TWA investigators leave no theory unturned Explosion on Flight 800 still an unsolved mystery


With the most promising explanations for the midair explosion of Trans World Airlines Flight 800 becoming increasingly difficult to prove, the eight-month investigation has turned into a nationwide scientific exploration of all conceivable theories, including such remote possibilities as the plane's being destroyed by debris falling from space or by natural gas rising from the ocean.

The widening of the search reflects investigators' fears that they will never be able to say precisely what ignited the explosion. Instead, they expect they will have to convince the public that they have ruled out a variety of possibilities -- anything from bombs and meteors to faulty wiring -- and have narrowed the possible causes to one or two that they can address.

Aviation investigators are pressing hard to show how the explosion in the plane's center fuel tank could have resulted from a mechanical malfunction in the tank and not some external force, criminal or natural. For months they have focused on the possibility that a spark could have ignited the fumes in a nearly empty fuel tank.

Working in a laboratory at the Wright-Patterson Air Force Base in Ohio, engineers have tried in the past two weeks to reconstruct the conditions within the tank, but they have not been able to generate a spark strong enough to cause a blast. Those tests are expected to continue for several weeks, if not months.

Since the morning after the crash July 17 off Long Island, N.Y., that killed 230 people, officials of the National Transportation Safety Board and the FBI have listed three possible causes: a bomb, a missile or a mechanical malfunction.

But since no clear evidence of any of those three has been found, the possibilities are growing to include some that investigators consider far-fetched.

They are working with scientists from military and intelligence agencies to determine whether it was possible that something falling from space hit the plane -- a tiny meteor or perhaps a piece of broken satellite the size of a BB.

And when a scientist at the Sandia National Laboratories in New Mexico recently wrote to the safety board that he suspected a bubble of natural gas rose out of the ocean, enveloped the plane and exploded, the agency dispatched a meteorologist who interviewed the scientist, then returned to Washington with some documents for further study.

"We're looking at anything that has any degree of probability until we have a reason not to," said Bernard Loeb, director of aviation safety for the transportation board.

The investigation has traveled well beyond the ocean, where scallop boats are still trawling for any remaining pieces of wreckage, and beyond a hangar in Calverton, N.Y., where a 90-foot section of the plane is being reconstructed.

Scientists and engineers at more than a half-dozen government-financed laboratories have become part of the search, studying everything from how metal changes when hit by a missile to whether a computer model of an explosion in the plane's center fuel tank can be developed.

The safety investigators are working with British aviation investigators and have consulted with their counterparts in Russia in an attempt to understand whether the final loud sound on the cockpit voice recorder was made by a fuel-air explosion or by a more rapid detonation, indicating a bomb or missile.

"I think it's entirely prudent to keep all things up on the board -- even space junk and meteors -- plus all the bomb and missile and mechanical theories," said James Kallstrom, an assistant FBI director and the head of the bureau's New York office. "We should keep an open mind on all of this."

The only theory that officials have ruled out -- emphatically so -- is the accusation renewed last week that a Navy missile shot down the plane and that the federal government was involved in a cover-up.

Officials said that Pierre Salinger, the former television correspondent and press secretary in the Kennedy White House who has become an advocate of the Navy missile theory, has relied on a misinterpretation of radar information and unsubstantiated conjecture to support his conclusions.

Now that more than 90 percent of the plane has been recovered and no evidence of a bomb or missile has been found, the investigation is increasingly focused on a mechanical malfunction.

Investigators announced in December that the 12,890-gallon center fuel tank was primed for an explosion because air-conditioning packs below it had heated the small amount of fuel, producing dangerous vapors. Board officials recommended ways of keeping fuel tanks below that temperature range.

Explosives experts have advised the board that searching for proof of the exact cause may be fruitless, since the blast probably destroyed conclusive evidence.

"It is not unusual, in a fire-related accident, for us not to identify a point of ignition," Loeb said. "The very existence of the act itself -- the fire, the explosion -- destroys the evidence."

With the public still focused on the crash and the possibility of a criminal act, the government is now in the midst of an intense endeavor to prove which ignition sources were possible and which could be ruled out.

Disproving any of the theories is at least as difficult as proving them. This is also true of the natural gas theory offered by Dick Spalding, the scientist at Sandia National Laboratory.

It was Spalding who said explosions attributed to gas bubbles rising out of Earth's crust had been described as flashes of light -- similar to what the witnesses saw when Flight 800 crashed.

He presented his suggestion that Flight 800 hit such a bubble in a letter to the safety board, where it was treated as another theory -- a far-out theory, to be sure. Because of its "leave no stone unturned" posture, it sent meteorologist Greg Salottolo to visit Spalding and hear him out.

"Greg seemed receptive," Spalding said, "although I think guardedly so."

Pub Date: 3/16/97

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