Turbine Engines

Question 1

What is the main difference between a turbofan and a turbojet engine?

Answer 1

A turbofan uses a fan to bypass air around the engine to provide thrust, allowing for additional thrust without increasing fuel flow.

Question 2

What are the major components in a gas turbine engine?

Answer 2

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

Question 3

What determines the amount of airflow through a turbine engine?

Answer 3

Forward speed of the aircraft, compressor speed, and air density.

Question 4

What are the two types of compressors commonly used in turbine engines?

Answer 4

Axial and centrifugal flow.

Question 5

What are two methods for attaching turbine engine rotor blades to their main rotor discs?

Answer 5

Dovetail and bulb, fur tree.

Question 6

What is a split compressor system also called?

Answer 6

Dual or twin spool compressors, which are connected to the turbine section with two rotor shafts, one inside the other.

Question 7

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

Answer 7

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

Question 8

What prevents the combustion chambers from burning?

Answer 8

Cooling air along the inside of the liner.

Question 9

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

Answer 9

Flame propagation during start.

Question 10

What functions do axial flow turbine nozzles perform?

Answer 10

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

Question 11

How is thermal stress relieved on a turbine disc?

Answer 11

By directing bleed air onto the face of the disc or by cutting grooves in the disc.

Question 12

What are carbon seals used for in turbine engines?

Answer 12

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

Question 13

What is shaft horsepower?

Answer 13

Torque developed.

Question 14

What are the main components of a typical APU?

Answer 14

Small power turbine and electrical generator.

Question 15

When is the greatest demand placed on an APU?

Answer 15

Supplying bleed air.

Question 16

How is an APU generally started?

Answer 16

Using an electrical starter and battery power.

Question 17

Where does the APU get its fuel supply from?

Answer 17

Main fuel tanks.

Question 18

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

Answer 18

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

Question 19

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

Answer 19

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

Question 20

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

Answer 20

After unloading by closing the bleed air valve, it is run for a specified amount of time to allow the EGT to cool and stabilize, typically three minutes. Abrupt shutdown without cooling could cause thermal shock damage.

Question 21

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

Answer 21

Intake airflow fuel pressure.

Question 22

What is fan blade shingling?

Answer 22

Overlapping of the middle of shrouds of the fan blade.

Question 23

What should a mechanic listen for during coast down of a turbofan or turbojet engine?

Answer 23

Rubbing sound or unusual noises from the engine.