US NTSB urges inspection of A300 rudders
Mar. 27, 2006
The US National Transportation Safety Board on Friday urged FAA to order immediate inspections of the inner skin of the composite rudder surfaces of certain A300 series aircraft in order potentially to avert the possibility of "a catastrophic failure of the rudder," NTSB Acting Chairman Mark Rosenker said in a statement.
The recommendations address a safety issue identified during the investigation by Airbus of a rudder from a FedEx A300-600. The rudder had been damaged during "routine maintenance," NTSB said, and was shipped to the manufacturer to assess the extent of the harm. In addition to the damage caused during the maintenance work, investigators found "a substantial area of disbonding between the inner skin of the composite rudder surface and the honeycomb core, which is located between two composite skins." This apparently was caused by hydraulic fluid contamination. The disbonding damage can spread during flight, tests revealed.
On March 6, 2005, an Air Transat A310-300 suffered an inflight loss of most of its rudder. The crew was able to land the plane. As a result of the continuing investigation into that incident, Airbus specified a one-time inspection for all A300 series aircraft equipped with the same kind of rudder and FAA issued an AD to that effect for US operators.
However, the FedEx disbonding event occurred in a part of the rudder not covered by the inspection. Furthermore, "it was determined that tap tests on the external surfaces of the rudder likely would not have disclosed the disbonding of an internal surface," according to NTSB.
Three weeks ago, Airbus issued All Operator Telexes notifying operators of the results of the investigation and providing guidance for inspecting the rudders. NTSB wants FAA to order all A300 series operators to "immediately (possibly before further flight) comply with four Airbus AOTs dated March 2, 2006." Any disbonding that occurs in the presence of hydraulic fluid contamination should be repaired or the rudder should be replaced as soon as possible, "well before the 2,500 flights specified in the AOTs," NTSB said.