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1_Sharper Edge ATPL > Airframe and Aircraft Systems > Flashcards

Airframe and Aircraft Systems Flashcards

1
Q

In a turbocharged or turbo-normalised engine, the fuel is added ___ the air is compressed.

A

After.

Note: If fuel was added beforehand, the fuel & air mixture could not be put through the hot compressor.

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2
Q

What is the critical alt. for a turbocharger?

A

The altitude at which the turbo can’t maintain the pressure required to produce the rated engine power. Above this altitude, engine performance will start decreasing.

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3
Q

What can cause a compressor stall?

A
  • Air entering the inlet at too steep an angle, causing turbulence
  • Dirt on the compressor blades (similar to frost on an airplane wing)
  • Wear or damaged compressor blades reduces their critical angle
  • Icing
  • If bleed or surge vales don’t open correctly
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4
Q

What is Ng/N1?

A

Ng or N1 is the RPM or a %RPM of the gas generator (compressor turbine). Also referred to as the low pressure spool.

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5
Q

What is Np or N2?

A

The rotational rate of the propeller turbine or power turbine.

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6
Q

How do Turboprops, Turbofans and Turbojets accelerate the air they take in?

A
  • Turboprop - very large mass of air, small acceleration
  • Turbofan - large mass of air, medium acceleration (more efficient)
  • Turbojet - large mass air, very high acceleration (high exhaust velocity = wasted energy).
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7
Q

What’s the air to fuel ratio of a turbine?

A

15:1

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8
Q

What controls cabin pressure in a pressurized aircraft?

A

Regulating outflow air

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9
Q

A turbocharger works by increasing the ___ of air to the engine.

A

mass

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10
Q

What is bypass ratio?

A

The ratio of air flowing through the bypass duct to air which flows through the combustion chamber.

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11
Q

What does the wastegate control in a turbocharger?

A

The wastegate controls the amount of exhaust gas that flows through the turbocharger. A fully open wastegate means very little or no exhaust gass will flow through the turbocharger, making is basically inoperative.

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12
Q

When are compressor stalls most likely to occur?

A

During accelerating or starting

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13
Q

What is Engine Pressure Ratio (EPR) and why is it important?

A

Ratio of turbine inlet air pressure to exhaust pressure. Indicator of engine health.

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14
Q

What stops the prop from reversing in flight?

A

Low pitch stops

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15
Q

What determines the level of boost in a turbocharged piston engine?

A

The wastegate which diverts exhaust gas through or around the turbocharger turbine.

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16
Q

Cabin pressure is regulated through a ___ inflow of bleed air and a ___ outflow of air through ___.

A
  • constant inflow
  • variable outflow
  • via outflow valves
17
Q

True/False - The majority of energy created by combustion in a turbojet is used to drive the compressors?

A

True

18
Q

What % of the air passing through the combustion chamber of a gas turbine is combusted with the fuel?

A

30%

19
Q

Thrust reversers on a turbofan are generally called ___ and operate by reversing ___.

A

Cascades, bypass air.

20
Q

Two purposes of the fuel additive “Prist”

A
  1. Fuel anti-freeze
  2. Prevents bacteria and fungal growth in the fuel tanks
21
Q

Engine bleed valves vs. Engine bleed air?

A

Engine bleed valves - prevent surges or stalls

Engine bleed air - provide bleed air to systems

22
Q

On a multi-spool turbojet, the starter motor normals turns the ___

A

HP spool.

23
Q

What do hydraulic accumulators do?

A

Smooth out pressure variations in a hydraulic system.

24
Q

3 limiting factors for turbojet engines?

A
  1. Inlet air temp
  2. Rotor speed
  3. Shaft torque
25
Q

What is the job of the stator veins between the axial compressors?

A
  • Reduce rotational component of airflow
  • Increase air pressure
  • Guide air to the next compressor at the correct angle
26
Q

How do you determine power output on a turboprop?

A

Prop RPM and Torque

27
Q

What does a diffuser tube do in a turbine engine?

A

Decrease airflow velocity and increase pressure

28
Q

What do you get from turbofan over a turbojet?

A
  • Acceleration of larger air mass
  • More thrust
  • Less noise
29
Q

An increase in oil pressure to the prop hub creates a ___ pitch, while a decrease causes the prop to ___

A

Fine, Feater

30
Q

How does the beta valve work when reverse is selected?

A

The beta valve opens allowing oil pressure to the prop hub.

31
Q

The term used in a free turbine to describe how combustion exhaust gas drives the power turbine?

A

Fluidic coupling

32
Q

In what situations is asymmetric thrust greatest?

A
  • high angles of attack
  • high power settings
33
Q

3 purposes of an APU (commonly in the tail)?

A
  • Electrical power
  • Pneumatic air
  • Can start the aircraft’s engines
34
Q

What do fusible tire plugs do?

A

Produce a controlled deflation if tire becomes too hot.

1_Sharper Edge ATPL (4 decks)

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