Dealing with explosive mixtures in the fuel tanks of transport aircraft used to be high on the NTSB’s most-critical list. The subject evolved after the 1996 explosion of the center fuel tank of a TWA Boeing 747 just after departure from JFK Airport.
The TWA crash and the ensuing investigation raised important issues that explain the difference between government agencies and why the NTSB is considered independent of political influence. After duct-taping thousands of bits of the fuselage of TWA 800 back together, the Safety Board determined the cause of the accident was the explosion of flammable fumes inside the aircraft’s nearly empty center fuel tank. That led to an NTSB recommendation to develop a method to prevent another such mishap.
NTSB Chairman Deborah Hersman told AIN that creating “The recommendation turned out to be the easy part. The real work began when the FAA [the recipient of the recommendation] pushed back, claiming there was no technology available to solve the problem.” The NTSB continued to pressure the agency. Twelve years later, the FAA and the industry developed a fix that was eventually applied to the affected aircraft of fleets around the globe.
In 2008, the FAA published a final rule that required the fuel/air mixtures in all fuel tanks remain below a prescribed flammability level for all newly manufactured aircraft that have more than 30 seats, as well as modifications to passenger-carrying aircraft manufactured after January 1, 1992, to achieve the same level of protection.
The issue came up again on July 13 when the FAA proposed a $13.57 million penalty against Boeing for failing to meet a number of FAA-mandated deadlines for the delivery of service instructions to prevent additional explosions in center fuel tanks. A Fuel Tank Flammability Rule gave both Airbus and Boeing until December 27, 2010 to provide those instructions to the agency for approval.
Airbus met the deadline, while Boeing was 301 days late delivering the paperwork on the Boeing 747 and 401 days late with information on the Boeing 757. The delays affected 383 Boeing aircraft then in service.