Re-examination of a 1997 loss-of-control incident involving an American Airlines Airbus A300-600 has led the US National Transportation Safety Board (NTSB) to determine that the aircraft probably experienced high vertical stabiliser loads.
As a safety precaution, engineers from Airbus and American Airlines are removing the vertical stabiliser of the aircraft involved in the 1997 incident to perform a non-destructive inspection.
Later this week NTSB investigators will join the engineers for an ultrasonic inspection to determine if the A300's stabiliser sustained any damage in the 12 May 1997 incident, in which an American A300-600 experienced a series of pitch, yaw and roll manoeuvres as its flight controls went through a period of oscillations for about 34s. During that period the aircraft fell from an altitude of 16,000ft (4,900m) to 13,000ft.
The NTSB said recently that analysis of the flight data recorder (FDR) from the American A300-600 that crashed on 12 November 2001 showed the sideslip loads on that aircraft's vertical stabiliser were of a magnitude almost certainly sufficient to break off its stabiliser and rudder – although the agency has not yet proved that they did so.
As part of its investigation into the causes of last November's crash, the NTSB looked again at the 1997 incident. The NTSB had previously determined its probable causes were the flightcrew's failure to maintain adequate airspeed while levelling off from a descent, which led to an inadvertent stall, and their subsequent failure to use proper stall recovery techniques. Another contributory cause was the flightcrew's failure to use the A300's autothrottle properly.
Recommendations
On 8 February the NTSB issued two safety recommendations noting that rapid reversing movements of an aircraft's rudder can, under certain circumstances, jeopardise the vertical stabiliser's structural integrity.
The NTSB is now reviewing the FDR data from the 1997 incident – which happened as the A300-600 was flying in the vicinity of West Palm Beach as it was descending for a landing at Miami – to calculate the forces to which the stabiliser was subjected.
The NTSB also confirmed that no replacement parts from a suspected falsely documented inventory of Airbus A300 spare parts found in a police investigation in Italy could have found their way on to the American A300-600 that crashed.
Agency investigators have traced the sources of all major components from American flight 587's tail assembly and have proved that they had either been on the aircraft since new or came from the original equipment manufacturers.
Source: Flight Daily News
