Board Cites Rudder Problems Encountered Before AA Airbus Went Down

The NTSB recently issued a safety recommendation to the European Aviation Safety Agency (EASA) regarding the November 2001 accident involving an American Airlines Airbus near JFK. Flight 587, which was flying to the Dominican Republic, went down in the Belle Harbor neighborhood of Queens. There were no survivors among the 260 passengers and crew, and five people on the ground were also killed.

The NTSB determined that the probable cause of the accident was "the in-flight separation of the vertical stabilizer as a result of the loads beyond ultimate design that were created by the first officer's unnecessary and excessive rudder pedal inputs. Contributing to these rudder pedal inputs were characteristics of the Airbus A300-600 rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Program." Flight 587 encountered wake turbulence from a Boeing 747 shortly after takeoff, and the pilot's steering response created severe strain on the rudder mechanism. Sounds of likely mechanical failures could be heard in the recorded data recovered from the plane's wreckage, as well as the pilots' attempts to right the aircraft.

Soon after its investigation commenced, the NTSB issued a safety recommendation for updates in training of all pilots of transport-category airplanes.

The "loads" referenced by the NTSB are aerodynamic stresses caused by rapid movement of the rudder in an attempt to combat the aircraft movement caused by the wake of the nearby Boeing 747. The report, however, also pointed to "characteristics of the Airbus A300-600 rudder system design and elements of the American Airlines Advanced Aircraft Maneuvering Program," as a contributing factor in the crash.

The Accident airplane was built in France, subject to European regulatory oversight. In its new recommendation, issued on August 4, 2010, the NTSB encourages modification of European certification standards to ensure safe handling qualities "in the yaw axis throughout the flight envelope," as well as instituting limits for the sensitivity of rudder pedals. The yaw axis refers to the axis about which the aircraft nose and tail moves side-to-side. The flight envelope refers to the outer boundaries of flight for which the aircraft is designed.

The NTSB recommendation involves limiting rudder movement so that the aerodynamic stresses or "loads" do not exceed the design maximums. The NTSB also suggests review and modification, if necessary, of all existing models of the Airbus A300-600 and A310 aircraft.

FMI: www.ntsb.gov/recs/letters/2010/a-10-119-120.pdf