Stalling and Spinning Flashcards
22.16.2 Explain the stalled condition of an aerofoil.
AOA of wing exceeds it’s critical angle (normally greater than 15*).
22.16.4 Explain basic stall speed and relate it to the lift formula.
(S) = PLANFORM area of the wings.
(CL) = lift coefficient, based on wing section an AOA.
(1/2Pv2) = Expression for dynamic energy also known as IAS.
Therefore LIFT = CL x 1/2Pv2 x S
Simplified as LIFT = AOA x IAS.
22.16.6 Describe typical symptoms and other indications of the approach to the stall.
Low and reducing IAS. Reduced Control effectiveness. Higher nose attitude. Quieter Cabin (less airflow over aircraft and less engine noise) Audible Stall warning (If fitted). Buffeting of control column.
22.16.8 Describe the changes in the airflow over the wing, movement of the CP, and aircraft attitude as the point of stall is reached.
When the critical angle is reached, the airflow transforms from a lamina flow to a turbulent one. This is due to the seperation point moving forward.
The CP was forward, but as the AOA reached critical the lamina flow has broken down, so too has the ability to produce sufficient lift. So at the stall CP moves rearward rapidly.
Nose attitude at the point of the stall has natural design tendancy to pitch down, due to C of G being ahead of CP. The only time this wouldn’t happen is if the C of G was rear of limits and behind CP, which would then cause a dangerous pitch up.
22.16.10 Explain the standard recovery from the stalled condition.
Control column forward reducing AOA unstalls the aircraft. - Full power only to minimize lost height & climb.
22.16.12 Describe how the following factors affect stalling speed: (a) aircraft weight.
Heavy = increases the requirement for more lift, therefore increases stall speed. Lighter has the opposite affect.
22.16.12 Describe how the following factors affect stalling speed: (b) load factor.
Load factor is an apparent increase in weight, so an increase LF, increases weight. This then increases the requirement for more lift, therefore increases stall speed
22.16.12 Describe how the following factors affect stalling speed: (c) power.
When approaching the stall the aircraft is an increased AOA. This higher nose attitude means that a part of thrust is acting in the vertical plane. Therefore reducing the requirement for lift and also the stall speed.
22.16.12 Describe how the following factors affect stalling speed: (d) altitude.
Altitude has no effect on the stall speed (IAS).
(Note:If we consider TAS, the stall speed will increase with an increase in altitude).
22.16.12 Describe how the following factors affect stalling speed: (e) the use of flaps and slats.
Flaps will increase the effective camber of wing, generating more lift which means the stall speed will reduce. Slats have the same affect on stall speed as they encourage air to adhere to the aerofoil which will delay separation of air.
22.16.12 Describe how the following factors affect stalling speed: (f) contamination of the wing surfaces.
Reduces CL max + adds weight increasing the stalling speed.
22.16.14 Describe the conditions which encourage a wing-drop at the stall.
Unbalanced flight approaching stall.
Use of aileron near stall and wing surface conditions.
Flaps may be at different angles if lowered.
Power has a tendancy to reduce AOA of inboard sections, encouraging a wing drop.
Also in climbing or descending turn varies the AOA on each wing, close to the stall could cause one to reach critical angle before the other.
22.16.16 Explain the design measures taken to reduce the tendency for wing-drop.
Flow-strip reduces tendency for tipping and encourages early flow separation.
22.16.18 Explain the caution against using aileron near or at the stalling angle.
If you use aileron close to the stall, the down going aileron increases AOA on that wing. This could stall one wing before the other.
- 16.20 Describe the standard technique for recovery:
(a) from a stall which has resulted in a wing-drop;
Reduce AOA. Use sufficient opposite rudder to stop the yaw. Smoothly roll wings level, also smoothly raise nose to horizon. Then application of full power.
