RECIPRO & GAS TURBINE - OXFORD

d

The term "Self Sustaining Speed" means that:
a. The aircraft can roll forward with no further opening of the throles.
b. The speed from which the engine can accelerate to full power within 5 seconds.
c. The engine will run independently of external help.
d. The speed from which the engine can accelerate to idle without the help of the starter motor.

d

A high energy ignition system works on the principle of:
a. Obtaining power from a step up transformer from the aircraft's A.C. power system.
b. Magneto static induction.
c. Fleming's Right Hand Rule.
d. Obtaining energy from the discharge of a capacitor.

b.

When gases pass through a convergent duct their:
a. Velocity and temperature increase and their pressure decreases.
b. Their velocity increases and their temperature and pressure decrease.
c. Their velocity decreases and their temperature and pressure increase.
d. They expand adiabatically.

d

Select the correct order of best propulsive efficiency, from low to high airspeed
a. High by-pass ratio turbo jet, Low by-pass ratio turbo jet, Pure turbo jet, Turbo-prop.
b. Low by-pass ratio turbo jet, Pure turbo jet, Turbo-prop, High by-pass ratio turbo jet.
c. Pure turbo jet, Turbo-prop, High by-pass ratio turbo jet, Low by-pass ratio turbo jet.
d. Turbo-prop, High by-pass ratio turbo jet, Low by-pass ratio turbo jet, Pure turbo jet.

a

The highest pressure in a gas turbine engine occurs:
a. Between the compressor and the combustion chamber.
b. In the combustion chamber.
c. In the jet pipe.
d. At the P1 probe.

c

In a turbo-fan engine, the fan speed is controlled by:
a. A reduction gear.
b. A waste gate.
c. The turbine.
d. Varying the pitch.

b

In a high ratio by-pass engine:
a. All of the air goes through both the low and high pressure compressors.
b. Not all the air goes through the high pressure compressor.
c. Not all the air goes through the low pressure compressor.
d. All the air goes through the high pressure compressor.

d

Modular construction:
a. Is only used on turbo-prop engines.
b. Cannot be used on high ratio engines.
c. Has a weight saving function.
d. Enables malfunctioning sections of the engine to be changed without changing the whole engine.

c

Gas turbine engine efficiency increases with:
a. An increase in volumetric efficiency.
b. An increase in ambient temperature.
c. A decrease in ambient temperature.
d. A decrease in ambient air pressure.

c

On a cold day, the idle speed of a gas turbine engine which has no fuel control unit compensation:
a. Is unaffected by temperature.
b. Will increase.
c. Will decrease.
d. Will increase by no more than 4%.

b

The By-Pass Ratio of an engine is the ratio of:
a. Primary air to tertiary air.
b. Cold stream air to that flowing through the hot core of the engine.
c. Exhaust gas pressure to air intake pressure.
d. Primary air to secondary air.

a

The Gas Turbine Engine uses the principle of:
a. Newton's Third Law of motion.
b. Creating thrust equal to the weight of the aircraft.
c. Expelling air at the same speed as that of the aircraft.
d. The fluid flywheel.

a

The addition of heat in a combustion chamber allows a:
a. Large expansion at a substantially constant pressure.
b. Large expansion at a constant volume.
c. Large expansion at a decreasing static pressure.
d. Minimum expansion at a constant volume.

c

In a divergent duct:
a. The pressure decreases and the temperature and velocity increases.
b. The pressure, velocity and temperature increases.
c. The pressure temperature increases and the velocity decreases.
d. The pressure decreases, the temperature increases and the velocity remains constant.

c

In a twin spool engine:
a. The L.P. compressor is connected to the H.P. compressor.
b. The H.P. turbine is connected to the L.P. compressor, the L.P. turbine is connected to the H.P. compressor.
c. The L.P. turbine is connected to the L.P. compressor, the H.P. turbine is connected to the H.P. compressor.
d. The H.P. turbine is connected to the L.P. turbine, the H.P. compressor is connected to the L.P. compressor.

d

A By-Pass Ratio of 5:1 means that:
a. 5 pounds of air is by-passed for every 10 pounds entering the engine intake.
b. 5 pounds of goes through the H.P. compressor for every 10 pounds that enters the intake.
c. 10 pounds of air goes through the by-pass for every 5 pounds that enters the intake.
d. 5 pounds of air is by-passed for every 1 pound that goes through the hot core of the engine.

b

Aft of the compressor:
a. The velocity of the airflow remains the same.
b. The velocity of the airflow decreases before the combustion chamber.
c. The velocity increases before the combustion chamber.
d. The air pressure decreases before the combustion chamber.

b

The fan in a ducted fan engine, is driven by:
a. The high pressure turbine.
b. The rearmost turbine.
c. The intermediate pressure turbine.
d. All of the above.

a

In a by-pass engine, the by-pass air:
a. Increases the air mass flow and therefore increases the propulsive efficiency.
b. Cools the combustion chamber and therefore increases the thermal efficiency.
c. Reduces the air mass flow and therefore increases the propulsive efficiency.
d. Increases the air mass flow and therefore reduces the propulsive efficiency.

d

The majority of the thrust of a:
a. Turbo-fan engine comes from the turbine exhaust.
b. Turbo-prop engine comes from the turbine exhaust.
c. Turbo-shaft engine comes from the free power turbine exhaust.
d. Turbo-fan engine comes from the by-pass air.

d

A Pure Turbo-Jet engine gives:
a. A small acceleration to a large mass of air.
b. A large acceleration to a large mass of air.
c. A small acceleration to a small mass of air.
d. A large acceleration to a small mass of air.

a

During the Brayton cycle, combustion takes place:
a. Continuously.
b. Once every revolution.
c. Once every other revolution.
d. Only during the start cycle.

c

In a high by-pass engine with a 'pitot' intake, with the engine running and the brakes on, what will P1 be in relation to P0?
a. Same
b. Greater
c. Less
d. 14.7psi

d

A pitot intake forms a ____________ duct______ the fan to ensure that the airflow ______ to ________ and achieves a ________
a. convergent - before - speeds up subsonic - pressure rise
b. divergent - after - slows down - subsonic - pressure rise
c. divergent - before - speeds up sonic - pressure drop
d. divergent - before - slows down subsonic - pressure rise

c

What effect will severe icing in the intake have on a high by-pass engine?
a. The axial velocity of the air will increase with a reduction in the angle of attack of the airflow with the compressor blades and a possible stall.
b. The axial velocity of the air will decrease with a reduction in the angle of attack of the airflow with the compressor blades and a possible stall.
c. The axial velocity of the air will decrease with an increase in the angle that the resultant airflow forms with the compressor blades chord line and a possible stall.
d. The axial velocity of the air will increase with an increase in the angle of attack of the airflow with the compressor blades and a possible stall.

b

Which of the following would be classed as prudent when carrying out Engine Ground Runs?
a. Only carry out engine runs with a tail wind
b. Fit debris guards when running
c. Only do ground runs on Tarmac
d. Only do ground runs on concrete

c

With an 'S' type intake, if the pilot selects max RPM while standing still, there is a strong possibility that:
a. The angle, which the relative airflow forms with the compressor blades, will become too small, which will cause the engine to stall and surge.
b. The angle, which the relative airflow forms with the compressor blades, will become too small, which will cause the engine to surge then stall.
c. The angle which the relative airflow forms with the compressor blades will become too large, which will cause the engine to stall and surge.
d. The angle, which the relative airflow forms with the compressor blades, will become too large, which will cause the engine to surge then stall.

d

Secondary air inlet doors are utilised:
a. When an aircraft is in the cruise
b. When the aircraft is near its maximum IAS.
c. When the rpm of the engine is low while stationary.
d. When the rpm of the engine is high when stationary.

a

What is the purpose of the supersonic diffuser in the variable throat intake?
a. Final reduction in velocity prior to compressor face.
b. Interim reduction in velocity to below Mach 1 prior to a further reduction in the subsonic diffuser.
c. Interim reduction in velocity to below Mach .5 prior to a further reduction in the
subsonic diffuser.
d. Increase in velocity prior to compressor face.

a

The purpose of an air inlet is to provide a relatively ________ supply of air to the ________ of the ________ compressor.
a. turbulent free - face - low pressure
b. turbulent face - low pressure
c. turbulent free - rear - low pressure
d. turbulent free - face - high pressure

d

In a pitot intake the term 'Ram Pressure Recovery' refers to the time when:
a. EPR has attained the take off setting.
b. The HP Compressor has reached its maximum.
c. The EPR has recovered to its optimum figure.
d. Intake pressure has been re-established to ambient pressure.

d

The effect on EPR with an iced up P1 probe with the RPM of the engine increasing
a. EPR would decrease.
b. No change.
c. EPR would momentarily decrease then increase.
d. EPR would increase.

b

The pressure ratio of a gas turbine engine compressor is:
a. Equal to the number of compression stages.
b. The ratio between compressor outlet and compressor inlet pressure.
c. The ratio between exhaust inlet and exhaust outlet pressure.
d. Never greater than 5 to 1.

a

The compressor idling speed of a gas turbine engine will increase:
a. At higher ambient temperature.
b. With higher than sea level density.
c. At altitudes lower than sea level.
d. At lower ambient temperature.

a

One stage of an axial flow compressor consists of:
a. One rotor assembly and one row of stator vanes.
b. One stator assembly and one row of guide vanes.
c. One rotor and one impeller assembly.
d. One impeller and one diffuser assembly.

d

The pressure rise across each stage of an axial flow compressor is:
a. Greater than that of a centrifugal compressor.
b. Between 3 and 5 to one.
c. Twice the inlet pressure.
d. Between 1.1 and 1.2 to one.

b

The ring of blades which sometimes precede the first rotor stage of an axial flow compressor are called:
a. The first stage stator blades.
b. The inlet guides vanes.
c. First stage diffuser blades.
d. Nozzle guide vanes.

c

As air passes through an axial flow compressor, a pressure rise takes place in:
a. The impeller and the diffuser.
b. The rotor blades only.
c. Both the rotor blades and the stator vanes.
d. The stator vanes only.

b

In the event of a surge occurring the correct action to be taken is:
a. To close the throttle quickly.
b. To close the throttle slowly.
c. To open the throttle fully.
d. To close the LP fuel valve.

c

Shrouding of stator blade tips is designed to:
a. Prevent tip turbulence.
b. Ensure adequate cooling.
c. Minimise vibration.
d. Prevent tip losses.

c

The cross sectional area of the air annulus is reduced as it approaches the combustion chamber:
a. To maintain the volume of the air under rising pressure.
b. To prevent an increase of the velocity of the air under rising pressure.
c. To maintain the speed of the air entering the engine.
d. To allow longer blades to be used in the latter stages of the compressor.

a

The attachment of blades to the compressor disc:
a. Allows slight movement to relieve stress concentration.
b. Is rigid.
c. Prevents them being contaminated by the atmosphere.
d. Allows slight movement because of the different expansion rates of the blades and the disc, which would otherwise cause center line closure.

c

Compressor blades are designed to produce:
a. A given pressure and velocity rise.
b. A constant flow over the engine speed range.
c. A steady velocity with a pressure rise over the engine speed range.
d. Turbulent flow into the combustion chamber.

a

A compressor blade will stall when:
a. The air axial velocity and rotational speed relationship is disturbed.
b. The mass air flow and speed relationship is constant.
c. The speed of the gas flow through the turbine falls below 0.4 Mach.
d. The compression ratio exceeds 10 to 1.

d

Compressor surge will occur when:
a. All stages are at maximum efficiency.
b. All stages are at maximum RPM.
c. There is a partial breakdown of airflow through the compressor.
d. All stages have stalled.

b

Cascade vanes are fitted in which part of the centrifugal compressor?
a. The air inlet
b. The outlet elbow
c. The impeller
d. The diffuser

d

The purpose of the diffuser vanes in a centrifugal compressor is to:
a. Increase the charge temperature.
b. Convert pressure energy into kinetic energy.
c. Increase the air velocity.
d. Convert kinetic energy into pressure energy.

c

The pressure rise across a centrifugal compressor:
a. Occurs in the impeller only.
b. Occurs in the diffuser only.
c. Is shared almost equally by the impeller and the diffuser.
d. Is always greater in the diffuser than in the impeller.

d

To gain a greater pressure ratio than 4:1:
a. Two centrifugal compressors can be placed in parallel.
b. The compressor diameter must be reduced.
c. The cascade vanes must be convergent.
d. Two centrifugal compressors can be placed in series with each other.

a

The major disadvantage of a centrifugal compressor is that:
a. It cannot cope with a large mass flow of air.
b. It cannot be used for a turbo jet engine.
c. A larger turbine must be used.
d. It is more prone to damage than the axial flow compressor

b

The purpose of cascade vanes is to:
a. Increase the velocity of the airflow prior to it entering the combustion chambers.
b. Turn the air smoothly through 90 degrees and complete diffusion.
c. Remove swirl from the airflow.
d. Swirl the air, ready for the next compression stage.

c

The type of compressor used to create radial airflow would be:
a. Positive displacement.
b. Axial.
c. Centrifugal.
d. Constant volume.

b

Under ideal conditions the pressure rise across a centrifugal compressor can be:
a. 1.1 or 1.2 to 1.
b. Not more than 4 to 1.
c. 1.5 to 1.
d. 30 to 1.

b

An advantage of a centrifugal compressor is that it is:
a. Dynamically balanced.
b. More robust and is easier to develop and manufacture.
c. Unaffected by turbulence.
d. Able to handle a larger mass of air than an axial flow compressor.

b

A compressor stall causes:
a. The vibration level to increase with a decrease in the turbine gas temperature.
b. An increase in the turbine gas temperature and the vibration level.
c. The rotation of the engine to stop suddenly.
d. The airflow through the engine to stop suddenly.

a

Air passing through a convergent duct experiences:
a. A decrease in temperature and pressure with an increase in velocity.
b. An increase in temperature and velocity with a decrease in pressure.
c. An increase in temperature and pressure with a velocity decrease.
d. Adiabatic expansion.

d

Fuel is regulated on rapid engine acceleration:
a. To prevent detonation in the combustion chambers.
b. Because the rapid response of the compressor might cause a flame out.
c. Because the cooling effect of too much fuel would cause a drop in pressure in the combustion chamber.
d. To prevent inducing a compressor stall and surge.

c

A compressor stall:
a. Is overcome by increasing the fuel flow.
b. Is a complete breakdown of the airflow through the compressor.
c. May only affect one stage or several stages of a compressor.
d. Is mechanical failure of the compressor.

b

Compressor blades increase in size:
a. From the root to the tip to increase the temperature.
b. From the high pressure section of the compressor to the low-pressure section.
c. From the low-pressure section of the compressor to the high-pressure section to maintain a constant airflow velocity.
d. From the tip to the root to decrease the temperature.

a

The occurrence of compressor stalls is limited by:
a. Bleed valves.
b. Nozzle guide vanes.
c. Swirl vanes.
d. Cascade vanes.

d

Bleed valves are automatically opened:
a. At maximum R.P.M. to prevent compressor stall.
b. At low R.P.M. to prevent the turbine stalling.
c. During engine acceleration to prevent turbine surge.
d. At low engine R.P.M to prevent the compressor stalling.

c

To prevent compressor stall at the rear of the compressor, bleed valves must be positioned:
a. At the rear stages of the compressor.
b. At the front stages of the compressor.
c. At the mid stages of the compressor.
d. At the intake of the engine.

c

A complete breakdown of airflow through a compressor is known as:
a. Compressor turbulence.
b. Compressor buffet.
c. Compressor surge.
d. Compressor seizure.

a

One indication that a compressor bleed valve has stuck closed at low R.P.M. is:
a. Possible compressor stall.
b. An inability to achieve full power.
c. That bleed air is reduced.
d. That the engine will stop.

d

Within the compressor:
a. Bleed valves are set to open at high R.P.M.
b. Pressure decreases.
c. Temperature decreases.
d. Temperature increases.

a

Bleeding compressor air for anti-icing will cause:
a. An increase in T.G.T., a decrease in thrust and an increase in S.F.C.
b. A decrease in T.G.T., an increase in thrust and a decrease in S.F.C.
c. An increase in R.P.M. and fuel flow.
d. An increase in R.P.M. and a decrease in fuel flow.

b

Variable inlet guide vanes:
a. Deflect air past the compressor.
b. Prevent compressor stall.
c. Deflect air past the turbine.
d. Induce air into a centrifugal compressor.

b

Compressor blades are twisted from root to tip:
a. To decrease the pressure.
b. To maintain a correct angle of attack.
c. To reduce the relative airflow.
d. To give added rigidity to the blade structure.

d

In a compressor:
a. The air temperature is steady with a pressure rise.
b. The air temperature falls with a pressure rise.
c. The drop in air temperature is inversely proportional to the pressure rise.
d. The air temperature rises with a pressure rise.

c

A stall in a gas turbine engine is most likely to occur with ______ Pressure Ratio and _____ Location in Compressor
a. High, Front
b. High, Back
c. Low, Back
d. Low, Front

c

Contamination of the compressor:
a. Is not likely to prove a problem if the aircraft is not flown at low level over the sea.
b. Will not decrease the performance of the engine if the fuel sulphur content does not exceed .001%.
c. Can seriously reduce the efficiency of the engine.
d. Can be reduced by periodically flying through thunderstorms.

d

The low pressure compressor of a high ratio by-pass engine:
a. Is driven by the high pressure turbine.
b. Rotates faster than the high-pressure compressor.
c. Is always a centrifugal compressor.
d. Is driven by the rearmost turbine.

d

The ratio of air to kerosene to give the greatest heat release during combustion is:
a. 45 : 1.
b. 130 : 1.
c. 12.5 : 1.
d. 15 : 1.

c

One advantage of an annular combustion chamber system is that:
a. The diameter of the engine is reduced.
b. There is unrestricted airflow at maximum r.p.m.
c. There are no flame propagation problems.
d. The air casing area is greater.

c

Of the total airflow entering the combustion chamber the percentage that is mixed with the fuel
and burnt is:
a. 10%
b. 40%
c. 20%
d. 60%

a

The combustion chamber drain valve is closed:
a. By combustion chamber gas pressure.
b. By a return spring.
c. By 12th stage compressor air pressure.
d. During a blow out cycle.

b

A cannular combustion system is:
a. A set of flame tubes, each of which is mounted in a separate air casing.
b. A set of flame tubes enclosed in a common air casing.
c. One common flame tube enclosed in a common air casing.
d. Superior to the annular system because it only requires one igniter.

c

It is necessary to have a combustion drain system:
a. To prevent pressure build up in the combustion chamber.
b. To allow moisture content in the fuel to drain away.
c. To allow any unburnt fuel to drain after shut down or a wet start.
d. To prevent the igniters becoming wetted by excess fuel.

a

The purpose of the tertiary airflow created in the combustion chamber is to:
a. Reduce the gas temperature and cool the flame tube.
b. Form a toroidal vortex, which anchors and stabilises the flame.
c. Reduce the gas temperature and cool the burner head.
d. Ensure complete combustion of the fuel.

b

A re-light envelope:
a. Shows the flame stability limits.
b. Shows airspeed and altitude limitations for an in-flight restart.
c. Shows fuel / air mixture limitations for an in-flight restart.
d. Contains the in flight re-start igniter plugs.

b

Swirl vanes in the combustion chamber:
a. Increase the velocity of the airflow.
b. Reduce the velocity of the airflow.
c. Prevent compressor stall.
d. Help to stabilize combustion.

d

The air entering the combustion chamber is divided; a small percentage is used in combustion, the rest:
a. Is syphoned off for airframe anti-icing purposes.
b. Is used only for cooling the gases before they exit the combustion chamber.
c. Is used to reduce the oil temperature and cool the turbine blades.
d. Is used to cool both the gases exiting the chamber and the walls of the air casing.

c

The effect on the temperature and pressure of the gases as they pass across the turbine is:
a. Their temperature decreases and their pressure rises.
b. Both their temperature and pressure increase.
c. Both their temperature and pressure decrease.
d. Their temperature increases and their pressure falls.

c

Nozzle guide vanes are fitted before the turbine:
a. To increase the velocity of the airflow.
b. To decrease the velocity of the gas flow therefore increasing its pressure.
c. To increase the velocity of the gas flow therefore reducing its pressure.
d. To increase the temperature of the gas flow.

b

One reason for shrouding turbine blades is:
a. To reduce "creep" which may occur in the blades.
b. To improve efficiency and reduce vibration.
c. To enable thinner blades to be used.
d. To minimise blade end erosion.

a

The blades are usually attached to the turbine disc by a "Fir Tree" root. A tight fit is ensured during operation:
a. By the action of centrifugal force.
b. By thermal expansion of the disc.
c. By blade compression loads and thermal expansion.
d. By torque loading and thermal expansion.

a

The main contributory factors which cause creep in turbine blades are:
a. High temperature and tensile loading.
b. High rpm and torque loading.
c. High rpm and high gas speeds.
d. High temperature and high gas speeds.

b

A free power turbine:
a. Has a clutch between the compressor and the power output shaft.
b. Has no mechanical connection with the other turbine or compressor shafts.
c. Has a direct drive with a free wheel unit.
d. Comes free with every 2,000 gallons of AVTUR.

a

The mixture of impulse and reaction blade shape in the average turbine blade is such that:
a. The inner half is impulse and the outer half is reaction.
b. The inner half is reaction and the outer half is impulse.
c. The leading edge is reaction and the trailing edge is impulse.
d. The trailing edge is reaction and the leading edge is impulse.

d

Blade creep is:
a. Movement of the turbine blades around the turbine disc.
b. Temporary expansion due to temperature change.
c. Temporary elongation due to centrifugal forces.
d. Permanent elongation due to heat and centrifugal force.

d

The net operating temperature of a gas turbine engine is limited by:
a. The materials from which the combustion chamber is constructed.
b. The amount of fuel which can be fed into the combustion chamber.
c. The ability of the compressor to pass sufficient air rearwards.
d. The materials from which the nozzle guide vanes and the turbine blades are constructed.

c

The impulse-reaction blade is twisted along its length so that:
a. There is a greater angle at the base than at the tip.
b. The gas flow is accelerated through the turbine.
c. The gas does equal work along the whole of its length.
d. The gas flow is decelerated through the nozzle guide vanes.

a

The velocity of the gases in the exhaust unit is held to:
a. 0.5 Mach to minimise turbulence.
b. 0.75 Mach to optimise the pressure distribution.
c. 0.85 Mach to maximise thrust.
d. Mach 1 to maximise acceleration.

b

The exhaust cone:
a. Straightens the gas flow before it goes into the turbine assembly.
b. Prevents the hot gases flowing across the rear turbine face.
c. Increases the velocity of the gases.
d. Decreases the pressure of the gas.

a

The propelling nozzle is designed to:
a. Increase the velocity and decrease the pressure of the gas stream.
b. Decrease the velocity and increase the pressure of the gas stream.
c. To increase the velocity and the pressure of the gas stream.
d. To decrease the velocity and the pressure of the gas stream.

b

A nozzle is said to be "choked" when:
a. The gas flow through it is subsonic.
b. The gas flow through it reaches its sonic value.
c. The gas temperature rises.
d. The gas flow through it is supersonic.

d

A choked nozzle:
a. Decreases thrust.
b. Gives additional pressure without the addition of heat.
c. Has no effect on thrust.
d. Implies that no further increase in velocity can be obtained without the increase of heat.

a

The exhaust gasses pass to atmosphere via the propelling nozzle which:
a. Is a convergent duct, thus it increases the gas velocity.
b. Converts kinetic energy into pressure energy.
c. Is a divergent duct, thus it increases the gas velocity.
d. Is a divergent nozzle, thus it increases the gas pressure.

c

The jet pipe is insulated from the airframe by:
a. Heat insulation materials.
b. A cooling air jacket.
c. A combination of cooling air and insulating material.
d. Semi-conducting geodetic structures.

c

The noise from a high ratio by-pass engine:
a. Is created mainly in the exhaust section.
b. Is high in the exhaust section because of the high velocity gas flow.
c. Is predominantly from the fan and the turbine.
d. Is greater than that from a turbo-jet engine of comparable power output.