Twa Flight 800 Tests Suggest Mechanical Failure But Investigators Caution Bomb Evidence May Turn Up

Extensive metallurgical tests conducted so far on wreckage of Trans World Airlines Flight 800 suggest that the Boeing 747 crashed as a result of a mechanical malfunction and not because of an explosive device, according to senior air safety and law enforcement investigators in the case.

In the 13 weeks since the July 17 crash, detailed analysis of debris from the plane’s center fuel tank, which blew up moments before the jet plunged into the Atlantic Ocean off Long Island, shows damage patterns that indicate a slower, less energetic explosion than that produced by a bomb or a missile, the officials said.

With more than 80 percent of the fuel tank and 90 percent of the total plane so far recovered, probers said the way in which much of the metal from the tank is bent, rather than shattered or pulverized, is consistent with “low order” explosion, or one that has less velocity and force than a bomb or missile detonation, known as a “high order” blast. Investigators also said the fractures in some of the debris are typical of a slower speed explosion.

Further, investigators said tests have shown that parts of the center fuel tank were blown in an outward direction, indicating the blast occurred somewhere inside it. At the same time, officials said they have found no signs of any metal being pushed in toward the tank - as would be the case if a bomb had been hidden nearby in the cabin.

“From a scientific standpoint, the fingerprints that we have here are more consistent with a low order than a high order explosion,” said one senior law enforcement official involved in the inquiry, who spoke on the condition of anonymity. “Clearly, the burned and twisted metal is not indicative of C-4 (a type of plastic explosive) or other high explosives.”

But officials cautioned that evidence of a bomb still may turn up on still-submerged shards of the jetliner. The investigator said a “shape bomb” could have been strategically hidden where it would have created a narrow, directed explosion that would leave few telltale signs.

In an interview this week, James K. Kallstrom, the FBI assistant director heading the criminal probe of the TWA crash, in which all 230 people aboard were killed, said, “The evidence of a high explosive could be very, very small.”

Almost from the moment Flight 800 exploded in midair shortly after takeoff from JFK International Airport, there have been three theories about what brought down the plane: a bomb, a missile or a catastrophic mechanical failure. Law enforcement officials have strongly pursued the theory that terrorists had planted a bomb, in part because the explosion occurred as the Atlanta Olympics were about to begin and because the circumstances resembled the terrorist downing of a Pan Am aircraft over Lockerbie, Scotland, in 1988.