13 Stalling

Question 1

Vs0?

Answer 1

Stall speed in landing configuration

Question 2

Vs1

Answer 2

Stall speed in specific configuration

Question 3

Vsr

Answer 3

Stall reference speed

Question 4

Vs1g

Answer 4

Stall speed in straight and level flight (1g)

Question 5

Wing Loading = ?

Answer 5

Wing Loading = Weight ÷ Wing Area

Question 6

Effect of Mass on stall speed

Answer 6

Stall speed increases

Question 7

Effect of flaps on stall speed

Answer 7

Lowering flaps reduces stall speed

Question 8

Effect of landing gear on stall speed

Answer 8

stall speed increases

Question 9

Effect of propeller thrust on stall speed

Answer 9

Stall speed reduces

Question 10

Effect of Jet thrust on stall speed

Answer 10

stall speed reduces

Question 11

Effect of CG on stall speed

Answer 11

stall speed goes up as CG moves forward

Question 12

Effect of swept back wings on stall speed

Answer 12

stall speed increases

Question 13

Effect of Altitudes on stall speed

Answer 13

none apart from at very high altitude (30-35k) at which point stall speed increases

Question 14

Effect of contamination on stall speed

Answer 14

stall speed increases

Question 15

Effect of maneuvering on stall speed

Answer 15

stall speed increases

Question 16

What is a stall?

Answer 16

As the AOA increases, the stagnation point moves down and under the aerofoil.

This means that the air flow has a longer distance to travel up and over and so looses energy.

The loss of energy means that the flow turns to a laminar flow more quickly and the turbulent flow has less energy.

The turbulent flow is more easily separated from the surface and so the separation point moves forward.

Eventually there is not enough distance between the leading edge and separation point for the pressure differential to act over and so the aerofoil looses lift.

This is a stall.

Question 17

Sharp Vs Large leading edge on critical AOA

Answer 17

A sharper leading edge means the air must work harder to get round and over the aerofoil.

Therefore more energy is lost.

A sharper leading edge will therefore stall at a lower AOA.

Question 18

Rectangular Wing stalling properties

Answer 18

• Least downwash at the root of the wing
• Effective AOA is greatest at root
• Stalls first at root
• Natural stall warning: buffeting of tail plane from turbulent air
• Close to CG so smaller wing drop moment
• CP moves aft of CG so pitches down in a stall
• Ailerons are outside of turbulent, ‘Stalled’ air

Question 19

Elliptical wing stall properties

Answer 19

• CL equal across whole wing
• Whole wing stalls at once
• Prone to severe wing drop
• Little to no warning (no buffeting)
• Ailerons are also stalled as they are in the turbulent air

Question 20

Tapered wing stall properties

Answer 20

• Least downwash at the centre of the wing
• Centre of the wing stalls first
• Ailerons are less effective as they are affected by some turbulent air
• Little warning

Question 21

Swept and tapered wing stalling properties

Answer 21

• Greatest downwash at the centre of the wing
• Least downwash at the tip
• Tips will stall first
• Cause severe wing drop
• Ailerons severely effected
• CP moves forward so pitches up in stall
• Downwash hits tail plain causing even more pitch up