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Module 15 > 15.3 > Flashcards

15.3 Flashcards

1
Q

What do the Inlets guide vanes do?

A

Straighten the airflow and direct it into the first stages of the compressor

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2
Q

Is the air inlet duct an airframe part, or part of the engine?

A

Airframe

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3
Q

What does the inlet vary according to?

A

The type of turbine engine

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4
Q

What do turboprop and turboshaft engines have to prevent FOD from entering?

A

Screens to cover the inlet

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5
Q

As aircraft speed increases, what happens to thrust? And what compensates for it?

A

It decreases so RAM air recovers it

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6
Q

What recovers as much of the total pressure of the free airstream as possible? And how?

A

The inlet by trapping air molecules and compressing it

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7
Q

What is “Ram recovery” or “Total pressure recovery”?

A

Added pressure at the inlet to increase pressure and airflow

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8
Q

The choice of configuration to the entrance of the duct depends on what?

A

Airspeed, altitude, attitude, location

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9
Q

Where are divided-entrance ducts located?

A

Military aircraft on either side of the fuselage

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10
Q

What two things can a divided duct be?

A

A wing-root inlet or a scoop

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11
Q

Disadvantage of divided ducts?

A

Drag

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12
Q

What is a major drawback in terms of designing the entrance duct in a divided entrance?

A

Having a reasonable length with a few bends as possible

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13
Q

Scoops at the side of the fuselage are used in devised entrance air inlets, where are they placed?

A

As far forward as possible

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14
Q

Why are side scoops placed as far forward as possible?

A

To permit a gradual bend toward the compressor inlet

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15
Q

What do turning vanes assist with in the side scoop?

A

The straighten the incoming air and prevent turbulence

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16
Q

What is a major disadvantage of the divided entrance inlets?

A

After sudden manoeuvres loss of power occurs in one engine so causes a pressure imbalance

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17
Q

In Variable-geometry ducts, what do the inlets act as?

A

Diffusers so they increase the static pressure but reduce velocity

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18
Q

The aft section of the duct does what to ensure it’s acting as a diffuser?

A

Increases its area

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19
Q

For very high speed aircraft what changes in order to compensate for the speed?

A

A variable geometry inlet duct

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20
Q

What are the three methods to diffuse the inlet air and slow it down at supersonic speeds?

A

Vary the area of the area inlet duct using a ramp or wedge
Use variable bypass arrangement
The use of a shockwave

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21
Q

What is the variable bypass arrangement?

A

It extracts part of the inlet airflow from the duct ahead of the engine

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22
Q

Why would you use a shockwave in an engine inlet in supersonic aircraft?

A

To decrease the velocity

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23
Q

What does a compressor inlet screen do?

A

Stops the engine from ingesting items

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24
Q

What are the disadvantages of inlet screens?

A

Loss of pressure and they are susceptible to contracting ice.

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25
Q

When are the screens retracted?

A

After take off and when ice formation is probable

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26
Q

What aircraft are screens not used on? Why?

A

Turbofan because they weigh a lot and the fan blades do not damage easily

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27
Q

When would you use a bell mouth compressor inlet?

A

When testing in a test cell

28
Q

What do the probes measure in a bell mouth duct inlet?

A

Pressure (total and static) and temperature

29
Q

What is the bell mouth attached to?

A

The moveable part of the test stand so moves with the engine

30
Q

What two parts is the bell mouth made up of?

A

A moving part and a non moving part so it can measure thrust

31
Q

What is the duct loss considered as in a bell mouth?

A

Zero

32
Q

What is the bell mouth mainly designed to obtain?

A

Aerodynamic frequency

33
Q

What does a bell mouth air intake look like?

A

A bell shaped funnel having carefully rounded shoulders which offer no air resistance

34
Q

How are inlets in turboprop and turboshaft heated?

A

By using electrical elements in the lip opening of the intakes

35
Q

What are deflector doors used for in turboprop and turboshaft?

A

To deflect ice or dirt away

36
Q

After the deflector doors where does the air pass through before entering the engine?

A

A screen

37
Q

What does a conical spinner do in turboprop and turbofan engines?

A

Does not allow ice to build up on the surface

38
Q

In dual spool engines, what allows the fan blades to rotate at low tip speed for best efficiency?

A

The fan is integral with the low pressure compressor

39
Q

How does the fan reduce damage from ingested foreign material?

A

It throws it radially outward and passes through the fan discharge rather than the core

40
Q

What is drawn from the engines to heat the inlet lip for anti icing?

A

Bleed air

41
Q

What prevents ice forming in the fan hub/spinner?

A

Warm air or uses a conical spinner

42
Q

What two effects can ice have on the engine inlet?

A

Disturb airflow so reduces performance on an engine leading to a compressor stall
Suck in ice which can damage the blades or inlet vanes

43
Q

What do turboprops use to provide anti icing to the inlet area?

A

Warm oil or hot air

44
Q

What is hot bleed air extracted from in the inlet extracted from?

A

The compressor stage of diffuser

45
Q

What is used if it is only the cowls that require anti icing?

A

Electrical heat strips

46
Q

In what pattern is hot air sprayed?

A

High pressure pattern

47
Q

What temperature does ice form at?

A

5 degrees in dry air or 7 degrees in moist air

48
Q

What can thermal systems be divided into?

A

Bleed air
Electrical heating

49
Q

What engines is bleed air extracted from?

A

High mass airflow engines from the HP compressor

50
Q

What valve is hot air passed through to provide surface heating to IGV’s, the spinner and the intake lip?

A

Pressure regulating bleed valve (anti-ice valves)

51
Q

What do anti ice valves protect against in the anti-ice system?

A

Over pressurised and limit of bleed air

52
Q

How can anti ice valve be operated?

A

Automatically via ice detection system and manually via flight deck

53
Q

Where is the air used for the aircraft intake anti icing ejected?

A

Overboard through small grilles

54
Q

Where is anti icing air ejected when used for the nose cone and IGVs?

A

Overboard or back to the LP compressor intake

55
Q

When does a solenoid operated driven air shut off valve open?

A

When a switch in a flight deck is triggered or ice detector detects a build up of ice

56
Q

Where does the anti ice system in the engine get air from?

A

Pneumatic system or directly from engine via engine anti ice valve

57
Q

What does the hot air flow through in the cowling?

A

Tiny holes in the Anti ice duct

58
Q

Where does the hot air leave the leading edge if the engine?

A

Through openings in the lower part

59
Q

In a regulator valve what is used to operate the valve when there is a valve or system failure?

A

Manual override

60
Q

What positions can the anti ice valves be locked in?

A

Open and Closed

61
Q

When the turbine engine is controlled by an ECC, it is linked to the ECC as part of what?

A

FADEC

62
Q

On turboprop and shaft engines, what do they tend to use for anti icing?

A

Electrical heat strips (electrothermal)

63
Q

When are electrical heat strips designed to operate? Why?

A

When the engine is running ONLY
They can overheat without air running over it

64
Q

Are electrothermal systems constantly on when engine is running?

A

No. They are cycled on and off as required by ambient conditions

65
Q
A

Module 15 (18 decks)

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