Turbine Engines

Front 1

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

Back 1

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.

Front 2

Name the major components in a gas turbine engine.

Back 2

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

Front 3

What determines the amount of airflow through a turbine engine?

Back 3

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

Front 4

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

Back 4

Axial and centrifugal flow compressors.

Front 5

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

Back 5

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

Front 6

What is a split compressor system?

Back 6

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

Front 7

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

Back 7

Can, Annular, Can Annular, and reverse flow annular

Front 8

What prevents the combustion chambers from burning?

Back 8

Cooling air along the inside of the liner.

Front 9

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

Back 9

For flame propagation during start.

Front 10

What functions do axial flow turbine nozzles perform?

Back 10

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

Front 11

How is thermal stress relieved on a turbine disc?

Back 11

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

Front 12

What are carbon seals used for in turbine engines?

Back 12

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

Front 13

What is shaft horsepower?

Back 13

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

Front 14

Name the main components of a typical APU.

Back 14

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

Front 15

When is the greatest demand placed on an APU?

Back 15

When supplying bleed air.

Front 16

How is an APU generally started?

Back 16

With its own electrical starter and battery power.

Front 17

Where does the APU get its fuel supply?

Back 17

From one of the aircraft's main fuel tanks.

Front 18

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

Back 18

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.

Front 19

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

Back 19

A load control valve modulates the pneumatic load to maintain EGT's within limits.

Front 20

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

Back 20

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.

Front 21

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

Back 21

Fuel pressure.

Front 22

What is fan blade shingling?

Back 22

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

Front 23

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

Back 23

Any rubbing sound or other unusual noises from the engine