Revision Questions BGT

Question 1

You would expect to find the highest gas temperature in a turbojet engine -

A. In the diffuser
B. At the beginning of the jet pipe
C. At the last stage of the turbine
D. At the inlet of the compressor

Answer 1

A. In the diffuser

The purpose of the diffuser (impeller) in a gas turbine is to to raise pressure and lower velocity

Question 3

Subsonic gas flow decreases in velocity and increases in pressure when flowing through -

A. A convergent duct
B. A divergent duct
C. A parallel duct
D. A helical duct

Answer 3

B. A divergent duct

Question 4

Turbojet aircraft range increases as altitude increases toward the optimum FL because at high altitude -

A. The decrease in mass airflow permits an increased fuel/air ratio
B. The higher ambient temperature results in a greater pressure rise through the engine
C. The engine can operate at design RPM to maintain an efficient wing angle of attack

Answer 4

C. The engine can operate at design RPM to maintain an efficient wing angle of attack

Question 5

Maximum gas pressure in a gas turbine engine is found -

A. Between the final compressor stage and the inlet to the combustion chamber
B. In the exhaust unit
C. At the downstream end of the combustion chamber
D. At the turbine entry point

Answer 5

A. Between the final compressor stage and the inlet to the combustion chamber

Question 6

The action which should be taken if a gas turbine compressor begins to stall during engine acceleration on start up is -

A. Open the throttle and watch rpm increase to optimum range
B. Close the throttle and manually operate the bleed valves
C. Shut off the fuel supply and maintain starter motor rotation

Answer 6

C. Shut off the fuel supply and maintain starter motor rotation

Question 8

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 the thrust output of a jet engine as aircraft speed increases
D. Cools the air as it enters the engine intact

Answer 8

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

Question 9

The term SFC (specific fuel consumption) means -

A. Units of fuel used per unit of thrust per hour
B. The actual amount of fuel per shaft horsepower developed
C. Amount of fuel used in a specified engine rpm range
D. Distance travelled per unit of fuel

Answer 9

A. Units of fuel used per unit of thrust per hour

Question 10

Engine pressure ratio (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 10

D. Jet pipe pressure engine to compressor inlet pressure

Question 11

Thrust is produced in a jet engine by -

A. Reaction to impingement of exhaust gases on the outside atmosphere
B. Reaction the pressure difference between exhaust and intake air pressures
C. The force required to accelerate a mass of air through the engine
D. Reaction to the temperature difference between compressor and turbines

Answer 11

C. The force required to accelerate a mass of air through the engine

Question 12

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 12

D. No turbulence and pressure higher than ambient

Question 13

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 13

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

Question 14

A turbofan is not as efficient as a turboprop at low speeds. This is because the 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 14

C. A lower air mass accelerated to a higher velocity

Question 15

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

A. Introduce the air into the engine at a lower speed
B. Increase the engine operating temperature
C. Alter the angle of the nozzle guide vanes
D. Reduce the engine operating RPM

Answer 15

B. Increase the engine operating temperature

Question 16

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 16

A. 4:1

Question 17

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

A. Allow the greatest temperature rise through the engine
B. Ensure the fuel lubricant properties are maintained
C. Stop chemical breakdown of the fuel
D. Ensure vapour release (vapour lock) does not occur

Answer 17

D. Ensure vapour release (vapour lock) does not occur

Question 18

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 turbines
D. The free power turbine is driven by the compressor

Answer 18

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

Question 19

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 19

C. The LP compressor is connected to the LP turbine

Question 20

Stator vanes in an axial flow compressor of a gas turbine engine convert air velocity into pressure by use of -

A. Divergent ducts
B. Axial vanes
C. Aerofoils
D. Convergent passages

Answer 20

A. Divergent ducts

Question 21

The device which automatically feathers the propellor in the event of engine failure is the -

A. NTS
B. Beta range 
C. Safety coupling 
D. Propellor brake
E. TSS

Answer 21

E. TSS

Torque Sensitive signal

Question 22

The most common type of high pressure fuel pumps used in gas turbine engine fuel systems are -

A. Centripetal
B. Centrifugal 
C. Impeller
D. Swash plate
E. Constant displacement

Answer 22

D. Swash plate

Question 23

An advantage of a centrifugal compressor over an axial compressor in a gas turbine engine is -

A. Increased power output
B. Reduced weight
C. Greater efficiency
D. Simplicity

Answer 23

D. Simplicity

Question 24

For a constant RPM in a gas turbine engine, a decrease in air density will result in -

A. Increased fuel flow and increased thrust output
B. Decreased fuel flow and increased thrust output
C. Increased fuel flow and decreased thrust output
D. Decreased fuel flow and decreased thrust output

Answer 24

D. Decreased fuel flow and decreased thrust output

Question 25

In a modern turbo prop aircraft the power lever is used to control -

A. Pitch and torque in the Beta range
B. Pitch only in the reverse thrust range
C. Pitch and torque in the normal flight (Alpha) range
D. Pitch and torque in all operating ranges

Answer 25

A. And torque in the Beta range

Question 26

For a turbo jet aircraft flying at a particular altitude at a constant power lever setting, an increase in air density will result in -

A. An increase in thrust and a decrease in fuel flow
B. An increase in thrust and an increase in fuel flow
C. A decrease in thrust and an increase in fuel flow
D. A decrease in thrust and a decrease in fuel flow

Answer 26

B. An increase in thrust and an increase in fuel flow

Question 27

To ensure optimal performance of rain repellant fluid, it should be used

A. Only I’m conjunction with windshield wipers
B. Only in light rain
C. Periodically in heavy rain
D. Prior to entering rain

Answer 27

C. Periodically in heavy rain

Question 28

The angle of attack of compressor blades in a gas turbine engine depends primarily on -

A. Compressor outlet pressure, air temperature and density
B. Compressor inlet temperature, indicated airspeed and RPM
C. True airspeed, RPM and compressor outlet pressure
D. Compressor inlet temperature, indicated airspeed and RPM

Answer 28

C. True airspeed, RPM and compressor outlet pressure

Question 29

In a turboprop powered aircraft the pilot controls the engine power output in flight -

A. By direct CSU control
B. By varying the fuel flow via the fuel control unit
C. By increasing prop RPM
D. By varying the prop blade angle

Answer 29

B. By varying the fuel flow via the fuel control unit

Question 30

The reason for oil/fuel heat exchangers in the fuel system of a large turbine powered aircraft is -

A. To prevent fuel vaporisation
B. To prevent ice formation clogging the fuel lines
C. To prevent ice formation clogging the fuel filter
D. To hear the oil and prevent excess viscosity

Answer 30

C. To prevent ice formation clogging the fuel filter

Question 31

In an axial flow compressor, the experiencing the greatest air loads are -

A. The stators
B. The large front rotors
C. The small rear rotors
D. The inlet guide vanes

Answer 31

C. The small rear rotors

Question 32

A method of airflow control in an axial flow compressor of a gas turbine engine is -

A. Variable nozzle guide vanes
B. Variable propelling nozzles
C. Variable stator vanes
D. Variable motor blades

Answer 32

C. Variable stator vanes