Revision Questions BGT Flashcards
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
A. In the diffuser
The purpose of the diffuser (impeller) in a gas turbine is to to raise pressure and lower velocity
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
B. A divergent duct
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
C. The engine can operate at design RPM to maintain an efficient wing angle of attack
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
A. Between the final compressor stage and the inlet to the combustion chamber
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
C. Shut off the fuel supply and maintain starter motor rotation
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
C. Raises the thrust output of a jet engine as aircraft speed increases
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
A. Units of fuel used per unit of thrust per hour
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
D. Jet pipe pressure engine to compressor inlet pressure
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
C. The force required to accelerate a mass of air through the engine
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
D. No turbulence and pressure higher than ambient
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
A. It accelerates a relatively large mass of air to a relatively low velocity
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
C. A lower air mass accelerated to a higher velocity
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
B. Increase the engine operating temperature
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
A. 4:1
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
D. Ensure vapour release (vapour lock) does not occur
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
A. The free power turbine shaft is independent of the other engine spools
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
C. The LP compressor is connected to the LP turbine
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
A. Divergent ducts
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
E. TSS
Torque Sensitive signal
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
D. Swash plate
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
D. Simplicity
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
D. Decreased fuel flow and decreased thrust output
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
A. And torque in the Beta range
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
B. An increase in thrust and an increase in fuel flow
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
C. Periodically in heavy rain
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
C. True airspeed, RPM and compressor outlet pressure
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
B. By varying the fuel flow via the fuel control unit
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
C. To prevent ice formation clogging the fuel filter
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
C. The small rear rotors
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
C. Variable stator vanes
