I generally agree with Chris Carpenter (Flight International, 17-30 December 2002), apart from his assertion that "restorative extra lift generated by the yaw does not affect the stalling angle". This would suggest a paradox, of a stalled wing generating lift.
The recent US National Transportation Safety Board hearing in New York about American Airlines flight AA587, the Airbus A300 accident in November 2001, quoted the example of another American Airlines flight, AA903, in May 1997. This was an A300-600 holding at 1,600ft (500m) near Miami, Florida. The aircraft stalled in a right bank and the pilot gave a bootful of left/top rudder to arrest the right roll. This was so aggressive that it started a series of roll oscillations and eight rudder reversals on the knife edge of flight and caused the ultimate fin load to be exceeded three times. The difference between AA587 and AA903 is time and luck.
This illustrates that a wing dropped in a stall can be raised with lift restored or stalled by holding back pressure on the yoke with rudder applied. Another American Airlines flight, AA191, [which crashed in Chicago] in May, 1979 is another example of a left wing stall due to migrating engine and pylon damage of the wing and premature slat retraction. Had the crew been aware of this unprecedented situation and used aggressive top rudder, catastrophe may have been avoided.
Aggressive control inputs in such escape manoeuvres should be used only in conjunction with other controls to mitigate the first control's unrestricted effect - in this case, rudder. I use a rigid drill of push, power, rudder, roll. The push unloads or unstalls the wing, or preserves stall margins; the power preserves speed and altitude; the rudder is used to raise a wing without loading it adversely and compromising Vmca margins; finally roll wings level when the ailerons have regained effectiveness. Rudder is the first to gain effectiveness and the last to lose it. Let's not be shy about it.
David Connolly Brussels, Belgium
Source: Flight International
