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Powerplant > Powerplant Oral questions > Flashcards

Powerplant Oral questions Flashcards

1
Q

What is the purpose of dynamic dampers on crankshafts?

A

They reduce engine vibration

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2
Q

What types of bearings are generally found in reciprocating engines?

A

Plain, Ball, and Roller bearings

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3
Q

Are the connecting rods used in each cylinder of a radial engine the same? Explain.

A

No. Radial engines use master and articulating rod assemblies

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4
Q

Name the different types of piston rings

A

Oil control, Compression, and oil scraper

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5
Q

Where should piston ring gaps be installed relative to each other, and Why?

A

Compression ring gaps should be staggered so that they do not align. This prevents excessive blow-by

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6
Q

What could result from incorrectly installed piston rings?

A

Excessive oil consumption

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7
Q

What purpose do oil control rings serve?

A

They regulate the thickness of the oil film on the cylinder walls

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8
Q

What is used to help prevent valve surge or floating in an aircraft engine?

A

Two or more springs are used on each valve

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9
Q

On engines equipped with hydraulic valve lifters, what should the running valve clearance be?

A

Zero

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10
Q

What is the purpose of valve overlap?

A

It allows better volumetric efficiency and lowerss cylinder operating temperatures

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11
Q

What indications are given in the event of a leaking or open primer while the engine is running?

A

The engine will not idle properly

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12
Q

When pulling a propeller through, a hissing sound is heard, indicating valve blow-by. What procedure should be performed next?

A

A compression check should be performed to identify the faulty cylinder

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13
Q

What is the purpose of performing a compression test?

A

To determine if the valves, pistons and rings are sealing properly

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14
Q

When an engine is overhauled, how is its total time affected? When an engine is rebuilt, how is its operating history affected?

A

The total time on the engine must be continued and the time since major overhaul is entered into the engine log. If the manufacturer rebuilds the engine, it is granted a zero-time status and is considered to have no previous operating history

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15
Q

What inspections should be performed after a propeller strike without sudden stoppage?

A
  1. Inspect engine mounts, the crankcase and the nose section for damage. 2. Inspect the oil and oil filters/screens for metal particles 3. inspect thee crankshaft or driveshaft for cracks and mis alignment
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16
Q

Name some of the precautions that should be performed prior to engine removal

A

Disconnect the battery turn off the fuel valves, chock the wheels, and if necessary install a tail stand

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17
Q

When inspecting a piston, where are cracks most likely to be found?

A

In those areas that are highly stressed; usually the base of the piston bosses, inside at thee junction of the bore and the walls, and the ring lands

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18
Q

What does it mean if an engine part is within “serviceable limits”?

A

It means that the part is within the manufacturers limits and can be used in an engine (does not require replacement)

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19
Q

What tools or instruments are used to inspect a cylinder barrel for out-of-roundness

A

A dial indicator or an inside micrometer is usually used to measure the top of the cylinder and at the skirt. A telescopic gauge and micrometer can also be used two readings should be taken 90 degrees to each other

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20
Q

How can a loose stud in an engine crankcase be repaired?

A

Remove the loose stud and inspect the hole for size and thread condition. It may be necessary to use an oversize stud or Heli-coil insert

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21
Q

What publication is used to check an engine for normal operation?

A

Manufacturers Maintenance Manual

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22
Q

A weak cylinder is found during a compression check. What must be inspected?

A

Pressure is transmitted equally in all directions

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23
Q

What purpose does an oil analysis serve?

A

Metal particles in the oil show normal and abnormal wear of the engine. This helps in evaluating the engines internal condition

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24
Q

What inspection should be performed on an engine that has been in storage?

A

Perform an inspection to determine if there is any corrosion damage

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25
Q

Where would a carburetor air temperature bulb be located?

A

In the ram air intake duct

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26
Q

What is the fuel pressure range on float-type carburetors?

A

3-5 psi

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27
Q

Name the basic components of a fuel indicator

A

The transmitter and the indicator

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28
Q

What unit of measure is generally used to indicate fuel flow?

A

Pounds or Gallons per hour

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29
Q

Why is fuel flow monitored?

A

To determine fuel consumption and engine performance

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30
Q

What does the manifold gauge indicate and how is it calibrated?

A

It measures the absolute pressure in the engine manifold and is calibrated in inches of mercury

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31
Q

What directly controls manifold pressure?

A

Throttle opening and engine rpm

32
Q

During engine operation, where should the propeller control be set when checking the manifold pressure?

A

Low pitch, high rpm

33
Q

Is the aircraft electrical system required to power a cylinder head temperature gauge?

A

No. A thermocouple is used as the electrical source

34
Q

What are the possible indications of an oil pressure transmitter or indicator malfunction?

A

A severe or sudden drop in oil pressure while the oil temperature remains normal and the oil supply remains full

35
Q

What does a tachometer indicate on a reciprocating engine?

A

Engine rpm

36
Q

Where should the thermocouple be installed on a reciprocating engine using a single probe cylinder head temperature system?

A

On the hottest cylinder

37
Q

Explain the main difference and advantage of turbofan engines

A

A turbofan engine uses a fan to bypass some air around the engine core and to provide thrust. The advantage is that this provides additional thrust without increasing fuel flow

38
Q

Name the major components in a gas turbine engine

A

Air inlet, compressor section, combustion section, turbine section, exhaust section, gearbox and accessory section

39
Q

What determines the amount of airflow through a turbine engine?

A

The forward speed of the aircraft, compressor speed, and air density

40
Q

Name the two types of compressors commonly used in turbine engines

A

Axial and centrifugal flow compressors

41
Q

Name two different methods for attaching turbine engines

A

Dovetail-type root or bulb type root or fir tree type root

42
Q

what is a split compressor system?

A

Also called dual or twin spool compressors, these are connected to the turbine section with two rotor shafts, one inside the other

43
Q

What are the different types of combustion chambers used in turbine engines?

A

Can, annular, can-annular, and reverse flow annular

44
Q

what prevents the combustion chambers from burning?

A

cooling air along the inside of the liner

45
Q

What is the purpose of the interconnecting tubes attached between can-type combustion chambers?

A

For flame propagation during start

46
Q

What functions do axial flow turbine nozzles perform?

A

They direct the mass airflow to drive the turbine rotor at a specific angle

47
Q

How is thermal stress relieved on a turbine disc?

A

By directing bleed air onto the face of the disk or by grooves being cut in the disk

48
Q

what are carbon seals used for in turbine engines?

A

They are used as oil seals for the rotor shaft bearings

49
Q

What is shaft horsepower?

A

It is an indication of the torque developed by a turboprop or turboshaft engine

50
Q

Name the main components of a typical APU

A

A small power turbine for power and bleed air, and an electrical generator.

51
Q

When is the greatest demand placed on an APU?

A

When supplying bleed air

52
Q

How is an APU generally started?

A

With its own electrical starter and battery power

53
Q

Where does the APU get its fuel supply

A

From one of the aircrafts main fuel tanks

54
Q

At what speed does a gas turbine APU operate and how is this speed maintained?

A

At or near its rated speed regardless of electrical or pneumatic loads imposed. The APU fuel control automatically adjusts the fuel flow to maintain the rated speed

55
Q

what is used to prevent a heavily loaded APU from exceeding it maximum EGT?

A

A load control valve modulates the pneumatic load to maintain EGTs within limits

56
Q

How is an APU shut down and why is this procedure used?

A

After the APU is unloaded by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize. This cool down period is typically three minutes. If a heavily loaded APU is abruptly shut down without any cooling down period, damage could occur as a result of thermal shock

57
Q

What powers the variable inlet guide vanes used on some APUs to regulate the compressor intake airflow?

A

Fuel Pressure

58
Q

What is fan blade shingling?

A

It is the overlapping of the midspan shrouds of the fan blade..

59
Q

When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?

A

Any rubbing sound or other unusual noises from the engine

60
Q

Why are compressor washes performed and what methods are commonly used?

A

TO remove any contaminants from the compressor section and improve engine performance. The fluid wash and abrasive grit wash are commonly used

61
Q

How can you tell if a turbofan or turbojet engine is out of trim?

A

There will be a high exhaust gas temperature at the target engine pressure ration for takeoff power.

62
Q

Name the different types of compressor blade damage that may be found during iinspection.

A

Dents, cracks, galling.. pitting, scratches, burrs, burns, gouges.

63
Q

What kind of markers can be used to mark the parts in hot and cold sections during repair?

A

Layout dye, delt tip marker, chalk.

64
Q

How does relative humidity affect turbine engines?

A

Negligible effect

65
Q

What criteria determines replacement of life limited turbine engine components

A

Cycles, hours, and/or calendar time

66
Q

If turbine blades are removed from a turbine disc, why should they be re-installed in the same location?

A

To maintain the balance of the turbine wheel

67
Q

How are gas turbine engine tachometers calibrated?

A

They are calibrated in percent RPM

68
Q

On a turbine engine, what is the engine pressure ratio and what does it indicate?

A

It is the ratio between the total inlet pressure and total turbine exhaust pressure and us used to indicate the thrust developed by the engine

69
Q

On a turbine engine, what does exhaust gas temperature (EGT) indicate and how is it obtained?

A

EGT is the average temperature of the turbine discharge gasses and is obtained by thermocouples placed near the turbine exit

70
Q

Can the EGT system on a turbine engine be checked without running the engine?

A

Yes, by checking the resistance of the thermocouples and circuits

71
Q

Name the three components on the Induction system of a reciprocating engine

A

The air scoop, carburetor or fuel control, and the intake manifold

72
Q

What could happen if the induction system becomes obstructed?

A

The engine may not be able to produce its rated power or it may nor run at all. This may also be an indication of a dirty air inlet filter

73
Q

How does induction icing affect engine performance

A

It causes a reduction in power and possible erratic operation

74
Q

How is induction icing categorized

A

As impact ice, fuel evaporation ice, and throttle ice

75
Q

What is the common method used to prevent induction system ice in a reciprocating engine?

A

Raise the temperature of induction air with a preheater

76
Q

What causes fuel evaporation ice?

A

Fuel evaporation ice is formed because of the decrease in air temperature resulting from evaporation of the fuel after it is introduced into the air stream

77
Q
A

Powerplant (1 decks)

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