15. Gas turbine engine - Q&A

During any stabilised running condition, the spill or half ball valve is

• always varying between fully closed and fully seated.
• lightly seated.
• open fully.

What type of intake is one that decreases gradually in area and then increases?

• Convergent.
• Convergent / Divergent.
• Divergent.

The velocity of supersonic air as it flows through a divergent nozzle

• decreases.
• increases.
• is inversely proportional to the temperature.

Gas pressure through the turbine section will generally

• increase.
• remain the same.
• decrease.

Power is adjusted in a gas turbine engine by

• increasing fuel flow.
• increasing air and fuel flow.
• increasing airflow to the combustion chamber.

An increase in the Ram Ratio of an intake will

• have no effect upon the temperature of the compressed air.
• increase the temperature of the compressed air.
• decrease the temperature of the compressed air.

Air bleed valves are

• closed at low RPM.
• open at high RPM.
• open at low RPM.

Which of the following influences the operation of an automatic fuel control unit on a turbojet engine?

• Exhaust gas temperature.
• Mixture control position.
• Burner pressure.

Kerosene will burn effectively at an air/fuel ratio of

• 150:1.
• 15:1.
• 45:1.

An exhaust cone placed aft of the turbine in a jet engine will cause the pressure in the first part of the exhaust duct to

• increase and the velocity to decrease.
• decrease and the velocity to increase.
• increase and the velocity to increase.

What are the principal advantages of the duplex fuel nozzle used in many turbine engines?

• Allows a wider range of fuels and filters to be used.
• Restricts the amount of fuel flow to a level where more efficient and complete burning of the fuel is achieved.
• Provides better atomization and uniform flow pattern.

What moves the swash plate away from the minimum stroke position?

• Reduced inlet pressure.
• A spring.
• Increased servo pressure.

Allowable damage on the first stage compressor blade is restricted to

• middle third of the blade to the outer edge.
• outer third of the blade to the outer edge.
• root end of the blade.

In a gas turbine engine, turbine section

• temperature decreases along with pressure and velocity.
• velocity decreases and pressure increases.
• velocity increases and pressure decreases.

If the bypass ratio is 0.7:1, the 0.7 pounds of air is

• fed into H.P compressor compared to 1 pound fed around it.
• fed around the engine to 1 pound fed into H.P. compressor.
• bypassed for every 1 pound at the intake.

The propulsive efficiency is

• low, with a low mass flow acceleration.
• high, with a low mass flow acceleration.
• high, with a high mass flow acceleration.

A free turbine is

• not directly connected to the power output shaft.
• connected directly to the propeller and compressor.
• connected directly to the power output shaft.

Specific fuel consumption at altitude will

• decrease.
• remain constant.
• increase.

When reconnecting a H.E.I.U., which cable must be reconnected first?

• It makes no difference.
• L.T. before H.T.
• H.T. before L.T.

With bleed valves open for anti-ice

• thrust is unaffected.
• thrust decreases, fuel consumption decreases.
• thrust decreases, fuel consumption increases.

When the A.P.U is running and pneumatics are on

• bleed valve is closed, surge valve is open.
• bleed valve is open, surge valve is closed.
• bleed valve is open, surge valve is modulating.

Turbine engine components are never manufactured by

• electrical resistance welding.
• argon arc welding.
• gas welding.

With a fixed throttle in a climb

• RPM will increase.
• RPM will remain constant.
• RPM will decrease.

Operating thrust reversers at low ground speeds can sometimes cause

• sand or other foreign object ingestion, hot gas re-ingestion.
• hot gas re-ingestion, compressor stalls.
• sand or other foreign object ingestion, hot gas re-ingestion, compressor stalls.

A gas turbine engine is stopped by closing

• H.P cock.
• L.P cock.
• throttle valve.