Powerplant Chapter 3 FAA ORAL questions - Turbine Engines Flashcards Preview

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Flashcards in Powerplant Chapter 3 FAA ORAL questions - Turbine Engines Deck (25):

Explain the main difference and advantage of turbofan over turbojet engines.

A turbofan engine uses a fan to bypass some air around the engine core and to provide thrust. The advantage is that this provides additional thrust without increasing fuel flow.


Name the major components in a gas turbine engine.

Air inlet, compressor section, combustion section, turbine section, exhaust section, gearbox and accessory section.


What determines the amount of airflow through a turbine engine?

The forward speed of the aircraft, compressor speed, and air density.


Name the two types of compressors commonly used in turbine engines.

Axial and centrifugal flow compressors.


Name the two types of compressors commonly used in turbine engines.

Axial and centrifugal flow compressors.


Name two different methods for attaching turbine engine rotor blades to the rotor disks.

Dovetail-type root -or- Bulb-type root -or- Fir tree-type root.


What is a split compressor system?

Also called dual or twin spool compressors, these are connected to the turbine section with two rotor shafts, one inside the other.


What are the different types of combustion chambers used in turbine engines?

Can, annular, can-annular, and reverse flow annular.


What prevents the combustion chambers from burning?

Cooling air along the inside of the liner.


What is the purpose of the interconnecting tubes attached between can-type combustion chambers?

For flame propagation during start.


What functions do axial flow turbine nozzles perform?

They direct the mass airflow to drive the turbine rotor at a specific angle.


how is thermal stress relieved on a turbine disc?


By directing bleed air onto the face of the disk, or by grooves being cut in the disk.


What are carbon seals used for on a turbine engines?

They are used as oil seals for the rotor shaft bearings.


What is shaft horsepower?

It is an indication of the torque developed by a turboprop or turboshaft engine.


What is the principal advantage of AC current over DC current?

They provide ground electrical and pneumatic power for aircraft systems when the engines are not running. Pneumatic power can be used for engine starting, ground heating or air conditioning, and anti-icing. Many APUs may also be used as an emergency source of inflight electrical power.


Name the main components of a typical APU.

A small power turbine for power and bleed air, and an electrical generator.


When is the greatest demand placed on an APU?

When supplying bleed air.


How is an APU generally started?

With its own electrical starter and battery power.


Where does the APU get its fuel supply?

From one of the aircraft's main fuel tanks.


At what speed does a gas turbine APU operate and how is this speed maintained?

At or near its rated speed regardless of electrical or pneumatic loads imposed. The APU fuel control automatically adjusts the fuel flow to maintain the rated speed.


What is used to prevent a heavily loaded APU from exceeding its maximum EGT?

A load control valve modulates the pneumatic load to maintain EGTs within limits.


How is an APU shut down and why is this procedure used?


After the APU is unloaded by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize. This cool down period is typically three minutes. If a heavily loaded APU is abruptly shut down without any cooling down period, damage could occur as a result of thermal shock.


What powers the variable inlet guide vanes used on some APUs to regulate compressor intake airflow?

Fuel pressure.


What is fan blade shingling?

It is the overlapping of the midspan shrouds of the fan blade.


When a turbofan or turbojet engine is shut down, what should a mechanic listen for during coastdown?

Any rubbing sound or other unusual noises from the engine.