FUNDAMENTALS

Question 1

What is acceleration due to gravity?

Answer 1

9.8 metres per second.

Question 2

How does a gas turbine, turbo fan and turbo prop engine produce thrust?

Answer 2

Accelerating ambient air.

Question 3

What is the single purpose of a turbojet engines?

Answer 3

Producing high velocity gases.

Question 4

On turbo jet aircraft what is all gas energy that isn’t used to drive the compressor and accessories converted into?

Answer 4

Thrust.

Question 5

What aircraft speeds are turbojet aircraft developed for?

Answer 5

High aircraft speeds

Question 6

What are 2 disadvantages of turbojet aircraft?

Answer 6

They are very loud and inefficient.

Question 7

How do turboprop aircraft engines produce thrust?

Answer 7

Small acceleration of a large quantity of air.

Question 8

Where can the turboprop propeller be driven from?

Answer 8

Directly from the compressor shaft or by a free turbine and a long centre drive shaft

Question 9

What is required to reduce the high gas turbine engine rotation speeds that can be managed by the propeller?

Answer 9

Reduction gearbox.

Question 10

Turboprop engines convert gas energy into torque. The are very efficient, but what does the propeller not permit?

Answer 10

High aircraft speeds.

Question 11

What spool are turbofan engines?

Answer 11

Twin or triple

Question 12

Normally, what do turbofan engines have to reduce the speed of the fan?

Answer 12

Nothing, the fan does not have a reduction gear box.

Question 13

What is the total thrust of turbo fan engines?

Answer 13

The sum of the thrust developed by the core engine and fan.

Question 14

What is weight measured in?

Answer 14

Newton’s.

Question 15

What is the formula for work?

Answer 15

Force x distance

Question 16

What is the formula for power?

Answer 16

Work / Time

Question 17

What is energy?

Answer 17

Capacity of a body to perform work.

Question 18

What can mechanical energy be divided into?

Answer 18

Potential energy (energy virtue by position)
Kinetic energy (energy virtue by movement)

Question 19

What type of engine is more fuel efficient?

Answer 19

Piston type

Question 20

What are disadvantages of the piston engine (only used on small aircraft)?

Answer 20

Performance decrease at higher altitudes

Ratio of weight and power decreases with size.

Question 21

What are the 4 types of gas turbine engine?

Answer 21

Turboprop
Turbo fan
Turbojet
APU

Question 22

What was the first gas turbine engine?

Answer 22

Turbojet

Question 23

Why are turbojet engines extremely loud?

Answer 23

High exhaust gas velocities.

Require too much fuel

Question 24

What force do engines create which moves the aircraft?

Answer 24

Propulsion.

Question 25

What is an engine which uses jet propulsion called?

Answer 25

A reaction engine. | Uses Newton’s law of motion

Question 26

What is the principle of jet propulsion?

Answer 26

A force is always created when a body of mass is accelerated.

Question 27

What must be done to accelerate the air?

Answer 27

Air pressure increase. | Mechanically with compressor, or thermally by increasing volume of air

Question 28

What is the formula for kinetic energy?

Answer 28

KE = 1/2 mV squared

Question 29

What is Newton’s first law called?

Answer 29

Law of inertia.

Question 30

What is the formula for force?

Answer 30

Mass x acceleration

Question 31

How much of the total thrust does the fan produce in a turbo fan engine?

Answer 31

80% dependent on the bypass

Question 32

On a modern turbo fan engine, what are the typical bypass ratios?

Answer 32

Between 4:1 and 9:1

Question 33

What are Most turbofan engines usually?

Answer 33

Short ducted. Long ducted Combined with separate exhausts

Question 34

What is the advantage of propfan engines to high bypass engines?

Answer 34

Have a higher bypass ration 90:1 | Use 20% less fuel

Question 35

Why are propfan engines not used on modern jet aircraft?

Answer 35

Due to mounting difficulties

Question 36

What is a non-modular engine design?

Answer 36

An engine built in one whole unit.

Question 37

What is an advantage of a Non-modular engine design?

Answer 37

Saved weight and was fully functional

Question 38

Where are non-modular engine designs commonly used?

Answer 38

Some APU’s and older aircraft. | Take the whole engine off to gain access to some places

Question 39

What are most modern jet aircraft engine constructions?

Answer 39

Modular design.

Question 40

What are modular design engines further developed into?

Answer 40

Major engine modules and sub-modules.

Question 41

What type of maintenance is a module replacement on modular design engines?

Answer 41

Minor maintenance - can be done by maintenance organisation

Question 42

What are the Advantages to the manufacturer in modular design?

Answer 42

- rotating parts pre balanced - less spare engines needed - more flexibility when changes to an individual part

Question 43

What are the advantages to an operator with modular engines?

Answer 43

- modules replaced without major disturbance - no rebalance when models changed - module can be replaced while engine remains on aircraft

Question 44

Where is aluminium alloy used in engines?

Answer 44

Gearbox housing, fan stator casings and other LOW LOADED parts of the fan module.

Question 45

Where are ceramic casings used in engines?

Answer 45

Combustor and high pressure turbine

Question 46

Where are steel alloys used in engines?

Answer 46

N1 drive shaft, engine bearings and structural frames.

Question 47

Where are cobalt parts used on engines?

Answer 47

Stator or the first part of the HP turbine. | Heat resistant

Question 48

Where are titanium based alloys used in engines?

Answer 48

Fan, LP compressor, and front stages of the HP compressor | Strong as steel but half as heavy

Question 49

Where are nickel based alloy used on engines?

Answer 49

HP compressor, combustion section, HP/LP turbines. | High centrifugal loads and high temps

Question 50

What is Newton’s third law referred to?

Answer 50

The law of action and reaction. | Every action has equal and opposite reaction

Question 51

What is the Brayton cycle?

Answer 51

Pressure energy increased Addition of heat energy Conversion to kinetic energy

Question 52

What’s the cycle of a four stroke piston engine?

Answer 52

Induction Compression Combustion Exhaust

Question 53

In what engine are the four stage cycle intermittent (one after the other) ?

Answer 53

Piston. | Gas is simultaneously

Question 54

What does a simultaneous (gas turbine) four process do?

Answer 54

More fuel burnt quicker producing greater power.

Question 55

What is the process of heating at constant pressure (isobaric heating)?

Answer 55

Pressure of air not rising during combustion but volume increasing. (Gas turbine engine)

Question 56

What conditions are there in isobaric heating?

Answer 56

No peak or fluctuating pressures

Question 57

What do the peak pressures make it necessary for piston engine to employ?

Answer 57

Cylinders of heavy construction and high octane fuels.

Question 58

What type octane fuels do gas turbine engines use?

Answer 58

Low octane fuels.