Ae Lab Manual

7/23/2019 Ae Lab Manual

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SRINIVASA

(Approved by AICT

An

DEPARTM

AERO ENGIN

ENGINEERING CO

, New Delhi and affiliated to Anna Universit

ISO 9001:2008 Certified Institution

PERAMBALUR 621212

NT OF AERONAUTI

NGINEERING

AE2355

E LABORATORY M

LEGE

, Chennai)

AL

NUAL



TABLE OF CONTENTS

AE2355AERO ENGINE LABORATORY MANUAL

Expt LIST OF EXPERIMENTS Page no

Introduction – piston engine

1 Dismantling of a piston engine

2 Engine (Piston Engine) - cleaning, visual inspection, NDT checks.

3 Piston Engine Components - dimensional checks.

4 Study of carburetor.

5 Piston – Engine reassembly.

6 Dismantling of a jet engine

7 Jet Engine – identification of components & defects.

8 Jet Engine – NDT checks and dimensional checks

9 Jet Engine – reassembly.

10 Engine starting procedures.



INTRODUCTION

PISTON ENGINE

Piston engines are internal combustion engines that burn a mixture of fuel and air inside a

combustion chamber. The chamber is provided with a piston that moves within the compression

chamber. The energy for the movement of the piston is provided by the air-fuel mixture. Piston

engines operate similar to the car and other automobile engines. In its basic operation, a valve in

the engine permits air into the chamber (called the cylinder) which is compressed by the moving

piston. When an appropriate compression is reached, fuel is allowed into the compressed air

through another inlet as a fine spray. Finally, the compressed fuel-air mixture is ignited with a

spark provided by a spark plug, which causes the mixture to explode violently. The explosive

power is used to move the piston back, and remove the exhaust gases from the compression

chamber. The return movement of the piston is conveyed to the wheel and fans of the aircraft

which causes it to rotate at high speed. In a propeller powered aircraft, much of the thrust is

created by the propellers, which creates the upward lift for the aircraft.

The general aircraft piston engine used for thrust generation, consist of the following basiccomponents. (1) Crank case, (2) Bearings, (3) Crankshaft, (4) Connecting rod assemblies (5)

Piston (6) Cylinders (7) Valves.

GAS TURBINE ENGINE:

The gas turbine is an internal combustion engine that uses air as the working fluid. The engineextracts chemical energy from fuel and converts it to mechanical energy using the gaseous

energy of the working fluid (air) to drive the engine and propeller, which in turn propel the

airplane. In the turbine engine, however, these same four steps occur at the same time but in

different places. As a result of this fundamental difference, the turbine has engine sections.

1. The inlet section

2. The compressor section

3. The combustion section (the combustor)

4. The turbine (and exhaust) section.

The turbine section of the gas turbine engine has the task of producing usable output shaft power

to drive the propeller. In addition, it must also provide power to drive the compressor and all

engine accessories. It does this by expanding the high temperature, pressure, and velocity gas

and converting the gaseous energy to mechanical energy in the form of shaft power.



EX. NO:1 DI

AIM:To dismantle a piston engin

TOOLS REQUIRED:

Special tools for notchin

Universal socket for spar

Selected spanner no: 6-1

Ring spanner no: 6-22

Adjustable spanner

Pliers, cutter and screwdr

Value depression tool

Crow foot spanner

THEORY:

Cylinders may be aligned in li

radially around the crankshaft.

of the same cylinder and this ha

Deltic. Some designs have set

engine. Internal combustion en

remove gases to and from the cysaid to be 2-stroke, 4-stroke or 6

a cycle.

SMANTLING OF A PISTON ENGINE

e and study its particular components.

crank shaft.

k plug

iver

ne, in a V configuration, horizontally opposi

pposed-piston engines put two pistons working

s been extended into triangular arrangements s

the cylinders in motion around the shaft, su

gines operate through a sequence of strokes

linder. These operations are repeated cyclically-stroke depending on the number of strokes it

Simple aircraft piston engine

e each other, or

at opposite ends

ch as the Napier

h as the Rotary

that admit and

and an engine isakes to complete



PROCEDURE:

1.

Remove spark plug and rocker curves.

2. Remove starter and accessories.

3. Turn the engine over such that cylinders are upper most.

4.

Remove controls completely with universal joints.

5. Remove air scoop, plug leads, distribution covers.

6. Remove induction system with carburetor.

7.

Unscrew push rod ball socket from rockers.

8.

Take out push rod and push rod covers.

9. Remove cylinder baffle plate.

10.

Remove cylinder.

11.

Remove piston rings.

12. Extract gudgeon pin, air clip.

13.

Withdraw gudgeon pin and piston. Remove magnetos.14.

Remove gearbox with timing gear cover.

15. Turn the engine cover on its stand. Remove starter.

16. Remove adaptor, thrust bearing cover and top cover.

17.

Detach big and bearing caps. Withdraw connecting rod.

18. Remove main, intermediate bearing caps.

19. Lift crankshaft. Unscrew idle gear hub bolt.

20.

Draw off gear wheel. Remove magneto drivers.

21.

Unscrew camshaft gagging the gear.

22. Remove camshaft rear bearing bush.

23.

Withdraw camshaft. Remove tappet and guides.24.

The parts are kept for visual inspection.

RESULT:

Thus the stripping of piston engine is carried according to instructions in the

manufacturer’s maintenance manual.

VIVA QUESTIONS:

Explain overhaul

What are the safety precautions while handling the engine?

Explain the purpose of push rod

What is the role of cam shaft

UNIVERSITY QUESTIONS:

1. Write the procedure for dismantling of aircraft piston engine.

2. Carry out the operation of stripping of piston engine.



EX. NO:2 ENGINE (PISTON ENGINE) - CLEANING, VISUAL INSPECTION,

NDT CHECKS

AIM:

To study about the different types of cleaning procedures, various inspection methods,

and NDT (Non Destructive Test) methods.

APPARATUS REQUIRED:

Aircraft component

Kerosene

Lubricating oil

French chalk

Methylated spirit

Heating source

CLEANING

It is necessary to clean the engine externally before disassembly and to clean the parts

after disassembly. Great care must be taken during the cleaning processes because the engine

parts can be seriously damaged by improper cleaning or applications of the wrong types of the

cleaners to certain engine parts. In every case, study the engine manufacturer’s recommendations

regarding cleaning procedures and comply with the directions provided by the manufacturer of

the cleaning agent or process.

In general two types of cleaning are required when an engine is overhauled.

a. Degreasing, for removal of oil, soft types of dirt and soft carbon (sludge)

b. De carbonizing, for removal of hard carbon deposits.

DEGREASING AFTER DISASSEMBLY

After the engine has been disassembled all oil and sludge should be removed from the parts

before further cleaning is attempted, because the additional cleaning processes are much more



effective after the surface oil has been removed. Two principal methods for removing the

lubricating oil and loose sludge are:

1. Washing in a petroleum solvent

2. Vapor degreasing

Washing in a petroleum solvent

Cleaning with petroleum solvent can be done in a special cleaning booth where the parts are

supported on a grill and sprayed with a solvent gun using air pressure of 50 to 100 psi (345-

690kPa). During the cleaning processes, particular care should be taken that all crevices, corners,

and oil passages are cleaned.

Vapor degreasing

A vapor degreaser consists of an enclosed booth in which a degreasing solution such as

trichloroethylene is heated until it vaporizes. The engine parts are suspended above the hot

solution, and the hot vapor dissolves the oil and soft residue.

Several terms are used to describe defects detected in engine parts during inspection.

1. Abrasion – A roughened area where material has been eroded by foreign material being

rubbed between moving parts or surfaces.

2. Burning – Surface damage due to excessive heat. It is usually caused by improper fit,

defective lubrication or over temperature.

3. Burr – A sharp or rough edge of metal, usually the result of machine working, drilling, or

cutting.

4. Chipping - The breaking away of small pieces of metal from a part as a result of careless

handling or excessive stress.

5. Corrosion – electrolytic and chemical decomposition of a metal, often caused by joining of

dissimilar metals in a situation where moisture exists. Surface corrosion is caused by moisture in

combination with chemical elements in the air.

6. Crack - A separation of metal or other material, usually caused by various types of stress,including fatigue stress resulting from repeated loads.

7. Dent- A small, rounded depression in a surface usually caused by the part being struck with a

rounded object.



8. Galling- A severe condition of chafing or fretting in which a transfer of metal from one part to

another. It is usually caused by the slight movement of mated parts having limited relative

motion and under high loads.

9. Nick- A sharp sided depression with a “V” shaped bottom, caused by careless handling of

tools and parts.

10. Pitting- Small, deep cavities with sharp edges, may be caused in hardened- steel surfaces by

high impacts or in any smooth part by oxidation.

11. Scoring- A series of deep scratches caused by foreign particles between moving parts, or

careless assembly or disassembly techniques

12. Scratches- Shallow, thin lines or marks, varying in degree of depth and with, caused by

presence of foreign particles during operation or contact with other parts during handling.

13. Indentation- Dent or depression in a surface caused by severe blows.

14. Peening- Depression in the surface of metal caused by striking of the surface by blunt

objects or materials.

15. Fretting- The surface erosion caused by very slight movement between two surfaces which

are tightly pressed together.



PROCEDURE:

I. For parts that can be removed from aircraft

a) For these components, hot fluid chalk method is used cleaning must be done

b)

A mixture of three parts of kerosene and one part of lubricating oil is heated at 90 – 95oC.

c) The removal components such as piston’s connection rods, cylinders, combustion

chamber are dipped in the hot fluid

d) Take the component out and dried out apply French chalk on it.

e) Extra French chalk is to be removed by tapping.

f) Then cool the component, the contraction of the piston on cooling will force the oil out of

any crank and stain the French chalk with a yellowish color.

II. For components that cannot be removed from aircraft.

a) For a components that cannot be removed from aircraft such as landing gear mounting,

cold fluid chalk method is used cleaning is done.

b)

French chalk is mixed with Methylated spirit and applied on the components that are to

be checked

c)

Excess chalk is removed by tapping.

d)

Methylated spirit will evaporate off leaving the cracks stain with French chalk

RESULT:

Thus the NDT checks have been performed on aircraft component.

VIVA QUESTIONS:

What are the NDT techniques used in inspection?

What techniques is used for inspecting internal defect

Explain some defects occur in piston engine components?

How to monitor the health of engine condition?


1. Carry out the NDT inspection on aircraft piston engine.

2. Write the procedure for NDT inspection of various components



EX. NO:3 PISTON ENGINE COMPONENTS - DIMENSIONAL CHECKS.

3.(a) VIEWING PROCEDURE OF CONNECTING ROD

AIM:

To perform maintenance and inspection on connecting rod.

TOOLS REQUIRED:

Surface plate

Micrometer

Dial gauge

Vernier caliper

Telescopic gauge

Tapered sleeve

Arbors

Plug gauge

THEORY:

Connecting rod is the link which transmits forces between the piston and crankshaft of an engine.

It transmits the reciprocating motion of the piston to the rotating movement of the crank shaft.

The principle type of connecting assemblies are the

Plain type

Fork and handle type

Articulated type





PROCEDURE:

1.

Check the connecting rod conditions, the big end caps for cracks and other surface

defects by hot oil and chalk method.

2. Check the rod for notches and abrasion.

3.

Measure small end diameter and compare with external diameter of gudgeon pin.

4. Check the nip in the big end bearings.

5. Measure and check the diameter with internal dimensions of cylinder bore gauge.

6.

To carry out the nip check, assemble connecting rod shell and cap as per assembly

sequence and tighten the bolts.

7. Tighten to 840 pounds inch and check diameter of big end bearing.

8.

Check connecting rod for alignment.

9. Check connecting rod bolts for elongation and nuts for threads.

10.

Check for hardness.



RECTIFICATION:

1. During the NIP check, if 0.004” doesn’t go inside machine the big end cap. If 0.006”

goes inside replace the bearing cap.

2.

Fitting and searing can be removed by stoning and polishing if not too deep.

RESULT:

Thus the connecting rod is viewed and its dimensions are measured as per instructions

in the manufacturers’ maintenance manual.

VIVA QUESTIONS:

Which type of material used to manufacture the connecting rod?

Different types of connecting rod?

What refer the big and small ends of connecting rod?

What is connecting rod?


1. Perform the inspection of piston connecting rod.



3.(b) VIEWING PROCEDURE OF CRANK SHAFT

AIM:

To view the crankshaft and check out its dimensions.

TOOLS REQUIRED:

Surface table

V-blocks

Dial indicator

Vernier caliper

Micrometer

Magnifying glass

THEORY:

The crankshaft transforms the reciprocating motion of the piston to rotating motion for turning

the propeller. It is a shaft composed of one or more cranks located at definite places between the

ends. Since the crank shaft is the backbone of the engine it is subjected to all forces developed

within the engine and hence should be strongly constructed.



FOUR THROW CRANKSHAFT

PROCEDURE:

1.

Check for cracks by contact current method.

2.

Check for corrosion, pitting etc..

3.

Check for ovality and taperness using micrometer.

4.

Check external dimensions of crank pin and journals.

5.

Carry out rip check before measuring internal dimensions.

6.

Check for central journal errors due to ovality.

7.

Check the crank web for parallelism.

8.

Check crank pin for parallelism. Error allowed is 0.0016” per unit length.

9. Check if propeller shaft has a tapered end in the hub.

10. Check propeller shaft for threads and keyways for burrs and beveling.

11. Check oil seal retainer and sealing for burrs and correct seating.

12. Carry out static and dynamic hardness tests.



RECTIFICATION:

1. Score, taper and ovality can be removed by grinding.

2.

Slight score and pitting can be removed by grinding or dressing with carbonundum or

polishing with emery paper.

RESULT:

Thus the crankshaft is viewed and its dimensions are checked with the manufacturers’

maintenance manual.

VIVA QUESTIONS:

What is the purpose of crankshaft?

What is a journal?

What is the purpose of counter weight?


1. Carry out the inspection on piston engine crankshaft.



3.(c) VIEWING PROCEDURE OF CYLINDER ASSEMBLY

AIM:

To perform the task of maintenance and inspection of cylinder assembly.

TOOLS REQUIRED:

DIP basket

Stud removing tool

Spark plug insert tool

Hand vice drill bit

Drift and bore gauge

THEORY:

The cylinder of an IC engine converts chemical heat energy of the fuel to mechanical energy and

transmits it through the connecting rods to the rotating crank shaft. The cylinder assembly used

for present day engines usually includes cylinder barrel, cylinder head, valve grid, valve seats,

rocker arms, cooking fins



CYLINDER BARREL

PROCEDURE:

CLEANING:

Clean the cylinder head with petroleum solvent. Dip it in petroleum agent using

cleaning basket.

VISUAL INSPECTION:1.

Inspect the cylinder head visually using a magnifying glass.

2.

Inspect the cylinder for

3. Loose damaged studs.(replace new ones)

4.

Loose spark plug (insert new oversize ones.)

5.

Loose cracked valve guide.

6. Damaged mounting ports, rocker box cover



7. Cracked or damaged fins

DIMENSIONAL CHECKS:

1. Check internal dimensions of intake and exhaust valves.

2. Check diameter and roundness of guide bore with gauge.

3.

Check wear and tear in rocker arm bush.

4. Dimension checks are done in processes.

CYLINDER BARREL:

TOOLS REQUIRED:

Cleaning basket

Feeler gauge

Dial gauge

Bore gauge

PROCEDURE:

CLEANING:

Clean the barrel using petroleum solvent dipping it on the cleaning basket.

VISUAL INSPECTIONS:

1.

In cooling fins, check for nicks and notches.

2. In barrel, check for cracks (result in rejection)

3.

In skirt, check for cracks, bends, and breaks.4.

In mounting flange, check for nicks, cracks and warping.

5. Inside the barrel inspect for corrosion and scoring.

DIMENSIONAL CHECKS:

1.

Maximum clearance between piston skirt and cylinder is 0.021”

2. Maximum taper of cylinder wall in 0.018”.

3. Maximum ovality is 0.018”.

RESULT:

Thus the inspection of the cylinder assembly is carried out as per instructions given in

manufacturer’s maintenance manual.

VIVA QUESTIONS:

What is cylinder head temperature?

Why fins are used?



What is cold spark plug?


1. Carry out the inspection on piston engine cylinder assembly.



3.(d) VIEWING PROCEDURE OF PISTON ASSEMBLY

AIM:

To carry out inspection on the piston assembly.

TOOLS REQUIRED:

Cleaning basket

Feeler gauge

Scale 12”

Telescopic gauge

Micrometer

Vernier caliper

THEORY:

The piston is a plunger that moves back and forth or up and down within the engine cylinder

barrel. It transmits the force of the burning and expanding gases in the cylinder through theconnecting rod to the engine crank shaft. As the piston moves down the cylinder, during intake

stroke, it draws in the air fuel mixture. As it moves up it compresses the charge. Ignition takes

place and the expanding gases cause the piston to move towards the crank shaft. The piston

forces the burnt gases out of the combustion chamber during the next stroke.



PISTON AND PISTON RINGS

PROCEDURE:

1.

Check for completeness of the piston assembly and clean it by dipping in petroleum

solvent using cleaning basket.

2. Examine the piston surface thoroughly for excessive pitting, cavaties or surface

distortion.

3. Check the piston rings, grooves, piston pinholes and holes base for any damage.

4.

Check side clearance between piston rings and piston (0.004”-0.0025”).

5. Check end clearance on wedge type piston rings.

6. Check inside diameter of piston pinhole (0.03”-0.004”).

7. Check clearance between piston skit and cylinder and piston dia top and bottom(0.021”).

8.

Check outside diameter of piston pin against inside diameter of hole in piston(0.0002”-

0.001”).

9. Measure fit between piston and plug and check outside diameter of plugs(0.0002”-

0.001”).

10. Examine two interior surface of piston pin hole for corrosion and fitting.



RESULT:

The maintenance and inspection of the piston assembly has been performed according

to manufacturer’s maintenance manual.

VIVA QUESTION:

What is manufacturer’s maintenance manual?

Explain the piston types?

Why piston rings are used?

What is meant by clearance?

What types of rings are used?


1. Carry out the inspection on piston assembly.



EXP.NO.4 STUDY OF CARBURETOR

Aim

To study about the requirements, construction, principles, and operation of the piston

engine Carburetor.

INTRODUCTION

A carburetor has only one purpose, and that is to deliver a finely atomized fuel at the

correct air-fuel ratio to the engine under all operating conditions. The carburetor mounts to the

engine’s air induction system. The intake system is also called intake manifold. The carburetor

often has an adaptor to match the opening and bolt patterns of the engine and carburetor base. A

downdraft carburetor mounts above the engine and an up-draft carburetor mounts below the

engine. Side-draft carburetors have a horizontal connection to the engine. Air entering thecarburetor comes from a duct that extends into the airplane’s airstream, either at the front of the

engine, or at its side. In some cases, the intake duct extends to the aircraft’s wings. Before the air

enters the carburetor, it may pass through an air filter in some applications, and through a valve

arrangement that allows hot air radiating from the engine exhaust pipe to mix into the air moving

to the carburetor. This valve arrangement provides carburetor heat that prevents ice formation in

the air duct and carburetor

There are two types of proportioning carburetors and there are two types of fuel injection

systems in use on aircraft. The simplest of the carburetors is the float-type. The other

proportioning carburetor is the pressure carburetor. Fuel injection systems differ in how the fuelis distributed. One system continuously sprays fuel into the air induction system, the other sprays

the fuel into the engine cylinder just when needed.

In addition to providing the correct fuel-air ratio, a carburetor:

• Is the point where the aircraft’s fuel system is connected.

• Measures how much air is entering the engine.

• Measures the correct amount of fuel for good combustion for the measured air.

• Delivers and mixes the fuel into the air moving in the air induction system

CARBURETOR WORKING

Venturi

The method most commonly used is with a venturi through which the airflow entering the

engine’s induction system. We know that the air velocity through the venturi must increase to



pass that same volume of air. The increase in velocity causes a pressure reduction that is in

proportion to the air velocity. A low pressure in the venturi (a partial vacuum) indicates that high

velocity air airflow is present. Because of this, the venturi’s variable vacuum represents the

volume of air passing through it. This method of determining the volume of air entering the

engine is much more reliable than most of the earlier methods

Main Metering System

The main metering system begins at the main metering jet, which establishes a specific

reduction in fuel pressure, as described earlier in the jet section of this article. The reduction in

pressure will be constant, no matter how much fuel flows through the jet. The fuel flows to the

main discharge nozzle, which is usually located in the center of the carburetor’s main airflow

venturi. Often, the main discharge jet is located within a small secondary or boost venturi

suspended in the center of the main airflow venturi. The reduced air pressure in the venturi

determines the amount of fuel drawn out of the discharge nozzle. The reduction in pressure isdependent upon the volume of air flowing through the venturi. The fuel will start flowing when

sufficient differential pressure lifts the fuel from the fuel bowl level up to the level of the nozzle

discharge openings. The amount of differential pressure controls the rate of fuel flow. The main

metering circuit will provide a constant fuel–air ratio at any engine speed and condition above

the engine’s idle speed. Experimentation found that admitting a small amount of air into the fuel

passage to the discharge nozzle reduced the fuel droplet size, resulting in better fuel vaporization.



This is an example of an air bleed as the jet in the airstream controls the amount of bleed air

admitted into the fuel passage

FLOAT TYPE CARBURETOR

Idle Circuit

When closed, the engine throttle has a very slight clearance that allows just enough air forthe engine to operate at idle speed. With the throttle set at idle, the engine continues drawing

whatever air is in the induction system into the engine cylinders, thereby reducing the pressure in

the intake manifold. The volume of air flowing through the carburetor is very low, and there is

not enough differential pressure to lift the fuel up to the outlet openings at the discharge nozzle.

An alternate fuel circuit meters fuel when the throttle is at idle. The idle system consists of a

small drilled hole that connects the main air circuit past the throttle to the idle circuit jet,



allowing the manifold pressure differential to draw fuel from the main metering fuel supply into

the main air circuit. The idle jet often has a tapered needle valve within it to adjust the fuel flow.

Some idle systems use an air bleed to control fuel flow. A small transfer orifice is located just

before air passes the closed throttle plate, near when it is nearest to the carburetor’s wall. This

feature is the "secondary idle orifice" The transfer orifice connects to the idle circuit fuel supply.

The orifice gradually transfers additional fuel into the main air circuit from the idle circuit fuel

supply as the throttle transitions from closed to open. Both the idle passage and the transfer

orifice are inactive when the air entering the pressure differential is below that needed to draw

fuel into the idle circuit.

Accelerator Pump Circuit

When the throttle is briskly opened, the idle passage no longer functions, as it relies on

the high velocity air moving between the throttle plate and the idle passage outlet. Once the

throttle opens, air quickly fills the intake manifold. With low engine speed, there is little air

flowing through the carburetor. The transfer slot cannot provide enough fuel, nor can the mainfuel discharge nozzle properly meter fuel, as there is a small delay as the fuel overcomes its

inertia. The engine will falter slightly until there is sufficient vacuum in either the main or the

idle circuit to start fuel flowing again. A small pump incorporated into the carburetor overcomes

this lack of fuel flow. It can be a vacuum operated diaphragm, a plunger or a simple well where

extra fuel is available for that purpose. Early carburetors used acceleration well. The well is a

small amount of fuel located at the base of the discharge nozzle that is available as needed. This

fuel was limited to just the volume of the well, as it could only refill at a low rate. The plunger

pump replaced the acceleration well. Either manifold vacuum or a mechanical linkage to the

throttle operated the plunger. When mechanically operated, as the throttle is opened the pump

plunger pushes a volume of fuel out of the pump, spraying it through passages leading to the

main air circuit. "Pumping" the throttle would make subsequent volumes spray into the intake

manifold, possibly flooding the engine with too much fuel, resulting in a fire. The linkage

arrangement, the volume of the pump and the size of the spray nozzle outlet determine the

characteristics of this accelerator pump.

Power Enrichment Circuit

An engine operating at full throttle may not have enough rpm to create the necessary

airflow, especially when operating under a heavy load. With a limited airflow and throttle wide

open, the fuel mixture may not have enough fuel carried with it into the engine cylinder, causinga leaner than normal combustion which may then run hotter than normal. The engine may also

run too hot when operating at full speed. Extra fuel overcomes these problems. The fuel added to

the normal mixture cools the cylinder walls as it evaporates just prior to combustion. This

cooling lowers the fuel-air mixture temperature. The cooler mixture lowers the temperature and

pressure in the combustion chamber, reducing the risk of detonation. The extra fuel comes from

the fuel in the fuel bowl. An enrichment valve and enrichment jet connect the fuel supply with



the fuel delivery nozzle. The enrichment valve is either a mechanical linkage connected to the

throttle, or a diaphragm lifted by the high venturi suction created by full-throttle operation,

connecting the fuel bowl to the enrichment jet. Some carburetor manufacturers refer to the

enrichment circuit as an "economizer circuit", in that there is reduced fuel consumption when the

valve is closed, thereby improving fuel economy at medium and low power levels. The engine

now has the correct fuel-air mixture necessary for all operating conditions found at engine idle,

take-off, and cruise power settings.

Mixture Control Circuit

Once at cruising altitude and speed, it is beneficial to reduce the amount of fuel

consumed in order to increase range or for economic operation, and that is the job of the mixture

control circuit. A manual control located near the pilot’s throttle control operates a device that

changes the overall fuel–air ratio to a slightly leaner cruise mixture. Leaning the mixture at

cruise power increases range and conserves fuel. The lower power level and the available engine

cooling allow operating with this leaner mixture, without causing harm to the engine. For thatreason the lean setting should never be used when full power is needed, or may be immediately

needed, such as when a landing turns into a missed approach, or when full power is needed to

arrest a high sink rate. The mixture control can provide a number of pre-determined mixture

settings, and stops the engine at the conclusion of the flight or engine run. Mixture settings start

at "Idle-cutoff", a position that closes the fuel passages, stopping fuel flow through the

carburetor. The mixture changes from lean to rich as the mixture control moves to its full rich

position.

RESULT:

Thus studied about requirements, construction, principle and operation of the

reciprocating engine carburetor.

VIVA QUESTIONS:

What the types of carburetor?

What is venturi?

What is the ratio of rich fuel/air mixture?


1. Describe briefly about the carburetor used in aircraft.



EX. NO: 5 REASSEMBLY OF PISTON ENGINE

AIM:

To reassemble the piston engine after inspection checks.

TOOLS REQUIRED:

Special universal socket for spark plug

Set spanners 6’-19’

Ring spanners 6’-22’

Adjustable spanner

Pliers and cutters

Screwdriver different sizes

Hammer

Value depression tool

Crow foot spanner

PROCEDURE:

1. Insert the tappet and the guides in the crank case.

2. Fix the camshaft after positioning bearing bush.

3. Fix the magneto drive gear.

4. Fix the idle gear and screw the hub bolt.

5. Fix the crankshaft and position the bearing caps.

6. Fix the connecting rod and the bearing caps.

7.

Position the top crankcase and then tighten all bolts and nuts.

8.

Fix the gearbox with timing gear cover.

9.

Fix the magnetos.

10.

Fix the position in the connecting rod.



SINGLE CYLINDER PISTON ENGINE

11.

Assemble the piston rings on the piston groove and insert the cylinder over piston and

tighten all cylinder large nuts.

12. Fix the cylinder baffle plates.

13.

Position the push rod covers and push rods.



14. Fix the rocker shafts.

15. Fix the induction system and carburetor.

16. Fix the air scoop, plug heads with distribution cover.

17.

Fix the carburetor controls with universal rods.

18. Fix the starter and other accessories.

19.

Fix the spark plug in cylinder head bush and tighten to connect torques and connect the

plug leads.

20. Fix the rocker covers.

RESULT:

Thus the piston engine in reassembled as per maintenance manual instruction

VIVA QUESTION:

What is ignition timing?

What is timing advance?

Define engine firing order?

What is backfiring?

UNIVERSITY QUESTION:

1. Write the procedure for reassembly of piston engine.



EX.NO:6 DISMANTLING OF A JET ENGINE

AIM:

To dismantle the turbojet engine in a proper sequence.

TOOLS REQUIRED:

¾ *1/4 BS or 12-13 set spanner

10-11 set of ring spanner


C-spanner

Common screw driver

Ball peen spanner

Pliers and side cutter

JET ENGINE



THEORY:

Air breathing jet engines are gas turbines optimized to produce thrust from the exhaust

gases, or from ducted fans connected to the gas turbines. Jet engines that produce thrust from the

direct impulse of exhaust gases are often called turbojets, whereas those that generate thrust with

the addition of a ducted fan are often called turbofans or (rarely) fan-jets. Gas turbines are alsoused in many liquid propellant rockets, the gas turbines are used to power a turbo pump to permit

the use of lightweight, low pressure tanks, which saves considerable dry mass.

PROCEDURE:

1. Loosen the fine nuts using appropriate spanner and r3emove the inlet case from the

accessory case.

2.

Loosen the 10 nuts using no 10-11 set of ring spanner and detach air casing fromcompressor case.

3.

Remove 15 bolts using no 8-9 set spanner. Detach compressor casing from diffuser.

4.

Loosen retaining nut with C-spanner and remove centrifugal impeller.

5.

Remove front roller bearing and the sleeve.

6.

Remove 2 ignition connection and fuel turners from the combustion chamber outer case.

7.

Now take out the turbine along with the shaft from the rear side.

8.

Take out the combustion chamber.

9.

Loosen the bolts and nuts from the exhaust pipe flange and detach the exhaust pipe from

the combustion chamber.

10.

Loosen the clamps of the propelling nozzle and disconnect the nozzle from the exhaust

pipe.

11. Keep all the removed parts separately in the cleaned tray in sequence so that there is no

possibility of mixing with each other.

12. Wherever blanking is required, blank it and place identification slips.

RESULT:

Thus the turbojet engine in dismantled and the components are studied.



VIVA QUESTION:

What is operating principle of jet engine?

What is the temp of air entering the combustion chamber?

How much should be turbine blade tip clearance?

What is compressor recovery wash?


1. Carry out the operation of dismantle the turbojet engine



EX.NO:7 JET ENGINES – IDENTIFICATION OF COMPONENTS & DEFECTS

AIM:

To study about the jet engine components and its defects.

APPARATUS REQUIRED:

Jet engine..

INTRODUCTION:

The major components of a jet engine are similar across the major different types of engines,

although not all engine types have all components. The major parts include:

Gas Turbine Major Components

Cold Section:

Air intake (Inlet) — The standard reference frame for a jet engine is the aircraft itself.

For subsonic aircraft, the air intake to a jet engine presents no special difficulties, and consists

essentially of an opening which is designed to minimize drag, as with any other aircraft

component. However, the air reaching the compressor of a normal jet engine must be travelling

below the speed of sound, even for supersonic aircraft, to sustain the flow mechanics of the

compressor and turbine blades. At supersonic flight speeds, shockwaves form in the intake

system and reduce the recovered pressure at inlet to the compressor. So some supersonic intakes

use devices, such as a cone or ramp, to increase pressure recovery, by making more efficient useof the shock wave system.

Compressor or Fan — The compressor is made up of stages. Each stage consists of

vanes which rotate, and stators which remain stationary. As air is drawn deeper through the

compressor, its heat and pressure increases. Energy is derived from the turbine passed along

the shaft.



Bypass ducts much of the thrust of essentially all modern jet engines comes from air from the

front compressor that bypasses the combustion chamber and gas turbine section that leads

directly to the nozzle or afterburner (where fitted).

The two common types of compressors are

1. Axial flow compressor.

2. Centrifugal flow compressor.

COMPRESSOR DEFECTS

1. Impeller damage due to bird hit, fatigue.

2. Hub damage

3. Tangential vanes (Diffuser) defects.



Diffuser section: - This section is a divergent duct that utilizes Bernoulli's principle to decrease

the velocity of the compressed air to allow for easier ignition. And, at the same time, continuing

to increase the air pressure before it enters the combustion chamber.

Hot section:

Combustor or Can or Flame holders or Combustion Chamber — this is a chamber where

fuel is continuously burned in the compressed air.

The primary function of combustion chamber is to burn the air /fuel mixture. The common types

of combustion chamber are

1. Can type combustion chamber

2. Annular type combustion chamber

3. Can- Annular type combustion chamber.

DEFECTS

1. IOD- internal object damage (confirmation through Boroscope)

2. Thermal stress

3. Cracks

4. Carbon deposits.



COMBUSTOR

Turbine — The turbine is a series of bladed discs that act like a windmill, gaining energy from

the hot gases leaving the combustor. Some of this energy is used to drive the compressor, and in

some turbine engines (i.e. turboprop, turboshaft or turbofan engines), energy is extracted by

additional turbine discs and used to drive devices such as propellers, bypass fans or helicopter

rotors. One type, a free turbine, is configured such that the turbine disc driving the compressor

rotates independently of the discs that power the external components. Relatively cool air, bled

from the compressor, may be used to cool the turbine blades and vanes, to prevent them from

melting.

Turbine is of two types. They are

1. Impulse type turbine,

2. Reaction type turbine

DEFECTS

1. Thermal stress

2. Fractured blade, disc

3. Missing blades



4. Rupture cracks

5. Creep

6. Fatigue fracture.

Afterburner or reheat (chiefly UK) — (mainly military) Produces extra thrust by burning extra

fuel, usually inefficiently, to significantly raise Nozzle Entry Temperature at the exhaust. Owing

to a larger volume flow (i.e. lower density) at exit from the afterburner, an increased nozzle flow

area is required, to maintain satisfactory engine matching, when the afterburner is alight.

Exhaust or Nozzle — Hot gases leaving the engine exhaust to atmospheric pressure via a

nozzle, the objective being to produce a high velocity jet. In most cases, the nozzle is convergent

and of fixed flow area.

DEFECTS

1. Discoloration

2. Thermal cracks

3. Fuel wash



4. Nozzle tip cracks

5. Deformation due to EGT

RESULT:

Thus the jet engine components and defects are studied

VIVA QUESTIONS:

What is EGT?

What is a creep?

Why it called gas turbine engine?


1. Identify the different components of jet engine and defects occurs on those components.



EXP.NO. 8 JET ENGINE NDT AND DIMENSIONAL CHECKS

Aim

To study about the jet engine NDT checks and dimensional checks on jet engine

components as per the engine maintenance manual.

NON-DESTRUCTIVE TESTING

Nondestructive testing or Non-destructive testing (NDT) is a wide group of analysis

techniques used in science and industry to evaluate the properties of a material, component or

system without causing damage. In aircraft maintenance it is important to inspect the mechanical

damage and assess the extent of the repair work. But in schedule maintenance it is a difficult to

finding the defects rapidly, as the maintenance of aircraft must be accomplished within

scheduled time and same to be released in time for commercial operation. During Nondestructivetesting (NDT) is the most economical way of performing inspection and this is the only way of

discovering defects. In simply we can say, NDT can detect cracks or any other irregularities in

the airframe structure and engine components which are obviously not visible to the naked eye.

Structures & different assemblies of aircraft are made from various materials, such as aluminium

alloy, steel, titanium and composite materials. To dismantle the aircraft in pieces and then

examine each component would take a long time, so the NDT method and equipment selection

must be fast and effective.

In the present trend of NDT application on aircraft 70-80% of NDT is performed on the

airframe, structure, landing gears and the rest carried out on engine & related components. Inorder to maintain the aircraft defects free and ensure a high degree of quality & reliability and as

a part of inspection program, usually following NDT methods are applied;1) Liquid penetrant 2)

Magnetic particle, 3) Eddy current 4) Ultrasonic 5) Radiography (x-ray/gama ray) 6)

Visual/Optical 7) Sonic/Resonance 8) Infrared Thermography.

Jet engine dimensional checks

Jet engine dimensional inspection consists of measuring specific components to ensure

that they are within the limits and tolerances given in the table of limits in the manual. Some of

the components are measured at each overhaul because only a small amount of wear or distortion

is permissible. Other components are measured only when condition found during visual

inspection, requires dimensional verification.

During overhauling after the cleaning of the components they are visually and

dimensionally inspected to establish their general condition and then further inspected for cracks.



Dimensional checks which are carried out on jet engine components

1. Compressor blade tip clearance with compressor shroud (to be checked and compared

with table of limits)

2. Turbine blade tip clearance with turbine shroud (to be checked and compared with

table of limits)

3. Length of the turbine blades are to be checked (elongation of blades take place due to

high temperature)

4. Internal and external diameter of the bearings and compressor, turbine shafts are

checked and compared with table of limits.

5. Jet nozzle diameter of the engine is checked and compared with the table of limits.

6. Some of the jet engines cordon shaft end play is checked and compared with table of

limits.

7. Internal and external splines are checked for dimension and compared with table of

limits.

8. Compressor blades and turbine blades cracks, dents, nicks

Result

Thus studied about the jet engine components NDT checks and dimensional checks

which are carried out as per the maintenance manual.

VIVA QUESTIONS:

What is the difference between reaction and impeller turbine?

What is twin spool engine?


1. Carry out dimensional checks on jet engine components .



EX.NO:9 ASSEMBLY OF TURBO JET ENGINE

AIM:

To assemble a turbojet engine in a proper sequence.

TOOLS REQUIRED:

¾ *1/4 BS or 12-13 set spanner



C-spanner

Common screwdriver

Ball peen spanner

plier and side cutter

PROCEDURE:

1.

Remove all blanking and clean them thoroughly.

2.

Attach air intake case front accessory by tightening all the 5 nuts using 12-13 set hammer

3. Attach air intake case rear to the compressor case by tightening all the nuts using 10-11

set ring spanner



4. Now assemble the compressor in the front and turbine at the rear of the shaft by inserting

the shaft in front of the diffuser case.

5.

Enclose the combustion chamber outer case over the flame tube and tighten all the 15

bolts.

6. Encage 2 ignitions and 5 fuel burners’ connection and tighten the nuts.

7.

Encage the exhaust pipe to combustion chamber outer case flange and tighten all the bolts

and nuts.

8. Attach the propelling nozzle to the rear side exhaust pipe and together with the clamp.

RESULT:

Thus the turbojet engine is assembled as per the maintenance manual instructions.

VIVA QUESTION:

How does the turbine transmit power to the compressor?

What are interconnectors?

What are two stage turbines?

What is the max r.p.m of a turbine engine?


1. Carry out the action of assembles a turbojet engine.



EXP.NO. 10 ENGINE STARTING PROCEDURE

AIM

To start the given airplane engine according to the maintenance manual instructions.

PRESTARTING INSPECTION:

The inspection is done to determine the general conditions of aircraft and engine.

EXTERNAL CHECKS:

1.

Head the airplane against wind direction.

2. Remove all protective covers and control locks.

3.

Position chocks in front and rear main wheel.

4.

Position carbon-di-oxide fire extinguisher midway between the port wing tip and cockpit.

5. Position technicians at port and starboard wing tips togive clearance before starting.

6.

All panels and cowlings should be in place, flaps open.

7.

Check fuel for water content and oil for grade.

8.

Turn the propeller 5-8 times to remove hydraulic locks.

9. Check for correct tyre pressure and shock strut extension.

INTERNAL CHECKS:

1. Slide the canopy open.

2.

Enter the cockpit and take a convenient position.

3.

Check instrument panel for completion and correction.

4.

Apply parking brakes to up position.5. Retract flaps to fully up position.

6.

Take clearance and switch on the battery.

7.

Open throttle approximately to 1/4th position.

8. Turn the booster pump “ON”

9.

Move mixture control to fuel rich position until steady flow.

10.

Return mixture control to idle cut off position.

11. Move throttle fully back and switch off booster pump.

PROCEDURE FOR STARTING THE ENGINE

PISTON ENGINE:

1. Turn the auxiliary fuel pump on if a/c is so equipped.

2. Place the mixture control to the piston recommended for the engine and carburetor

combination being started. As a general rule, the mixture control should be in the ‘idle

cut off’ position for pressure type carburetors and in the ‘full rich’ for float type

carburetors.



3. Many light a/c are equipped with a mixture control pull rod which has no defended

intermediate position when such controls are pushed in flush with the instrument panel

the mixture is set in the ‘full rich’ position conversely when the control rod is fulled all

the way out the carburetor is in the ‘idle cut off’ or ‘full bean’ position. Unmarked

intermediate position b/w these two extremes can be selected by the operator to achieve

any desired mixture setting.

4. Open the throttle to a position that will provide 1000 to 1200 rpm.

5. Leave the preheat or alternate air control in the ‘cold’ position to prevent damage and fire

in case of backfire. This auxiliary heating devices should be used of ten the engine warms

up. The improve fuel vaporization, prevent fouling of the spark plug oil formation and

climate icing in the induction system.

6.

Energize the starter after the propeller has made at least two compile revolutions and twin

the ignition switch on one engine equipped with on induction vibrator turn switch to the

‘both’ position. When starting on engine; that uses on impulse coupling magnetic turn by

ignition switch to the ‘left’ position. Place the ignition switch to the ‘start’ when themagnetic incorporation a retard breaker assembly. Do not crank the engine continuously

with the starter for more than 1 minute. Allow a 3 to 5 minute period for cooling the

starter between successive attempts. Otherwise the starter may be burned out due to

overheating.

7. Move the primer switch to ‘on’ intermittently or prime with one or three stokes of

priming pump, depending of on how the aircraft is equipped. When the engine begin to

fire, hold the primer on, while gradually opening throttle to obtained smooth operation.

8.

After the engine is operating smoothy on the primer, move the mixture control to the ‘full

rich’ position. Release the primer as soon as drop in r.p.m indicates the engine in

receiving additional from the carburetor.

JET ENGINE:

1. Place the start selector switch to the desired engine and the start arming switch (if so

equipped) to ‘start position’

2.

Turn the a/c boost pumps on

3. Place the fuel and ignition switch on

4.

Position the low rpm switch in low or normal (high)

5.

Make sure that the power lever is in the ‘start’ position: If the propellar is not at the ‘start’

position. Difficulty may be encountered in making a start.6. Depress the start switch and if printing is necessary depress the primer button.

7.

Make sure the fuel pump parallel light comes on at or above 2200 rpm and remains on

upto 900 rpm.

8. Check the oil pressure and temperature maintain the power level at the ‘start’ position

until the specified minimum oil temperature is reached.

9.

Disconnect the ground power supply.



RESULT:

Thus the starting procedure and pre-flight inspections are performed in aircraft engine

and studied.

VIVA QUESTION:

What is a need of booster pump?

What equipment is driven from the engine?

How is the maximum r.p.m. controlled?

What is a starting by-pass?


1. Write the aircraft engine starting procedure.



MANUAL PREPARED BY:-

S. RAJKUMAR M.E.,

ASSISTANT PROFESSOR,

AERONAUTICAL ENGINEERING,

SRINIVASAN ENGINEERING COLLEGE,

PERAMBALUR.

*** THANK YOU ***

Ae Lab Manual

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