Slipping & Skidding Stalls
The ‘slipping’ manoeuvre can be thought of as a ‘cross-control’ stall. The objective of this demonstration is to show the effects of uncoordinated flight on stall behaviour and the importance of rudder coordination while turning.
The aerodynamic effects of this sort of stall can be startling as it can happen with very little warning and can be deadly if it occurs near the ground. You can expect to experience a large pitch change, bank angle change and the aircraft may even end up inverted (start of a spin). Application of the standard stall recovery procedure without delay will prevent the situation from worsening.
The key difference between the two:
- Slipping turn is an uncoordinated manoeuvre with excess yaw opposite to the direction of turn.
- Skidding turn is an uncoordinated manoeuvre with excess yaw in the same direction as the turn.
A skidding stall is most likely to occur in the circuit during a poorly planned and executed base-to-final approach turn in which the aeroplane overshoots the runway centerline and the pilot attempts to correct. This leads to increased bank angle, increased elevator back pressure, and applying rudder in the direction of the turn. The difference in lift between the inside and outside wing will increase, resulting in an unwanted increase in bank angle. At the same time, the nose of the aircraft slices downward through the horizon. The natural reaction to this may be for the pilot to pull back on the control column, increasing the AOA towards critical.
To situation can be prevent by anticipating the effect of wind on the ground track and initiating the turn earlier with a reduced angle-of-bank. If in doubt, GO AROUND.
How to fly the manoeuvre:
Prior to starting, establish a safe altitude for entry and recovery from a spin. This may be recommended in the aircraft POH/AFM.
1.) HASELL Checks - Gear down, flaps UP (to prevent over stressing)
2.) Reduce power to idle, and maintain altitude until speed reduces to best glide speed
3.) Select the glide attitude and trim to maintain
4.) Roll into a co-ordinated medium-bank turn (30 degrees angle-of-bank left or right)
5.) Apply excess rudder (slip or skid as desired)
6.) Apply appropriate aileron to maintain the angle-of-bank
7.) Increase elevator back pressure to maintain pitch attitude
8.) When the stall occurs, apply standard stall recovery
Recovery from this upset condition typically requires a stall recovery followed by an unusual attitude recovery.
Due to the nature of this exercise, it is recommended that you practise with an instructor if you have limited spinning experience and review the spin recovery technique for your aircraft type before attempting.