1. 6.07 Stalls References: FTGU pages 18, 35-38
Theory of Flight
6.07 Stalls
References:
FTGU pages 18, 35-38

2. Review What are the two main types of drag?
2. Is it possible to eliminate induced drag? Why or why not?
What is one way to increase lift?
What are some ways to minimize drag?
Answers:
1. Induced and Parasite
2. Not entirely, it is the drag created by parts of the aircraft that create lift. A larger aspect ration can minimize it.
3. Increase angle of Attack.
4. Retractable gear, keeping the aircraft clean, streamlining

3. 6.07 Stalls MTPs: Laminar Flow Definition of a Stall
Critical Angle of Attack
Centre of Pressure
Stalls
Factors affecting stalls

4. Laminar Flow Boundary Layer – The thin layer of airflow over the wing
Laminar Layer – Smooth portion of the boundary layer nearest the leading edge of the wing
Transition/Separation Point – Point on wing where the boundary layer becomes turbulent
Turbulent layer – Turbulent portion of the boundary layer at the trailing edge of the wing

5. Stall
What is a stall?
When a wing is no longer capable of producing enough lift to counteract the weight of the aircraft
As a result, can no longer be maintained

6. Point on a wing where total aerodynamic pressure acts
Centre of Pressure
Point on a wing where total aerodynamic pressure acts

7. Centre of Pressure
Centre of pressure moves forward as angle of attack increases to the point of a stall
After a stall the centre of pressure moves rapidly back
The movement of the centre of pressure causes an aircraft to be unstable

8. Critical Angle of Attack
Angle of attack above which air will cease to flow over the wings and a stall will occur

9. Critical Angle of Attack
Most aircraft have a stall angle of positive
15 to 20 degrees

10. Stall
Centre of pressure and separation point move forward to point of stall and lift production is increased
Angle of attack is increased beyond critical angle of attack
Wing stops producing lift and stalls
Centre of pressure moves rapidly backward

11. Stall An aircraft can stall…
1) When the critical angle of attack is exceeded
2) At any airspeed if the critical angle of attack is exceeded
3) At any altitude if the critical angle of attack is exceeded

12. Stall
Symptoms of a Stall
Buffeting

13. Factors affecting a Stall
Centre of Gravity
Weight
Turbulence
Turns (and load factor)
Snow, Frost, Ice

14. Factors affecting a Stall
Centre of Gravity (C of G)
C of G too far forward
Loading on the horizontal tail surfaces increase
Overall weight of aircraft increases
Stall speed increases
C of G too far aft
Decreased longitudinal stability
Violent stall characteristics
Poor stall recovery (very dangerous!)
Stall speed decreases

15. Factors affecting a Stall
Weight
The more weight on an aircraft means that it must fly at a higher angle of attack
Therefore the critical angle of attack will be reached at a higher airspeed
Attitude to fly straight and level
2500 lbs, 90kts (closer to the critical A of A)
1000 lbs, 90 kts
Start of a trip
End of a trip

16. Factors affecting a Stall
Turbulence
Upward vertical currents cause the airplane to increase its angle of attack
Could result in the aircraft stalling if flying near the stall speed

17. Factors affecting a Stall
Turns
As angle of bank increases the load factor also increases
Therefore, an increased angle of attack is required to maintain level flight in the turn
Subsequently, the stall speed in a turn increases
Just like adding more weight to an aircraft

18. Turns and Stall Speeds

19. Factors affecting a Stall
Snow, Frost, and Ice
Accumulation of snow, frost, and ice affects a wing’s ability to produce lift
Increase in stall speed

20. Factors affecting a Stall
Increase stall speed
Forward C of G
More weight
Turbulence
Greater angle of bank
Decrease in stall speed
Aft C of G

21. Confirmation Check

22. Confirmation Draw the movement of the C of P leading up to the stall.
What are some factors that increase the stall speed.

23. Confirmation 3. When can an aircraft stall?
4. What are the symptoms of a stall?

24. Stall Recovery