Explosion in fuel tank caused TWA Flight 800 crash, investigators say

WASHINGTON (CNN) -- Four years after TWA Flight 800 erupted in a ball of flames off the Long Island coast, federal accident investigators Wednesday formally blamed the explosion on volatile vapors in the plane's fuel tank, and issued its third set of recommendations to address the problem.

The National Transportation Safety Board said evidence is conclusive that the explosion originated in the Boeing 747's center wing tank -- a 13,000-gallon capacity tank that was holding only 50 gallons at the time.

The more vexing problem, the board said, was determining what caused the vapors to explode. The most likely ignition source, they said, was a possible electrical short circuit between the low-voltage wire used by the fuel gauges and high-voltage wires used in other airplane systems.

VIDEO CNN's Carl Rochelle explains the course of the NTSB investigation into the crash of TWA Flight 800 Play video (QuickTime, Real or Windows Media) CNN's Carl Rochelle reports from the NTSB meeting and shows video of wreckage Play video (QuickTime, Real or Windows Media)     MESSAGE BOARD Air safety

The board also assailed the decades-old philosophy of addressing the risk of explosion by reducing possible ignition sources, rather than reducing the volatility of fuel tank contents.

That philosophy is flawed "because experience has demonstrated that all possible ignition sources cannot be predicted and reliably eliminated," the board's report says.

The Federal Aviation Administration is studying ways to reduce volatility by infusing fuel tanks with inert nitrogen gas -- a safety step used in military aircraft for decades.

The latest NTSB recommendations are the third set issued by the agency as a result of the July 1996 explosion that killed all 230 people aboard the New York to Paris-bound jumbo jet.

Specifically, the NTSB urges the FAA to:

  •  Examine the design practices of Boeing and other manufacturers to eliminate potential ignition hazards involving fuel tank components.

  •  Review aircraft design wiring specifications to make sure low voltage fuel tank wires are separated from high voltage wires.

  •  Require manufacturers to take steps to eliminate potentially hazardous silver-sulfide deposits on components inside fuel tanks.

  •  Require the companies to improve training of maintenance of personnel so they will recognize and repair wiring problems in aging aircraft.

In earlier efforts to deal with the problems, the board in December 1996 recommended changes designed to reduce vapors in fuel tanks; in April of 1998, it recommended changes in airplane wiring.

Hall said the TWA flight 800 accident was caused by a chain of events "set in motion years before by the manufacturer's and the FAA's design and certification policy"

The FAA has adopted most of the recommendations -- issuing almost 40 orders for design, maintenance and operational changes. But the NTSB noted it is taking time to phase in the improvements.

"The fleet is very much the way it was," NTSB investigator Bernard Loeb said, adding, "If we thought the fleet was unsafe, we would (ground airplanes.) We just think the fleet can be made safer."

NTSB staffers and board members spent much of the two-day hearing discounting theories that TWA 800 explosion was caused by a missile, a bomb or some other explosive device.

While numerous witnesses observed a streak of light near the plane, there is no evidence of an explosive detonation, the board said. The streak of light was the result of burning fuel falling from the exploding plane, they said.

"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," Hall said at the beginning of the two-day meeting. "These people do a grievous injustice to the many dedicated individuals, civilian and military, who have been involved in this investigation."

The approved report reads, tersely, "The in-flight breakup of TWA flight 800 was not initiated by a bomb or a missile strike."

CNN Producer Mike Ahlers contributed to this report.

NTSB: Electrical fault most likely led to TWA 800 crash
August 22, 2000
NTSB begins review of TWA crash probe
August 21, 2000
Missiles test-fired to rule out TWA 800 theory
June 1, 2000
Boeing delayed handing over study of fuel tanks to TWA 800 investigators
October 30, 1999
FAA proposes rules to reduce risk of fuel tank explosions
October 28, 1999

Specials: TWA Flight 800

Flight 800 Independent Researchers Organization
National Transportation Safety Board
The Boeing Company
FAA
TWA
Aviation Safety Institute

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