BGT Flashcards
1
Q
You would expect to find the highest gas velocity in a turbojet engine
A
At the end of the exhaust nozzle
2
Q
The purpose of a diffuser in a gas turbine engine is to:
A
Lower velocity and raise pressure
3
Q
The correct statement regarding the variations of MSL full throttle thrust of a jet engine is:
A
Thrust decreases as air temperature increases
4
Q
You would expect to find the highest gas pressure in a turbojet engine:
A
In the diffuser
5
Q
You would expect to find the highest gas temperature in a turbojet engine:
A
In the combustion chamber
6
Q
The engine core of a turbofan refers to:
A
The compressor, combustion chambers, turbines and exhaust
7
Q
The maximum thrust output of a turbojet engine will increase with:
A
A decrease in ambient air temperature
8
Q
The effect an increase in altitude alone will have on the Low Pressure compressor of a gas turbine engine if constant thrust is maintained is:
A
RPM will decrease
9
Q
A pure turbojet engine in comparison to a turbofan engine has:
A
No bypass air
10
Q
Subsonic gas flow decreases in velocity and increases in pressure when flowing through:
A
A divergent duct
11
Q
Ram effect
A
Raised the thrust output of a jet engine as aircraft speed increases
12
Q
In passing through the turbine section of a pure turbojet engine:
A
Gas pressure reduces, velocity increases and temperature decreases
*think of a turbine as convergent
13
Q
Tertiary creep in a turbine blade of a gas turbine engine means:
A
Blade creep to the point where it would be detrimental to continue to run the engine
14
Q
Gas turbine engine compressor stall may be caused by:
A
Unstable airflow through the compressor
15
Q
The maximum gas pressure in a gas turbine is obtained:
A
At the compressor exit
16
Q
For a given RPM, thrust output from a gas turbine engine will be greatest:
A
At MSL under ISA conditions
17
Q
If a compressor blade stall occurs in a gas turbine engine:
A
The smooth flow of air over the blading breaks away and causes an interruption of airflow through the engine
18
Q
The purpose of variable inlet guide vanes in a gas turbine engine is to:
A
Prevent compressor blade stall during operation off design RPM
19
Q
Turbojet aircraft range increases as altitude increases toward the optimum FL because at high altitude:
A
The engine can operate at design RPM to maintain an efficient wing angle of attack
20
Q
The use of bleed air from a gas turbine engine compressor for anti-icing equipment will result in:
A
An increase in the gas temperature, reduced thrust and an increase in SFC
21
Q
Maximum gas pressure in a gas turbine engine is found:
A
Between the final compressor stage and inlet to the combustion chamber
22
Q
The main reason for a limit on the maximum gas temperature in a gas turbine engine is:
A
To prevent overheating of the turbine
23
Q
Burning fuel in the combustion chambers of a gas turbine engine is necessary to:
A
Increase the volume and velocity of the gases
24
Q
On leaving the compressor in a gas turbine engine, the air passes through:
A
Divergent ducts which lower the velocity and raise the pressure of the air
25
When an aircraft is parked overnight, to reduce fuel tank condensation you would:
Keep the tanks as full as possible
26
In a free turbine turboprop engine, the propeller is driven by:
Only the rear LP turbine(s)
27
The action which should be taken if a gas turbine compressor begins to stall during engine acceleration on start up is:
Shut off the fuel supply and maintain starter motor rotation
28
The term SFC means
Units of fuel used per unit of thrust per hour
29
Some turbojet engine turbine blades shrouded at the tips to:
Prevent gas leaking past blade tips, increase rigidity and reduce vibration
30
The fuel flow in a jet engine is increased. Thrust increases because exhaust gas:
Velocity increases
31
The times the surge bleed valve is open and closed during normal gas turbine engine operation are:
Open from idling to nearly design RPM then closed up to max RPM
32
The propulsive efficiency of a turboprop decreases with an increase in speed because:
Of compressibility effects on the blades
33
The gas turbine cycle (Brayton) is called an open or continuous cycle because:
All events are occurring at the same time
34
A modest increase in speed in a slow flying jet aircraft leads to a small initial decrease in maximum thrust available because:
The difference between exhaust and intake velocities is reduced
35
Pressure through the combustion chambers in a gas turbine engine:
Is constant or falls slightly
36
To prevent melting of the turbine wheels, the hot gases from the combustion chambers in a gas turbine engine are cooled by:
Air
37
Engine Pressure Ratio (EPR) is the ratio of:
Engine compressor inlet pressure to jet pipe pressure
38
When climbing in a jet engine aircraft, the engine parameter which would stay constant if the thrust lever setting remained unchanged is:
RPM
39
Thrust is produced in a jet engine by:
The force required to accelerate a mass of air through the engine
40
Fuel boost pumps in a jet aircraft fuel system are usually located in:
The fuel tanks
41
Most modern turbofan engines have 2 or more spools (shafts) because:
This allows compressors to run closer to their ideal RPM
42
An ideal jet engine air intake delivers air to the compressor with:
No turbulence and pressure higher than ambient
43
Air that is bypassed in a turbofan engine:
Does not go through the compressor
44
One compressor bleed outlet is for cabin pressurisation and air conditioning. Another is used to:
Prevent compressor stall and surge when operating off design RPM
45
The row of stator blades after each row of rotating compressor blades is designed to:
Convert kinetic energy to pressure energy
46
The turbofan is more efficient than the turbojet because:
It accelerates a relatively large mass of air to a low velocity
47
Apart from bigger stronger fan blades, a turbofan enjoys better FOD protection than a pure turbojet because:
Most of the air bypasses the engine
48
A turbofan is not as efficient as a turboprop at low speeds. This is because the turbofan has:
A lower air mass accelerated to a higher velocity
49
A turboprop cannot operate at the high speeds of a turbofan because the turboprop has:
Shockwaves at the prop tips at high Mach number
50
A free turbine turboprop uses a smaller starter motor than other turboprops because:
Only the engine core is rotated for starting
51
One way to increase the performance of a jet engine is to:
Increase the engine operating temperatures
52
Of a turbofans total air intake, 20% passes through the core. This bypass ratio is nearest to:
4:1
*20% through the engine, 80% bypasses the engine
20/80 = 1/4
But because it’s asking about bypass first = 4:1
53
Turboprops are usually designed for what type of flying:
Low speed, short routes
54
An aircraft may need to dump fuel, to ensure that the total fuel supple is not dumped:
Use of standpipes in the fuel dumping system
55
A turbofan produces less thrust at takeoff than a smaller size turboprop because
Turboprop is very efficient at modestly accelerating a large mass of air
56
With a constant speed turboprop engine, power output is controlled by fuel flow. The pilot controls this by:
Control of the fuel flow control unit
57
The primary engine power gauge of a turboprop is the:
Torque gauge
58
One reason why jet aircraft use kerosene and not AVGAS is that kerosene has:
A higher flashpoint
*And high calorific value
Low volatility
Lubricant properties
59
An APU of a 767 may be operated:
Whenever it is required
60
The purpose of the fuel system filter bypass in a gas turbine engine is:
To ensure fuel flow even though the filter is blocked
61
If a turbojet thrust reverse unlocked light comes on during flight:
The situation is potentially critical, show down the engine if yaw, loss of airspeed or buffet is detected
62
The main reason for stating an upper limit to fuel temperature is:
To ensure vapour lock (vapour release) does not occur
63
An APU auto-shutdown will not be caused by:
Underspeed
*Will auto-shutdown for overspeed, low oil pressure and fire
64
The document in which you would find the optional fuels approved for a particular aircraft is:
In the aircraft flight manual
65
The additives normally found in F35 jet fuel (Jet A1) used in Australia is:
None
66
The engine instrument which would not be found on a turbofan aircraft is:
Torque
(Because N1=tq)
67
An APU does not directly provide:
Hydraulic pressure
68
The inflight problem a turbine engine with low flight idling RPM may have is:
Flame out on descent
69
A desirable quality of jet fuel is:
Lubricant properties
*And high flash point
High calorific value
Low voltality
70
Air turbine starters for gas turbine engines normally:
Cannot be used if the APU or another engine or compressed air source is not available
71
The safeguards used to prevent inadvertent engine thrust reverser deployment in flight are:
An auto stow mechanism and mechanical and electrical interlocks and isolation valves which prevent full reverse thrust unless the thrust levers are at idle and the reversers are fully deployed
72
In a gas turbine engine with a free power turbine:
The free power turbine shaft is independent of the other engine spools
73
The advantages of an axial flow compressor compared to a centrifugal flow compressor of the same frontal area in a gas turbine engine are:
Higher pressure ratios and greater mass airflow
74
A torque meter in a turboprop aircraft is required for the operation of the:
Autofeather system
75
A transport jet aircraft is filled to max. Fuel by volume (full tanks) with kerosene of a lower specific gravity. Compared to using kerosene with a higher specific gravity, the max range of the aircraft with the low SG will be:
Reduced
76
Concerning the connection of turbines and compressors in a gas turbine engine:
The LP compressor is connected to the LP turbine
77
Regarding the measurement of temperature in a gas turbine engine
JPT measures jet pipe gas temperature
*EGT = exhaust gas
ITT = inter turbine
TOT = turbine outlet
78
With regard to thermal ice protection systems using engine bleed air:
When used on an engine intake, thermal ice protection should be regarded as anti-icing
79
One of the limitations of air starting system on a gas turbine engine is:
The requirement for an APU, another engine or a ground unit to provide compressed air
80
The purpose of a propeller brake on a turbo prop is:
To prevent the propeller windmilling when the engine is shut down and to allow the engine to be run at idle power on the ground without turning the propeller
81
The function of a safety couple in a turboprop engine is:
To decouple the engine from the gearbox in the event of a prop overspeed
82
The function of a negative torque system in a turboprop us to:
Increase the propeller blade angle to prevent the turbine from being driven by the propeller
83
The EPR gauge in a jet aircraft measures:
The pressure ratio between the exhaust air and intake (ambient) air
84
The N1 gauge in a turbofan engine indicates:
Fan RPM
85
As a turbofan powered aircraft climbs through the tropopause, thrust will:
Reduce at a greater rate compared to below the tropopause
86
The use of bleed air from a gas turbine engine for various services will result in most loss of performance during:
Take off and climb
87
In a turboprop installation, the term power plant refers to:
The gas turbine engine, gearbox and propeller
88
The reverse thrust system on a turbojet aircraft has interlocks to prevent:
Full reverse thrust until the reversers are in the full reverse position
89
With reference to a gas turbine engine:
TGT is the temperature of the gas between the turbine stages
90
A 727 is maintaining a constant flight level and the TAS is increased from 180kts to 460kts. Thrust available at maximum thrust will:
Decrease then increase
91
The fuel flow transmitter in the fuel system of a large jet transport category aircraft is located:
At the outlet from the fuel control unit
92
Turbojet engine compressor blade angle of attack is primarily determined by:
Engine RPM and TAS
93
As the thrust levers of a turbojet engined aircraft are advance for takeoff:
Fuel flow increases causing a higher EGT and increased RPM
94
The pressure rise in the centrifugal compressor of a gas turbine engine occurs in:
Both the impeller and the diffuser
95
Gas turbine engine compressor blades do not usually require thermal anti ice protection because:
The centrifugal action of the rotor blades prevents ice accretions
96
On a wet day takeoff in a jet engined aircraft, the ignitor plugs may be selected to continuous ignition. In this case the characteristics of the spark will be:
Low value joules at a high voltage to preserve the ignitor plugs and the ignition unit
*High and voltage both have ‘g’ in them so they go together
97
With an air turbine starter system on a large modern jet engine, the starter is disengaged:
Automatically by the starter clutch at a predetermined RPM
98
The primary purpose of the APU in large jet transport category aircraft is for:
Electrical and pneumatic supply on the ground
99
The design feature which is not an advantage of the annular combustion chamber design in a modern gas turbine engine compared to other multi chamber designs is:
Greater structural integrity
*Advantages are: improved combustion efficiency
Less cooling air required
Elimination of flame propagation problems within chambers
Reduced wight and cost
Compact
100
A particular turbine fuel has a specific gravity of 0.8 at a given temperature. A temperature rise of 20o will result in a calorific value (energy) for the fuel which is:
The same energy value as for the original temperatures per KG of fuel
101
The function of the torque meter in a turboprop powered aircraft is to:
Monitor shaft output power
102
A probable result of a hot start in a gas turbine engine is:
Torching of the exhaust section
103
Regarding the measurement of temperature in a gas turbine engine:
JPT measures jet pipe temperature
*EGT is exhaust gas temp
ITT is inter turbine temp
104
The ram air effect on a turbojet engine results in a conversion of:
Kinetic energy in the airstream into pressure
105
Boost pumps in the fuel system of a large jet transport category aircraft are generally:
Gear type or impeller type
106
Regarding the functioning of the reverser thrust system on a high bypass turbo fan engine:
Blocker doors are used to divert the cold stream
107
The takeoff run of a turbofan powered aircraft will be increased by:
Increased altitude
*lower altitude means higher density so shorter takeoff run
108
The use of bleed air on takeoff in a large turbojet engined aircraft will result in:
Higher EGT
109
The effect of a change in temperature on the specific gravity of AVTUR is:
SG decreases as temperature increases
*Specific gravity is how heavy the fuel is
When temp gets higher, fuel gets lighter
110
The ideal air:fuel ratio for a turbine engine is:
15:1
111
The section of the APU which supplies compressed air to start the main engines on a large jet transport aircraft is:
The compressor
112
The purpose of the air shroud on an atomised type (duplex) fuel spray nozzle in the combustion chamber of a gas turbine engine is:
To reduce carbon deposits around the nozzle tip and cool the nozzle
113
The function of variable inlet guide vanes in a gas turbine engine is:
To prevent compressor blade stall when the engine is operating at low RPM
114
The gas turbine engine component which acts to straighten the airflow before exiting the engine is:
The rear turbine exhaust cone support struts in the jet pipe
115
Turbofans and turbojets are preferred over turboprops for speeds over about 350kts because:
Turboprops have reduced propulsive efficiency at high speeds
116
Reverse thrust on a turbofan or turbojet is not as effective as forwards thrust because:
The angle of the reverse thrust is not directly opposing the aircraft motion
117
The most common method of ice protection used on the propellers of a turboprop aircraft is:
Electrical
*Think of king air - check electrical amps in run ups so it’s electrical
118
The following statements correctly lists the differences between kerosene and wide cut turbine aviation turbine fuel:
Kerosene has a lower volatility than wide cut fuel
*Kerosene is Jet A
*Wide cut is Jet B
*Volatility is how easily it evaporates so if it’s got a low volatility then it doesn’t evaporate easily
119
The most common type of starter motor found on large modern jet transport aircraft turbine engines is:
Air turbine starters
120
The effect on the maximum static thrust output of a turbojet engine at MSL with changes in ambient temperature and pressure is:
Static thrust decreases with an increase in temperature and decreased pressure
121
The effect on the maximum static thrust output of a turbojet engine at MSL with changes in ambient temperature and pressure is:
Static thrust decreases with an increase in temperature and decreased pressure
122
The function of bleed valves in the compressor of a gas turbine engine is:
To increase the mass airflow over the early compressor stages at low engine RPM
123
The changes in the gas flow within the combustion chamber of a gas turbine engine are:
Volume increases, temperature increases, pressure decreases or remains constant
124
Air in the combustion chamber of a gas turbine engine is slowed to:
Reduce possibility of a flame out
125
Turbine fuel requires:
High calorific value
*Desirable - high flashpoint, low volatility
126
A particular turbofan engine has 3 shafts. N1 refers to:
The slowest shaft
127
An advantage of the centrifugal flow compressor over the axial flow compressor is:
It’s cheaper and more robust
*Axial is more efficient
128
A symptom of a hung start with a gas turbine engine is:
No rise in RPM
129
Operating a jet engine at design RMP will give the:
Minimum SFC
130
Jet engine design RPM is:
Slightly less than maximum RPM
*92-98%
131
With regard to transport category aircraft fuel systems, the true statement is:
A. Fuel gauges provide the only method of accurately determining fuel on board before commencing a flight
B. Measurement of fuel quantity on board may only be conducted on a level surface
C. Fuel on board may be determined by use of readings from dipsticks combined with tables and a sight gauge to correct for uneven terrain
D. Fuel used meters are the only reliable method of accurately determining fuel on board before commencing a flight
Fuel on board may be determined by use of readings from dipsticks combined with tables and a sight gauge to correct for uneven terrain
132
The purpose of standpipes serve in an aircraft fuel system is:
They prevent unintentional dumping of the entire fuel tank contents
133
The ideal air:fuel mixture ratio for kerosene is:
15:1
134
The component of a gas turbine engine which directs the airflow into the compressor is:
The inlet guide vanes
135
The function of interconnectors between multiple combustion chambers in a gas turbine engine is:
Equalise operating pressure and allow combustion propagation between chambers
