A new rule, titled Reduction of Fuel Tank Flammability in Transport Category Airplanes, has been has been issued by the U.S. Department of Transportation and incorporated into the regulations of the Federal Aviation Administration (FAA). The rule requires "operators and manufacturers of transport category airplanes to take steps that, in combination with other required actions, should greatly reduce the chances of a catastrophic fuel tank explosion."The new FAA rule, hailed by the National Transportation Safety Board (NTSB) as an important step in aviation safety that will save lives, arose in part from the NTSB's findings regarding the TWA Flight 800 accident in 1996. TWA Flight 800, a Boeing 747 en route from New York to Paris, exploded minutes after taking off from JFK Airport, killing 230 people. The NTSB investigation determined that the probable cause of the TWA Flight 800 crash was "an explosion of the center wing fuel tank, resulting from ignition of the flammable fuel/air mixture in the tank."
The NTSB subsequently called upon the FAA to require design or operational changes that would preclude the operation of large airplanes with explosive fuel-air mixtures in the fuel tank. In NTSB Safety Recommendation A-96-174, published in December of 1996, the Board recommended that the FAA give significant consideration to the development of airplane design modifications, such as nitrogen-inerting systems, and to apply such modifications to newly certificated airplanes and, where feasible, to existing airplanes. The new FAA rule is in response to that recommendation.
The new fuel tank flammability reduction requirements specify that new aircraft must have the technology built in, and that older aircraft be retrofitted with the system. Boeing and Airbus passenger aircraft with heated center wing tanks and manufactured before 2009 now must be retrofitted with a flammability reduction means, such as a fuel tank inerting system, or with ignition mitigation means, such as polyurethane foam. A fuel tank inerting system fills air space inside the tank with an inert (i.e., non-flammable) gas such as nitrogen.
The retrofit requirement excludes cargo aircraft. The rule will apply to both Boeing and Airbus passenger and cargo aircraft manufactured after 2009.
If you are interested in all the fine details of the new rule, here is the link to the full text: Reduction of Fuel Tank Flammability in Transport Category Airplanes - U.S. Dept. of Transportation (233 page 'pdf file)
