One possible reason for the use of rudder in the American Airlines Airbus A300 accident near New York Kennedy in November 2001, despite the aircraft not having a high angle of attack, could be basic light-aviation training.

If the preceding Boeing 747's wake turbulence had caused a sudden wing drop, it may have felt remarkably like a stall to a pilot with a lot of light aviation experience. If the symptoms had been misidentified as a stall, basic light-aviation experience would have dictated the need for kicking in a lot of opposite rudder. However, as the A300 was not at the stall and had a lot of airspeed and controllability, this rudder input would have simply flicked (rolled) the aircraft the other way in a manner that a light aircraft at speed would not (light aircraft just yaw, with little roll, at any speed).

Now the pilot would have been really confused, as the symptoms would have felt just like a light aircraft at the point of stall, where one has just put in too much rudder and the yaw had stalled the opposite wing. Not understanding that the wing drops were being caused by the rudder inputs, the pilot may then have put in the opposite rudder to counteract the second "stall", which would have merely rolled the aircraft the other way. The result would have been two or three massive rudder inputs at high airspeeds that would have ripped off the rudder.

This incident calls into question the wisdom of reducing airway separation to 5nm (9km). This distance may be fine on approach, but in the cruise only gives 45s separation from the leading aircraft. We now experience more severe turbulence than ever as aircraft climb and descend in front.

Capt Ralph Tuttle Cheshire, UK

Source: Flight International