BGT Revision Questions

Question 1

The correct statement regarding the variations of MSL full throttle thrust of a jet engine is -

A. Thrust increases as air temp increases
B. Thrust decreases as air temp increases
C. Thrust increases as humidity increases
D. Thrust increases as air pressure decreases

Answer 1

B. Thrust decreases as air temp increases

Question 2

The ‘Engine Core’ of a turbofan refers to -

A. the fan
B. the compressor, combustion chamber, turbine and exhaust
C. the N1 spool
D. The accessory drive shaft

Answer 2

B. the compressor, combustion chamber, turbine and exhaust

Question 3

If constant thrust is maintained with an increase in altitude, the LP compressor -

A. will stall more readily
B. Discharge pressure will increase
C. RPM will increase
D. RPM will decrease

Answer 3

C. RPM will increase

Question 4

Ram effect -

A. has a negligible effect on the efficiency of a jet engine as aircraft speed varies
B. lowers the efficiency of a jet engine as aircraft speed increases
C. raises thrust output of a jet engine as aircraft speed increases
D. cools the air as it enters the engine intake

Answer 4

C. raises thrust output of a jet engine as aircraft speed increases

Question 5

In passing through the turbine section of a pure turbojet engine

A. Gas pressure, velocity and temp all decrease
B. gas pressure and temp increase, velocity decreases
C. gas pressure remains constant and temp decreases
D. gas pressure reduces, velocity increases and temp decreases

Answer 5

D. gas pressure reduces, velocity increases and temp decreases

Question 6

A modest increase in speed in a slow flying jet aircraft leads to a small initial decrease in thrust available because -

A. of intake choking
B. combustion chamber back pressure increasing
C. Ram pressure decreasing
D. the difference between exhaust and intake velocities is reduced

Answer 6

D. the difference between exhaust and intake velocities is reduced

Question 7

EPR is the ratio of -

A. engine compressor inlet pressure to propelling nozzle pressure
B. engine compressor outlet pressure to jet pipe pressure
C. engine compressor discharge pressure to turbine discharge pressure
D. jet pipe pressure engine to compressor inlet pressure

Answer 7

D. jet pipe pressure engine to compressor inlet pressure

Question 8

When climbing in a jet engine aircraft, the engine parameter which would stay constant if the thrust lever setting remained unchanged -

A. RPM
B. EPR
C. EGT
D. TRQ

Answer 8

A. RPM

Question 9

Modern turbofan engine have 2 or more spools (shafts) because -

A. this allows the compressors to run closer to their design RPM
B. manufacturing is simpler and cheaper
C. maintenance is simplified
D. shaft strength is increased

Answer 9

A. this allows the compressors to run closer to their design RPM

Question 10

An ideal jet engine air intake delivers air to the compressor with -

A. no turbulence and pressure lower than ambient
B. no turbulence and temperature higher than ambient
C. No turbulence and velocity higher than ambient
D. No turbulence and pressure higher than ambient

Answer 10

D. No turbulence and pressure higher than ambient

Question 11

The turbofan is more efficient than the turbojet because -

A. it accelerates a relatively large mass of air to a relatively low velocity
B. it accelerates a relatively small mass of air to a relatively high velocity
C. it accelerates a relatively small mass of air to a relatively low velocity
D. it accelerates a relatively large mass of air to a relatively high velocity

Answer 11

A. it accelerates a relatively large mass of air to a relatively low velocity

Question 12

Turbofans are not as efficient as turbo props at low speeds. This is because a turbofan has -

A. A lower air mass accelerated to a lower velocity
B. A higher air mass accelerated to a higher velocity
C. A lower air mass accelerated to a higher velocity
D. A higher air mass accelerated to a lower velocity

Answer 12

C. A lower air mass accelerated to a higher velocity

Question 13

One way to increase the performance of a jet engine would be to -

A. introduce air into the engine at lower speed
B. increase the engine operating temperature
C. alter the angle of the nozzle guide vanes
D. reduce engine operating RPM

Answer 13

B. increase the engine operating temperature

Question 14

Of a turbofans total air intake, 20% passes through the core. This bypass ratio is nearest to

A. 4:1
B 5:1
C 1:4
D 1:5

Answer 14

A. 4:1

Question 15

The main reason for stating an upper limit to fuel temperature is -

A. to allow the greatest temperature rise through the engine
B. to ensure the fuel lubricant properties are maintained
C. to stop chemical breakdown of the fuel
D. to ensure vapour release (vapour lock) does not occur

Answer 15

D. to ensure vapour release (vapour lock) does not occur

Question 16

In a gas turbine engine with a free power turbine -

A. the free power turbine shaft is independent of the other engine spools
B. the free power turbine drives the compressor
C. a free power turbine wheel is independent of all other turbine wheels
D. the free power turbine is driven by the compressor

Answer 16

A. the free power turbine shaft is independent of the other engine spools

Question 17

Compared to using fuel with a higher SG, the max range of an aircraft with low SG fuel will be -

A. reduced
B. increased
C. unaffected

Answer 17

A. reduced

Question 18

Concerning the connection of turbines and compressors in a gas turbine engine -

A. the LP compressor is connected to the HP compressor
B. the LP compressor is connected to the HP turbine
C. The LP compressor is connected to the LP turbine
D. The HP compressor is connected to the LP turbine

Answer 18

C. The LP compressor is connected to the LP turbine

Question 19

In a turbo prop installation, the term ‘power plant’ refers to -

A. the compressor, combustion chamber and the turbine
B. the gas turbine, gearbox and propellor
C. the gas turbine and gearbox
D. the propellor and gearbox

Answer 19

B. the gas turbine, gearbox and propellor

Question 20

On a wet takeoff, the igniter plugs may be selected to continuous ignition. In this case the characteristics of the spark will be -

A. high value (joules) at low voltage to prevent overheating of the nozzle guide vanes
B. low value (joules) at high voltage to preserve the igniter plugs and ignition unit
C. high value (joules) at high voltage to ensure a fast relight in the event of a flame out
D. low value (joules) at low voltage to conserve battery power

Answer 20

B. low value (joules) at high voltage to preserve the igniter plugs and ignition unit

Question 21

A design feature which is not an advantage of an annular (modern) combustion chamber is -

A. improved combustion frequency
B. less cooling air required
C. elimination of flame propagation
D. reduced weight and cost
E. compact
F. greater structural integrity

Answer 21

F. greater structural integrity

Question 22

A fuel has a SG of 0.80 at a given temp. A rise of 20C will result in a calorific (energy) value for the fuel which is -

A. the same energy value per litre of fuel
B. the same energy value per kg of fuel
C. less energy per kg of fuel
D. more energy per kg of fuel
E. more energy per litre of fuel

Answer 22

B. the same energy value per kg of fuel

Question 23

The function of a torque meter is to -

A. brake the propellor
B. feather the propellor
C. lock the propellor at the fine pitch lock
D. monitor shaft output power

Answer 23

D. monitor shaft output power

Question 24

A probable result of a hot start is -

A. stable turbine temps
B. torching of the exhaust section
C. Excessive compressor temps
D. excessive turbine RPM

Answer 24

B. torching of the exhaust section

Question 25

The following statements correctly list the differences between kerosene and wide cut fuel -

A. kerosene has a lower flashpoint than wide cut fuel
B. kerosene has a lower boiling point than wide cut fuel
C. kerosene has a lower volatility than wide cut fuel

Answer 25

C. kerosene has a lower volatility than wide cut fuel

Question 26

The function of bleed valves in the compressor of a gas turbine engine is -

A. to increase the mass airflow over the early compressor stages at low RPM
B. to increase the mass airflow over the rear compressor stages at low engine RPM
C. to increase the mass airflow over the early compressor stages at high engine RPM
D. to increase the mass airflow over the rear compressor stages at high engine RPM

Answer 26

A. to increase the mass airflow over the early compressor stages at low RPM

Question 27

The changes in the gas flow within the combustion chamber are -

A. volume increases, temperature increases, pressure decreases or remains constant
B. velocity decreases, temperature decreases, pressure increases or remains constant
C. volume decreases, temperature increases, pressure decreases
D. velocity decreases, temperature and pressure increase

Answer 27

A. volume increases, temperature increases, pressure decreases or remains constant

Question 28

The function of interconnectors between multiple combustion chambers is to -

A. equalise operating pressure and allow combustion propagation between chambers
B. equalise operating temperature and allow combustion propagation between chambers
C. equalise mass flow velocity and prevent flame propagation between chambers
D. equalise mass flow density and allow flame propagation between chambers

Answer 28

A. equalise operating pressure and allow combustion propagation between chambers

Question 29

Compared to a high bypass turbofan, a pure turbojet engine has -

A. More thrust at the same mass flow
B. A lower power to weight ratio
C. Lower SFC
D. Higher propulsive efficiency

Answer 29

A. More thrust at the same mass flow