Stalling

Question 1

What happens to the separation point at the critical AoA?

Answer 1

Moves well forward and causing large increase in turbulence over the wing

Question 2

At what point does the separation point move well forward and causing large increase in turbulence over the wing?

Answer 2

Critical AoA

Question 3

What effect does not encourage the formation of low static pressure areas above a wing?

Answer 3

Turbulent flow

Question 4

How does turbulent flow disrupt lift generation?

Answer 4

It prevents the formation of low static pressure above a wing

Question 5

At what point does a stall occur?

Answer 5

Critical AoA

Question 6

At the critical AoA, what does the Centre of Pressure do?

Answer 6

Moves rearwards rapidly

Question 7

The stalling of an aerofoil is what?

Answer 7

Significant breakdown for streamline flow into turbulence over a wing

Question 8

What causes a buffet in a stall?

Answer 8

Turbulent flow over the tailplane

Question 9

What causes the nose to drop in a stall?

Answer 9

Rearwards movement in the centre of pressure

Question 10

The centre of pressure’s rearward movement in a stall has what marked effect?

Answer 10

Nose will drop

Question 11

Despite the ability of a stall to occur at various attitudes, airspeeds etc., what flight factor is generally constant in a stall?

Answer 11

A specific AoA

Question 12

What lift factor affects stalling speed?

Answer 12

Square-root of lift

Question 13

That IAS at the stall depends on the square root of the lift means that…

Answer 13

Anything that requires the generation of extra lift will increase the indicated stalling speed

Question 14

Load factor and stalling speed relationship

Answer 14

If load factor increases, so will the stalling speed

Question 15

How would you work out a new stalling speed from an increased load factor?

Answer 15

The square root of the increase in load factor

Question 16

What CG change has the same effect as an increase in weight?

Answer 16

CG moves forward

Question 17

Why does CG moving forward have the same effect as an increase in weight?

Answer 17

Down force is required from the tailplane

Question 18

What CG change has the same effect as a decrease in weight?

Answer 18

CG moves aft

Question 19

How does wing loading affect stall speed?

Answer 19

Low wing loading means a lower stall speed

Question 20

Does stalling IAS vary with altitude?

Answer 20

No

Question 21

How does stalling IAS vary with altitude?

Answer 21

It doesn’t vaary - it remains constant

Question 22

Why will an altitude variation not affect stalling IAS?

Answer 22

Altitude variations do not affect C-Lift Max (which is a function of the stalling speed)

Question 23

How does power affect stalling speed?

Answer 23

It is less in a power-on stall

Question 24

How does power reduce stalling speed?

Answer 24

High nose attitude (nearing the stall) allows thrust to have a vertical component and off-load the wings so less lift is required

Question 25

How does thrust off-load wings in an approaching stall?

Answer 25

The aircraft will have a high nose attitude so the thrust will have a vertical component and thus reduce the lift required from the wings

Question 26

How does power-on affect the stalling of the wing?

Answer 26

Slipstream will generate lift from inner wing, so outer wing may stall first

Question 27

Why might the outer wing stall first in a particular kind of stall?

Answer 27

Power-on stall means inner wings generate lift from slipsttream and outer wings do not

Question 28

Why is it more preferable for inner wings to stall first before outer wings?

Answer 28

Inner wing has a shorter moment arm thaan the outer so a lesser rolling moment is produced

Question 29

How may an aircraft be designed so that its inner wings stall before its outer wings?

Answer 29

A wing washout will mean greater AoA at the wingroot will create a stall before the lower AoA at the wingtip

Question 30

In what two ways does ice increase stalling speed?

Answer 30

Ice-accretion on the wings prevents lift generation at lower AoA
Ice increases weight

Question 31

Where is the stagnation point of a wing at positives AoA?

Answer 31

Loweer surface of the leading edge (not visible from some cockpits)

Question 32

What is the blanking of an elevator?

Answer 32

Poor elevator control due to turbuence over the tailplane

Question 33

How are stalls with flaps extended quite sudden and rapid?

Answer 33

Flaps have increased drag so any speed loss will be rapid

Question 34

How is yaw prevented in a stall with flaps?

Answer 34

Using rudder, not ailerons

Question 35

Why should ailerons not be used in a stall with flaps?

Answer 35

Ailerons will deepen the stall on the wing with the downgoing aileron

Question 36

Why do swept-wing aircraft enter a deep stall?

Answer 36

Their wingtips are aft of the CG and will stall first, thus creating a nose-up moment which further increases the AoA

Question 37

Relation of wingtips and CG on a swept-wing aircraft?

Answer 37

Wingtips sit aft of the CG

Question 38

What happens to the wings entering a spin?

Answer 38

Outer wing speeds up, more lift, rises, AoA decreases
Inner wing slows down, less lift, fallls, AoA increases and stalls

Question 39

What stage comes between a stall and a fullly-developed spin?

Answer 39

Autorotation

Question 40

What are the stages of an autorotation?

Answer 40

Roll, sideslip, nose drop and rotation rate increases

Question 41

What occurs to instrumentation in a spin?

Answer 41

The coordination ball will settle in the bottom left corner irrespective of spin direction