Crashed jet too close to 747 say investigators

NEW YORK - Investigators yesterday homed in on the possibility that turbulence caused by a jumbo jet contributed to the crash of American Flight 587, saying the two planes took off less than the standard two minutes apart.

"We do not know whether this contributed in any way to the actual accident, but we are looking at this very closely," said Marion Blakey, chairwoman of the National Transportation Safety Board.

"Wake turbulence," the swirl of air behind a plane, can endanger others flying too close behind or below. It has been blamed for at least one crash in the past.

Walter Sheriff, a retired American Airlines captain who studies the phenomenon, said the wake turbulence from the four-engine 747 could have struck the Airbus A300 with "tornado-like lateral force".

Investigators are trying to establish whether such turbulence caused Flight 587 to break up three minutes after takeoff from John F. Kennedy Airport on Tuesday, killing all 260 on board and up to five on the ground.

Standard protocol says there should be at least two minutes between takeoffs. But Ms Blakey said it appeared there was less than that between Flight 587 and a Japan Air Lines Boeing 747 that left ahead of it from the same runway.

"We believe that in fact it was 1 minute and 45 seconds in terms of the actual distance."

She did not explain why this was so, but said it appeared that air traffic controllers followed proper procedure.

She said tower clearances for the two takeoffs came 2 minutes and 20 seconds apart.

Pointing to a map of the two planes' flight paths, she said that although the jumbo jet's path was 240m above Flight 587's, the winds probably pushed the turbulence lower.

The cockpit voice recorder from Flight 587's final minutes revealed two rattling noises and indicated the pilots complained about the wake of another plane before their aircraft went down.

The Federal Aviation Administration has set minimum distances for planes flying near each other, based on aircraft size.

Ms Blakey said Flight 587's other black box, its flight data recorder, had given investigators data on the last minutes of the doomed flight.

Both of the plane's engines have been recovered. Authorities have not ruled out sabotage or other causes but have said all signs point to a mechanical failure.

"That does not mean we have concluded there was no crime," said Attorney-General John Ashcroft. "We simply have no evidence to date of a crime of terrorism."

The flight data recorder monitors nearly 200 separate functions in the European-made A300, including rudder movements.

The tail fin was fished out of Jamaica Bay, a short distance from the crash site and the rudder was found nearby. The rudder, which is supported by the tail fin, gives an airplane directional stability.

The 8.1m tail fin was ripped off the fuselage cleanly, as if it had been sliced by a knife.

Safety records show the same plane was severely shaken when it hit air turbulence at cruising altitude seven years ago in an episode that injured 47 people. An aviation consultant said the plane could have been weakened by the earlier encounter.

Investigators are reviewing records, interviewing maintenance employees and asking questions about the 1994 incident.

They said both engines were relatively intact, which seemed to discount speculation that one of them blew apart and propelled pieces into the body of the plane. They also cast doubt on the theory that birds had been sucked into the engines.

- REUTERS

Full coverage: Crash of Flight 587