Only 12 minutes after taking off for Paris from John F. Kennedy International Airport, as it headed out over the Atlantic off the coast of Long Island, TWA Flight 800 exploded in the evening sky, showering the ocean at dusk with burning fuel, pieces of the 747 jumbo jet and the bodies of all 230 people aboard.
It would take investigators four years to painstakingly piece together the clues before they could say why it blew up.
Neither a bomb nor missile brought down the big Boeing jet. Rather, a tiny electrical spark of unknown origin ignited explosive fuel vapors in the center wing tank, the National Transportation Safety Board finally ruled.
"Airliner fuel tanks are as flammable today as they were 10 years ago," the safety board said Thursday, just ahead of the 10th anniversary of the TWA crash, on July 17, 1996.
Although "significant safety improvements have been implemented" in the decade since the crash, more needs to be done to avoid another accident like TWA Flight 800, the board said.
Mark Rosenker, acting safety board chairman, said the Federal Aviation Administration and the industry are moving too slowly to get a fuel-inerting system on commercial passengers jets and cargo planes to eliminate the possibility of a fuel tank explosion.
And the board wants the system to protect fuel tanks in the wings, not just the center tank, as currently proposed by the FAA, he said.
"The longer we wait, the possibility of a catastrophic explosion remains," Rosenker said in an interview. "The objective is to eliminate these fuel tank explosions as quickly as we can."
Rosenker praised The Boeing Co. for its work at developing a fuel-inerting system that is being evaluated.
"I applaud Boeing and commend them for their leadership in this area," he said. "We are very pleased to see the progress they are making."
Four Boeing jets now in service with airlines were retrofitted with a system that pumps inert nitrogen gas into the center fuel tank as the fuel is used. This prevents the buildup of potentially explosive fuel vapors.
Liz Verdier, Boeing's jetliner safety spokeswoman, would not identify the airlines that are using the jets - two 747s and two next generation 737s. But Boeing hopes to have the system ready to install in its factory-built planes starting in 2007, she said. The system would initially go into 747s and then 737s, followed by 767s and 777s, she said.
Depending on the size of the plane, the system would cost from $100,000 to $300,000 per jet, she said.
That's the cost of retrofitting planes. Boeing would not charge customers anything extra for planes that come from the factory with the system already installed, she said.
It works by removing nitrogen from air that is bled off the engines. On modern jets, air is bled off the engines to power certain systems.
The Boeing 787 that is now in development will come from the factory with an inerting system, but it will use an onboard tank filled with nitrogen. That's because the more-electric 787 will be the first commercial jetliner that does not use bleed air from the engines.
The 787 inerting system will pump nitrogen into the fuel tanks in the wings as well as the center tank.
The Boeing system now being evaluated on the four planes, and the one that will be used on factory-built jets, only pumps nitrogen into the center wing tank. That's because the center tanks are above air-conditioning packs, which can act as a heat source. On TWA 800, the plane's air-conditioning system was running for a long time while the plane was on the ground in New York, and this heated fuel vapors in the center tank to an explosive level, according to the NTSB's final report on the accident.
But Rosenker said it makes sense to use the inerting system for the entire wing and not just the center tank.
"We believe if you can do one tank you can do them all, and if you do them all, you eliminate the problem altogether," he said.
The FAA said Thursday that the board's suggestion will be considered, but it noted there is far less chance of fuel in the wing ever exploding than fuel in the center tank, which is only flammable during 12 percent to 26 percent of a flight.
The FAA issued a proposed rule last year that would require operators and manufacturers of transport-category aircraft to take steps to reduce the likelihood of fuel tank vapors exploding by requiring a fuel-inerting system. But the industry has resisted this move because of the cost.
The FAA has said it is moving forward with the proposed rule, but has not said when it might be made final.
The Air Transport Association, which represents U.S. airlines, is strongly opposed to the rule. Airbus has also come out against it.
In a news release Thursday, the FAA said flying is "far safer" today than it was 10 years ago.
Since 1996, the FAA said, it has issued more than 100 directives that have addressed various fuel tank safety issues.
But the NTSB noted in its release that since the TWA accident, there have been two fuel tank explosions on jetliners. One occurred in 2001, in the center wing tank of a Boeing 737 parked at the terminal in Bangkok, Thailand.
The board is currently investigating the explosion last month in the left wing fuel tank on a Transmile Airlines 727 cargo plane in Bangalore, India.
The plane was waiting to be towed and only the auxiliary power unit was running. Although the source of the explosion has not yet been determined, the board said Thursday that had the plane been flying, the explosion would have torn off the wing and the crash would not have been survivable.
P-I aerospace reporter James Wallace can be reached at 206-448-8040 or firstname.lastname@example.org.
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