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FAA orders fuel tank safety systems on jets

From Kathleen Koch and Beth Lewandowski
CNN Washington Bureau

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Air Transportation
Disasters and Accidents
Federal Aviation Administration (FAA)

WASHINGTON (CNN) -- Federal aviation officials Tuesday announced plans to require airplane manufacturers Boeing and Airbus to retrofit 3,800 aircraft with onboard systems to prevent fuel tank explosions such as the one thought to have downed a TWA jet in 1996.

In addition, newly manufactured jumbo jets, including the Boeing 737 and 747 and the Airbus A320 and A380, will be required to have the systems.

"We can close the book on center fuel tank explosions," Federal Aviation Administration Administrator Marion Blakey said Tuesday in making the announcement.

Blakey said another accident similar to the TWA 800 crash that killed 230 people likely would happen if the government did not act. The agency's statistical risk analysis put the likely risk at four crashes in the next 25 years as a result of center fuel tank explosions.

The new systems, called inerting systems, would pump nitrogen-enriched air into aircraft fuel tanks, lowering the amount of oxygen in fuel vapors and reducing flammability.

"This is an elegantly simple system" developed by the FAA and tested last year, Blakey said. The agency estimates the cost to outfit one plane with the system at $140,000 to $220,000.

The systems, which will add an additional 200 pounds to the weight of each plane, will cost the airlines about $14,000 per plane in additional fuel costs per year.

Aircraft manufacturer Boeing is developing a similar system, based on the work done by the FAA, and already has agreed to install it in its new 737s, 747s and 777s.

Airbus officials said there are no current-carrying wires or ignition sources in their fuel tanks so they are uncertain how the new requirement applies to their aircraft.

But FAA's Blakey said the agency had done testing of Airbus center fuel tanks and found the risk of explosions caused by sparking wires or other ignition sources similar to the risk found in Boeing tanks.

The FAA said the final rule with details on the precise type of system required will be issued later this year. That rule will set a deadline of seven years for retrofitting planes.

Meanwhile, the FAA has issued more than 60 directives to airlines and manufacturers requiring them to keep fuel in center tanks to make them less volatile and eliminate possible sources of ignition, including faulty wiring.

The July 17, 1996, explosion of TWA Flight 800 off Long Island, New York, brought the issue of center fuel tank flammability to public attention. All 230 people onboard the aircraft died in the crash.

The National Transportation Safety Board could not definitively determine the cause of the explosion but ruled out a bomb or missile attack. Investigators theorized that a combination of factors, including hot summer weather, a center fuel tank full of vapors and a spark from a wire running through the tank, likely caused the blast.

Three other accidents also have been linked to center fuel tank explosions, including a March 2001 Thai Airways International explosion on a runway in Bangkok, Thailand, that was free of fatalities; a May 1990 Philippine Airlines explosion on the ground that caused the deaths of eight passengers; and a 1989 Avianca crash due to a bomb detonation in the cabin that led to a center fuel tank blast and the deaths of 107 people aboard.

When the safety board first recommended inerting systems on all aircraft, the FAA and the airline industry resisted, says such systems were impractical and too expensive. FAA engineer Ivor Thomas is credited with coming up with a lower-cost alternative.

Thomas determined that hot air from jet engines could be cycled into empty center fuel tanks through a filter that would take oxygen out and keep nitrogen in, making the atmosphere inside the fuel tank inert -- or nonflammable.

But he also determined that less nitrogen was needed to keep the tanks inert than previously had been thought, meaning a lighter, less expensive system could be used.

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