BGT Knowledge Q&A

Question 1

What is best described as a system having multiple stages of rotating aerofoil blades and fixed vanes, large mass flow with high efficiency.

Answer 1

An axial flow compressor.

Question 2

During takeoff in a turbine powered aircraft, correct engine operating technique would be for the pilot to advance the power lever until:

Answer 2

the engine torque limit or the turbine temperature limit is reached, whichever occurs first.

Question 3

Which of the following properties does an accelerating gas flow exhibit?

Answer 3

A constant total energy.

Question 4

How is RPM typically measured in a turboshaft engine?

Answer 4

By measuring compressor outlet pressure, since compressor outlet pressure is proportional to engine RPM.

Question 5

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

Answer 5

Temperature, density and pressure all increase, while velocity decreases.

Question 6

Which of the gas flows from a turbofan engine is used to generate reverse thrust?

Answer 6

The cold stream flow from the bypass duct.

Question 7

What is the definition of compressor pressure ratio?

Answer 7

The ratio of the final stage outlet pressure to first stage inlet pressure.

Question 8

Turbine powered helicopters and agricultural aircraft are often left running during short stops:

Answer 8

because the stop/start cycles are where most damage/wear is done to engines.

Question 9

Bleeding significant amounts of air off the compressor leads to:

Answer 9

a decrease in engine efficiency.

Question 10

Which of the following is an advantage of a free turbine propulsion system?

Answer 10

With a free turbine propulsive system the propellor or helicopter rotor can be held stationary while the engine is started, or stopped while the engine is still running.

Question 11

An advantage of a free turbine propulsion system would be:

Answer 11

the ability to stop rotor blades while the engine is still running.

Question 12

What type of oil pump is generally utilised on turbine engines?

Answer 12

A gear type.

Question 13

What is the function of the inlet guide vanes?

Answer 13

To guide the incoming airflow onto the first row of rotary vanes at the best angle of attack.

Question 14

What is the normal shape of the duct formed by the exhaust nozzle on a subsonic turbofan engine?

Answer 14

Convergent.

Question 15

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

Answer 15

divergent

Question 16

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

Answer 16

prevent metal to metal contact.

Question 17

A similarity between turbine and reciprocating engines is that:

Answer 17

both are internal combustion engines.

Question 18

Multiple, separate interconnected chambers within a common air casing, encircling the turbine shaft, describes:

Answer 18

a can-annular combustion chamber.

Question 19

What is the primary function of the nozzle diaphragm?

Answer 19

To maximise the velocity of the gas exiting the combustion section ,and to direct the gases at the optimum angle onto the turbine blades.

Question 20

What are the two main types of intake on turbofan engined aircraft?

Answer 20

Divided and pitot.