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M15 Lewis > 15.3 > Flashcards

15.3 Flashcards

1
Q

Whats total head pressure

A

Pressure of the air when bought to rest in front of wings and intakes

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2
Q

What’s a RAM ratio

A

The ratio of the total pressure at inlet to the compressor to the stand pressure of air mov8ng through the duct

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3
Q

Whats the difference between a convergent duct and a divergent duct

A

Convergent= inlet duct gets smaller
Divergent= inlet duct gets wider

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4
Q

What happens to static pressure in a divergent duct

A

Increases static pressure

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5
Q

What can cause air disturbances into the engine inlet

A

Damage to intake case
Ice build up
Crosswinds during low speed operation

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6
Q

What speed should the airflow be into the compressor for it to be considered to flow smoothly

A

0.4 and 0.7 Mach

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7
Q

During flight air intakes convert kinetic energy to what and what affect does this have on the airflow

A

Pressure energy
Ans this slows the airflow

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8
Q

What’s the most efficient inlet configuration for subsonic flights

A

Pitot type quasi circular diffuser

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9
Q

What characteristic do intake lips have to prevent flow separation and what must be considered about this characteristic

A

Well rounded but must not be to thick as thin lips are required at high speeds to maintain performance

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10
Q

What speeds are pitot types intake designs practical for

A

Low Mach numbers up to Mach 1.5

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11
Q

What’s sub critical condition

A

When rpm of engines reduced causing pressure in inlet to increase meaning that less air can enter causing the shockwave to detach and move closer upstream

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12
Q

What’s the efficiency of pitot intakes

A

96-99%

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13
Q

What’s the efficiency of wing root intakes

A

87-95%

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14
Q

What’s the efficiency of side intakes

A

80-89%

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15
Q

What’s the efficiency of turbo prop intakes

A

74-82%

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16
Q

What happens to velocity and pressure of supersonic airflow after a normal shockwave

A

Velocity drop to subsonic and pressure rises

17
Q

What is the energy that isn’t converted into pressure energy after a normal shockwave converte£ into

A

Unusable heat

18
Q

What shockwaves more intense a normal or oblique

A

Normal

19
Q

What’s the disadvantage or a normal shock diffuser

A

It causes an abrupt loss of efficiency as Mach number increases

20
Q

How many shocks are produced by variable geometry air inlet ducts at supersonic flight and what are they

A

4

3 are oblique
1 is normal

21
Q

What two negative affects does ice have on air inlets

A

Disturbed airflow
Can damage fan blades

22
Q

What are requirements for engine anti icing systems

A

Reliable
Ease of maintenance
No excess weight penalty
No loss of engine power

23
Q

What two things can be used to protect spinner come from ice formation

A

Hot oil and rubber spikes

24
Q

What part of the engine is the hot bleed air used for engine de icing bled from

A

HP compressor

25
Q

What’s the role of the anti icing valves in engine

A

To prevent over pressurisation and to limit the amount of bleed air to be used from engine so it doesn’t affect the engine performance

26
Q

What’s used to eject the air used to de ice inlets overboard

A

Grills

27
Q

When does the amber light on the engine anti icing switch turn on

A

It’s on until the low pressure switch senses a duct pressure of more than 5 psi

28
Q

What type of electrical supply is used to power electrical inlet ant icing systems

A

AC OR DC

29
Q

What’s the difference between continuously heated and intermittently heated elements

A

Continuously heated elements prevent formation of ice ( anti ice ) and intermittently heated elements allow a thin layer of ice to build and then heated to cause it to break away ( de ice )

30
Q

What time and temp do FAST ice protection cyclic sequences operate at? SLOW ice protection cyclic sequences?

A

Fast= 2 mins between -6 and 10 degrees
Slow= 6 mins below -6

31
Q

What are type of damage are heater mats examined for

A

Splits, wrinkling, tears and discolouration

M15 Lewis (18 decks)

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