GRAHAM WARWICK / WASHINGTON DC & DAVID LEARMOUNT / LONDON
Airbus and Boeing aircraft to be affected by requirement that "could eliminate up to four accidents in the next 25 years"
An estimated 1,019 Airbus and 2,795 Boeing aircraft operated by US airlines will have to be retrofitted with fuel-tank inerting systems at an expected $600 million cost under a notice of proposed rulemaking (NPRM) that the Federal Aviation Administration plans to publish later this year.
The NPRM will require production aircraft to be delivered with inerting systems installed within one to two years of the final rule taking effect, which is expected in 2005. The Airbus A380 and Boeing 7E7 will be required to have inerting systems "in place before certification", says FAA administrator Marion Blakey.
Fuel-tank inerting systems will be required in aircraft where air-conditioning systems can cause heating of centre-wing fuel tanks. Airbus types named are the A320, A300-600, A310 and A330. All Seattle-built Boeings will be affected, but no former McDonnell Douglas designs or regional jets because their flammability risk is low, says John Hickey, director of the FAA's aircraft certification service.
Boeing has begun certification work on an FAA-designed onboard nitrogen-inerting system and "has stepped up to a production cut-in", says Hickey. Airbus, not having suffered a tank explosion, argues its fuel-system designs are less vulnerable, but will not comment until the NPRM is published. The company is testing an FAA-provided prototype system in an A320.
"Boeing has already agreed to equip the 7E7," says Blakey. Discussions are continuing with Airbus, but the A380 "has to have the system" by the time deliveries to US airlines begin in 2008, she says. While the A380-800 does not have a centre tank, Hickey says the FAA's analysis suggests "the cheek tank volume is so large, and the heat dissipation lower, that they retain heat and have a higher flammability risk" than wing tanks.
The NPRM will propose that in-service aircraft be retrofitted with inerting systems over seven years from the final rule taking effect. The FAA estimates the installed cost will range from $140,000 to $220,000 depending on aircraft type. To avoid overloading heavy-maintenance centres, Hickey says, the agency is considering a phased approach requiring the "most vulnerable" types - the A320, 737 and 747 - to be retrofitted first.
Blakey says the NPRM will not mandate installation of the FAA-developed inerting system, but instead set a flammability specification, leaving room for development of other techniques to keep the fuel/air vapour mix in tanks below the flammable level.
Source: Flight International
