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M15 > M15.03 Inlets > Flashcards

M15.03 Inlets Flashcards

1
Q

Air enters the engine via?

A

The engine air intake

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2
Q

If the air if the air inlet duct gets wider it’s a?

A

Divergent inlet

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3
Q

A divergent duct does what to the air passing through?

A

. Velocity decreases
. Static Pressure increases
. Temperature increases

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4
Q

The air intake has a inlet duct and inlet nose, what does the nose do?

A

Helps smooth out the airflow

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5
Q

Air disturbances can be caused by?

A

. Damage to the intake nose
. Ice build up
. Cross winds

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6
Q

In order for air to flow smoothly to the compressor, what velocity does it need to be?

A

Between 0.4 - 07 Mach (307-537mph)

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7
Q

Air intakes are designed to decrease airflow speed by?

A

Converting kinetic energy to static pressure without shocks or lose of aircraft speed

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8
Q

The condition of an air inlet are present?

A

In ground and during flight

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9
Q

Subsonic ducts are shaped to ensure?

A

Even pressure distribution to the compressor
Else could cause compressor stall

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10
Q

What is the most efficient subsonic inlet configuration?

A

Pitot type quasi-circular diffuser

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11
Q

To reduce the risk of airflow separation, how are the inlets shaped for subsonic?

A

Inlet lip is well rounded with a thicker radius
(However at high speeds, the inlet lip needs to be thin)

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12
Q

When engines are mounted under the wing, what can happen?

A

Ground vortex’s (mini tornados) can form, which is swelled by the inlet, further decreases performance.

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13
Q

Another thing that can effect the performance of an inlet is?

A

Crosswinds

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14
Q

The subsonic air inlet duct form a divergent or convergent duct??

A

Divergent, which means it gets wider which would increase the static pressure

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15
Q

At transonic speeds the inlet is designed to keep the shock waves out and reduce the speed, how is this done?

A

By using a normal shockwave diffuser to decelerate the airflow to speed compressor can cope with.

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16
Q

What will the normal shockwave do to the air entering the transonic inlet?

A

Reduce the velocity to subsonic
Increase pressure
Increase temperature

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17
Q

What is critical condition??

A

When a Cross section of the inlet must allow the maximum engine airflow requirements at only one specific Mach number and altitude

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18
Q

What is sub-critical condition?

A

When RPM demand is reduced the shock wave detaches from the inlet lip and moves upstream of inlet, which causes bow wave to form and Mach number to decrease

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19
Q

What is super- critical condition??

A

When RPM demand is increases to more than the inlet can cope with, it causes a pressure drop which causes the shock wave to be swallowed, which allows supersonic airflow in the inlet. Which results in couples shockwaves and turbulence.

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20
Q

Duct inefficiencies or 1% will cause a loss of thrust of what %?

A

1-4% of thrust loss

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21
Q

Three types of shock waves that can form on inlets?

A

. Normal
. Oblique
. Bow wave

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22
Q

What occurs when a normal shock wave takes place??

A

Velocity abruptly drops to subsonic and pressure rises

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23
Q

During a normal shock wave, a lot of pressure is generated, is this all usable??

A

No, large amount is turned into heat energy

24
Q

When would an oblique shockwave take place?

A

When the airflow is force to change direction

25
Q

What happens after an oblique shock wave?

A

Less serve magnitude and flow, decreases a bit but stays supersonic

26
Q

When do normal shock waves take place?

A

At low supersonic airspeed and stand perpendicular to the airflow

27
Q

Bow shock wave?

A
28
Q

What does the normal shock inlet employ?

A

A single normal sock wave at the inlet to slow the air to subsonic

29
Q

At what speeds can the normal shock inlets work at?

A

Slow speeds, not suitable for Hugh speeds as it causes a reduction in pressure/ efficiency (30% at Mach 2)

30
Q

What does the oblique shock inlet do?

A

Employed a series of external oblique shock waves to slow the supersonic airflow before the normal shock occurs, that way the normal wave would on,y be weak, causing only a small loss of efficiency

31
Q

What is diffuser buzz?

A

When a normal shock wave is swallowed and expelled continuously at high speeds
(Buzz due to sound it makes)

32
Q

How can you overcome a diffuser buzz?

A

By using a variable geometry inlet

33
Q

How do variable geometry air inlets work?

A

. At supersonic - produces multiple oblique shock waves then followed by a normal shock wave.
. At transonic - a normal shock is formed

34
Q

At a high Mach number how many oblique waves and normal waves are formed??

A

3 oblique waves and then 1 normal wave

35
Q

What are the two negative effects of ice in engine inlets?

A

. Disturbed airflow - decreases performance
. Engine sucks ice up and damages

36
Q

All jet engine have for ice?

A

Thermal anti ice systems

37
Q

What are the requirements of anti ice systems?

A

. Reliable
. Easy maintenance
. No excess weight
. No reduction of enshrine power

38
Q

What are the two types of thermal anti ice systems?

A

. Bleed air
. Electrical heating

39
Q

What system only protects the engine spinner and intake lip?

A

Bleed air system

40
Q

What other methods protect the engine spinner?

A

. Hot oil pumped around inside the spinner
. Rubber spikes - causes unbalance then spins off

41
Q

Where is the bleed air from??

A

Engine HP compressor

42
Q

What do anti ice valves protect against?

A

Over pressurisation and limits the bleed air

43
Q

Where does waste anti ice air go?

A

Over board via small grills

44
Q

How are anti ice valves selected and operated?

A

Electrically selected and pressure operated

45
Q

On the engine intake thermal anti ice ins, the amber light will illuminate until?

A

The low pressure switch senses a duct pressure of more than 5 psi

46
Q

Where is duct over pressure signalled?

A

ECAM or EICAS

47
Q

What engine are electrical anti ice systems normally used on?

A

Turboprop

48
Q

What is the electrical power supplied to heater mats?

A

AC or DC

49
Q

What type of heater mats are there?

A

Continuous and intermittent

50
Q

What is the purpose of continuous heated elements?

A

Prevent ice formation in leading edge, intake and spinners

51
Q

What is the purpose of intermittent heated elements?

A

. Situated behind continuous heated mats
. During heat OFF allows thin layer of ice to build up
. During heat ON rapidly melts the ice

52
Q

To ensure ice breaks off easily on intermittent heat mats, what is there??

A

The elements are divided into separate segments

53
Q

At +10 to -6 degrees what ice protection cycle is used and for how long?

A

. Fast
. 2 minutes

54
Q

At below -6 degrees what ice protection cycle is used and for how long?

A

. Slow
. 6 minutes

55
Q

What are continuity of heater checks?

A

Check correct resistance, carried our at prescribed inspections and following repairs

56
Q

What do insulation resistance check for?

A

To see if there is any breakdown of insulation between heater mats/ elements

57
Q

What are heater mats examined for?

A

. Splits
. Wrinkles
. Tears
. Discolouration

M15 (10 decks)

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