Chapter 1

Question 1

The working theory of a gas turbine engine is according to

Answer 1

Newton’s 3rd law

Question 2

The thrust force generated is according to

Answer 2

Newton’s 2nd law

Question 3

The compressor in a running gas turbine engine is turned by the

Answer 3

Compressor turbine

Question 4

What is thrust?

What is generated by?

How is it generated?

Answer 4

the force that propels an object in one direction

the force generated by the engine to propel the aircraft forward

thrust is generated through the reaction of the accelerating mass of air

Question 5

What are the main modules of a gas turbine engine?

Answer 5

Inlet

Compressor

Combustion Chamber

Turbine

Exhaust

Question 6

What are the main functions of a compressor in a gas turbine engine?

Answer 6

add energy to the gas

increase the pressure of the gas

increase the temperature of the gas

Question 7

What are the main functions of the combustion chamber?

Answer 7

add energy to the gas

increase the velocity of the gas

increase the temperature of the gas

Question 8

What turns the turbine in a gas turbine engine?

Answer 8

the hot air from the combustion chamber

Question 9

What can be said about the pressure of the gas in the combustion chamber?

Answer 9

pressure is constant in the combustion chamber

Question 10

What are the main functions of the turbine in a gas turbine engine?

Answer 10

The turbine extracts energy from the hot gases exiting the combustion chamber.

The turbine will then turn the compressor

Question 11

What can be said about the gas’s velocity, temperature, and pressure at the turbine stage of the gas turbine engine?

Answer 11

velocity increases

temperature and pressure decreases

Question 12

What happens at the exhaust of a gas turbine engine?

Answer 12

the remaining air that exits the exhaust will produce thrust

Question 13

What equation can be to explain the effects of a convergent/divergent passage at subsonic flow?

Answer 13

mass flow rate equation

mass flow rate = density x area x velocity

Question 14

In a convergent passage at supersonic airflow, what can be said about the changes in velocity and pressure?

Answer 14

velocity decrease

pressure increase

Question 15

In a divergent passage at supersonic airflow, what can be said about the changes in velocity and pressure?

Answer 15

velocity increase

pressure decrease

Question 16

Which part of the engine is where the pressure is the highest?

Answer 16

combustion chamber/compressor outlet

Question 17

which part of the engine holds the highest temperature?

Answer 17

the turbine inlet temperature

Question 18

which part of the engine is the highest stress region in terms of temperature and pressure?

Answer 18

turbine inlet temperature

Question 19

what are the two types of thrust producing gas turbine engines?

Answer 19

turbojet engine

turbofan engine

Question 20

what are the two types of torque producing gas turbine engines?

Answer 20

turbo-shaft engine

turboprop engine

Question 21

how do turbojet engines produce thrust?

Answer 21

by accelerating a small mass of air to a very high velocity to product thrust

Question 22

how do turboprop engines produce thrust?

Answer 22

by giving a small acceleration to a big mass of air to produce thrust

Question 23

Why is a reduction gearbox needed in a turboprop engine?

Answer 23

the propeller in a turboprop engine needs to rotate at a lower RPM than the turbine, thus a reduction gearbox is used. This is to ensure the velocity does not exceed M1.0 to prevent the blade from stalling.

Question 24

a free turbine is a turbine that is?

Answer 24

A free turbine is not mechanically connected with the compressor

Question 25

what is meant by a 3 stage axial flow compressor?

Answer 25

the compressor has 3 stages. Axial means the air goes in and comes out linearly, in the same direction

Question 26

what is meant by a centrifugal compressor?

Answer 26

it is a compressor whereby : air goes in linearly air goes out diagonally usually at a 90 degree angle

Question 27

What is the airworthiness standard chapter for aircraft engine in FAR

Answer 27

FAR Part 33

Question 28

describe an air-breathing gas turbine engine

Answer 28

an engine that uses atmospheric air as a working fluid

Question 29

What is inlet momentum drag (ram drag)?

Answer 29

inlet momentum drag (ram drag) is the difference between gross thrust and net thrust

Question 30

What causes inlet momentum drag(ram drag)?

Answer 30

- inlet momentum drag(ram drag) is caused by the momentum of the mass of air entering the engine inlet - inlet momentum drag(ram drag) is caused by the increasing speed of air that enters the engine inlet

Question 31

inlet momentum drag(ram drag) causes ?

Answer 31

reduced thrust

Question 32

For aviation applications, turboshaft engines are only used on?

Answer 32

APU & helicopters

Question 33

What is the main purpose of the turbofan engine?

Answer 33

to turn the fan.

Question 34

Compare the propulsive efficiency of turbojet turboprop and turbofan engines

Answer 34

1. turbojet engines have low propulsive efficiency at low altitudes and low airspeed. its propulsive efficiency will increase with an increase in altitude and airspeed because it is best used at high altitude and high airspeed 2. turboprop engines have high propulsive efficiency at low altitudes and low airspeed. Its propulsive efficiency will decrease rapidly with an increase in altitude and airspeed 3. turbofan engines have low propulsive efficiency at low altitudes and low airspeed. Its propulsive efficiency will increase with an increase in altitude and airspeed **up to sonic speed**

Question 35

compare the thrust-specific fuel consumption (TSFC) of turbojet, turboprop, and turbofan engines.

Answer 35

1. turbojet engines have relatively high TSFC at low altitudes and low airspeed however its TSFC will decrease with an increase in altitude and airspeed. 2. turboprop engines have low TSFC at low altitudes and low airspeed however its TSFC will increase with an increase in altitude and airspeed. 3. the TSFC of a turbofan engine falls in between a turbojet engine and a turboprop engine.

Question 36

compare the takeoff roll between turbojet engine and turboprop engine

Answer 36

turbojet engine requires a longer takeoff roll turboprop engine requires a shorter takeoff roll

Question 37

compare the frontal area between turbojet and turboprop engines

Answer 37

turbojet - smaller frontal area, reduced ground clearance issues turboprop - large frontal area, requires longer landing gear

Question 38

describe propulsive efficiency

Answer 38

it refers to the fuel consumption vs thrust produced by the engine

Question 39

what is (TSFC)?

Answer 39

It refers to thrust-specific fuel consumption. it measures the fuel efficiency of an engine design with respect to its thrust output. LOW TSFC = high efficiency HIGH TSFC = low efficiency

Question 40

What are the advantages of a gas turbine engine over a reciprocating engine? ## Footnote **V.F.F.L.A.S.H.**

Answer 40

Very High power to weight ratio far less vibration fewer moving parts low lubricating oil cost and consumption ability to generate higher thrust smaller in size high operation speeds

Question 41

what are the disadvantages of gas turbine engines compared to a reciprocating engine? C.U.M.D.

Answer 41

Cost is much greater - stronger and more heat resistant materials required usually less fuel-efficient, especially at idle machining operations are more complex delayed response to changes in power settings