Exam 3

Question 1

Which type of compressor can be described as short in length, spoke like in design, relatively simple to manufacture, with high compression per stage?

1. A centripetal compressor.
2. A centrifugal compressor.
3. A turbine compressor.
4. An axial flow compressor.

Answer 1

.B

Question 2

How do bucket reversers function?

1. By blocker doors in the bypass duct moving to blank off the cold fan air redirecting it forward.
2. By cascade vanes in the nacelle surrounding the bypass duct opening to allow the cold fan air to flow outward and forward.
3. By blocker doors external to the exhaust duct moving to blank off the hot exhaust gases redirecting them forward.
4. By blocker doors inside the exhaust duct moving to blank off the hot exhaust gases redirecting them forward.

Answer 2

C.

Question 3

A turbofan engine in the cruise produces 60000 lb of thrust and burns 20000lb of fuel an hour. What is the specific fuel consumption (SFC) of the engine?

1. 0.33
2. 0.25
3. 0.80
4. 0.85

Answer 3

A.

Question 4

When talking about turbine blades, what is “creep”?

1. The cyclic lengthening and subsequent shortening of turbine blades each time the engine is started and shutdown.
2. The changing of the turbine blade shape due to FOD ingestion.
3. The lateral movement of turbine blades within their mounting on the disc.
4. The permanent lengthening of the turbine blade due to high temperatures and centrifugal reaction.

Answer 4

D.

Question 5

For a gas at constant pressure, the temperature in a closed vessel will be directly proportional to its volume.

1. This is an expression of Boyle’s Law.
2. This is an expression of the first law of thermodynamics.
3. This is an expression of Newton’s Second Law.
4. This is an expression of Charles’ Law.

Answer 5

.D

Question 6

A combustion chamber’s liner and associated gas flow control and metering devices are designed to:

1. separate and control the gas flow for cooling and combustion and to create a region of low velocity recirculation of the air in the primary zone.
2. bleed off a portion of the gas flow for cooling of the turbine discs and sealing of the turbine shaft bearings.
3. accelerate the gas flow and increase its pressure prior to the gases entry into the burning zone.
4. recirculate the air for repeat burning and to reduce CO emissions

Answer 6

A

Question 7

What are the primary functions of air seals in a turbine engine?

1. To pressurise labyrinth and carbon seals and cool hot section areas.
2. To prevent turbine outlet gas flow escaping through the nozzle system.
3. To prevent ram air from escaping from the air inlet system.
4. To pressurise the compressor rotor area and cool hot section areas.

Answer 7

A.

Question 8

How is a demand by the pilot for more thrust handled mechanically in a turbine engine?

1. The power lever is connected to a fuel control which senses compressor inlet temperature, exhaust gas temperature, compressor outlet pressure and engine RPM.
2. The power lever is connected to the fuel pump which provides more fuel pressure. This is sensed by the fuel nozzle sensors which inject more fuel into the combustion chamber.
3. The power lever is connected to a fuel control which contains a governor to maintain RPM.
4. The power lever is connected to the fuel nozzle apparatus which allows more fuel into the burner.

Answer 8

A.

Question 9

Which of the following is an advantage of a centrifugal compressor, compared to an axial flow compressor?

1. A centrifugal compressor allows for a smaller engine diameter for a given mass flow capacity.
2. A centrifugal compressor is more robust and relatively easier to manufacture.
3. A centrifugal compressor produces lower compressor discharge velocities relative to the intake velocity.
4. A centrifugal compressor can achieve higher overall compression ratios more efficiently.

Answer 9

B.

Question 10

How does the temperature, density, pressure and velocity of a gas flow vary through a convergent duct at supersonic speed?

1. Temperature, density, pressure and velocity all decrease.
2. Temperature, density, pressure and velocity all increase.
3. Temperature, density and pressure all increase, while velocity decreases.
4. Temperature, density and pressure all decrease, while velocity increases

Answer 10

C.

Question 11

What is the function of the inlet guide vanes?

1. To decelerate and guide the incoming airflow onto the first row of stator vanes at the best angle of attack.
2. To keep FOD and ice from the first compressor stage.
3. To guide the incoming airflow onto the first row of rotary vanes at the best angle of attack.
4. To accelerate and guide the incoming airflow onto the first row of rotary vanes at the best angle of attack.

Answer 11

.C

Question 12

How do supersonic air intake ducts decelerate the airflow to a subsonic condition prior to compressor entry?

1. By employing drag devices such as ballows.
2. By employing devices which cause shockwaves.
3. By their divergent design.
4. By their convergent design.

Answer 12

B.

Question 13

A prominent cockpit indication of a compressor stall during engine start-up would be a:

1. surging noise, a rise on EGT and fluctuations in RPM.
2. surging noise and fluctuating oil pressure.
3. poor acceleration rate and high EPR.
4. sudden increase in fuel flow, fluctuating EGT and high RPM.

Answer 13

A.

Question 14

There are three general types of combustion chamber. The most easily serviced is totally external to the engine, the second is a dual ring system and the third is an efficient combination of two others. Select the list which contains the three in the order described.

1. Annular, Can, Can-annular.
2. Can-annular, Can, Annular.
3. Can, Annular, Torroid-annular.
4. Can, Annular, Can-annular.

Answer 14

D.

Question 15

How are turbine discs usually cooled?

1. By spraying oil onto the face of the disc.
2. By feeding bypass air into the hot gas stream beyond the combustion outlet.
3. By feeding a low pressure air supply from the exhaust through and onto the face of the disc.
4. By feeding a supply of high pressure air from the compressor onto the face of the disc.

Answer 15

D.

Question 16

Typically the lubrication systems of high bypass turbofan engines is _______ pressure _____ sump.

1. low wet
2. high wet
3. low dry
4. high dry

Answer 16

D.

Question 17

What are the two exhaust gas flows of a turbofan engine called?

1. External and internal.
2. Hot stream and cold stream.
3. Convergent and divergent.
4. Donut and core.

Answer 17

B.

Question 18

Equivalent horsepower is:

1. the power delivered to a helicopter main rotor gearbox on a turboshaft engine.
2. the power delivered to the propeller on a turboprop engine.
3. brake horsepower corrected for density changes.
4. shaft horsepower plus the effect of residual jet thrust on a turboprop engine.

Answer 18

D.

Question 19

What is the difference between a turboprop and a turboshaft?

1. With a turboprop the shaft is connected to a propeller gearbox, with a turboshaft the shaft is connected to something other than a propeller gearbox.
2. Turboprop engines are only fitted to fixed wing aircraft, while turboshaft engines are only fitted to helicopters.
3. There is no difference between turboprops and turboshafts, they are two names for the same type of engine.
4. With a turboprop the output from the engine is fed to the propeller through a gearbox, with a turboshaft the output shaft from the engine is connected directly to the propeller.

Answer 19

A.

Question 20

An advantage of a free turbine propulsion system would be:

1. much cheaper to manufacture and service.
2. the ability to stop rotor blades while the engine is still running.
3. the propellor turns the engine, so no gearbox is necessary.
4. slower engine starting and therefore less fuel use.

Answer 20

B.

Question 21

What is the effect on SFC of increasing compressor pressure ratio for a given fuel flow?

1. SFC will increase because an increase in compressor outlet pressure will cause a decrease in outlet velocity.
2. SFC will increase because increased compressor discharge pressure generates a lower turbine inlet temperature and increases engine thrust.
3. SFC will decrease because increased compressor discharge pressure generates a higher turbine inlet temperature and increases engine thrust.
4. SFC will decrease because an increase in compressor outlet pressure will cause a decreased turbine inlet temperature.

Answer 21

.C

Question 22

For a gas at constant pressure, the temperature in a closed vessel will be directly proportional to its volume. This is an expression of:

1. Newton’s First Law.
2. the first law of thermodynamics.
3. Boyle’s Law.
4. Charles’ Law.

Answer 22

D.

Question 23

Which instrument(s) indicate the thrust output of a turbofan engine?

1. Engine torque.
2. Turbine temperature.
3. EPR and/or N1.
4. Fuel flow

Answer 23

C.

Question 24

What are the two types of inner section design of can-annular or annular combustion chambers?

1. Segmented and baffled.
2. High flow and low flow.
3. Convergent and divergent.
4. Through flow and reverse flow.

Answer 24

D.

Question 25

What are the normal indications of a flame-out on a turbofan engine?

1. EPR, N1, turbine temperature and fuel flow decrease.
2. EPR and fuel flow increase, with an N1 and turbine temperature decrease.
3. EPR and fuel flow decrease, with an N1 and turbine temperature increase.
4. EPR and N1 decrease, with a turbine temperature and fuel flow increase.

Answer 25

A.

Question 26

What is the cause of creep in turbine blades?

1. An overspeed or overtemp of the engine.
2. An imperfection in the blade construction.
3. High temperatures and centrifugal reaction.
4. Poor blade design.

Answer 26

C.

Question 27

The primary function of a turbine engine’s lubrication system is to:

1. prevent metal to metal contact.
2. clean metal particles from the turbine shaft bearings.
3. cool the internal bearings.
4. protect the turbine blades from corrosion.

Answer 27

A.

Question 28

The shape of the intake duct on a turbofan engine is:

1. constant diameter.
2. divergent.
3. convergent.
4. fractious.

Answer 28

B.

Question 29

How does a turboprop engine compare to a reciprocating engine of the same power output?

1. Turboprop engines are lighter.
2. Turboprop engines lose power more rapidly as TAS increases.
3. Turboprop engines are less reliable.
4. Turboprop engines are less costly to purchase.

Answer 29

A.

Question 30

Which components of a turbojet engine contribute to rearward acting forces?

1. The turbine and the propelling nozzle.
2. The turbine and the compressor.
3. The diffuser and the combustion chamber.
4. The compressor and the exhaust cone.

Answer 30

A.