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M15 > FUNDAMENTALS > Flashcards

FUNDAMENTALS Flashcards

1
Q

What is acceleration due to gravity?

A

9.8 metres per second.

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2
Q

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

A

Accelerating ambient air.

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3
Q

What is the single purpose of a turbojet engines?

A

Producing high velocity gases.

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4
Q

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

A

Thrust.

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5
Q

What aircraft speeds are turbojet aircraft developed for?

A

High aircraft speeds

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6
Q

What are 2 disadvantages of turbojet aircraft?

A

They are very loud and inefficient.

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7
Q

How do turboprop aircraft engines produce thrust?

A

Small acceleration of a large quantity of air.

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8
Q

Where can the turboprop propeller be driven from?

A

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

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9
Q

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

A

Reduction gearbox.

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10
Q

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

A

High aircraft speeds.

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11
Q

What spool are turbofan engines?

A

Twin or triple

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12
Q

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

A

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

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13
Q

What is the total thrust of turbo fan engines?

A

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

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14
Q

What is weight measured in?

A

Newton’s.

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15
Q

What is the formula for work?

A

Force x distance

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16
Q

What is the formula for power?

A

Work / Time

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17
Q

What is energy?

A

Capacity of a body to perform work.

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18
Q

What can mechanical energy be divided into?

A 
Potential energy (energy virtue by position)
Kinetic energy (energy virtue by movement)
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19
Q

What type of engine is more fuel efficient?

A

Piston type

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20
Q

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

A

Performance decrease at higher altitudes

Ratio of weight and power decreases with size.

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21
Q

What are the 4 types of gas turbine engine?

A

Turboprop
Turbo fan
Turbojet
APU

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22
Q

What was the first gas turbine engine?

A

Turbojet

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23
Q

Why are turbojet engines extremely loud?

A

High exhaust gas velocities.

Require too much fuel

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24
Q

What force do engines create which moves the aircraft?

A

Propulsion.

25
Q

What is an engine which uses jet propulsion called?

A

A reaction engine.

Uses Newton’s law of motion

26
Q

What is the principle of jet propulsion?

A

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

27
Q

What must be done to accelerate the air?

A

Air pressure increase.

Mechanically with compressor, or thermally by increasing volume of air

28
Q

What is the formula for kinetic energy?

A

KE = 1/2 mV squared

29
Q

What is Newton’s first law called?

A

Law of inertia.

30
Q

What is the formula for force?

A

Mass x acceleration

31
Q

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

A

80% dependent on the bypass

32
Q

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

A

Between 4:1 and 9:1

33
Q

What are Most turbofan engines usually?

A

Short ducted.
Long ducted
Combined with separate exhausts

34
Q

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

A

Have a higher bypass ration 90:1

Use 20% less fuel

35
Q

Why are propfan engines not used on modern jet aircraft?

A

Due to mounting difficulties

36
Q

What is a non-modular engine design?

A

An engine built in one whole unit.

37
Q

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

A

Saved weight and was fully functional

38
Q

Where are non-modular engine designs commonly used?

A

Some APU’s and older aircraft.

Take the whole engine off to gain access to some places

39
Q

What are most modern jet aircraft engine constructions?

A

Modular design.

40
Q

What are modular design engines further developed into?

A

Major engine modules and sub-modules.

41
Q

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

A

Minor maintenance - can be done by maintenance organisation

42
Q

What are the Advantages to the manufacturer in modular design?

A
  • rotating parts pre balanced
  • less spare engines needed
  • more flexibility when changes to an individual part
43
Q

What are the advantages to an operator with modular engines?

A
  • modules replaced without major disturbance
  • no rebalance when models changed
  • module can be replaced while engine remains on aircraft
44
Q

Where is aluminium alloy used in engines?

A

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

45
Q

Where are ceramic casings used in engines?

A

Combustor and high pressure turbine

46
Q

Where are steel alloys used in engines?

A

N1 drive shaft, engine bearings and structural frames.

47
Q

Where are cobalt parts used on engines?

A

Stator or the first part of the HP turbine.

Heat resistant

48
Q

Where are titanium based alloys used in engines?

A

Fan, LP compressor, and front stages of the HP compressor

Strong as steel but half as heavy

49
Q

Where are nickel based alloy used on engines?

A

HP compressor, combustion section, HP/LP turbines.

High centrifugal loads and high temps

50
Q

What is Newton’s third law referred to?

A

The law of action and reaction.

Every action has equal and opposite reaction

51
Q

What is the Brayton cycle?

A

Pressure energy increased
Addition of heat energy
Conversion to kinetic energy

52
Q

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

A

Induction
Compression
Combustion
Exhaust

53
Q

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

A

Piston.

Gas is simultaneously

54
Q

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

A

More fuel burnt quicker producing greater power.

55
Q

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

A

Pressure of air not rising during combustion but volume increasing.

(Gas turbine engine)

56
Q

What conditions are there in isobaric heating?

A

No peak or fluctuating pressures

57
Q

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

A

Cylinders of heavy construction and high octane fuels.

58
Q

What type octane fuels do gas turbine engines use?

A

Low octane fuels.

M15 (18 decks)

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