http://www.ntsb.gov/Recs/letters/2002/A02_01_02.pdf...Further, the Safety Board has learned that sequential full opposite rudder inputs (sometimes colloquially referred to as “rudder reversals”)—even at speeds below the design maneuvering speed 1—may result in structural loads that exceed those addressed by the requirements. In fact, pilots may have the impression that the rudder limiter systems installed on most transport-category airplanes, which limit rudder travel as airspeed increases to prevent a single full rudder input from overloading the structure, also prevent sequential full opposite rudder deflections from damaging the structure. However, the structural certification requirements for transport-category airplanes do not take such maneuvers into account; therefore, such sequential opposite rudder inputs, even when a rudder limiter is in effect, can produce loads higher than those required for certification and that may exceed the structural capabilities of the aircraft.
This safety issue was identified in connection with the Safety Board’s ongoing investigation of the November 12, 2001, accident involving American Airlines flight 587, an Airbus Industrie A300-600. 2 Flight 587 was destroyed when it crashed into a residential area of Belle Harbor, New York, shortly after takeoff from John F. Kennedy International Airport (JFK), Jamaica, New York. Before impact, the vertical stabilizer and rudder separated from the fuselage. ....
Before the separation of the vertical stabilizer and rudder, flight 587 twice experienced turbulence consistent with encountering wake vortices from a Boeing 747 that departed JFK ahead of the accident aircraft. The two airplanes were separated by about 5 (statute) miles and 90 seconds at the time of the vortex encounters. During and shortly after the second encounter, the flight data recorder (FDR) on the accident aircraft recorded several large rudder movements (and corresponding pedal movements) to full or nearly full available rudder deflection in one direction followed by full or nearly full available rudder deflection in the opposite direction. 4 The subsequent loss of reliable rudder position data is consistent with the vertical stabilizer separating from the airplane. The cause of the rudder movements is still under investigation. Among the potential causes being examined are rudder system malfunction, as well as flight crew action.
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Preliminary calculations by Safety Board and Airbus engineers show that large sideloads were likely present on the vertical stabilizer and rudder at the time they separated from the airplane. Calculations and simulations show that, at the time of the separation, the airplane was in an 8° to 10° airplane nose-left sideslip while the rudder was deflected 9.5° to the right. Airbus engineers have determined that this combination of local nose-left sideslip on the vertical stabilizer and right rudder deflection produced air loads on the vertical stabilizer that could exceed the airplane’s design loads. The Board notes that, at the time the vertical stabilizer and rudder separated from the airplane, the airplane was flying at 255 knots indicated airspeed(KIAS), which is significantly below the airplane’s design maneuvering speed of 273 KIAS.
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