問題一覧
1
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.
3 and 5.
2
Jet engine turbine blades removed for detailed inspection must be reinstalled in
the same slot
3
The blending of blades and vanes in a turbine engine
should be performed parallel to the length of the blade using smooth contours to minimize stress points.
4
One function of the nozzle diaphragm in a turbine engine is to
Direct the flow of gases to strike the turbine blades at the desired angle.
5
Some high-volume turboprop and turbojet engines are equipped with two-spool or split compressors. When these engines are operated at high altitudes, the
low-pressure rotor will increase in speed as the compressor load decreases in the lower density air.
6
A gas turbine engine comprises which three main sections?
Turbine, compressor, and combustion.
7
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
increase and the velocity to decrease.
8
The compression ratio of an axial-flow compressor is a function of the
number of compressor stages.
9
The compression ratio of an axial-flow compressor is a function of the
number of compressor stages.
10
If a turbine engine is unable to reach takeoff EPR before its EGT limit is reached, this is an indication that the
compressor may be contaminated or damaged.
11
Which turbine engine compressor offers the greatest advantages for both starting flexibility and improved high- altitude performance?
Split-spool, axial-flow.
12
Who establishes the recommended operating time between overhauls (TBO) of a turbine engine used in general aviation?
The engine manufacturer.
13
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.
1,2
14
Continued and/or excessive heat and centrifugal force on turbine engine rotor blades is likely to cause
creep
15
The procedure for removing the accumulation of dirt deposits on compressor blades is called
field cleaning.
16
The stators in the turbine section of a gas turbine engine
increase the velocity of the gas flow.
17
What is the first engine instrument indication of a successful start of a turbine engine?
A rise in the exhaust gas temperature.
18
In what section of a turbojet engine is the jet nozzle located?
Exhaust
19
The recurrent ingestion of dust or other fine airborne particulates into a turbine engine can result in
erosion damage to the compressor and turbine sections.
20
What turbine engine section provides for proper mixing of the fuel and air?
Combustion section.
21
Which two elements make up the axial-flow compressor assembly?
Rotor and stator.
22
Three types of turbine blades are
impulse, reaction, and impulse-reaction.
23
The purpose of a bleed valve, located in the beginning stages of the compressor, in an aircraft gas turbine engine is to
vent some of the air overboard to prevent a compressor stall.
24
An advantage of the axial-flow compressor is its
high peak efficiency.
25
Who establishes mandatory replacement times for critical components of turbine engines?
The engine manufacturer.
26
What type igniter plug is used in the low tension ignition system of an aircraft turbofan engine?
Self-ionizing or shunted-gap type plug.
27
The velocity of subsonic air as it flows through a convergent nozzle
increases
28
When starting a turbine engine,
a. a hot start is indicated if the exhaust gas temperature exceeds specified limits.
29
Hot section inspections for many modern turbine engines are required
on a time or cycle basis.
30
What are the two functional elements in a centrifugal compressor?
Impeller and diffuser.
31
Hot spots in the combustion section of a turbojet engine are possible indicators of
malfunctioning fuel nozzles.
32
How does a dual axial-flow compressor improve the efficiency of a turbojet engine?
Higher compression ratios can be obtained.
33
(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 thove statements,
both No. 1 and No. 2 are true.
34
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,
neither No. 1 nor No. 2 is true.
35
If the RPM of an axial-flow compressor remains constant, the angle of attack of the rotor blades can be changed by
changing the velocity of the airflow.
36
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.
1,2,5
37
The velocity of supersonic air as it flows through a divergent nozzle
increases
38
Where do stress rupture cracks usually appear on turbine blades?
Across the leading or trailing edge at a right angle to the edge length.
39
In a gas turbine engine, combustion occurs at a constant
pressure
40
What is meant by a double entry centrifugal compressor?
A compressor with vanes on both sides of the impeller.
41
The pressure of supersonic air as it flows through a divergent nozzle
decreases
42
What is the proper starting sequence for a turbojet engine?
Starter, ignition, fuel.
43
Which of the following types of combustion sections are used in aircraft turbine engines?
Multiple-can, annular, and can-annular.
44
Generally, when starting a turbine engine, the starter should be disengaged
after the engine has reached self-accelerating speed.
45
In which type of turbine engine combustion chamber is the case and liner removed and installed as one unit during routine maintenance?
Can
46
What is the function of the stator vane assembly at the discharge end of a typical axial-flow compressor?
To straighten airflow to eliminate turbulence.
47
Some engine manufacturers of twin spool gas turbine engines identify turbine discharge pressure in their maintenance manuals as
Pt7
48
Compressor field cleaning on turbine engines is performed primarily in order to
prevent engine performance degradation, increased fuel costs, and damage or corrosion to gas path surfaces.
49
Using standard atmospheric conditions, the standard sea level temperature is
59°F
50
Main bearing oil seals used with turbine engines are usually what type(s)?
Labyrinth and/or carbon rubbing.
51
Hot spots on the tail cone of a turbine engine are possible indicators of a malfunctioning fuel nozzle or
a faulty combustion chamber.
52
What should be done initially if a turbine engine catches fire when starting?
Turn off the fuel and continue engine rotation with the starter.
53
What is the possible cause when a turbine engine indicates no change in power setting parameters, but oil temperature is high?
Engine main bearing distress.
54
The stator vanes in an axial-flow compressor
convert velocity energy into pressure energy.
55
Turbine nozzle diaphragms located on the upstream side of each turbine wheel are used in the gas turbine engine to
increase the velocity of the heated gases flowing past this point.
56
A cool-off period prior to shutdown of a turbine engine is accomplished in order to
allow the turbine wheel to cool before the case contracts around it.
57
What is meant by a shrouded turbine?
The turbine blades are shaped so that their ends form a band or shroud.
58
What is used in turbine engines to aid in stabilization of compressor airflow during low thrust engine operation?
Variable guide vanes and/or compressor bleed valves.
59
In a turbine engine with a dual-spool compressor, the low speed compressor
seeks its own best operating speed.
60
Where is the highest gas pressure in a turbojet engine?
In the entrance of the burner section.
61
A purpose of the shrouds on the turbine blades of an axial- flow engine is to
reduce vibration.
62
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.
1,4
63
What term is used to describe a permanent and cumulative deformation of the turbine blades of a turbojet engine?
Creep
64
What is the primary advantage of an axial-flow compressor over a centrifugal compressor?
Greater pressure ratio.
65
In a dual axial-flow compressor, the first stage turbine drives
N(2) compressor.
66
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
stators
67
The non-rotating axial-flow compressor airfoils in an aircraft gas turbine engine, are called
stator vanes.
68
Standard sea level pressure is
29.92” Hg.
69
Severe rubbing of turbine engine compressor blades will usually cause
galling
70
What is the function of the inlet guide vane assembly on an axial-flow compressor?
Directs the air into the first stage rotor blades at the proper angle.
71
Reduced blade vibration and improved airflow characteristics in gas turbines are brought about by
shrouded turbine rotor blades.
72
Anti-icing of jet engine air inlets is commonly accomplished by
engine bleed air ducted through the critical areas.
73
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?
Turbine blades.
74
A weak fuel to air mixture along with normal airflow through a turbine engine may result in
a lean die-out.
75
Newton’s Law of Motion, generally termed the “Law of Momentum,” states:
Acceleration is produced when a force acts on a mass. The greater the mass, the greater the amount of force needed.
76
In an axial-flow compressor, one purpose of the stator vanes at the discharge end of the compressor is to
straighten the airflow and eliminate turbulence.
77
What is the primary factor which controls the pressure ratio of an axial-flow compressor?
Number of stages in compressor.
78
The function of the exhaust cone assembly of a turbine engine is to
straighten and collect the exhaust gases into a solid exhaust jet.
79
What is the profile of a turbine engine compressor blade?
A reduced blade tip thickness.
80
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.
1,4,5
81
A turbine engine hot section is particularly susceptible to which kind of damage?
Cracking
82
What type of turbine blade is most commonly used in aircraft jet engines?
Impulse-reaction.
83
The two types of centrifugal compressor impellers are
single entry and double entry.
84
Newton’s First Law of Motion, generally termed the Law of Inertia, states:
Everybody persists in its state of rest, or of motion in a straight line, unless acted upon by some outside force.
85
The turbine section of a jet engine
drives the compressor section.
86
The fan rotational speed of a dual axial compressor forward fan engine is the same as the
low-pressure compressor.
87
The Brayton cycle is known as the constant
pressure cycle.
88
What is the purpose of the dump valve used on aircraft gas turbine engines?
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.
89
When starting a turbine engine, a hung start is indicated if the engine
fails to reach idle RPM.
90
The abbreviation Pt7 used in turbine engine terminology means
the total pressure at station No. 7.
91
When the leading edge of a first-stage turbine blade is found to have stress rupture cracks, which of the following should be suspected?
Over temperature condition.
92
What are the two basic elements of the turbine section in a turbine engine?
Stator and rotor.
93
The highest heat-to-metal contact in a jet engine is the
turbine inlet guide vanes.
94
When aircraft turbine blades are subjected to excessive heat stress, what type of failures would you expect?
Stress rupture.
95
The pressure of subsonic air as it flows through a convergent nozzle
decreases
96
What is the purpose of the diffuser section in a turbine engine?
To increase pressure and reduce velocity.
97
Which of the following is the ultimate limiting factor of turbine engine operation?
Turbine inlet temperature.
98
In the dual axial-flow or twin spoil compressor system, the first stage turbine drives the
N(2) compressor.
99
Which of the following engine variables is the most critical during turbine engine operation?
Turbine inlet temperature.
100
(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,
neither No. 1 nor No. 2 is true.