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ATPL POF > Stalling > Flashcards

Stalling Flashcards

1
Q

Does the wing stall at the stalling (critical) angle of attack?

A

NO

It is the angle at which the wing produces maximum lift before stalling

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2
Q

How does aspect ratio affect the effective angle of attack

A

Low aspect ratio = High effective AOA

high aspect ratio = low effective AOA

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3
Q

On a rectangular wing, what part stalls first and why

A

The root

Because there is a greater downwash at the tip causing a smaller effective angle of attack

Less downwash at the root causing s greater effective angle of attack

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4
Q

Why is it more favourable to have a stall start at the wing root

A

Turbulent air hits the tailplane causing natural buffer = stall warning

Ailerons remain in un-stalled flow for longer = some lateral control

Wing drop is less pronounced

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5
Q

How does effective angle affect the aircraft stalling angle

A

Greater effective angle

Less the stalling angle

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6
Q

How does downwash affect the stalling angle

A

Bigger the downwash the bigger the stall angle of attack

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7
Q

What part of an elliptical wing stalls first

A

The training edge

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8
Q

Why does an elliptical wing have undesirable stall characteristics

A

Stall is sudden

Little / no buffer on tailplane

Ailerons ineffective

Large roll rates if wing drops

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9
Q

Where does a moderately tapered wing stall first

A

The middle

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10
Q

What are the stall characteristics of a moderately tapered wing

A

No stall warning (buffer)

Ailerons quickly become ineffective

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11
Q

Where does a highly tapered - swept wing stall first

A

Wingtip

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12
Q

Highly tapered / swept wing stall characteristics

A

Wing tip stalls first

Can have big roll rate (if one wing stalls first)

Ailerons don’t work well

No buffet (warning)

Centre of pressure moves forwards = pitch up

Increased downwash at wing root increases tailplane downforce = increasing AOA

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13
Q

What type of aircraft if most likely to be involved in a deep stall

A

Low tapered wing, sweepback and high elevator

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14
Q

What causes a deep stall

A

The cp moving forward on the wing causing the aircraft to pitch back, this puts the elevator into the turbulent wake of the stalled wing losing its effectiveness

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15
Q

What does a wing fence do

A

reduced spanwise flow on a sweptwing aircraft by creating a physical boundary to help try and prevent the wing tip stalling first

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16
Q

What does a vortilon do

A

Attached to leading edge

During High angles of attack it protrudes into upper wing spanwise flow

Causes tight High energy turbulent “barrier” to try prevent spanwise flow

To try and stop wing tip stalling first

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17
Q

How does washout and reduced camber stop wingtip stall

A

Washout out means the tip is at a lower angle of attack than the wing root

Meaning that it won’t reach its critical angle as soon

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18
Q

What thickness-chord ratio has the highest stalling AOA

A

A high thickness to chord ratio

(Big leading edge radius) increases the AOA

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19
Q

What can be added to the wing root to try and make the wing root stall first

A

A stall strip on the leading edge

Makes a sharper leading edge

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20
Q

What thickness - chord ratio has the most progressive stall

A

High thickness - chord ratio

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21
Q

What thickness - chord ratio has the least progressive stall

A

Low thickness- chord ratio

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22
Q

What is wing loading

A

The aircrafts weight divided by the wing area

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23
Q

What affect does wing loading have on stalling angle of attack

A

Harder you make the wing work the lower the stalling angle of attack

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24
Q

What affect does trailing edge flaps have on the stalling angle

A

Reduce the stalling angle

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25
Q

How can ailerons affect the stall

A

A wing which is close to the stall if aileron is used (aileron down) this has the same affect as a trailing edge flaps and reduces the stall angle (therefor putting the wing into a stall)

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26
Q

How does weight affect stalling speed

A

More weight = more wing loading required = faster sleep when Cl = max

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27
Q

How does landing gear affect the stall speed

A

Landing gear creates drag Infront of cg = downward moment = greater downforce required from tailplane = created lift required from wings

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28
Q

How does thrust from a propeller affect stalling speed

A

The air behind the propeller (slipstream) creates high energy, fast air over the wing meaning it can create more lift for a slower airspeed

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29
Q

How does a jet engine affect stall speed

A

At high angles of attack there is a vertical component to the thrust which acts with the lift reducing the lift required therefor reducing the speed required

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30
Q

How does cg affect stalling speed

A

Forward cg = more downforce from tailplane required = more lift from main wing required to counteract = higher stall speed

31
Q

How does a sweepback wing affect stall speed

A

Because sweepback isn’t perpendicular to airflow = Clmax is less therefor faster speed is required

32
Q

How does high altitude affect stall speed

A

Below 300kt TAS Air has plenty of time to move round wing

Above 300kt TAS air has less time to move round wing

More energy required = higher stall speed

33
Q

How does contamination affect stall speed

A

More weight = higher stall speed

Turns airflow into turbulent airflow = more energy used = separation earlier = stall speed higher

34
Q

What is load factor

A

The ratio of lift to weight

35
Q

What increases load factor

A

Turning, pulling out of a dive

When additional lift over that required to balance the weight is needed

36
Q

What is the equation for load factors in a turn

A

1/cosangle

37
Q

What is the equation for load factor

A

Lift / weight

38
Q

What will the load factor be if lift = weight

A

1

39
Q

What will the load factor be if lift is less than weight

A

<1

40
Q

What will the load factor be if lift is greater than weight

A

> 1

41
Q

What is autorotation

A

Occurs after the stall but before the spin is fully established (first 360°)

42
Q

What causes autorotation

A

During stall when one wing stalls more than the other = more drag on that wing = yaw = spin

Outer wing travels faster = more lift = roll

43
Q

What is the first stage of a spin

A

Incident spin (first 360°)

44
Q

What is the 2nd stage of a spin

A

Fully developed spin

45
Q

What is the 3rd stage of a spin

A

Recovery

46
Q

How does cg affect the spin

A

Further forward the cg the more nose down moment = the steeper the spin

47
Q

How does the lateral distribution of weight affect a stall

A

Weight at wing tip = when wing stalls greater moment = steeper roll

48
Q

What is an incipient spin

A

The autorotation before the first full turn

49
Q

What is a fully developed spin

A

When the aircraft has completed the first 360° and is yawing rolling and pitching

50
Q

How to recover from a fully developed spin

A

Close power
Oppose yaw with opposite rudder
Install by pushing column forward (neutral)

51
Q

What is the difference between a spin and a dive?

A

A dive is NOT a stalled condition

52
Q

What are classic aerodynamic indications of a stall

A

Increase buffet intensity

Possible wing drop

An abrupt nose down pitch

Loss of altitude

53
Q

How to tell you are stalling in a swept wing aircraft

A

Artificial stall warning systems and stall prevention systems are critical to the safe operation of swept wing aircraft

54
Q

Are artificial stall warning systems required in every aircraft

A

Required for all aircraft

Essential for aircraft with limited aerodynamic stall warning

55
Q

What are the different artificial stall warnings

A

Audio warning

Warning lights

Indicators on primary flight display

Stick shakers

Stick pushers

56
Q

How does the flapper stall switch work

A

Activated when stagnation point is “behind” / underneath flapper switch

Not a true AOA indication

57
Q

How does a AOA vane work

A

Aligns itself to the relative airflow

58
Q

Where do forward sweep aircraft stall first

A

The root

59
Q

How does a fixed AOA probe work

A

2 pressure channels

When air doesn’t hit channels straight on one of them has higher pressure than the other one

Computer works out the difference to determine the AOA

60
Q

How does a rotating AOA probe work

A

There are 2 channels

When AOA changes the pressure is unequal in the channels

Motor rotates probe until channels are of equal pressure

Computer calculates the angle

61
Q

What do the pitch limit indicators show you (eyebrows)

A

Maximum safe pitch up angle

62
Q

In what aircraft are stick shakers and pushers found

A

Conventional flying control systems eg Boeing

63
Q

What to do to recover from a stick pusher

A

Apply thrust

Disconnect the autopilot

Trim

Allow the airspeed to build

Once stick pusher deactivates pitch up smoothly into climb attitude

64
Q

What is the EASA regulations in cs 23 for Vs1

A

Must be 1.2 x Vs1 at 50ft

65
Q

What is the EASA regulations for Vs0 for cs23

A

Must be 1.3 x Vs0 at 50 foot

66
Q

How are Vs1 and Vs0 calculated

A

With engines idol, power off , cg max forwards, max mass

67
Q

What is Vsr

A

Reference stall speed

Is a CAS airspeed defined by manufacturer which may not be less than 1G stall speed

68
Q

What is the cs25 regulations for Vsr1

A

At 35 feet must be 1.13 x Vsr1

69
Q

What is the cs25 regulations for Vsr0

A

At 50 foot must be 1.23 x Vsr0

70
Q

What is another name for Vsr

A

Vs1g

71
Q

What is the v speed for when lift collapses

A

Vs

Vs = 0.94 x Vs1g

72
Q

What are the stall warmer required safety margins

A

Greatest out of 5kts or 5% of Vs or Vsr

73
Q

What is the stick pusher safety margins

A

Greatest out of 2kts it 2%

ATPL POF (12 decks)

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