The US FAA on 18 July will issue a final rule that will require US airlines to retrofit as many as 2,730 Boeing and Airbus single-aisle and widebody aircraft with fuel inerting systems, costing the industry $435 million over 35 years.
Including inerting systems that will be required on new aircraft models starting in 2010, the total cost of the ruling over the time period is expected to be $1 billion.
Under the rule, manufacturers will have two years to investigate which aircraft will need to be modified, followed by seven years to retrofit the aircraft at an expected cost of about $150,000 to $400,000 per aircraft.
The rule comes almost 12 years after the centre fuel tank exploded on TWA Flight 800 on climbout from New York’s JFK airport on 17 July 1996, killing all 230 on board.
Speaking to reporters at the US NTSB’s training facility outside of Washington DC, where most of the aircraft has been reassembled for training purposes, DOT Secretary Mary Peters said the new rule would provide a “full safety answer” to the two-fold problem of ignition sources in tanks and explosive fuel-air mixture, a “known problem on large passenger aircraft”.
The NTSB determined that a spark inside the tank combined with an explosive fuel-air mixture brought down TWA 800.
In the aftermath of the investigation, the FAA in 2001 issued a special rule that required manufacturers to analyze fuel systems for potential ignition sources.
FAA director of certification John Hickey says hundreds of sources were identified and fixed through more than 100 airworthiness directives.
However Hickey said that it would be difficult if not impossible to locate all sources, hence the need for inerting systems.
The FAA had initially determined that an onboard fuel-air inerting system would cost the industry on the order of $20 billion, but engineers later discovered lower cost methods that would reduce the oxygen concentration on average to 12%, down from 21% in air, at the same time boosting the concentration of inert nitrogen.
Though not removed completely, the FAA determined that 12% oxygen concentration in a centre tank is low enough to acceptably reduce the probability of a fuel tank explosion.
The agency issued a proposed rule for inerting systems three years ago.
Acting FAA administrator Bobby Sturgell says the final rule, which will be published Friday, 18 July and is different from the 2005 version, “will close the door on fuel tank explosions”.
Source: flightglobal.com's sister premium news site Air Transport Intelligence news
Flight Archive: TWA Flight 800
Source: Flight International
