Wake effect probed in crash

Associated Press

NEW YORK — Investigators raised the possibility Wednesday that turbulence from the wake of a Boeing 747 led to the crash of American Flight 587, saying the doomed Airbus A300 took off less than the standard two minutes after the jumbo jet.

"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 planes flying too close behind or below. The phenomenon has been blamed for at least one deadly crash in the past.

Investigators want to know whether it caused Flight 587 to break apart three minutes after takeoff from Kennedy Airport on Monday, killing all 260 people aboard and as many as five on the ground. The plane’s tail assembly sheared away and its twin engines fell off as the jet went down.

Standard protocol says there should be at least two minutes between takeoffs. However, Blakey said it appeared there was less than that between Flight 587, a European-made A300, and a Japan Air Lines 747 that left ahead of it from the same runway.

"We believe that in fact it was 1 minute and 45 seconds," Blakey said.

She said it appears air traffic controllers followed proper procedure, and that tower clearances for the two takeoffs came 2 minutes and 20 seconds apart.

But investigators believe there was a delay from the time Japan Air Lines got clearance to take off and the time it actually did so, NTSB spokesman Ted Lopatkiewicz said.

Pointing to a map of the two planes’ flight paths, Blakey noted that although the jumbo jet’s path was 800 feet 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.

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 with "tornadolike lateral force."

Authorities have not ruled out sabotage or other causes but have said all signs point to mechanical failure.