AA Maintains Crash Caused By Design Flaw

From the start, NTSB investigators probing the crash of American Airlines Flight 587 in November, 2001, have concentrated on co-pilot Sten Molin's manipulation of the rudder pedals. Just after taking off from JFK Airport in New York, the aircraft encountered extreme turbulence. Attempting to counteract the turbulence, co-pilot Molin actuated the rudder of the Airbus A300-600 at a speed of 250 kts. To this point, theories have suggested that Molin over manipulated the rudder, causing the aircraft's vertical stabilizer to snap completely away from the airframe. The aircraft spun into a residential area of Queens, killing 265 people.

But now, an outside expert hired by the NTSB, suggests the very design of the aircraft could have played a major part in the crash. That plays right into American's argument that the rudder design on the A300-600 is flawed and that Airbus is to blame. It's the centerpiece of an ongoing argument between American and the European aircraft company and, in itself, is already controversial.

The vice chairman of the mechanical and aeronautical engineering department at the University of California/Davis, Ronald Hess, has reportedly found the rudder controls of the A300-600 are much more sensitive than the rudder controls on other, comparable aircraft. His findings, accepted into evidence by the NTSB, finds that the A300-600 rudder controls are extremely sensitive to air crew input.

USA Today reports Hess concludes the November 12, 2001 accident is "consistent" with a rare phenomenon that is somewhat akin to over steering a skidding car. Instead of stabilizing the aircraft, Molin's rudder application made things worse, eventually leading to the delamination of the entire 27-foot tall vertical stabilizer.

American has come under fire during the NTSB investigation for the way it teaches pilots to use the rudder in extreme situations. The agency also criticized the rudder controls in American's A300 simulators as not truly representing the behavior of those controls in actual flight. But American says its training is no different than that of other airlines.

But in his report to the NTSB, USA Today says Hess cited extreme sensitivity in the rudder controls of an A300-600 -- especially at higher speeds.

NTSB documents show that, during his preflight, Molin applied 65 pounds of pressure to each rudder pedal. The pedals moved a total of four inches and performed as advertised. But just 85 seconds after takeoff, at 250 kts, the pedal moved just 1.3 inches and required far less pressure from Molin's foot, once it was in motion.

That's an important distinction. Rudder pedals are designed so that it takes deliberate pressure -- at least 20 pounds, in the case of the A300-600 -- to move them. That way, you can't accidentally kick a rudder pedal and throw the aircraft into an uncontrollable skid. But once the Airbus rudder is in motion, Hess found that it took far less pressure to move it to the stops. He reported to the NTSB that it only took another 10 pounds of pressure, whereas the rudder controls on a Boeing 767 under similar conditions, requires 63 additional pounds of pressure before fully articulating one way or the other.

Airbus spokesman Clay McConnell says the amount of pressure required to move the rudder from stop to stop wasn't a factor in the AA 587 accident because Molin applied far more pressure on the pedals than would have been required in any comparable aircraft. The company says the A300-600 and the A310, which share the same rudder design, have flown 16 million hours since being introduced in the early 1980s, and "there has never been an issue with rudder pressure."

FMI: www.ntsb.gov