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M11 Aircraft Systems > 11.1.2 > Flashcards

11.1.2 Flashcards

high speed flight

1
Q

how may times is the speed of sound in water than air

A

4.3

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2
Q

4 speed ranges

A

subsonic , transonic , supersonic, hypersonic

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3
Q

subsonic speed range

A

up to 0.8

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4
Q

supersonic speed range

A

1.2-5

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5
Q

transonic speed range

A

0.8-1.2

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6
Q

hypersonic speed range

A

above mach 5

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7
Q

what property of air changes with the onset of transonic flight

A

air becomes compressible

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8
Q

what is mach number

A

aircraft speed / speed of sound

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9
Q

what is crit mach number

A

fastest speed aircraft can go without becoming subject to supersonic airflow

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10
Q

what wing design delays onset of crit mach

A

Swept wing

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11
Q

where does supersonic airflow first occur on an aerofoil

A

upper surface

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12
Q

what forms on upper surface when crit mach is reached

A

shockwave

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13
Q

what happens to airflow behind a shockwave

A

large increase in static pressure & flow separation

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14
Q

what do u oblique shockwaves do

A

slow supersonic airflow before shockwave occurs

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15
Q

where are oblique shockwaves employed

A

in the intakes

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16
Q

what happens to air velocity in an expansion wave

A

It increases

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17
Q

why does flow separation occur behind a shockwave

A

boundary layer does not have enough kinetic energy to withstand the large increase in static pressure

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18
Q

when does a bow wave form

A

flight speed exceeds speed of sound

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19
Q

which wing profile is known as wing loaded

A

Transonic

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20
Q

advantages of rear loaded profile

A

lighter, greater fuel capacity, less drag, less sweepback, smaller wing, better low speed charactericts

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21
Q

how is tuck under avoided

A

mach trim system

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22
Q

what drag increases due to vortex generators

A

Parasitic Drag

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23
Q

method of reducing wave drag

A

area rule

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24
Q

where does shockwave first form on wing

A

wing root

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25
Q

two types of shockwaves

A

normal and oblique

26
Q

what shockwave causes an increase in velocity in airflow

A

none, only expansion wave causes increase in velocity

27
Q

how does vortex generator re-energise the boundary layer

A

transfers energy from free airflow to the boundary layer

28
Q

when does the boundary layer separate from aerofoil section

A

when the normal shockwave forms

29
Q

what effect does aerodynamic heating have on metal

A

they lose strength

30
Q

what point is airflow over a wing at its maximum but below speed of sound

A

Critical mach number

31
Q

normal swept wing angle

A

30 degrees

32
Q

transonic wing profile

A

flatter upper surface
curved leading edge
thinner trailing edge
than normal

33
Q

how is shock stall corrected

A

with horizontal stabiliser

34
Q

where is c.o.g located on balance control surface

A

on hinge line

35
Q

how is high speed turn controlled by flying control surfaces

A

aileron and roll spoilers

36
Q

what automatic system of the horizontal stabiliser corrects tuck under

A

Mach trim

37
Q

how many ailerons fitted to large aircraft

A

4 , 2 outbound, 2 inbound

38
Q

when do inbound ailerons operate

A

low speed and high speed

39
Q

when do outbound ailerons operate

A

low speed only

40
Q

aluminium strength lose how much strength at temperatures over 250 degrees

A

80%

41
Q

On a swept wing where does it stall first

A

Tip

42
Q

Dutch roll is movement is in which direction

A

Yaw and roll

43
Q

What are Kruger flaps

A

Leading edge flap hinges

44
Q

How are peto tubes heated

A

Electrically

45
Q

What is the artificial feel system used for

A

Required for power operated systems

46
Q

Where does shockwaves form

A

Highest point of camber

47
Q

when does a bow wave form

A

Above speed of sound

48
Q

What does vortex generator do

A

Re-energises boundary layer

49
Q

Purpose of swept wing

A

Aerodynamic purposes creating a longer thinner wing with an angle of 30 degrees

50
Q

Why do transonic profiles perform well in transonic reigons

A

There’s no flow separation behind the shockwave as this flow would generate lift

51
Q

If velocity increases what happens to the centre of pressure

A

Moves rearwards

52
Q

How is centre of pressure moving rearward offset

A

By horizontal stabiliser

53
Q

What are the waves formed by supersonic flow

A

Shock waves and expansion waves

54
Q

How can we increase critical Mach

A

Decreasing camber and increasing chord

55
Q

What happens during stall shock

A

Lift increases and drag decrees

56
Q

What happens to crit mach with a thicker camber

A

Crit Mach lowers

57
Q

How much faster is speed of sound in water than air

A

4.3 times out of

58
Q

How much faster is speed of sound in air than water

A

4.3 times slower

59
Q

What’s another name for flight tabs

A

Servo tab

60
Q

Where is the balance panel effective

A

High speeds

M11 Aircraft Systems (23 decks)

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