Boeing fails to pinpoint TWA 800 crash cause

By Jim Wolf

WASHINGTON, Aug 10 (Reuters) - Boeing Co. (NYSE:BA - news) said on Thursday a four-year, $32 million in-house investigation had failed to pinpoint even so much as the possible spark of the 1996 mid-air explosion of TWA Flight 800, one of its jumbo jets, that killed all 230 people on board.

But the wreckage showed no signs of the Boeing 747-100's having been bombed nor hit by a missile, contrary to conspiracy theories that have circulated widely, company officials said in summarizing their part of the largest transportation accident probe in history.

All 230 people aboard died when the Paris-bound aircraft exploded and fell into the Atlantic off Long Island on July 17, 1996, 14 minutes after takeoff from New York's John F. Kennedy Airport.

In an April 28 submission to the National Transportation Safety Board, which heads the federal investigation, Boeing attributed the crash to ``an ignition of flammable vapours in the centre wing tank, resulting in a loss of structural integrity of the aircraft.''

Briefing reporters in suburban Arlington, Va., company officials said on Thursday they had been unable to determine the ignition source and declined to name any likely candidates.

``We're going to leave that'' to the five-member safety board, which is to consider on August 22-23 its final report on the probable cause of the crash, Ron Hinderberger, director of aircraft safety for Boeing's commercial airplane group, said.

``There would be nothing that would please us more than to say 'we found it','' Hinderberger said, referring to whatever sparked the explosion. Not uncovering it was ``bothersome,'' he conceded.

INVESTIGATION BOOSTS SAFETY

But he said the hunt had identified ways to enhance fuel tank system safety, including a recommendation that airplane operators use air-conditioning carts when on the ground to lower fuel-tank temperatures when the thermometer tops 60 degrees Fahrenheit (15.6 degrees Celsius).

Dennis Floyd, the Seattle-based company's chief engineer for airplane safety, said the investigation has prompted 48 service bulletins recommending design, maintenance and/or inspection improvements across the Boeing fleet, the most to result from any accident by far. Eleven others are in the works.

Although Boeing declined to name a suspected cause, it said none of the recovered fuel system components showed any evidence of having sparked the events suspected of blowing up the airliner.

Similarly, no evidence was found that any of the 747-100's fuel quantity indicators, probes or wiring were the culprits, the company said in its report to the safety board.

``Boeing's examination of the recovered wreckage did not reveal any evidence of bomb damage on the structure or damage that could be expected from a missile impact,'' Hinderberger said.

He said Boeing was ``in agreement'' with a conclusion by the head of a safety board-appointed task force that witness accounts were of scant value in determining the cause.

Several tales of an upward-streaking light in the sky at the time of the crash have fuelled conspiracy theories centred on a missile of a type that could have been launched from boats in the area.

In March, the safety board's ``witness group'' said it had reviewed 755 interviews carried out by the Federal Bureau of Investigation, calling them ``poorly suited for purposes of an aircraft accident investigation.''

Still, investigators test-fired heat-seeking, shoulder-fired ``Stinger'' missiles from a Florida beach in April to compare what witnesses reported and the sights and sounds a missile would make in the lighting and atmospheric conditions akin to those that prevailed that evening on the Long Island coast.