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Old 05-03-2006, 02:36 PM
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ADIRU
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Default Part 1

April 16, 2006

Mr. Bob Benzon
Deputy Chief, Major Investigations
National Transportation Safety Board
NTSB Headquarters
490 L’Enfant Plaza
Washington, D.C. 20594

Mr. John Hickey
Federal Aviation Administration
Aircraft Certification Service
Office of the Director (AIR-1)
800 Independence Avenue SW, Suite 800 East
Washington, DC 20591

Dear Sirs,

Beginning in the spring 2002, as pilots assigned to fly the A-300-600 for American Airlines, we became concerned about issues raised in the investigation of the crash of AA Flight 587 in Belle Harbor, NY on November 12, 2001. As the investigation went on, in order to address these concerns, several of us formed an ad hoc group to gather information and opinion from a variety of experts on aircraft rudder design, aircraft systems, aviation safety, carbon composite engineering, composite inspection methods and other topical areas of the accident investigation. After thorough analysis, we filed our concerns, as is mandated by both company policy and FAA directive, with the NTSB and FAA, along with American Airlines, in 2002 and 2003.

Among the concerns that our group made known were:

 That visual inspection techniques presently used to verify the integrity of composite materials are inadequate;
 That the structural certification requirement for the rudder and vertical stabilizer for ALL commercial aircraft should be re-evaluated, especially when considering composites;
 That A300/A310 flight control systems have had a disproportionate number of serious malfunctions/failures, resulting in uncommanded rudder movements; this is a safety concern;
 That the inherent qualities of composite materials and our present understanding of their properties may make them unsuitable for major load-bearing structures.
 That the A300 design philosophy in certain areas (e.g. -- rudder limiter and vertical stabilizer attachment) may need to be reviewed for appropriateness, when …(considering) characteristics of composite materials;
 That pilot training has been seriously deficient in regards to what constitutes safe versus unsafe application of flight controls;
 That when considering the cumulative deficiencies of composite technology, certification standards, rudder design and flight control malfunctions; serious consideration should be given to grounding the A300-600 fleet until such time as the safety of the flying public can be assured.

On March 24, 2006, the NTSB issued a Safety Recommendation that urged the FAA to, among other things, require inspections of A-300/A-310 rudders immediately, dramatically rejecting an Airbus All Operators Telex (AOT) that instead called for an inspection exemption for some A-300/A-310 aircraft and an extended period of flight on the rest of the aircraft prior to inspection or delay in repair after discovery of damage. This recommendation was remarkable because it told of delamination that had occurred on a FedEx A300 rudder, discovered when damaged in a hangar test. The discovery was significant because, according to the NTSB, it implicated intrusion into the composite material composing the rudder by hydraulic fluid as a cause for “propagation” of the delamination, and that the normal inspection methods used to insure composite integrity would not have discovered this damage:

Further examination of the disbonded area revealed traces of hydraulic fluid. Hydraulic fluid contamination between the honeycomb skin and the fiberglass composite skin can lead to progressive disbonding, which compromises the strength of the rudder. Tests on the damaged rudder also revealed that disbonding damage could spread during flight.

The investigation found that the areas specified in the AOT did not include the areas in which the disbonds were found on the incident rudder. Further, it was determined that tap tests on the external surfaces of the rudder likely would not have disclosed the disbonding of an internal surface.
--NTSB Safety Recommendation, March 24, 2006