NEWPORT, R.I. -- After a harrowing 40-second dive in which EgyptAir Flight 990 lost half its altitude, the jetliner climbed nearly 8,000 feet before plummeting again and breaking apart, radar data released last night indicated.
Although National Transportation Safety Board officials refused to speculate about what happened on board the doomed airliner Sunday, the finding raised assumptions that its pilots managed to regain control of the aircraft before a final catastrophic crash into the Atlantic Ocean, killing 217 people.
The radar data show the airplane following a straight path from its cruising altitude of 33,000 feet through its fall to 16,700 feet shortly before 2 a.m. EST, about 30 minutes after it left John F. Kennedy International Airport in New York.
The plane held its straight heading as it climbed to 24,000 feet. It then swerved and descended to 10,000 feet in a half-minute, at which point radar picked up the apparent breakup of the aircraft.
"The [final] descent was rapid," said John Clark, deputy director of the NTSB's office of research and engineering.
NTSB Chairman James Hall and the agency's investigator-in-charge, Gregory Phillips, spent much of last night discussing engine thrust reversers, which some observers have focused on as a possible cause of the Boeing 767 crash.
Pilots who flew the plane reported to the NTSB that one of its engine thrust reversers was not working and had been deactivated.
In a 1991 crash, 233 people were killed when a Lauda 767 slammed into a jungle hilltop in Thailand after its thrust reversers deployed about 10 minutes into the flight. Boeing then redesigned the mechanism that controls the thrust reverser. The reversers are used after touchdown, to slow the plane on the runway.
EgyptAir made the recommended changes to the thrust reversers on the Flight 990 plane in 1993, the airline said.
Yesterday, EgyptAir officials said one of Flight 990's thrust reversers had been deactivated before the flight left Cairo last week because maintenance crews there found a leak in the system that controls the reversers. The flight met regulations for safe flying, U.S. investigators said, because airplanes are allowed to fly with only one operating thrust reverser.
Several aviation experts discounted the possibility of thrust reversers contributing to the Flight 990 crash.
If a thrust reverser were to malfunction during flight, the engine would fire in the opposite direction, causing the plane to turn sharply, likely sending the plane spinning out of control, they suggested.
At an elevation of 33,000 feet, Flight 990's cruise altitude, several aviation officials said, the pilots would have had time to regain control of the plane, discounting the possibility of a thrust reverser problem.
Pub Date: 11/04/99