On Sun, 21 Mar 2004 22:36:45 GMT, (John
Bailey) wrote:

http://www.nytimes.com/2004/03/21/nyregion/21plane.html is a report of
the maneuvering by both Airbus and American Airlines to get in their 2
cents, pilot training vs inadequate design, in the crash of AA Flt 587
over Queens.

Remarks in response to the original post assume the actual failu
the rudder failing catastrophically, was due to the pilot responding
in an excessive way to a situation in which yaw needed to be
controlled. These resonses do not mention the fact that the yaw
needing to be controlled AND the excessive response came from a
characteristic of the plane itself. This inadequacy is described in
the Times article.
Here is the key quote:
(quote)
But the author of the study, Ronald A. Hess of the University of
California, said that the design of the rudder was conducive to such
oscillations. One problem, he found, was that on the A-300, the amount
of force needed to start moving the rudder was relatively high, and
the total range of motion allowed at that speed was only a little over
an inch, making it very difficult to apply any amount of rudder less
than its full extension. In addition, rudder application does not move
the plane instantly, and the delay might encourage a pilot to keep
applying the rudder until the aircraft moved further than the pilot
intended, according to Mr. Hess's analysis. The natural reaction would
then be to apply the rudder in the opposite direction. (end quote)

I could accept such (lurking instability) on a
military fighter plane, but such an accident waiting to happen in a
commercial airliner seems unconscionable.

Pilot induced oscillation is the result of a failure of the controls
design to take into account the inherent lag of the human control
response. In the F86D at high speed, low altitude, the human simply
could not control the pitch of the plane, once it began oscillating.
The recourse was to let the plane fly out of the situation and hope it
was pointed in the right direction when it emerged. Many hot pilots
were red faced after insisting it was the pilots fault and then
finding themselves unable to avoid the maneuver. Apparently the most
notorious case occured when the squadron commander at Selfridge AFB,
lead a flyby formation, reaching levels of oscillation that had his
wingtips generating vortex fog.

John Bailey
http://home.rochester.rr.com/jbxroads/mailto.html