NTSB Rules on TWA Jet Crash Cause

Tuesday, August 22nd 2000, 12:00 am

By: News On 6

WASHINGTON (AP) â€” Four years after TWA Flight 800 plunged into the ocean, killing all 230 people aboard, investigators have reached ``the inescapable conclusion'' that the plane was brought down by an explosion of fuel vapors in its center wing tank.

``The bottom line is that our investigation confirmed that the fuel-air vapor in the center wing tank was flammable at the time of the accident, and that a fuel-air explosion with Jet A fuel was more than capable of generating the pressure needed to break apart the center wing tank and destroy the airplane,'' said Bernard S. Loeb, director of aviation safety for the National Transportation Safety Board.

Loeb summarized the investigators' findings as the board began a two-day session discussing the crash, its causes and possible safety measures that need to be taken.

Loeb indicated the investigators have yet to determine exactly what ignited the blast, but said an electrical short appears the most likely cause.

``The crash of Flight 800 graphically demonstrates that even in one of the safest transportation systems in the world, things can go horribly wrong,'' said NTSB Chairman Jim Hall.

Speculation about the cause of the crash has ranged from a spark in electrical wiring to turbulence caused by another aircraft to bombs and even a missile.

Both Loeb and Hall stressed that bombs and missiles have been ruled out.

``High-energy explosions leave distinctive damage signatures such as severe pitting, cratering, hot gas washing, and petaling. No such damage was found on any portion of the recovered airplane structure,'' said Loeb.

Hall added, ``It is unfortunate that a small number of people, pursuing their own agendas, have persisted in making unfounded charges of a government cover-up in this investigation.''

The Boeing 747 crashed on July 17, 1996, shortly after taking off from John F. Kennedy Airport in New York en route to Paris.

The long, costly investigation has led to extensive changes in design and regulation that are expected to improve safety in the years to come.

Shortly after the crash, investigators determined that the plane's almost-empty center fuel tank exploded, but they have not settled on the source of ignition.

One possibility that has been widely discussed is electrical wiring passing near or through the fuel tank.

The plane had spent considerable time waiting for takeoff on the runway, and air conditioners located beneath the fuel tank could have caused it to overheat.

Since the focus shifted toward the fuel tank, the Federal Aviation Administration has ordered 37 corrective actions for commercial airliners. Among them are replacing sharp-edged fuel probes that might damage wires, keeping pumps idle unless they are submerged in fuel, installing protective sleeves on wiring in tanks and developing electronic devices to suppress power surges in wiring.

Beth Erickson, head of aircraft certification for the FAA, said the agency has reviewed the history of fuel tanks on 10,000 commercial and noncombat military planes and found few problems.

Industry also participated, reporting a week ago that a three-year study concluded airline fuel tanks are safe.

The Air Transport Association, the airline industry's trade association, said more than 100,000 work hours were spent inspecting 990 aircraft operated by 160 airlines as part of the program.

Erickson said the FAA determined that three factors are needed for a fuel-tank explosion: flammable vapors, oxygen and an ignition source.

Changes are being made in all three areas: eliminating sparks; inerting, or filling the empty area of fuel tanks with nitrogen rather than allowing in air that contains potentially flammable oxygen; reducing vapors by keeping tanks fuller; cooling fuel tanks; and changing fuel formulas.

Early in the investigation the possibility of a bomb led the government to tighten security procedures. Investigators have not reported evidence of explosives, either from a bomb or a missile.

Eyewitness reports of streaks of light seen nearby on the night of the crash have continued to plague investigators and to fuel conspiracy theories. That led the NTSB to go so far as to test-fire missiles to determine just what witnesses might have been able to see on the night of the crash.

This month a group of skeptics in Springfield, Mass., sued the government seeking details of its inquiry into the crash, including radar data and information on material found with some of the victims' bodies.

Retired Navy pilot William Donaldson, a vocal critic of the investigation, issued a statement Monday contending that the government is determined to cover up the cause of the crash.