John, I agree that maneuvers involving full and abrupt control inputs above maneuvering speed can overstress components and lead to deformation or failure. It's an industry standard and should be well understood by all pilots. (I learned some new aspects of VA in reading the NTSB Accident Report.) But after this accident, Airbus issued a bulletin quoted below. The source for this is the
NTSB Aircraft Accident Report
NTSB/AAR-04/04 PB2004-910404 Notation 7439B.
"1.18.4.1.2 Airbus Flight Crew Operating Manual Bulletin
In March 2002, Airbus issued A310/A300-600 FCOM Bulletin number 15/1,
“Subject No. 40, Use of Rudder on Transport Category Airplanes, in response to the Safety Board’s recommendations.” The bulletin emphasized proper operational use of the rudder and highlighted certification requirements and rudder control system design characteristics. The bulletin included the following information in a box labeled “CAUTION:”
Sudden commanded full, or nearly full, opposite rudder movement against a sideslip can generate loads that exceed the limit loads and possibly the ultimate loads and can result in structural failure. This is true even at speeds below the maximum design maneuvering speed, VA. (emphasis mine)
Certification regulations do not consider the loads imposed on the structure when there is sudden full, or nearly full, rudder movement that is opposite of the sideslip.
The bulletin also made the following operational recommendation:
RUDDERS SHOULD NOT BE USED:
– To induce roll, or
– To counter roll, induced by any type of turbulence.
Whatever the airborne flight condition may be, aggressive, full or nearly full, opposite rudder inputs must not be applied. Such inputs can lead to loads higher than the limit, or possibly the ultimate loads and can result in structural damage or failure.
The rudder travel limiter system is not designed to prevent structural damage or failure in the event of such rudder system inputs.
Note: Rudder reversals must never be incorporated into airline policy….[165]
As far as dutch roll is concerned, yaw damper action and natural aircraft damping are sufficient to adequately dampen dutch roll oscillations. The rudder should not be used to complement the yaw damper.
Note: Even if both yaw damper systems are lost, the rudders should not be used to dampen the dutch roll. Refer to the YAW DAMPER FAULT procedure.
At the public hearing on this accident, the American Airlines A300 fleet standards manager testified that American had not received “such specific limitations or prohibited maneuvers on the rudder use” before the flight 587 accident."
Here's a section discussing Pilot understanding on VA:
2.5.3 Pilot Guidance on Design Maneuvering Speed
During this accident investigation, the Safety Board learned that many pilots might have an incorrect understanding of the meaning of the design maneuvering speed (VA) and the extent of structural protection that exists when the airplane is operated below this speed.
From an engineering and design perspective, maneuvering speed is the maximum speed at which, from an initial 1 G flight condition, the airplane will be capable of sustaining an abrupt, full control input limited only by the stops or by maximum pilot effort. In designing airplanes to withstand these flight conditions, engineers consider each axis (pitch, roll, and yaw) individually and assume that, after a single full control input is made, the airplane is returned to stabilized flight conditions. Full inputs in more than one axis at the same time and multiple inputs in one axis are not considered in designing for these flight conditions.
The American Airlines managing director of flight operations technical told the Safety Board, during a postaccident interview, that most American Airlines pilots believed that the airplane would be protected from structural damage if alternating full rudder pedal inputs were made at an airspeed below maneuvering speed. The American Airlines A300
fleet standards manager confirmed this belief during testimony at the Board’s public hearing for this accident. The Board notes that the American Airlines A300 Operating Manual contained only one reference to design maneuvering speed, which indicated that it was the turbulence penetration speed (270 knots). However, as evidenced by flight 587, cyclic rudder pedal inputs, even when made at airspeeds below maneuvering speed, can result in catastrophic structural damage. (emphasis mine)
My thoughts...
This accident report is a fascinating read and deals with many factors in the accident including inappropriate pilot rudder control inputs, light rudder force input/high sensitivity, rudder limiter design and limitations, vertical stabilizer attach methods and materials, pilot training, etc. Like most accidents, it's not just one failure that causes the accident, but a series of events/issues/failures that combine to cause the crash.
Thanks for posting this thread. Great stuff here.
