both pilots seats are equipped with a "ive-point restraint system which com(ines the "unction o"

conventional type seat (elts, a crotch strap and an inertia reel equipped dou(le-strap shoulderharness in a single assem(ly

4 CABIN DOORS

CABIN ENTRY DOORS

:ntry to and eit "rom the aircra"t is accomplished through an entry door on each side o" the ca(inand on the Dassenger version only, through a two-piece, airstair type on the right side ! cargo dooron the le"t side can also (e used "or ca(in entry

CREW ENTRY DOORS

The le"t crew entry door incorporates a conventional interior and eterior door handle, a loc)override )no( a )ey-operated door loc) and an opena(le window The right crew entry doorincorporates a conventional interior and eterior door handle and manually operated inside door

loc)

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To open either door "rom the outside, rotate the handle down and "orward to the @D:7 position Toclose the door "rom the inside, place the handle in the C@*: position and pull the door shut thenrotate the handle "orward to the !TCH:= position hen the handle is rotated to the !TCH:=

position, an over-center action will hold it in position

The loc) override )no( on the inside o" the le"t door provides a means o" overriding the outside doorloc) "rom inside the aeroplane To operate the override, pull the )no( and rotate it in the placardeddirection to unloc) or loc) the door

PASSENGER ENTRY DOOR

The passenger door consists o" an upper and lower section hen opened, the upper section swingsupward and the lower section drops down providing integral steps The upper door sectionincorporates a conventional eterior door handle with a separate )ey operated loc), a push (utton

eterior door handle release and an interior door handle which snaps into a loc)ing receptacle +" theupper door is not properly latched, a red light la(elled =@@3 !37+7G will illuminate on theannunciator panel

The lower door "eatures a "lush handle which is accessi(le "rom either inside or outside Thishandle is designed so that when the upper door is closed, the handle cannot (e rotated to the open

position The lower door also contains integral door support ca(les and a door lowering device

To enter the aircra"t through the passenger entry door, depress the eterior push(utton doorrelease, rotate the eterior door handle on the upper door section cloc)wise to the open positionand raise the door to the over-center position 3elease the lower section (y pulling up on the inside

door handle and rotating the handle to the open position ower the door section until it issupported (y the integral support ca(les

=o not use the outside )ey loc) to loc) the door prior to "light since the door could not (e opened"rom the inside i" it were needed in an emergency evacuation

CARGO DOORS

! two-piece cargo door is located on the le"t side o" the "uselage The door is divided in an upperand a lower section hen opened, the upper section swings upwards and the lower section swings"orward The upper section o" the door incorporates a conventional eterior door handle with a

separate )ey operated loc) and on the Dassenger version only, a push(utton eterior emergency doorhandle release and an interior door handle which snaps into a loc)ing receptacle +" the upper door isnot properly latched, a red light la(elled =@@3 !37+7G, will illuminate on the annunciator

panel

The lower door "eatures a "lush handle which is accessi(le "rom either inside or outside Thishandle is designed so that when the upper door is closed, the handle cannot (e rotated to the open

position

+n an emergency do not attempt to eit the Cargo version through the cargo doors without outsideassistance *ince the inside o" the upper door has no handle, eit "rom the aeroplane through these

doors without outside assistance is not possi(le

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=o not use the outside )ey loc) to loc) the door prior to "light since the door could not (e opened"rom the inside i" it were needed in an emergency evacuation

5 WARNING SYSTEMS

ANNUNCIATOR PANEL

! green coloured lamp indicates a normal or sa"e condition in the system !n am(er lamp indicates acautionary condition eists which may or may not require immediate corrective action ! red lampindicates a ha6ardous condition requiring immediate corrective action

Two annunciator panel "unction switches, la(elled !D T:*T and =!F;7+GHT are located to thele"t o" the panel By pressing !D T:*T all annunciators are illuminated and (oth "uel-selector-o""warning horns are activated ith the =!F;7+GHT *+TCH in the =!F position, any annunciatorthat is illuminated will (e at "ull intensity +n the 7+GHT position it provides intensity down to a

preset minimum dim level "or the green lamps and the "ollowing am(er lamps/

e"t and right "uel low

*tand(y electrical power inoperative

*tand(y electrical power on

The intensity can (e controlled (y the :7G +7*T lighting rheostat ! lamp may (e etinguished (ypushing on the "ace o" the light assem(ly and allowing it to pop out To reactivate the annunciator,

pull the light assem(ly out slightly and push it (ac) in

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FUEL SELECTORS OFF WARNING SYSTEM

The system consists o" redundant warning horns, a red annunciator light la(elled A: *::CT

@, actuation switches and electrical hardware The dual aural warning system is powered throughthe *T!3T C@7T circuit (rea)er ! non-pulla(le A: *: !37 circuit (rea)er is installed inseries to protect the integrity o" the starter system The annunciator is powered "rom the !77A7D!7: circuit (rea)er The warning system "unctions as "ollows/

A# BOTH SELECTORS OFF

The red A: *::CT @ annunciator illuminates @ne "uel select o"" warning horn isactivated

B# DURING ENGINE START WITH EITHER SELECTOR OFF

The red A: *::CT @ annunciator illuminates Both "uel select o"" warning hornsare activated

C# ONE SELECTOR OFF AND FUEL REMAINING IN THE TANK BEING USED IS

LESS THAN 25 GALLONS

The red A: *::CT @ annunciator illuminates @ne "uel select o"" warning horn isactivated

+" the A: *: !37 circuit (rea)er has popped or the *T!3T C@7T circuit (rea)er has (een

pulled, the red A: *::CT @ annunciator will illuminate even with (oth tan)s @7

STALL WARNING SYSTEM

! vane-type stall warning unit is "itted in the leading edge o" the le"t wing The unit is electricallyconnected to the stall warning horn located overhead o" the pilotIs position +t senses a change inair"low over the wing and operates the warning horn at airspeeds (etween and 10 )nots a(ove thestall in all con"igurations The system is protected (y the *T! 37 circuit (rea)er The vane andsensor unit is equipped with a heating element operated (y the *T! H:!T switch and is

protected (y the *T! 37 circuit (rea)er

O"ERSPEED WARNING SYSTEM

!n airspeed pressure switch in the pitot-static system is used to actuate an airspeed warning horn inthe event o ecessive airspeed The horn is located (ehind the headliner in the area a(ove the pilotand will sound when the airspeed eceeds Emo %1$ +!*& ! warning signal will also (e heard inthe pilot>s headsets

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6 LANDING GEAR AND BRAKE

SYSTEM

LANDING GEAR

The landing gear is a "ied-gear, tricycle type with steera(le nose wheel and two main wheels Toimprove operation "rom unpaved sur"aces, the standard nose gear "or) and tyres can (e replaced (y a#J etended nose gear and oversi6ed tyres The main landing gear has a 4tear away5 "eature whichreduces damage to the "uselage structure

ain gear shoc) a(sorption is provided (y tu(ular spring-steel main landing gear struts and aninterconnecting spring-steel tu(e (etween the two main landing gear struts The interconnecting tu(ereduces (ending in the "uselage landing gear (ul)heads

7ose gear shoc) a(sorption is provided (y an oil-"illed shoc) strut com(ined with a drag lin) springproviding vertical and a"t displacement restraint ail-sa"e "eatures o" the drag lin) include a(sorptiono" some energy even with complete oil loss and retains the nose gear in the event o" torque lin)"ailure

7ose gear steering is accomplished (y using the rudder pedals ! spring-loaded steering (ungee,which is connected to the nose gear and to the rudder (ars, will turn the nose gear through an angleo" 1< each side o" centre By applying di""erential (ra)ing the degree o" turn may (e increased up to?< each side o" centre +" the nose wheel is turned (eyond its limits during towing, a "rangi(le stopwill "racture and the over travel indicator (loc) hanging on a small ca(le, will "all into view alongside

the nose strut

BRAKE SYSTEM

! single-disc, hydraulically-actuated (ra)e is "itted on the in(oard side o" each main landing gearwheel :ach (ra)e is connected (y a hydraulic line to a master cylinder attached to each pilotIsrudder pedal To set the par) (ra)e, apply (ra)e pressure and pull the handle a"t To release the

par)ing (ra)e, push the handle "ully in

! (ra)e "luid reservoir located .ust "orward o" the "irewall on the le"t side o" the engine compartment

provides additional (ra)e "luid "or the (ra)e master cylinders The "luid in the reservoir should (emaintained (etween the +7 and !K level prior to each "light The (ra)e system uses + H-?0? hydraulic "luid This "luid is a mineral (ase type and is a "lamma(le petroleum product andcoloured red *ystems using mineral (ase "luids incorporate synthetic ru((er seals

ater model aeroplanes %208B010#0 and a(ove& have metallic type (ra)es hen conditions permit,hard (ra)ing is (ene"icial in that the resulting higher (ra)e temperatures tend to maintain proper

(ra)e gla6ing and will prolong the epected (ra)e li"e The ha(itual use o" light and conservative(ra)e application is detrimental to metallic (ra)es

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7 TURBINE ENGINE THEORY

Tur(ine engines are made up o" the "ollowing sections/

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!ir inlet

Compressor

Com(ustion section

Tur(ine

:haust

!ccessory section

*upport systems %starter, lu(rication, "uel and auiliary components such as anti-icing, air-

conditioning and pressurisation&

AIR INLET DUCT

The purpose o" the air inlet duct is to channel the incoming air to the compressor with the least

possi(le loss o" energy +n addition to the design o" the inlet, three other varia(les determinehow much air will pass through the compressor/

!m(ient air density

!irspeed o" the aircra"t

3otational speed o" the compressor

COMPRESSORS

Two main "unctions o" the compressor are to supply compressed air to the (urners plus supply (leedair to "ul"il various engine and air"rame system requirements To supply compressed air to the

(urners, the compressor increases the pressure o" the mass o" air that is channelled through the airinlet ducts and routes it to the (urners in the amount and pressure required

Bleed air might (e tapped o"" any o" the various compressor stages ith each successive stage thepressure and temperature o" the air increases The speci"ic stage "or (leed air etraction isdetermined (y the temperature and pressure required "or the .o(

THE CENTRIFUGAL COMPRESSOR

The compressor accelerates the air"low (y slinging it outward "rom the centre o" the compressorwheel The primary components o" the centri"ugal compressor are the impeller %rotor&, a diffuser%stator& and a compressor manifold The impeller catches the incoming air and accelerates it outwardtoward the di""user The purpose o" the di""user vanes is to direct the air "rom the impeller to themani"old at the gentlest angle possi(le to retain the maimum amount o" energy !nother purpose o"the di""user is to provide the com(ustion cham(er with air at the correct velocity and pressure "ormaimum e""iciency The air is allowed to epand into a divergent duct !s the air spreads out, thevelocity drops and the static pressure increases ultiple stages are connected (y a system o"convergent and divergent ducts to compress and direct the air"low to succeeding stages at the properangle

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!dvantages o" centri"ugal compressors/

High pressure rise per stage Ap to 10/1 in a single stage

Good e""iciency %compression& over a wide rotational speed range, idle to "ull power

*implicity o" manu"acture and low cost ow weight

ow starting power requirements

ore resistant to "oreign o(.ect damage

=isadvantages o" centri"ugal compressors/

arge "rontal area "or a given air"low

ore than two stages is not practical due to energy loss in the air"low when ma)ing the turn

"rom one impeller to the net

THE A!IAL FLOW COMPRESSOR

The air"low "ollows a path parallel to the ais o" rotation, hence the name !ir"low is compressed (yaccelerating it across multiple compressor stages !ir"low passes through a convergent duct to "orceit into an even smaller area The si6e o" the compressor (lades decreases "rom the "irst to the last to"ollow the narrowing design o" the convergent duct

The main elements o" an aial-"low compressor are rotors and stators 3otor (lades are "ied on arotating spindle and "orce air rearward in the same manner as a "an The rotor (lades are preset at aspeci"ic angle and are contoured similar to small propeller (lades *tators, which are stationary

(lade-type air"oils, are located (etween each compressor stage The stators act as a di""user in eachstage converting part o" the energy air into pressure (y slightly slowing down the air They also directthe air"low into succeeding compressor stages at the correct angle

The "irst set o" stators, located (e"ore the compressor stage, is re"erred to as inlet guide vanes.!similar set o" guide vanes, calledstraightening vanes, might (e located at the compressor eit tostop the eiting air mass "rom rotating as it moves "orward into the com(ustion cham(er

!dvantages o" aial "low compressors/

High pea) e""iciencies %compressor pressures ratio& created (y its straight through design

allowing higher ram e""iciency Higher pea) e""iciencies %pressure& attaina(le (y addition o" compression stages i" desired

*mall "rontal area "or a given air"low resulting in low drag

=isadvantages o" aial "low compressors/

=i""iculty and high cost o" manu"acture

3elatively high weight

High starting power requirements

ow pressure rise per stage

Good e""iciency only over a narrow rotational speed range

Eery suscepti(le to "oreign o(.ect damage

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COMPRESSOR STALLS

The angle at which the incoming air meets the compressor (lades varies as a result o" the air>s

velocity and the compressor>s rotational speed The (lade>s com(ined in"luence "orms a vector that iscalled the angle o" attac) !n im(alance (etween the two vector quantities might stall the air"low

By de"inition, a compressor stall occurs when the air mass travelling through the compressor slowsdown and stops +n etreme cases the air"low might even reverse direction !n engine compressorstall may (e noted (y a single or multiple loud 4popping5 noise "rom the engine compartment Thesituation may (e resolved (y reducing the power to a point where the 4popping5 discontinues andslowly advancing the throttle to the required setting The use o" (leed air may also help eliminateengine compressor stalls i" this situation is encountered

Compressor (lades stall "or numerous reasons/

!nything that alters the proper operation o" the compressor (lades such as (lade "ailure, "oreigno(.ect damage, etc

! "uel miture that is to lean

!(rupt pitching movement

:cess "uel "low

:ngine operating speeds well a(ove or (elow normal recommended operating speed

THE COMBUSTION CHAMBER

The com(ustion cham(er houses the "uel no66les and igniters uel is mied with the compressed airin the com(ustion cham(er The temperature o" the air as it leaves the compressor is L#1


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cham(er ehaust gasses into mechanical energy to operate the compressor and other accessories!pproimately ?0 - 80 percent o" the total energy o" the ehaust gasses go to that purpose Thetur(ine section is a divergent duct :ach stage is larger in diameter than the preceding stage tocompensate "or loss o" energy through each stage This allows an equal sharing o" the load (etween

stages

*tators or tur(ine guide vanes are located in "ront o" and (etween each tur(ine stage to smooth theair"low and properly direct it to the net tur(ine wheel High energy air"low stri)es the tur(ine (ladesat an angle !s the air"low does not easily change direction, it imparts a pressure upon the tur(ine

(lades which causes a turning "orce upon the wheel The tur(ine stages are mounted on the samesha"t with the compressor stages

THE E!HAUST

The ehaust section, which is located directly (ehind the tur(ine section has two primary purposes/produce ehaust gas high eit velocity and minimise ehaust gas tur(ulence The purpose o" theehaust cone is to channel all ehaust gasses as they are discharged "rom the tur(ine (lades andcom(ine them into a single, cohesive gas stream ied struts also serve as a sta(ilising in"luence onthe gas and minimise the swirling motion +" this were not done, ehaust gasses would eit the engineat an approimate '< angle resulting in unwanted drag

TURBOPROP ENGINE POWER CON"ERSION

There are two power output tur(ine designs/ the "ied sha"t design and the "ree tur(ine engine

THE FI!ED SHAFT DESIGN

@ne central sha"t mounts the compressor and the tur(ine The sha"t etends "orward into the gear(owhere high 3D is converted to low 3D suita(le to drive the propeller !ll rotating componentswithin a "ied sha"t engine rotate together !dvantages o" a "ied sha"t system include controlleddescent capa(ility due to prevention o" windmilling overspeed and rapid reverse thrust availa(ility

THE FREE TURBINE

!n air"low couple is utilised (etween the gas generator and power tur(ine sha"t The gas generator

tur(ine powers the compressor The power tur(ine drives into the reduction gear(o in the samemanner as the "ied tur(ine The gear(o converts high 3D low torque input into usa(le low 3Dhigh torque power Because a "ree tur(ine system allows the propeller to operate independent o" thecompressor, there are several advantages/

Better control o" propeller speed

The propeller can (e held at very low rpm during taiing, with low noise and low (lade erosion

The engine is easier to start, especially in cold weather

The propeller and the gear(o do not directly transmit vi(rations into the gas generator

! propeller (ra)e can (e installed during turnarounds

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19/73

PT6 OPERATING PRINCIPLES

!ir enters the engine through an annular plenum cham(er "ormed (y the compressor inlet case "romwhere it is directed to the compressor The compressed air passes through di""user ducts which turn

it 90< in direction +t is routed through straightening vanes to the com(ustion cham(er The airchanges direction to enter the com(ustion cham(er liner where it reverses direction and is miedwith "uel

uel is in.ected into the com(ustion cham(er via 1' simple %single ori"ice& no66les The miture isthen ignited (y two igniters :panding gases reverse direction and pass through the compressortur(ine guide vanes to the compressor tur(ine The still epanding air passes through a second set o"stators to drive the power tur(ine Gas "rom the power tur(ine is ehausted via the ehaust

8 POWER PLANT8 POWER PLANT

DESRIPTION

The Dratt M hitney Canada +nc or DT?!-11'! %C208B& is a "ree tur(ine engine with twoindependent tur(ines @ne driving a compressor in the gas generator section ! second driving thereduction gearing "or the propeller The compressor section has # aial stages and 1 centri"ugalstage @ne stage compressor tur(ine @ne stage power tur(ine

The engine is "lat rated at ?$ *HD %18? "oot-pounds o" torque at 1900 3D varying linearly to

19$0 "oot-pounds o" torque at 1800 rpm Below 1800 3D, the maimum torque remainsconstant at 19$0 "oot-pounds& Torque is the measured amount o" sha"t horsepower delivered tothe propeller The torque (ending "orce is caused (y the resistance o" the air pushing against theadvancing (lade !t a lower rpm the (lade angle is increased to ta)e a (igger 4(ite5 o" airthere"ore increasing the resistance and hence the torque

The gas generator speed is #$,00 rpm at 100 7g a permissi(le speed is #8,100 rpm at101? 7g The power tur(ine speed is ##,000 3D at a propeller sha"t speed o" 1900 3D

The engine is supported in a steel 9-element space "rame This "rame attaches to the "irewall at points To minimise directional and longitudinal deviations with changes in thrust, the engine iscanted at #< nose-down and < to the right

ENGINE CONTROLSNGINE CONTROLS

POWER LE"ER

The power lever is connected through lin)age to a cam assem(ly mounted in "ront o" the CA +tcontrols engine power, via pneumatic control o" the metering valve, "rom maimum ta)e o"" power

(ac) through idle to "ull reverse thrust The power lever has !K, +=:, B:T! and 3:E:3*:range positions The lever selects propeller pitch when in B:T! range The B:T! range ena(les the

pilot to control propeller (lade pitch "rom idle thrust to through a 6ero or no thrust condition tomaimum reverse thrust

19


20/73

=o not move the power lever into the B:T! range when the propeller is "eathered as the propellerreversing lin)age can (e damaged

EMERGENCY POWER LE"ER

The emergency power lever is connected through lin)age to the manual override lever on the CA+t governs "uel supply to the engine should a pneumatic "ailure in the CA occur ! pneumatic "ailurewill result in the "uel "low decreasing to idle %'8 7g at sea level and 2 7g at 000 "t&

The emergency power lever has 7@3!, +=: and !K positions The 7@3! position isused "or all normal engine operation when the CA is operating normally and power is selected (ythe power lever The range "rom +=: to !K positions governs engine power and is used when a

pneumatic mal"unction has occurred in the CA and the power lever is ine""ective ! mechanical stopin the lever slot requires that the emergency power lever (e moved to the le"t to clear the stop (e"ore

it can (e moved "rom the 7@3! position

The )no( has cross hatching and is visi(le when the lever is in the !K position !lso, theemergency power lever is annunciated on the annunciator panel when the lever is out o" the normal

position These precautions are intended to preclude starting o" the engine with the emergencypower lever in any position other than 7@3!

The emergency power lever and its associated manual override system is considered to (e anemergency system and should only (e used in the event o" a "uel control pneumatic mal"unction

or starting ensure that the emergency power lever is in the normal position otherwise an over

temperature or hot start may result

hen using this lever in the override position engine response may (e more rapid than when usingthe power lever as the "uel is not metered Atilise slow and smooth movement o" the emergency

power lever to avoid engine surges and;or eceeding +TT, 7g and torque limits The emergencypower lever may have a dead (and such that no engine response is o(served during the initial"orward travel "rom the +=: position hen using the emergency power lever, monitor gasgenerator 3D when reducing power near idle, to )eep it "rom decreasing (elow ? 7g in "light

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21/73

PROPELLER CONTROL LE"ER

The propeller control lever is connected to the propeller control governor mounted on the "rontsection o" the engine +t controls propeller governor settings "rom maimum 3D to "ull "eather

The propeller control lever has !K, +7 and :!TH:3 positions The !K position is usedwhen high 3D is desired and governs the propeller speed at 1900 3D Dropeller control leversettings "rom the !K position to +7 permit the pilot to select desired propeller 3D "or thecruise The :!TH:3 position is used "or shutdown to stop rotation o" the power tur(ine and the"ront section o" the engine @nce the gas generator is shut down no lu(rication is availa(le androtation o" the "orward section is not desira(le !lso, "eathering the propeller when the engine is shutdown minimises propeller windmilling during windy conditions ! mechanical stop in the lever slotrequires that the propeller control lever (e moved to the le"t to clear the stop (e"ore it can (e movedinto or out o" the :!TH:3 position

The propeller lever operates a speeder spring inside the primary governor to reposition the pilotvalve, which results in an increase or decrease o" propeller rpm or propeller "eathering, thepropeller control lever li"ts the pilot valve to a position that causes complete dumping o" highpressure oil, allowing the counterweights and "eathering spring to change the pitch

FUEL CONDITION LE"ER

The "uel condition lever is connected through lin)age to a com(ined lever and stop mechanism onthe CA The lever and stop also "unction as an idle stop "or the CA rod +t controls the minimum3D o" the gas generator tur(ine %7g& when the power lever is in the +=: position

The "uel condition lever has CAT@, @ +=: and H+GH +=: positions The CAT@position cuts all "uel to the "uel no66les @ +=: positions the control rod stop to provide an3D o" 2 7g H+GH +=: provides an 3D o" ? 7g

$UADRANT FRICTION LOCK

! quadrant "riction loc), located on the right side o" the pedestal, is provided to minimise creeping o"the engine controls once they have (een set The loc) increases the "riction on the engine controlswhen rotated cloc)wise

ENGINE INSTRUMENTS

TOR$UE INDICATOR

The torque indicator indicates the torque (eing produced (y the engine @ne some Cargo versionsthe torque-indicator system is powered (y 28-volt =C power @n the other cargo versions and

passenger versions, the torque indicator is pressure actuated

Two independent lines enter the (ac) o" the torque indicator @ne line measures engine torquepressure and the other the reduction gear(o internal pressure The torque indicator monitors theengine torque pressure and converts this pressure into an indication o" torque in "t-l(s

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22/73

7ormal operating range %green arc& is "rom 0 to 18? "t-l(s The alternate power range %stripedgreen arc& is "rom 18? "t-l(s to 19$0 "t-l(s The maimum torque %red line& is 19$0 "t-l(s andmaimum ta)e o"" torque %red wedge& is denoted (y JT@J at 18? "t-l(s

PROPELLER RPM INDICATOR

The instrument is mar)ed in increments o" 0 3D and indicates propeller speed in revolutions perminute The instrument is electrically operated "rom the propeller tachometer generator which ismounted on the right side o" the "ront case 7ormal operating range %green arc& is "rom 1?00 to1900 rpm The maimum %red line& is 1900 rpm

ITT INDICATOR

The +TT %intertur(ine temperature& indicator displays the gas temperature (etween the compressorand the power tur(ines 7ormal range %green arc& is 100


23/73

OIL TEMP GAGE

The instrument is operated (y an electrical-resistance type temperature sensor which receives power"rom the aeroplane electrical system inimum temperature %red line& is -'0


24/73

2'


25/73

H@T mar)ing& or prior to the "irst "light o" the day %!K C@= mar)ing& +" more than 10 minuteshas elapsed and oil is still warm per"orm an engine dry motoring run (e"ore chec)ing the oil level

!s the oil tan) is pressurised at # to ? psi, ensure that the oil dipstic) is securely latched down

@perating the engine with less than the recommended oil level and with the dipstic) cap unlatchedwill result in ecessive oil loss and eventual engine stoppage

IGNITION SYSTEM

Tur(ine engine ignition systems are designed to initially ignite the "uel;air miture, which will thensustain the com(ustion on its own The ignition system consists o" 2 igniters, an ignition eciter, 2high tension leads, an ignition monitor light, an ignition switch and a starter switch

:ngine ignition is provided (y 2 igniters in the engine com(ustion cham(er The igniters are

energised (y the ignition eciter mounted on the right hand side o" the engine compartment:lectrical energy "rom the ignition eciter is transmitted through 2 high-tension leads to the ignitersin the engine ! green annunciator, la(elled +G7+T+@7 @7, will illuminate when electrical power is

(eing supplied to the igniters

+gnition is controlled (y an ignition switch and a starter switch The ignition switch has twopositions, 7@3! and @7

NORMAL POSITION

!rms the system so that ignition will (e o(tained when the starter switch is placed in the *T!3T

position +t is used "or ground starts and air starts with starter assist

ON POSITION

Drovides continuous ignition regardless the position o" the starter switch The use o" ignition "oretended periods o" time will reduce ignition system component li"e However, the ignition should (eturned @7 to provide continuous ignition under the "ollowing conditions/

!ir starts without starter assist

@peration on water or slush covered runways

=uring "light in heavy rain

+nadvertent icing encounters until the inertial (ypass separator has (een in (ypass "or minutes

7ear "uel ehaustion as indicated (y the

3:*:3E@+3 A: @ light

STARTING SYSTEM

The main "unction o" the starter switch is control o" the starter "or rotating the gas generator portion

o" the engine during start +t also provides ignition during starting The starter;generator "unctions asa motor "or starting +t will motor the gas generator section until a speed o" '? 7g !t '? 7g the

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26/73

staring cycle will automatically (e terminated The starter switch has # positions, @, *T!3T and@T@3

OFF POSITION

The ignition system is de-energised This is the normal position at all times ecept during engine startor engine clearing

START POSITION

3otates the gas generator section o" the engine !lso energises the ignition system provided theignition switch is in the 7@3! position hen the engine has started the start switch must (e

placed in the @ position to activate the generator *tarter contactor operation is indicated (y theam(er *T!3T:3 :7:3G+P:= annunciator

MOTOR POSITION

otors the engine without having the ignition circuit energised This position is spring loaded (ac)to the @ position !n interloc) (etween the @T@3 position o" the starter switch and the ignitionswitch, prevents the starter "rom motoring unless the ignition switch is in the 7@3! positionThis prevents unintentional motoring o" the engine with the ignition on

! minimum (attery voltage o" 2' volts is not always an indication that the (attery is near "ull chargeor in a good condition This is especially true "or a nicad (attery , which maintains a minimum no-load voltage o" 2' volts even at 0 or less charge condition There"or, i" the gas generatoracceleration is less than normally o(served, return the "uel condition lever to CAT@ and

discontinue the start

ENGINE START CONSIDERATIONS

+" no +TT rise is o(served within 10 seconds a"ter moving the "uel condition lever to @ +=:,

or +TT rapidly rises to 1090


27/73

!"ter an a(orted start "or whatever reason, it is essential (e"ore the net start attempt to allow

adequate time to drain o"" un(urned "uel ailure to do so could lead to a hot start, a hot strea)leading to hot section damage, or torching o" (urning "uel "rom the engine ehaust on the net

success"ul ignition

! dry motoring, within starter limitations a"ter con"irming that all "uel drainage has stopped,ensures that no "uel is trapped (e"ore the net start

+" the *T!3T:3 :7:3G+P:= annunciator "ails to go out a"ter engine start, the generator will

not "unction (ecause the start contactor may (e stuc) closed The (attery switch should (eturned o"" and the engine should (e shut down i" such an indication is o(served

AIR INDUCTION SYSTEM

The engine air inlet is located at the "ront o" the engine nacelle to the le"t o" the propeller spinner3am air entering the inlet "lows through the ducting and an inertial separator system (e"ore enteringthrough a circular plenum cham(er where it is directed to the compressor guide vanes Thecompressor air inlet incorporates a screen which will prevent entry o" large particles, (ut does not"ilter the air

INERTIAL SEPARATOR SYSTEM

!n inertial separator system in the air inlet duct prevents moisture particles "rom entering thecompressor air inlet plenum when in (ypass mode +t consists o" two movea(le vanes and a "ied

air"oil which, during normal operations route the air through a gentle turn into the compressor airinlet plenum

+n the BFD!** position the vanes are positioned so that the inlet air is "orced to eecute a sharpturn in order to enter the inlet plenum !ny moisture particles are separated "rom the inlet air anddischarged over(oard through the inertial separator outlet in the le"t side o" the cowling

+nertial separator operation is controlled (y a T-handle located on the lower instrument panel Thehandle is la(elled BFD!**-DA, 7@3!-DA*H The inertial separator should (e in theBFD!** position under the "ollowing conditions/

3unning the engine on the ground or in "light in visi(le moisture with an @!T o" '


28/73

E!HAUST SYSTEM

The primary ehaust is attached to the right side o" the engine a"t o" the propeller reduction gear(o! secondary pipe, "itted over the end o" the primary ehaust, carries the gasses away "rom the

cowling into the slipstream The .uncture o" the primary ehaust pipe and the secondary ehaust ductis located directly (ehind the oil cooler

*ince the secondary ehaust duct is o" a larger diameter then the primary ehaust pipe, a venturie""ect is produced (y the "low o" the ehaust This venture e""ect creates a suction (ehind the (ehindthe oil cooler which augments the "low o" cooling air through the cooler This additional air "lowimproves oil cooling during ground operation o" the engine

=o not leave the power lever in B:T! mode "or more than #0J with a right crosswind as the podmay (e damaged

ENGINE FUEL SYSTEM

The engine "uel system consists o" an oil-to-"uel heater, an engine-driven "uel pump, a "uel controlunit, a "low divider and dump valve, a dual "uel mani"old with 1' simple no66les and two "uel drainvalves The system provides "uel "low to satis"y the speed and power demands o" the engine

OIL'FUEL HEATER

uel is delivered "rom the reservoir to the oil-to-"uel heater The oil-to-"uel heater utilises heat "romthe engine lu(rication system to preheat the "uel ! "uel temperature-sensing oil (ypass valve

regulates the "uel temperature (y either allowing oil to "low through the heater circuit or (ypass it tothe oil tan)

FUEL PUMP

uel enters the :=D "uel pump through a $' micron "ilter The inlet screen is spring-loaded andshould it (ecome (loc)ed, the increase in di""erential pressure will overcome the spring and allowun"iltered "uel to enter the pump cham(er

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29/73

The pump increases the "uel pressure and delivers the "uel to the CA via a 10 micron "ilter in thepump outlet ! (ypass valve in the pump (ody ena(les un"iltered, high pressure "uel to enter the CAin the event o" this "ilter (ecoming (loc)ed

FUEL CONTROL UNIT

The CA consists o" a "uel metering section, temperature compensating section, a compressortur(ine %7g& governor, a pneumatic computing section, a manual override system and a powertur(ine %7"& governor

The CA determines the proper "uel schedule to provide the power required as esta(lished (y thepower lever This is accomplished (y controlling the speed o" the compressor tur(ine %7g& :nginepower output is directly dependent on compressor tur(ine speed The CA governs 7g, there(yactually governing the power output o" the engine Control o" 7g is accomplished (y regulating theamount o" "uel supplied to the com(ustion section o" the engine

A# METERING SECTION

The metering valve input is supplied with "uel at pump pressure %D1& The "uel pressureimmediately a"ter the metering valve is called metered "uel %D2& which "lows to the "ueldivider The (ypass valve maintains a constant "uel pressure di""erential %D1 - D2& across themetering valve The metering valve consists o" a contoured needle operating in a sleeve andregulates the "low o" "uel (y varying the ori"ice area The ori"ice area o" the metering valve ischanged (y the valve movement to meet speci"ic engine requirements

uel pump pressure %D1& in ecess o" requirements is returned to the "uel pump ! "uel cut-o"" valve is situated downstream o" the metering valve +t provides a positive means o"

shutting o"" "uel "low to the engine =uring normal operation the valve is "ully open ando""ers no restriction o" "uel "low to the divider The valve is operated (y a cut-o"" lever whichis mechanically lin)ed to the CA

B# PNEUMATIC COMPUTING SECTION

The computing section consists o" an acceleration (ellows and a governing (ellowsconnected to a common rod The end o" the acceleration (ellows is attached to the (odycasting and provides an a(solute pressure re"erence The governor (ellows is secured in the

(ody cavity and its "unction is similar to that o" a diaphragm ovement o" the (ellows istransmitted to the metering valve via a torque tu(e assem(ly This tu(e is positioned during

assem(ly to provide a "orce in a direction tending to close the metering valve, while the(ellows act against this "orce to open the metering valve

Third stage tur(ine discharge pressure %D#& is split up into D and Dy pressure D and Dyvary with changing engine operating conditions as well as inlet air temperature Dy pressureis applied to the outside o" the governor (ellows, while D pressure is applied to the inside o"the (ellows and the outside o" the acceleration (ellows !ny change in Dy will there"ore havemore e""ect on the diaphragm than an equal change in D pressure due to the di""erence ine""ective area hen (oth pressures increase simultaneously, as during acceleration, the

(ellows move downwards and the metering valve moves in an opening direction hen Dydecreases as the desired 7g is approached, the (ellows will travel to reduce the opening o"

the metering valve hen (oth pressures decrease simultaneously the (ellows will move

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30/73

upwards and reduce the metering valve opening (ecause Dy is more e""ective than D Thisoccurs during deceleration and moves the metering valve to the minimum "low stop

C# COMPRESSOR TURBINE (N%) GO"ERNOR

The power lever incorporates a speed scheduling cam which depresses an internal rod whenthe power lever is advanced The governor lever is pivoted and one end operates against anori"ice to "orm the governor valve The enrichment lever is also pivoted and actuates a "luted

pin which operates against the enrichment hat valve The speed scheduling cam appliestension to the governor spring which applies a "orce to close the governor valve Theenrichment spring (etween the enrichment and governor levers provides a "orce to open theenrichment valve !s the drive sha"t rotates, it in turn rotates a ta(le on which the governor"lyweights are mounted !s the 7g increases, centri"ugal loading causes the "lyweights tomove outwards This in turn moves the 7g plat"orm upwards overcoming the enrichmentspring "orce, closing the enrichment valve and opening the governor valve

D# MANUAL O"ERRIDE SYSTEM

The retaining plate and cover containing the governor (ellows stop are replaced (y a sha"tand stop assem(ly +" operated, it pushes against the end o" the governor (ellows to open themetering valve and increase the "uel "low

E# POWER TURBINE (N*) GO"ERNOR

+n the event o" a power tur(ine overspeed condition, a governing ori"ice in the 7" governingsection is opened (y "lyweight action o" the governor Dy pressure is (led o"" to theatmosphere hen this occurs, Dy pressure acting on the CA governor (ellows decreases

and moves the metering valve in a closing direction, thus reducing "uel "low This in turndecreases 7g speed and consequently 7" speed

F# OPERATION

1# ENGINE STARTING

The starting cycle is initiated with the Dower ever placed in the +=: position andthe uel Condition ever in the CAT@ position The ignition and starter areswitched on, and when the required 7g speed is attained, the uel Condition ever is

placed in the @ +=: position ollowing ignition, the engine accelerates to idle

speed =uring the starting sequence, the metering valve in the CA is in a low "lowposition The "low divider schedules the metered "uel "rom the CA, (etween theprimary and secondary no66les uel is delivered to the com(ustion cham(er through10 primary and ' secondary no66les etered "uel is delivered initially (y the primaryno66les, with the secondary no66les cutting in a(ove a certain value

#0


31/73


32/73

!s the compressor accelerates, the discharge pressure %D#& increases This creates anincrease in D and Dy pressure, which is modi"ied D# pressure !s Dy pressure acts ona greater area, the (ellows are "orced down causing the main metering valve to movein an opening direction :cess "uel supplied (y the "uel pump will pass via the

(ypass valve (ac) to the tan) hen 7g approaches idle speed, the centri"ugal "orceo" the 7g governor "lyweights (egin to overcome the governor spring "orce and openthe governor valve, (leeding o"" Dy pressure This creates a D;Dy di""erential whichcauses the metering valve to move in a closing direction until the required idle speed"uel "low is o(tained !ny variation "rom the selected speed will (e sensed (y the 7ggovernor "lyweights and will result in an increased or decreased weight "orce

2# ACCELERATION

!s the power lever is advanced a(ove the idling position, the speed scheduling cam isrepositioned moving the cam "ollower lever to increase governor spring "orce The

governor spring then overcomes the "lyweights and moves the governor lever,closing the governor valve D and Dy immediately increase, causing the meteringvalve to move in an opening direction!s 7g and consequently 7" increase, the propeller governor increases the pitch o" the

propeller (lades to control 7" at the selected speed and applies the increased poweras additional thrust !cceleration is complete when the centri"ugal "orce o" thegovernor "lyweight again overcomes the governor spring and opens the governorvalve

3# GO"ERNING

@nce the acceleration cycle has (een esta(lished, any variation in engine speed "romthe selected speed will (e sensed (y the 7g governor "lyweights and will result inincreased or decreased weight "orce This change in weight "orce will cause thegovernor valve to either open or close which will (e re"lected (y the change in "uel"low necessary to re-esta(lish the selected speed

4# ALTITUDE COMPENSATION

!ltitude compensation is automatic since the acceleration (ellows assem(ly in theCA is evacuated and a""ords an a(solute pressure re"erence Compressor dischargeair %D#& is a measurement o" engine speed and density D is proportional to D#, so itwill decrease with a decrease in air density This is sensed (y the acceleration (ellows

which act to reduce "uel "low on acceleration at altitude

5# DECELERATION

hen the Dower ever is retarded, the speed scheduling cam raised, reducing thegovernor spring "orce and allows the governor valve to move in an opening directionThe resulting drop in Dy pressure moves the metering valve in a closing directionuntil it contacts the " minimum "low stop This stop ensures su""icient metered "uel"low to the engine to prevent "lameout The engine continues to decelerate until thegovernor "lyweight "orce decreases to (alance the governor spring "orce at the set

position

6# RE"ERSE THRUST

#2


33/73

3everse thrust can (e o(tained at any propeller speed hen the Dower ever ismoved to the A 3:E:3*: position it will increase compressor tur(ine speed%7g& and propeller reverse pitch The propeller governor is maintained in anunderspeeding condition in the reverse thrust range (y controlling propeller speed

with the 7" governing section o" the propeller control+" 7" eceeds the desired speed the 7" governing ori"ice will open to decrease Dypressure in the computing section o" the CA and cause a reduction in "uel "low and7" speed, there(y limiting the propeller speed and maintaining the C*A in anunderspeed condition

7# ENGINE SHUTDOWN

The engine is shut down (y moving the uel Condition ever to the CAT@position uel is returned to the pump inlet via the (ypass passages uel in theprimary and secondary mani"olds is drained via the dump valve ports in the "lowdivider and dump valve 3esidual "uel is allowed to drain into the "uel drain can

ENGINE ACCESSORIES

!ll engine-driven accessories with the eception o" the propeller governor and propeller tachometer-generator are mounted on the accessory gear(o at the rear o" the engine

OIL PUMP

The oil pump is located in the lowest part o" the oil tan) and is driven (y the accessory gear sha"t

FUEL PUMP

The engine driven "uel pump is driven through a gear sha"t and splined coupling The couplingsplines are lu(ricated (y oil mist "rom the auiliary gear(o through a hole in the gear sha"t uel"rom the oil-"uel-heater enters the pump through a $' micron "ilter The pressure is (oosted andenters the CA through a 10 micron pump outlet "ilter ! (ypass valve ena(les un"iltered "uel toreach the CA in the event o" a (loc)age !n internal passage originating at the CA, returns (ypass"uel "rom the CA to the pump inlet downstream o" the inlet screen

N% TACHO GENERATOR

The 7g tacho-meter produces electric current which is used in con.unction with the gas generator3D indicator

##


34/73

TOR$UE METER

The torquemeter is located within the power reduction gear(o +t is a hydro-mechanical deviceconnected to the "irst-stage reduction gear to provide an indication o" engine output +t consists o" a

cylinder, piston and an oil metering-type plunger 3otation o" the "irst-stage reduction output drivering gear is resisted (y a helical spline which imparts an aial movement to the "irst stage ring gearand the torquemeter piston This "orces the piston onto the oil valve plunger allowing engine oil toenter the cylinder This movement continues until the oil pressure within the torquemeter is equal totorque (eing applied to the "irst-stage ring gear

! (leed hole is located in the torquemeter cylinder to allow a continuous "low o" oil and to (leedpressure o"" when power is reduced hen engine oil is supplied to the plunger valve, it acts as avaria(le inlet metering ori"ice The (leed hole acts a "ied cali(rated lea) @n acceleration, there ismore oil supplied than (leeding away, so the pressure (uilds up in the torquemeter cylinder

STARTER+GENERATOR

The starter;generator is a 28 volt, 200 ampere engine driven unit +t "unctions as a motor "or startingand, a"ter engine start, as a generator "or the electrical system hen operating as a starter, the speedsensing switch in the starter;generator will automatically shut down the starter, there(y providingoverspeed protection and automatic shuto"" +t is aircooled (y an integral "an and (y ram air ducted"rom the "ront o" the engine cowling

ITT SENSING SYSTEM

The +TT sensing system is designed to give the pilot an accurate indication o" engine operating

temperatures ta)en (etween the compressor and power tur(ines +t consists o" 8 individual chromel-alumel thermocouple pro(es connected in parallel :ach pro(e protrudes through a threaded (oss onthe power tur(ine stator housing into an area ad.acent to the leading edge o" the o" the powertur(ine vanes

PROPELLER GO"ERNOR

*ee section 8

PROPELLER O"ERSPEED GO"ERNOR

*ee section 8

ENGINE FIRE DETECTION SYSTEM

The engine "ire detection system consists o" a heat sensor in the engine compartment, a warning lighton the annunciator panel and a warning horn

The heat sensor consists o" # "lei(le, closed loops :ach section o" the loop is made up o" a singlewire surrounded (y a continuous string o" ceramic (eads contained in an inconel tu(e The outershell is connected to ground at the "irewall and the wire inside is connected to the control (o The

(eads have a characteristic that causes them to lower their electrical resistance when the sensingelement reaches its preset temperature value

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The core material in (oth elements prevents electrical current "rom "lowing at normal temperatureshen the elements are eposed to increasing temperatures, a current "lows (etween the signal wireand ground The control (o detects a change in resistance in the loops and will illuminate the:7G+7: +3: light and trigger the warning horn

The "ire warning is initiated when temperatures in the engine compartment eceed '2< %"irewall&,?2< %around the ehaust& or '0< %rear engine compartment& ! test switch, la(elled +3:=:T:CT T:*T, is located ad.acent to the annunciator panel hen depressed, the :7G+7: +3:annunciator will illuminate and the "ire warning horn will sound, indicating that the "ire warningcircuitry is operstional The system is protected (y a 4pull-o""5 type circuit (rea)er la(elled +3:=:T, positioned third row and second "rom the le"t

ENGINE REDUCTION GEAR SYSTEM

The gear(o contains a two stage planetary gear chain, three accessory drives and propeller sha"t

The "irst-stage reduction gear is contained in the rear case, while the second stage reduction gear,accessory drives and propeller sha"t are contained in the "ront case

Torque "rom the power tur(ine is transmitted to the "irst-stage reduction gear, "rom there to thesecond-stage reduction gear and then to the propeller sha"t 3eduction ratio is "rom a maimum

power tur(ine speed o" ##000 3D down to a propeller speed o" 1900 3D

CHIP DETECTORS

Two chip detectors are installed on the engine, one on the underside o" the reduction gear(o andone on the underside o" the accessory gear(o case The chip detectors are electrically connected

to an annunciator, la(elled CH+D =:T:CT@3 The annunciator will illuminate when metal chipsare present in one or (oth o" the detectors By itsel" this does not demand immediate action (ut i"accompanied (y signs o" engine distress %erratic engine operation or "luctuation in engine powergage indications&, engine operation may (e continued at the discretion o" the pilot consistent withcrew sa"ety

OIL BREATHER DRAIN CAN

*ome aircra"t have an oil (reather can mounted on the right lower engine mount truss This cancollects any engine oil discharge coming "rom the accessory pads "or the alternator drive pulley,starter;generator, air conditioner compressor and the propeller sha"t seal +t should (e drained a"terevery "light

The allowa(le quantity o" oil discharge per hour o" engine operation is 1' cc "or aeroplanes withair conditioning and 11 cc "or aeroplanes without +" the quantity o" oil drained "rom the can isgreater than speci"ied, the source o" the lea)age should (e identi"ied and corrected

! PROPELLER

The engine is equipped with a cCauley aluminum, constant speed, "ull-"eathering, reversi(le,single-action, governor controlled, three (laded propeller

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! setting is introduced into the governor with the propeller control lever The propeller uses oilpressure which opposes the "orce o" springs and counterweights to o(tain the correct pitch "or theengine load @il pressure "rom the propeller governor drives the (lades toward low %"ine& pitch%increasing 3D&

*prings and counterweights drive the (lades toward high %coarse& pitch %decreasing 3D&The source o" oil pressure is "urnished (y the engine oil system, (oosted in pressure (y the governorgear pump and supplied to the propeller hu(

PROPELLER GO"ERNOR

The propeller governor is located in the 12 oIcloc) position on the "ront case o" the reductiongear(o +t com(ines the "unctions o" a normal propeller governor %C*A&, a reversing %B:T!& valveand a power tur(ine %7"& governor into a single unit

CONSTANT SPEED MODE

Ander normal "light conditions, the governor acts as a C*A (y maintaining propeller speed selected(y the pilot +" the Dower ever is pushed "orward, the CA simply schedules an increase in "uel

"low Thus, e""ectively more energy is availa(le to turn the tur(ine The tur(ine is "orced to a(sor(the etra energy that is transmitted to the propeller in the "orm o" torque +" there were no governor,the propeller speed would increase +nstead the (lade angle increases to maintain a constant propeller3D and the propeller is allowed to ta)e a larger (ite o" air, hence the increase in torque

There"or, the governor varies the propeller (lade pitch angle to match the load to the engine torquein response to changing "light conditions ! spring-loaded pilot valve is installed in a drivesha"tcentre(ore within the propeller governor Dorts in the drivesha"t and the position o" the pilot valve inthe sha"t, control the direction o" oil "low within the housing The rotating sha"t with the rotating"lyweights determine the position o" the pilot valve while opposing spring load on the valve is varied

(y the speed ad.usting lever at the head o" the governor The speed ad.usting lever is connected tothe Dropeller Control ever in the coc)pit

OPERATION

A# ON'SPEED CYCLE

ith the Dropeller Control ever set to a desired 3D and the propeller (lade at thecorrect pitch angle to a(sor( the power developed (y the engine, the centri"ugal "orce o"the rotating "lyweights (alances the "orce o" the governor speeder spring This condition

positions the pilot valve so that the valve oil ports are closed and no oil "low occurs(etween the propeller oil pump and the propeller servo piston

B# UNDERSPEED CYCLE

Anderspeeding occurs when the propeller 3D "alls (elow the set 3D Governor springtension overcomes the reduced "lyweight "orce and pivots them inwards, "orcing the pilot

valve downward and opening the oil ports

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This allows a "low o" pressure oil "rom the governor pump to the propeller servo pistonwhich, in turn, overcomes the com(ined "orces o" the propeller counterweights and returnsprings to reduce propeller (lade pitch angle This reduces the load and allows propeller3D to increase This increased 3D is sensed (y the governor "lyweights which "orce the

pilot valve upwards until an equili(rium (etween speeder spring tension and centri"ugal"orce o" the "lyweights is achieved causing the oil ports to close

C# O"ERSPEED CYCLE

+n an overspeed condition, the governor "lyweights pivot outward and overcome thegovernor speeder spring tension and raise the pilot valve This uncovers the ports in thedrive gearsha"t and allows pressure oil in the propeller servo to "low into the reductiongear(o sump

!s the propeller (lade angle increases, the load on the engine increases and propeller 3D

decreases This in turn causes the centri"ugal "orce on the "lyweights to decrease, allowingthe speeder spring tension to return the "lyweights to the vertical position, causing the pilotvalve to cover the ports and (loc) the oil supply "rom the servo piston

LOW PITCH STOP

=uring the approach to land when the Dower ever is closed and the Dropeller ever is in themaimum position the propeller (lades are sitting on the low pitch stop at 1?


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The geometry o" the power lever lin)age through the cam (o is such that power lever movement"rom idle to "ull "orward thrust has no e""ect on the position o" the B:T! valve However when the

power lever is moved into the reverse thrust range, the reversing lever pulls the B:T! valve (ac)

low o" oil to the propeller dome is re-esta(lished and the (lades will move through low pitch andinto a negative pitch range !s the propeller moves into low pitch, the "eed(ac) ring moves "orwardin an attempt to close the B:T! valve and prevent any "urther pitch change This cannot occur whilethe propeller reversing lever continues to move towards "ull reverse and pull the B:T! valve (ac)

!s the power lever is moved "urther into the reverse range, the (lade angle decreases and the 7gsimultaneously increases to approimately 8 - 88 The power tur(ine governor %7"& section o"the propeller governor is simultaneously reset to approimately 9 3D (y the reset lever andassociated interconnecting rod *election o" reverse thrust also repositions the CA arm to increase"uel "low and consequently power output

FEATHERING

oving the speed ad.usting lever towards a preset "eathering stop raises the pilot valve anddecreases the oil pressure to the propeller servo piston This decrease in oil pressure allows the

piston to move under the in"luence o" "eathering and return springs, to rotate the propeller (lades to,a positive coarse pitch or "eathering position regardless o" governor "lyweight "orce acting on the

pilot valve The "eathered (lade angle is 88


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=uring reverse operation, the 7" governor is set (elow the propeller governor selected speed Thisacts to control propeller speed via the CA servo system and thus reduce the power generated (ythe gas generator to (elow required setting %approimately less than the selected propellerspeed&

+n the event o" a tur(ine overspeed, an air (leed ori"ice in the propeller governor is opened (y"lyweight action to (leed o"" compressor discharge pressure %Dy& through the governor andcomputing section o" the CA Compressor discharge pressure, acting on the CA governor

(ellows, decreases and moves the metering valve in a closing direction

PROPELLER O"ERSPEED GO"ERNOR

The propeller overspeed governor is installed in parallel with the propeller governor and is mountedat the 10 o>cloc) position on the "ront case o" the reduction gear(o +t is incorporated to control

any propeller overspeed condition (y immediately (ypassing pressure oil "rom the propeller servo tothe reduction gear(o sump

hen an engine overspeed occurs, the increased centri"ugal "orce sensed (y the "lyweightsovercomes the spring tension, li"ts the pilot valve and (ypasses propeller pitch change mechanism oil

(ac) to the reduction gear(o This permits the com(ined "orces o" the counterweights and returnsprings to move the (lades toward a coarse pitch position, a(sor(ing the engine power and

preventing "urther engine overspeed

! solenoid valve, which resets the governor to a value (elow its normal overspeed setting providesground testing The overspeed governor test switch is located on the le"t side o" the instrument

panel hen depressed, a solenoid is actuated on the propeller overspeed governor *peeder springpressure is reduced and "lyweights move out at a lower speed to simulate anoverspeed conditionDropeller 3D is restricted when the power lever is advanced =uring the test the propeller 3Dshould not eceed 1$0 L ?0 3D

1" FUEL SYSTEM

COMPONENTS

Two vented, integral "uel tan)s with shuto"" valves, a "uel selectors o"" warning system, a "uelreservoir, an e.ector "uel pump, an electric auiliary (oost pump, a reservoir mani"old assem(ly, a"irewall shuto"" valve, a "uel "ilter, an oil-to-"uel heater, an engine-driven "uel pump, a "uel controlunit, a "low divider, dual mani"olds, 1' "uel no66le assem(lies and a "uel drain can and drain

SYSTEM

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uel "lows "rom the tan)s through two shuto"" valves at each tan) uel "lows (y gravity "rom theshuto"" valves in each tan) to the "uel reservoir The reservoir is located at the low point in the "uelsystem

! head o" "uel is maintained around the e.ector (oost pump and auiliary (oost pumps which arecontained within the reservoir uel in the reservoir is pumped (y the e.ector (oost pump or (y theelectric auiliary (oost pump to the reservoir mani"old assem(ly The e.ector (oost pump is driven (ymotive "uel "rom the CA +t normally provides "uel "low when the engine is operating +n the evento" "ailure o" the e.ector (oost pump, the electric auiliary (oost pump will automatically turn on, oncondition that the (oost pump switch is in the 7@3 position The auiliary (oost pump is alsoused to supply "uel during starting

uel in the reservoir mani"old assem(ly "lows through the "uel shuto"" valves located on the a"t sideo" the "irewall uel is then routed through the "uel "ilter located on the "ront side o" the "irewall The"ilter incorporates a (ypass "eature

uel is then routed through the oil-to-"uel heater to the engine driven pump through a $' microninlet screen The inlet screen is spring-loaded and should it (ecome (loc)ed, the increase indi""erential pressure will overcome the spring and allow un"iltered "uel to "low into the pumpcham(er The pump increases the pressure and delivers it to the CA via a 10-micron "ilter ! (ypassvalve and cored passages in the pump (ody ena(les un"iltered high pressure "uel to "low to the CAin the event the outlet "ilter (ecomes (loc)ed

The CA meters the "uel and directs it to the "low divider The "low divider schedules the metered"uel (etween the 10 primary and ' secondary "uel mani"olds The result is an even, e""icient spray

pattern through all operational speeds +n the primary spin cham(er a change in direction puts a

spinning motion on the "uel and esta(lishes the proper spray angle and helps with atomisation !tthat point the "uel is discharged "rom the primary no66le !s the engine accelerates "rom start-up, the"uel pressure (egins to increase !t approimately 90 psi, it causes the "low divider to open and parto" the incoming "uel "low is channelled to the secondary spin cham(er rom the no66les the "uel isdistri(uted to the com(ustion cham(er

hen the "uel cut-o"" valve in the CA closes during engine shutdown, (oth primary and secondary"uel no66les are connected to a dump valve port 3esidual "uel in the mani"old drains into a "ireproo"can on the "ront le"t side o" the "irewall This can should (e drained daily

uel venting is essential to system operation ! complete (loc)age o" the vent system will result indecreased "uel "low and eventual engine stoppage Eenting is accomplished (y chec) valve equippedvent lines "rom each tan) @ne vent "rom each tan) protrudes "rom the trailing edge o" the wing atthe tips The "uel reservoir is also vented to (oth wing tan)s

FIREWALL SHUTOFF "AL"E

! manual shuto"" valve is located on the a"t side o" the "irewall +t ena(les the pilot to shut o"" all "uel

"rom the reservoir to the engine The shuto"" valve is controlled (y a red push-pull )no( la(elled

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FUEL FLOW INDICATOR

The "uel "low indicator indicates "uel consumption in pounds per hour (ased on Jet A"uel low o""uel is measured downstream o" the CA .ust (e"ore (eing routed to the "uel divider hen (attery

power is removed, the indicator needle will stow (elow 6ero in the @ position

FUEL $UANTITY INDICATORS

uel quantity is measured (y "our transmitters in each tan) and indicated (y two electrically operated"uel quantity indicators The indicators measure volume and are cali(rated in pounds %(ased on theweight o" Net ! "uel on a standard day ?,$ l(s;gal at 1


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par)ed with one wing low on a sloping ramp The drain valves are constructed so that a Dhillipsscrewdriver can (e used to depress the valve and then twist to loc) it in the open position

The drain valve "or the reservoir consists o" a recessed T-handle hen pulled out, "uel "rom the

reservoir drains out the rear "uel drain pipe located ad.acent to the drain valve The drain valve "orthe "uel "ilter consists o" a drain pipe which can (e depressed upwards to drain "uel "rom the "ilter +"contamination is detected, drain all "uel drain points again Ta)e repeated samples o" all "uel drain

points until all contamination has (een removed

FUEL DRAIN CAN

hen the engine is shut down, residual "uel in the engine drains into a "uel drain can mounted onthe "ront le"t side o" the "irewall The can should (e drained once a day or at intervals noteceeding ? shutdowns ! drain valve on the (ottom side o" the cowling is provided to drain the

"uel into a suita(le container

FUEL PUMP DRAIN RESER"OIR

To control epended lu(rication oil "rom the engine "uel pump drive coupling area and provide away to determine i" "uel is lea)ing past the "uel pump seal a draina(le reservoir collects allowa(ledischarge o" oil and any "uel seepage The reservoir is mounted on the "ront le"t side o" the"irewall +t should (e drained once a day or at intervals not eceeding ? shutdowns ! quantity o"up to # cc o" oil and 20 cc o" "uel discharge per hour o" engine operation is allowa(le +n addition,a CA (earing "ailure will (e indicated (y a (lue dye in the epended oil This requires immediate

attention and under no circumstances should the aircra"t (e "lown (e"ore this situation is corrected

11 ELECTRICAL SYSTEM

The aircra"t is equipped with a 28 volt dc electrical system The system uses a 2' volt (attery as asource o" electrical energy and a dual purpose starter-generator !n optional stand(y alternator isavaila(le "or the use as a stand(y source in the event o" the main generator system mal"unctioning

ELECTRICAL BUSES

Dower is supplied to the electrical and avionics circuits through 2 general, 2 avionics and a (attery(us The (attery (us is energised continuously "or the memory )eep alive, cloc) and ca(in;courtesylights The two general (uses are on any time the (attery switch is turned on !ll =C (uses are onany time the (attery switch and two avionics switches are turned on

STARTER'GENERATOR

The starter-generator is mounted on the engine accessory gear(o and is driven (y the engine

through a splined sha"t +t is cooled (y an integral "an and a (last tu(e located a(ove the right"orward cowling +t "unctions as a motor during engine start and as a generator a"ter starting

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+n the starter mode it is powered (y either the (attery or an eternal power source !"ter enginestart, the generator output is 28 volt and 200 amp hen operating as a generator, it supplies

power to operate the electrical systems and maintains the (atteryIs state o" charge The unit is

controlled (y a generator control unit

GENERATOR CONTROL UNIT (GCU)

The GCA is mounted inside the ca(in on the le"t "orward "uselage sidewall +t provides the electricalcontrol "unctions necessary "or the operation o" the starter-generator +t provides automatic startercutout at '? 7g Below '? the starter-generator "unctions as a starter !(ove '? it "unctions asa generator when the starter switch is @

The GCA provides voltage regulation plus high voltage protection reverse current protection !

rheostat increases the resistance in the "ield circuit and less current "lows through the "ield windingresulting in a decrease in the strength o" the magnetic "ield The rotating armature now turns in awea)er "ield with the result o" a lower generator output voltage

! di""erential relay switch protects the generator "rom reverse current "rom (attery voltage +t isessentially an on;o"" switch that is controlled (y the di""erence in voltage (etween the (attery (us andthe generator output The di""erential relay switch connects the generator to the electrical system>smain (us whenever generator voltage eceeds (us voltage (y at least 0 volt +" on the other hand,

(us voltage eceeds generator output voltage, the reverse current relay opens and ta)es thegenerator o""-line +n the event o" the a(ove, the generator is automatically disconnected "rom the

(uses and the red G:7:3!T@3 @ annunciator illuminates

GROUND POWER MONITOR

The ground power is located inside the electrical power assem(ly mounted on the le"t side o" the"irewall This unit senses voltage applied to the eternal power receptacle and closes the eternal

power contactor when the applied voltage is within limits %2' - 28 volts and 800 - 1$00 amp&

+t also senses airplane (us voltage and will illuminate the E@T!G: @ annunciator when the (usvoltage drops to 2' volts

GROUND SER"ICE PLUG RECEPTACLE

The eternal power receptacle is installed on the le"t side o" the engine compartment near the"irewall +t permits the use o" an eternal power source "or starting and lengthy maintenance on thele"t side o" the engine compartment

:ternal power control circuitry is provided to prevent eternal power and the (attery "rom (eing

connected together during starting The ground service circuit incorporates polarity reversal andover-voltage protection

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E!TERNAL POWER SWITCH

The eternal power is a guarded toggle-type switch with the "ollowing positions/

OFF POSITION

Battery power is provided to the main (us and to the starter circuit :ternal power cannot (eapplied to the main (us ith the generator switch in the @7 position, power is applied to thegenerator control circuit

STARTER POSITION

:ternal power is applied to the starter circuit only Battery power is applied to themain (us 7o

generator power is availa(le in this position +" eternal power drops o"" during the start cycle, theeternal power switch must (e placed in the @ position to reconnect the (attery to the starter i"motoring is required

BUS POSITION

:ternal power is applied to the main (us 7o power is availa(le to the starter The (attery, i"desired, can (e connected to the main (us and the eternal power (y the (attery switch Batterycharge should however (e monitored to avoid overcharge

BATTERY

The system uses a 2' volt lead-acid (attery with a capacity o" ' amp-hr or a 2' volt 7i-cad (atterywith a '0 amp-hr capacity The 7i-cad (attery has a longer service li"e, high discharge and shortrecharge capa(ility

THERMAL RUNAWAY

+" "or any reasons a cell>s temperature increases, its voltage and internal resistance decreases Three"actors lead to increasing a cell>s temperature/

:cessively high discharge rate

:cessively high am(ient conditions, particularly with a poorly or improperly ventilated (attery

compartment

=eterioration o" the plates> separator material, which allows oygen "rom the positive plate to

interact with a negative plate where it will chemically interact with the cadmium and generateheat

The (eginning o" the pro(lem is an ecessive discharge rate @n short legs in +C at night, the(attery is constantly (eing drained and recharged, which generates ecessive (attery temperature=ue to the way individual cells are installed in the (attery case, the outer cells dissipate heat through

the sides o" the case and as a result run slightly cooler than the middle cells !s the (atterytemperature rises, it is the inner cells that get the hottest

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The generator attempts to recharge the (attery (y supplying su""icient current to the cells !s the celltemperature increases, its resistance decreases simply helping the generator The ecessive currentcauses the cells to overheat even more, "urther reducing their resistance The porous plastic strip

(etween the individual plates (rea)s down, "urther complicating the pro(lem !t this point, shuttingo"" the generator will stop the pro(lem

eanwhile, the inner cell>s internal resistance and voltage (ecomes so low that the voltage o" thegood cells surrounding it will (e higher (y comparison and they will (egin to "eed the (ad cellshen any cell (egins to receive voltage "rom a surrounding cell, isolating the (attery "rom thegenerator will no longer have any e""ect the (attery is sel"-destructing The only remaining solutionis to land as soon as possi(le

BATTERY HOT ,-%./

This am(er light illuminates when the (attery temperature is 1'0 - 1?0


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RESET AND TRIP

These positions are momentary and are spring loaded (ac) to @7 position +" the G:7:3!T@3@ or E@T!G: @ lights illuminate, place the switch momentarily in the 3:*:T position to

restore generator power +" erratic operation is o(served, the system can (e shut o"" (y placing theswitch momentarily in the T3+D position !"ter a suita(le waiting period, generator operation may (erecycled (y placing the generator switch momentarily to 3:*:T

ON POSITION

The GCA will automatically control the generator line contactor "or normal generator operation

C208 Technical Lectures

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