Key Upgrade Still up in the Air

In a filing to the FAA, the powerful Air Transport Association, which represents major airlines, said the changes were unnecessary and too expensive, and said that new measures to prevent electrical sparks from igniting fumes are sufficient to prevent another catastrophe.

Rosenker said that the FAA has made significant progress in some areas. For example, there are now fleetwide inspections and reviews of fuel tank design. In addition, fuel pumps, fuel quantity indicating systems, in-tank wiring and operational procedures have been modified to make systems safer.

"The crash of TWA 800 was a watershed event for the air carrier industry," Rosenker said. "In the intervening years, a lot of thought and effort has been devoted to the issues raised by this accident, and the public is safer for it."

Safety's slow progress

Officials have had mixed success in getting airlines to fix the fuel vapor and wiring problems that brought down TWA flight 800.

(1) FUEL VAPORS

Problem: Fuel, combined with accumulating oxygen in the center tank, can ignite and explode. Officials are pushing airlines to install inerting systems to reduce oxygen in their planes' fuel tanks. (See diagram at left)

STATUS: None have been installed on commercial planes. Airlines say the changes are unnecessary and expensive. If officials finalize their ruling on this, airlines would likely have 7-10 years to make the fix.

(2) FAULTY WIRING

PROBLEM: Flight 800 investigators found that a spark from aging wiring likely caused an explosion in the center tank.

STATUS: Officials have made recommendations to address wiring problems. Inspections and maintenance of fuel pumps, wiring and other electrical components have been improved.

How inerting works

Air drawn in by plane's engines (A) is fed into inerting system. Inside, membranes separate nitrogen from oxygen (B) Oxygen is vented into atmosphere (C) and nitrogen, which is inert, is put into the center fuel tank (D). With less than 12 percent oxygen in the tank, fuel vapors are less likely to ignite. Inerting system can also be used with wing tanks.

SOURCE: National Transportation Safety Borard; Federal Aviation Administration; Boeing

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