...While Exploding Fuel Tanks Get More Time

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And while no one has so much as broken a nail because of the nose gear issue, hundreds have been killed because of exploding fuel tanks and, according to the FAA's proposed AD, more such calamities are "virtually certain to occur." The agency has issued a Notice of Proposed Rulemaking (NPRM) that will not require the installation of specific hardware to address fuel-tank explosions, but rather will set flammability standards for the ullage, the space in the tank not occupied by fuel. It will be up to manufacturers and airlines to meet those standards, something the FAA says was not thought practical a few years ago but which is now economically viable. The most likely method of making the tanks explosion-proof is by displacing oxygen in the ullage with inert gases. The system developed by the FAA and industry passes compressed air through a membrane that separates nitrogen and pumps it into the tanks, preventing combustion. The agency and industry jointly researched such systems and Boeing has since applied for certification of a system it intends to install on all its new 747s. The focus used to be on eliminating sources of ignition but the NPRM says it's not likely that can be accomplished. If something isn't done, the FAA's computer models suggest that over the next 50 years fuel-tank explosions would claim at least nine aircraft.