November 19, 2012 1 Comment
I just posted several new short videos on my YouTube channel that demonstrate accelerated stalls, incipient spins from stalls, and an intentional spin. The videos, captured during flights in my Extra 300L, show the effects of stalling with coordinated controls and no yaw, stalling while yawing the airplane while turning with “top” and “bottom” rudder, and an intentional spin from a straight-ahead, slow-deceleration stall. I’ve also included a “quiz” video that shows more stalls while turning. See if you can predict which way the stall will break from each of the stalls.
In these videos, I deliberately allowed the stalls to progress to show the effects of misapplied flight controls. If I had applied down-elevator immediately at the first sign of a stall, the departures wouldn’t be apparent. You can’t go wrong following the PARE sequence (described by Rich Stowell) whenever the airplane departs and begins an incipient spin, but if you stop the stall immediately, you regain control of the airplane and can stop a spin from developing. That’s the key takeaway from these videos. At the first sign of a stall or impending departure, unload (relax back pressure and/or apply forward yoke/stick) to keep the stall from progressing. The first instinct of many (most) pilots when a wing drops during a stall is to apply aileron to try to stop the roll, and that action delays recovery and tends to aggravate the stall. In the initial stages of a stall/departure, push first; correct the roll later.
As the Airplane Flying Handbook notes (see “Fundamentals of Stall Recovery” in Chapter 4 on p. 4-4):
First, at the indication of a stall, the pitch attitude and angle of attack must be decreased positively and immediately. Since the basic cause of a stall is always an excessive angle of attack, the cause must first be eliminated by releasing the back-elevator pressure that was necessary to attain that angle of attack or by moving the elevator control forward. This lowers the nose and returns the wing to an effective angle of attack. The amount of elevator control pressure or movement used depends on the design of the airplane, the severity of the stall, and the proximity of the ground. In some airplanes, a moderate movement of the elevator control—perhaps slightly forward of neutral—is enough, while in others a forcible push to the full forward position may be required. An excessive negative load on the wings caused by excessive forward movement of the elevator may impede, rather than hasten, the stall recovery. The object is to reduce the angle of attack but only enough to allow the wing to regain lift.
The FAA also recently published AC 120-109: Stall and Stick Pusher Training (PDF) to clarify and emphasize the proper recovery from stalls. That AC notes in part that:
This AC emphasizes reducing the angle of attack (AOA) at the first indication of a stall as the primary means of approach-to-stall or stall recovery…Stall training should always emphasize reduction of AOA as the most important response when confronted with any stall event.
Core principals of this AC include:
- Reduction of AOA is the most important response when confronted with a stall event.
- Evaluation criteria for a recovery from a stall or approach-to-stall that does not mandate a predetermined value for altitude loss and should consider the multitude of external and internal variables which affect the recovery altitude. (Reference: Safety Alerts for Operators (SAFO) 10012, Possible Misinterpretation of the Practical Test Standards (PTS) Language “Minimal Loss of Altitude”).
- Realistic scenarios that could be encountered in operational conditions including stalls encountered with the autopilot engaged.
- Pilot training which emphasizes treating an “approach-to-stall” the same as a “full stall,” and execute the stall recovery at the first indication of a stall.
- Incorporation of stick pusher training into flight training scenarios, if installed on the aircraft.
It’s important to understand how a stall develops into a departure, incipient spin, and then developed spin. You can, for example, see the difference between the type of stall/departure/incipient spin that occurs when you stall out of a yawing turn, and what you see during a deliberate spin from slow-deceleration, wings-level stall. This is why competent stall/spin/upset recovery training is valuable. You need to experience and practice a variety of situations.
The recommended stall recovery (and the one that APS teaches) is: Push – Power – Rudder – Roll – Climb