問題一覧
1
Which statement is true regarding jet engines?
At the higher engine speeds, thrust increases rapidly with small increases in RPM.
2
What is the primary advantage of an axial-flow compressor over a centrifugal compressor?
Greater pressure ratio
3
(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,
both No. 1 and No. 2 are true.
4
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
5
The abbreviation Pt7 used in turbine engine terminology means
the total pressure at station No. 7
6
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.
7
The air passing through the combustion chamber of a turbine engine is
used to support combustion and to cool the engine.
8
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.
9
What is the primary factor which controls the pressure ratio of an axial-flow compressor?
Number of stages in compressor
10
What must be done after the fuel control unit has been replaced on an aircraft gas turbine engine?
Retrim the engine.
11
At what point in an axial-flow turbojet engine will the highest gas pressures occur?
At the compressor outlet
12
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.
13
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.
1, 2, and 4
14
(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.
15
Reduced blade vibration and improved airflow characteristics in gas turbines are brought about by
shrouded turbine rotor blades
16
The exhaust section of a turbine engine is designed to
impart a high exit velocity to the exhaust gases.
17
If, during inspection at engine overhaul, ball or roller bearings are found to have magnetism but otherwise have no defects, they
must be degaussed before use.
18
When starting a turbine engine, a hung start is indicated if the engine
fails to reach idle RPM.
19
A condition known as ‘hot streaking’ in turbine engines is caused by
a partially clogged fuel nozzle
20
A turbine engine compressor which contains vanes on both sides of the impeller is a
double entry centrifugal compressor
21
The two types of centrifugal compressor impellers are
single entry and double entry
22
What term is used to describe a permanent and cumulative deformation of the turbine blades of a turbojet engine?
Creep
23
The function of the exhaust cone assembly of a turbine engine is to
straighten and collect the exhaust gases into a solid exhaust jet.
24
Which of the following influences the operation of an automatic fuel control unit on a turbojet engine?
Burner pressure
25
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.
26
The highest heat-to-metal contact in a jet engine is the
turbine inlet guide vanes
27
A weak fuel to air mixture along with normal airflow through a turbine engine may result in
a lean die-out
28
What is the purpose of the diffuser section in a turbine engine?
To increase pressure and reduce velocity.
29
The diffuser section of a jet engine is located between
the compressor section and the burner section
30
The compressor stators in a gas turbine engine act as diffusers to
decrease the velocity of the gas flow
31
The non-rotating axial-flow compressor airfoils in an aircraft gas turbine engine, are called
stator vanes
32
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 and 4
33
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
34
The pressure of subsonic air as it flows through a convergent nozzle
decreases
35
What is the major function of the turbine assembly in a turbojet engine?
Supplies the power to turn the compressor.
36
Why do some turbine engines have more than one turbine wheel attached to a single shaft?
To extract more power from the exhaust gases than a single wheel can absorb.
37
Severe rubbing of turbine engine compressor blades will usually cause
Galling
38
What type of turbine blade is most commonly used in aircraft jet engines?
Impulse-reaction
39
What is the profile of a turbine engine compressor blade?
A reduced blade tip thickness
40
Turbine blades are generally more susceptible to operating damage than compressor blades because of
exposure to high temperatures.
41
Which of the following engine variables is the most critical during turbine engine operation?
Turbine inlet temperature
42
At what stage in a turbine engine are gas pressures the greatest?
Compressor outlet
43
Anti-icing of jet engine air inlets is commonly accomplished by
engine bleed air ducted through the critical areas.
44
The turbine section of a jet engine
drives the compressor section.
45
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.
46
Stator blades in the compressor section of an axial-flow turbine engine
decrease the air velocity and prevent swirling.
47
In a dual axial-flow compressor, the first stage turbine drives
N(2) compressor
48
The fan rotational speed of a dual axial compressor forward fan engine is the same as the
low-pressure compressor
49
The Brayton cycle is known as the constant
pressure cycle
50
What is one purpose of the stator blades in the compressor section of a turbine engine?
Control the direction of the airflow.
51
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
52
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
53
An advantage of the centrifugal-flow compressor is its high
pressure rise per stage
54
A turbine engine hot section is particularly susceptible to which kind of damage?
Cracking
55
What are the two basic elements of the turbine section in a turbine engine?
Stator and rotor
56
When aircraft turbine blades are subjected to excessive heat stress, what type of failures would you expect?
Stress rupture
57
Which of the following is the ultimate limiting factor of turbine engine operation?
Turbine inlet temperature
58
In the dual axial-flow or twin spoil compressor system, the first stage turbine drives the
N(2) compressor
59
Standard sea level pressure is
29.92” Hg