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Aircraft Maintenance > Turbine Engines > Flashcards

Turbine Engines Flashcards

1
Q

At what point in an axial-flow turbojet engine will the highest gas pressures occur?

A

at the compressor outlet

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2
Q

One function of the nozzle diaphragm in a turbine engine is to

A

direct the flow of gases to strike the turbine blades at the desired

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3
Q

What is the profile of a turbine engine compressor blade?

A

A reduced blade tip thickness

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4
Q

The fan rotational speed of a dual axial compressor forward fan engine is the same as the

A

low pressure compressor

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5
Q

The abbreviation Pt7 used in turbine engine terminology means

A

the total pressure at station no. 7

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6
Q

The blending of blades and vanes in a turbine engine

A

should be performed parallel to the length of the blade using smooth contours to minimize stress
points

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7
Q

What turbine engine section provides for proper mixing of the fuel and air?

A

combustion section

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8
Q

In a gas turbine engine, combustion occurs at a constant

A

pressure

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9
Q

Which statement is true regarding jet engines?

A

at the higher engine speeds, thrust increases rapidly with small increases in rpm

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10
Q

Some high-volume turboprop and turbojet engines are equipped with two-spool or split compressors.
When these engines are operated at high altitudes, the

A

low pressure rotor will increase in speed as the compressor load decreases in the lower density air

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11
Q

Turbine nozzle diaphragms located on the upstream side of each turbine wheel, are used in the gas
turbine engine to

A

increase the velocity of the heated gases flowing past this point

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12
Q

Where is the highest gas pressure in a turbojet engine?

A

in the entrance of the burner section

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13
Q

An exhaust cone placed aft of the turbine in a jet engine will cause the pressure in the first part of the
exhaust duct to

A

increase and the velocity to decrease

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14
Q

What is the function of the stator vane assembly at the discharge end of a typical axial-flow compressor?

A

to straighten airflow to eliminate turbulence

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15
Q

The turbine section of a jet engine

A

drive the compressor section

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16
Q

When starting a turbine engine,

A

a hot start is indicated if the exhaust gas temperature exceeds specified limits

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17
Q

In the dual axial-flow or twin spool compressor system, the first stage turbine drives the

A

N2 compressor

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18
Q

During inspection, turbine engine components exposed to high temperatures may only be marked with
such materials as allowed by the manufacturer. These materials generally include
1. layout dye.
2. commercial felt tip marker.
3. wax or grease pencil.
4. chalk.
5. graphite lead pencil.

A

1,2 and 4

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19
Q

When starting a turbine engine, a hung start is indicated if the engine

A

fail to reach idle rpm

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20
Q

What are the two basic elements of the turbine section in a turbine engine?

A

stator and rotor

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21
Q

The function of the exhaust cone assembly of a turbine engine is to

A

straighten and collect the exhaust gases into a solid exhaust jet

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22
Q

What are the two functional elements in a centrifugal compressor?

A

impeller and diffuser

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23
Q

What must be done after the fuel control unit has been replaced on an aircraft gas turbine engine?

A

re trim the engine

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24
Q

If, during inspection at engine overhaul, ball or roller bearings are found to have magnetism but otherwise have no defects, they

A

must be degaussed before use

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25
Q

A turbine engine compressor which contains vanes on both sides of the impeller is a

A

double entry centrifugal compressor

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26
Q

What is the first engine instrument indication of a successful start of a turbine engine?

A

rise in exhaust gas temperature

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27
Q

Some engine manufacturers of twin spool gas turbine engines identify turbine discharge pressure in
their maintenance manuals as

A

pt7

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28
Q

Who establishes the recommended operating time between overhauls (TBO) of a turbine engine used in
general aviation?

A

the engine manufacturer

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29
Q

The basic gas turbine engine is divided into two main sections: the cold section and the hot section.
(1) The cold section includes the engine inlet, compressor, and turbine sections.
(2) The hot section includes the combustor, diffuser, and exhaust sections.
Regarding the above statements,

A

neither no. 1 nor no. 2 is true

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30
Q

(1) Welding and straightening of turbine engine rotating airfoils does not require special equipment.
(2) Welding and straightening of turbine engine rotating airfoils is commonly recommended by the
manufacturer.
Regarding the above statements,

A

neither no. 1 nor no. 2 is true

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31
Q

Turbine engine components exposed to high temperatures generally may NOT be marked with
1. layout dye.
2. commercial felt tip marker.
3. wax or grease pencil.
4. chalk.
5. graphite lead pencil.

A

3 and 5

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32
Q

Who establishes mandatory replacement times for critical components of turbine engines?

A

the engine manufacturer

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33
Q

Main bearing oil seals used with turbine engines are usually what type(s)?

A

labyrinth and/or carbon rubbing

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34
Q

How does a dual axial-flow compressor improve the efficiency of a turbojet engine?

A

higher compression ratios can be obtained

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35
Q

Three types of turbine blades are

A

impulse, reaction and impulse reaction

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36
Q

Which statements are true regarding aircraft engine propulsion?
1. An engine driven propeller imparts a relatively small amount of acceleration to a large mass of air.
2. Turbojet and turbofan engines impart a relatively large amount of acceleration to a smaller mass of
air.
3. In modern turboprop engines, nearly 50 percent of the exhaust gas energy is extracted by turbines to
drive the propeller and compressor with the rest providing exhaust thrust.

A

1 and 2

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37
Q

An advantage of the axial-flow compressor is its

A

high peak efficiency

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38
Q

What is one purpose of the stator blades in the compressor section of a turbine engine?

A

control the direction of the airflow

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39
Q

What is the purpose of the diffuser section in a turbine engine?

A

to increase pressure and reduce velocity

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40
Q

Where do stress rupture cracks usually appear on turbine blades?

A

across the leading or trailing edge at a right angle to the edge length

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41
Q

In which type of turbine engine combustion chamber is the case and liner removed and installed as one
unit during routine maintenance?

A

can

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42
Q

The diffuser section of a jet engine is located between

A

the compressor section and the burner section

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43
Q

When the leading edge of a first-stage turbine blade is found to have stress rupture cracks, which of the
following should be suspected?

A

over temperature condition

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44
Q

Turbine blades are generally more susceptible to operating damage than compressor blades because of

A

exposure to high temperature

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45
Q

Which of the following is the ultimate limiting factor of turbine engine operation?

A

turbine inlet temperature

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46
Q

The recurrent ingestion of dust or other fine airborne particulates into a turbine engine can result in

A

erosion damage to the compressor and turbine sections

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47
Q

Which of the following engine variables is the most critical during turbine engine operation?

A

turbine inlet temperature

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48
Q

Reduced blade vibration and improved airflow characteristics in gas turbines are brought about by

A

shrouded turbine rotor blades

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49
Q

Which turbine engine compressor offers the greatest advantages for both starting flexibility and
improved high-altitude performance?

A

split spool, axial flow

50
Q

Jet engine turbine blades removed for detailed inspection must be reinstalled in

A

the same slot

51
Q

An advantage of the centrifugal-flow compressor is its high

A

pressure rise per stage

52
Q

The highest heat-to-metal contact in a jet engine is the

A

turbine inlet guide vanes

53
Q

Which two elements make up the axial-flow compressor assembly?

A

rotor and stator

54
Q

The two types of centrifugal compressor impellers are

A

single entry and double entry

55
Q

Between each row of rotating blades in a turbine engine compressor, there is a row of stationary blades
which act to diffuse the air. These stationary blades are called

A

stators

56
Q

Standard sea level pressure is

A

29.92”hg

57
Q

Using standard atmospheric conditions, the standard sea level temperature is

A

59 degrees F

58
Q

When aircraft turbine blades are subjected to excessive heat stress, what type of failures would you
expect?

A

stress rupture

59
Q

In an axial-flow compressor, one purpose of the stator vanes at the discharge end of the compressor is
to

A

straighten the airflow and eliminate turbulence

60
Q

Hot section inspections for many modern turbine engines are required

A

on a time or cycle basis

61
Q

A purpose of the shrouds on the turbine blades of an axial-flow engine is to

A

reduce vibration

62
Q

In a dual axial-flow compressor, the first stage turbine drives

A

N 2 compressor

63
Q

What should be done initially if a turbine engine catches fire when starting?

A

turn off the fuel continue engine rotation with the starter

64
Q

What is the proper starting sequence for a turbojet engine?

A

starter, ignition, fuel

65
Q

A weak fuel to air mixture along with normal airflow through a turbine engine may result in

A

lean die out

66
Q

What is used in turbine engines to aid in stabilization of compressor airflow during low thrust engine
operation?

A

variable guide vanes and/ or compressor bleed valves

67
Q

In a turbine engine with a dual-spool compressor, the low speed compressor

A

seeks its own operating speed

68
Q

What is the function of the inlet guide vane assembly on an axial-flow compressor?

A

Directs the air into the first stage rotor blades at the proper angle

69
Q

Hot spots on the tail cone of a turbine engine are possible indicators of a malfunctioning fuel nozzle or

A

faulty combustion chamber

70
Q

The stator vanes in an axial-flow compressor

A

convert velocity energy into pressure energy

71
Q

The velocity of subsonic air as it flows through a convergent nozzle

A

increases

72
Q

The velocity of supersonic air as it flows through a divergent nozzle

A

increases

73
Q

The pressure of subsonic air as it flows through a convergent nozzle

A

decreases

74
Q

The pressure of supersonic air as it flows through a divergent nozzle

A

decreases

75
Q

Anti-icing of jet engine air inlets is commonly accomplished by

A

engine bleed air ducted through the critical areas

76
Q

Generally, when starting a turbine engine, the starter should be disengaged

A

after the engine reached self-accelerating speed

77
Q

What is the primary advantage of an axial-flow compressor over a centrifugal compressor?

A

greater pressure ratio

78
Q

The purpose of a bleed valve, located in the beginning stages of the compressor, in an aircraft gas
turbine engine is to

A

vent some of the air overboard to prevent compressor stall

79
Q

What is meant by a double entry centrifugal compressor?

A

a compressor with vanes on both sides of the impeller

80
Q

What is the major function of the turbine assembly in a turbojet engine?

A

supplies the power to turn the compressor

81
Q

Stator blades in the compressor section of an axial-flow turbine engine

A

decrease the air velocity and prevent swirling

82
Q

A gas turbine engine comprises which three main sections?

A

turbine, compressor and combustion

83
Q

What type of turbine blade is most commonly used in aircraft jet engines?

A

impulse reaction

84
Q

What is the primary factor which controls the pressure ratio of an axial-flow compressor?

A

number of stages in compressor

85
Q

The non-rotating axial-flow compressor airfoils in an aircraft gas turbine engine, are called

A

stator vanes

86
Q

(1) In a turbine engine axial-flow compressor, each consecutive pair of rotor and stator blades constitutes a pressure stage.
(2) In a turbine engine axial-flow compressor, the number of rows of stages is determined by the amount of air and total pressure rise required.
Regarding the above statements,

A

both no. 1 and no. 2 are true

87
Q

The air passing through the combustion chamber of a turbine engine is

A

use to support combustion and to cool the engine

88
Q

The stators in the turbine section of a gas turbine engine

A

increase the velocity of the gas flow

89
Q

The compressor stators in a gas turbine engine act as diffusers to

A

decease the velocity of the gas flow

90
Q

The procedure for removing the accumulation of dirt deposits on compressor blades is called

A

field cleaning

91
Q

Which of the following may be used to accomplish internal inspection of an assembled turbine engine?
1. Infrared photography.
2. Ultrasound.
3. A borescope.
4. Fluorescent penetrant and ultraviolet light.

A

3

92
Q

What is the possible cause when a turbine engine indicates no change in power setting parameters, but
oil temperature is high?

A

engine main bearing distress

93
Q

A turbine engine hot section is particularly susceptible to which kind of damage?

A

cracking

94
Q

Dirt particles in the air being introduced into the compressor of a turbine engine will form a coating on
all but which of the following?

A

turbine blades

95
Q

Severe rubbing of turbine engine compressor blades will usually cause

A

galling

96
Q

Which of the following influences the operation of an automatic fuel control unit on a turbojet engine?

A

burner pressure

97
Q

If a turbine engine is unable to reach takeoff EPR before its EGT limit is reached, this is an indication that
the

A

compressor maybe contaminated or damaged

98
Q

The Brayton cycle is known as the constant

A

pressure cycle

99
Q

Continued and/or excessive heat and centrifugal force on turbine engine rotor blades is likely to cause

A

creep

100
Q

If the RPM of an axial-flow compressor remains constant, the angle of attack of the rotor blades can be
changed by

A

changing the velocity of the airflow

101
Q

The compression ratio of an axial-flow compressor is a function of the

A

number of compressor stages

102
Q

Which of the following variables affect the inlet air density of a turbine engine?
1. Speed of the aircraft.
2. Compression ratio.
3. Turbine inlet temperature.
4. Altitude of the aircraft.
5. Ambient temperature.
6. Turbine and compressor efficiency.

A

1,4,5

103
Q

Which of the following factors affect the thermal efficiency of a turbine engine?
1. Turbine inlet temperature.
2. Compression ratio.
3. Ambient temperature.
4. Speed of the aircraft.
5. Turbine and compressor efficiency.
6. Altitude of the aircraft.

A

1,2,5

104
Q

Why do some turbine engines have more than one turbine wheel attached to a single shaft?

A

to extract more power from exhaust gases than a single wheel can absorb

105
Q

The exhaust section of a turbine engine is designed to

A

impart a high exit velocity to the exhaust gases

106
Q

Which of the following types of combustion sections are used in aircraft turbine engines?

A

multiple can, annular and can annular

107
Q

A cool-off period prior to shutdown of a turbine engine is accomplished in order to

A

allow the turbine wheel to cool before the case contracts around it

108
Q

What type igniter plug is used in the low tension ignition system of an aircraft turbofan engine?

A

self ionizing or shunted gap type plug

109
Q

What is meant by a shrouded turbine?

A

the turbine blades are shaped so that their ends form a band or shroud

110
Q

What term is used to describe a permanent and cumulative deformation of the turbine blades of a
turbojet engine?

A

creep

111
Q

What is the purpose of the dump valve used on aircraft gas turbine engines?

A

the fuel is quickly cut off to the nozzles and the manifolds are drained preventing fuel boiling off as
a result of residual engine heat

112
Q

At what stage in a turbine engine are gas pressures the greatest?

A

compressor outlet

113
Q

In what section of a turbojet engine is the jet nozzle located?

A

exhaust

114
Q

1) Accumulation of contaminates in the compressor of a turbojet engine reduces aerodynamic
efficiency of the blades.
(2) Two common methods for removing dirt deposits from turbojet engine compressor blades are a fluid
wash and an abrasive grit blast.
Regarding the above statements,

A

both no.1 and 2 are true

115
Q

Hot spots in the combustion section of a turbojet engine are possible indicators of

A

malfunctioning fuel nozzles

116
Q

Which of the following can cause fan blade shingling in a turbofan engine?
1. Engine over speed.
2. Engine over-temperature.
3. Large, rapid throttle movements.
4. FOD.

A

1,4

117
Q

Compressor stall is caused by

A

a high angle of attack airflow through the first stages of compression

118
Q

A condition known as ‘hot streaking’ in turbine engines is caused by

A

a partially clogged fuel nozzle

119
Q

Compressor field cleaning on turbine engines is performed primarily in order to

A

prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas
path surface

120
Q

Newton’s First Law of Motion, generally termed the Law of Inertia, states:

A

everybody persist in its state of rest, or of motion in a straight line, unless acted upon by some
outside force

Aircraft Maintenance (9 decks)

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