Three years before rapid rudder movements ripped the tail off American Airlines Flight 587, Airbus told aviation authorities that repeatedly reversing the rudder of a A300-600 could overstress the tail section, but nobody apparently gave that information to pilots.
A transcript of the plane's cockpit voice recorder, in fact, indicates that the crew may never have suspected that the tail had come off. The wide-body plane crashed into a neighborhood in the New York City borough of Queens in November 2001, killing 260 people on the plane and five on the ground.
"What the hell are we into?" co-pilot Sten Molin asked pilot Edward States. "We're stuck in it."
While the meaning of Molin's statement is not clear, it appears that he thought the plane was being thrown about by the wake of a Japan Airlines Boeing 747 that had taken off just ahead of him. States apparently agreed.
"Get out of it, get out of it," the captain said. That was the last sound on the recording, which abruptly stopped as the plane began flopping through the air, shedding its engines.
The National Transportation Safety Board yesterday began four days of hearings on the Nov. 12 crash with a statement from chief investigator Robert Benzon saying the board is still looking at whether the co-pilot moved the rudder himself, as most investigative sources believe, or it moved because of some rudder anomaly.
In just seven seconds, Flight 587's rudder -- the panel at the rear of the vertical tail section -- moved hard right, hard left, right, left and right again, creating forces that ripped the vertical tail off. Normally a pilot would not use the rudder in flight except to compensate for an engine failure.
Much of the testimony and documents involved what aviation authorities call "human factors": What did the co-pilot know? How was he trained? What might he have felt or seen that would lead him to jam the rudder repeatedly?
But one of the most interesting documents came out of an earlier investigation of an incident involving an Airbus A300-600. On May 12, 1997, an American Airlines flight approaching Miami suddenly began gyrating, bouncing passengers around. The plane made an emergency landing in Fort Lauderdale.
The safety board cited a series of pilot errors but made no recommendations regarding rudder use.
But Airbus, in an Aug. 12, 1998, submission to the safety board, warned that overuse of the rudder can cause a plane to "sideslip" at angles that can overstress the tail.
"This is probably not well understood by many line pilots, but it has a significant impact on an airplane's stability and control," Airbus said in a submission from Yves Benoist, its director of flight safety.
Rudder reversals, it warned, "can lead to structural loads that exceed the design strength of the fin and other associated airframe components." The submission said pilots should be informed of "the hazards of inappropriate rudder use during a windshear encounter, wake turbulence recovery, or recovery from low airspeed."
The Airbus submission was also sent to the Federal Aviation Administration, the French accident investigation agency, American Airlines, and two of the carrier's unions.
The submission also dealt with other issues, however, and the rudder recommendations apparently received little notice. After last November's crash of Flight 587, however, the safety board said it had become apparent that most pilots do not know the danger of overusing the rudder and recommended that they be informed.
It is not the first time that the subject of rudder use was brought up. In 1997, Airbus, Boeing and the FAA sent a letter to American Airlines suggesting that its training program for recovery from sudden aircraft upsets included too much emphasis on rudder use. American replied that the company does not emphasize rudder use and in fact warns pilots against overuse.
American spokesman John Hotard said yesterday that Airbus never followed up on the letters by making a change to operations manuals that pilots and American operations personnel see.
Other documents introduced at the hearing delved into what the co-pilot might have felt when the wake hit, and on his history of training and rudder use.
Investigators interviewed several pilots who flew with Molin, and they gave him generally high marks. American Airlines pilot John Francis LaVelle said Molin had "hands of silk" in flying the plane.
But LaVelle said Molin "had one strange tendency: to be very aggressive on the rudder pedals." LaVelle said Molin told him his methods were in line with American's training.
No other pilots interviewed mentioned excessive rudder use.