WASHINGTON - After a four-year, $36 million investigation the National Transportation Safety Board closed its books on the crash of TWA Flight 800 and recommended changes in aircraft wiring and better fuel systems.
The board formally concluded on Wednesday that the Boeing 747 was destroyed by an explosion in its center fuel tank, probably triggered by a short circuit. It asked the Federal Aviation Administration to examine aircraft wiring practices, review wiring design specifications and require improvements.
The FAA has 90 days to respond to the recommendations. Board Chairman Jim Hall said that during the TWA investigation his agency has sent 11 other recommendations to the FAA, and it has acted or is taking action on most of them.
Speculation on the cause of the crash off the coast of New York's Long Island, which killed all 230 aboard, has ranged from maintenance problems to a bomb, a missile, and even a meteorite. In a two-day hearing concluding its investigation the board struggled to disprove those theories.
Joseph Lychner of Houston, who lost his wife, Pam, a former TWA flight attendant, and his two young daughters, Shannon and Katie, in the disaster, found little comfort at the hearing.
''The presentation by the NTSB has been excellent but there have been no surprises. The center fuel tank blew up and killed my family, and the loved ones of the other family members. That is not supposed to happen, is it?'' Lychner said.
Michel Breistroff from Paris, whose son Michel, 24, had been about to join the French Olympic hockey team, is not convinced the plane was brought down by a mechanical problem. He said he had lingering doubts about a missile or some other non-mechanical means.
''They have been explaining to me but inside my head I don't fully believe what they are saying. I wish I could be convinced so I could be free,'' Breistroff said.
The board spent much of Wednesday afternoon focusing on the missile theory, stressing that no radar returns show the presence of a missile.
Eyewitness reports generally support the evidence of an internal explosion, though a few mention a streak of light before the plane went down.
Investigator David L. Mayer said that the first explosion in the moving airplane would have looked like a small, moving light followed, a few seconds later, by a fireball as the plane broke up and fuel from other tanks went into the blaze. The fireball then would break up as the pieces fell into the ocean.
''There is a remarkable consistency of the accounts and most seem to be describing the breakup of the accident airplane,'' Mayer said.
Some witnesses who reported seeing a streak from the ground didn't include that in their first description, only adding it later after the idea had been raised in the news, he added.
''Witness statements only help solve the puzzle, physical evidence is almost always the key,'' said board member John Goglia.
Earlier Wednesday the board raised the question of aging aircraft. The TWA Flight 800 plane was 25 years old.
''The longer an airplane is around, the more changes and modifications it needs,'' said Hall, adding that it is not clear the industry is paying enough attention to these problems.
The Federal Aviation Administration and the aviation industry have launched aging aircraft programs to study the needs of older planes and how to deal with them.
Goglia, a former aviation mechanic, stressed that the mere age of an aircraft does not mean it's not safe. ''A properly maintained airplane can last forever,'' he said.
Robert Swaim of the board's aviation engineering division said, however, that inspections of a number of commercial aircraft showed increasing problems as the planes got older.
''We looked at other planes from other carriers and other countries,'' Swaim said. Inspectors found worn insulation, improper wiring repairs, open splices that should have been sealed and lint on circuit breakers.
Bernard Loeb, the board's aviation safety director, cautioned that investigators were not saying the problem had reached the level of planes being unsafe.
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