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But did the pilots overreact in trying to compensate for the slight wake encounter? After the plane shook the second time, co-pilot Molin was working the controls, and a voice is heard on the plane's recorder asking for "max power," possibly indicating that the plane was beginning to stall, or at least slow dramatically. "You don't go to max power unless you're too slow," says Denny Kelly, a former commercial pilot who is now an independent accident investigator. "Why were they going too slow? Was it turbulence? Something external? Or some problem in the cockpit?"
Both pilots had completed American's advanced-maneuvering training program, which teaches them how to recover from unexpected trouble--including wake turbulence from a Boeing 747. Both pilots most likely were aware of the July 1999 "Industry Training Aid" on procedures for recovering from disruptions or "upsets" in flight. That study emphasized the need for careful, even delicate handling of the controls during an unexpected event. "Too much rudder pressure applied too quickly or held too long may result in loss of directional control," the study warned.
The release on Thursday of information gleaned from the flight-data recorder added support for the theory that the pilots might unintentionally have magnified a relatively minor problem. The jolts that swung the aircraft side to side appear to have been caused by the pilots. "Pilot-induced loads," says NTSB investigator Tom Haueter, "were higher than the wake loads." The rudder was "deflected" 10[degrees], according to the NTSB. Most pilots interviewed last week said a rudder should only be deflected, or moved, a few degrees. Sources told TIME that the rudder may have been jammed even farther over than the NTSB is publicly acknowledging.
In 10 of 15 fatal Airbus accidents prior to AA 587, crew confusion regarding the Airbus computer systems was considered to be a factor. After some of those accidents, Airbus made changes in software or its suggested procedures so that in extreme conditions the crew can override some of the planes' automated systems.
The Airbus A300 that crashed was a middle-age jet delivered to American in 1988, meaning it was not completely fly-by-wire (i.e., computer controlled), and clearly the pilots were the ones doing the flying, not the autopilot. But there have been incidents in which the onboard computer programs have frozen just as the ones in your personal computer do. In May 1999, an American Airlines plane experienced what is called "uncommanded" rudder movements, jamming the rudder pedals. The pilot used other controls to land the plane.
Airbus has also been at the forefront in replacing metal with carbon-fiber composite materials--the materials that constituted the failed tail fin. The tail section of the A300 is made with a composite of plastic reinforced with carbon fiber. Composites have properties of strength and flexibility that are in some cases better than those of metal. The sophisticated U.S. B-2 Stealth bomber is made with composites and can withstand G forces in excess of those that commercial jets are designed to handle.