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M15 > 15.3 Inlet > Flashcards

15.3 Inlet Flashcards

1
Q

What are IGVs

A

Inlet Guide Vanes

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2
Q

What is the purpose of IGVs?

A

To straighten airflow and direct it into the compressor first stage.

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3
Q

What is the inlet duct a part of?

A

The airframe, not the engine.

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4
Q

What happens to velocity, pressure and temperature at a divergent duct?

A

V decrease.
P increases.
T increases.

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5
Q

What happens to velocity, pressure and temperature at a convergent duct?

A

V increases.
P decreases.
T decreases.

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6
Q

How does supersonic air behave a convergent and divergent ducts?

A

Oppositely to subsonic air.

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7
Q

On what engines can screens be found?

A

Turboprop and turboshaft.

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8
Q

What is the purpose of screens?

A

They cover the inlet to prevent FOD.

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9
Q

On what aircraft are divided entrance ducts found?

A

High speed military aircraft.

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10
Q

What are the 2 types of divided ducts?

A

Wing root inlet or scoop inlet.

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11
Q

What is the purpose of the turning vanes in the side scoop inlet?

A

They assist to straighten air preventing turbulence.

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12
Q

What is the design drawback of divided entrance ducts?

A

Trying to design them to a reasonable length with as few bends as possible.

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13
Q

Why is it difficult to obtain sufficient air scoop?

A

High drag.

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14
Q

What is the problem with sudden flight manoeuvres for divided entrance ducts?

A

They cause imbalance in RAM air pressure between the 2 ducts, causing a slight power loss.

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15
Q

What is the purpose of a variable geometry duct?

A

To provide the correct amount of air into the engine inlet.

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16
Q

What is the purpose of the inlet duct of a variable geometry duct?

A

To act as a diffuser= divergent duct.

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17
Q

What does the inlet duct of a variable geometry duct do to airs velocity and pressure?

A

V decreases.
P increases.

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18
Q

What does the inlet duct of a variable geometry duct do to airs velocity and pressure?

A

V decreases.
P increases.

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19
Q

How is the inlet of a variable geometry duct designed on a supersonic aircraft?

A

A sharp lip.

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20
Q

What is the purpose of the variable geometry duct varying the inlet area?

A

To manipulate the normal shockwave to occur at intake.

21
Q

In relation to a variable geometry duct, what are the 3 methods to diffuse inlet air to slow air to subsonic speed?

A

Vary the inlet area.
Use variable airflow bypass arrangement.
A shockwave in the airstream.

22
Q

On what engines is a compressor inlet screen used?

A

Turboshaft and turboprop.

23
Q

What are the problems with the compressor inlet screen?

A

Causes loss in duct pressure.
Susceptible to icing.

24
Q

When is the retractable compressor inlet screen retracted?

A

After take off or in icing conditions.

25
Q

What is the problem with the retractable compressor inlet stage?

A

Prone to mechanical failure.

26
Q

When is the bell mouth compressor inlet used?

A

During testing only.

27
Q

What is the purpose of the bell mouth compressor inlet?

A

To obtain very high aerodynamic efficiency as duct loss is considered zero.

28
Q

What is the purpose of deflector doors in a turboprop and turboshaft compressor inlet?

A

To deflect ice and dirt away from the intake.

29
Q

What is the purpose to the conical spinner?

A

Doesn’t allow ice to build up.

30
Q

On what engines the conical spinner used?

A

Turboprop and turbofan.

31
Q

What is the purpose of the fan in turbofan engine inlet section?

A

Reduce engine damage due to FOD.

32
Q

What is used for inlet lip anti icing in a turbofan engine inlet section?

A

Warm bleed air draw from LP compressor of engine.

33
Q

What is used for turboprop inlet area anti icing?

A

Warm oil from the engine oil reservoir.

34
Q

What is used if only the engine cowls require anti icing?

A

Electrical heat strips.

35
Q

What is the thermal system subdivided into ?

A

Bleed air and electrical heating.

36
Q

On what engines is bleed air from the HP compressor used for anti icing?

A

On engines with high mass airflow.

37
Q

What does bleed air provide surface heating of?

A

IGVs, spinner, inlet lip.

38
Q

What is the purpose of anti ice valves?

A

Protect against over pressurisation and limit bleed air to prevent engine power loss.

39
Q

How can anti ice valves be operated?

A

Mechanically or automatically.

40
Q

When does the anti ice valve open?

A

When manually selected or when the ice is detected on the sensor.

41
Q

Anti icing valves are electrically selected, pressure operated and have cockpit indications for what?

A

Valve not in selected position.
High pressure.
Low pressure.
High temperature.
Low temperature.

42
Q

How is the regulator valve controlled?

A

Solenoid controlled.

43
Q

What function is available in case of valve or system failure?

A

Manual override.

44
Q

Anti icing with electronic engine control is controlled by what?

A

FADEC.

45
Q

What is the electro thermal anti icing system?

A

Electrical heat strips.

46
Q

When are electrical heat strips designed to operate?

A

When engine is running without air passing over it.

47
Q

What effect does increased aircraft speed have on thrust?

A

Decreases it.

48
Q

What is RAM recovery/ total pressure recovery?

A

Added pressure at engine inlet increases pressure and airflow to the engine.

49
Q

Why must a turbofan engine duct have a sufficiently straight section?

A

To ensure smooth airflow due to high airflow.

M15 (18 decks)

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