Airbus prepares to retrofit modifications to the ultra-long-range -500 on safety grounds after US certification snub

Airbus is having to retrofit modifications to the A340-500's fuel system after the US Federal Aviation Administration refused to approve the design of an auxiliary fuel tank in the ultra-long-range airliner on safety grounds.

Although the -500 shares much commonality with the larger A340-600, it is unique in having a 19,930 litre (5,260USgal) rear centre tank (RCT). According to Airbus, this is a permanently installed fuel tank located in the lower fuselage outside the pressurised area, aft of the centre landing gear bay.

As originally designed, the integral fuel tank used the fuselage skin as its outer wall, but Flight International has learned the FAA was concerned about the crashworthiness of this configuration. Airbus says a Kevlar liner is being developed for the tank to meet the requirements of the FAA's conditional certification issued in January, although the European Joint Aviation Authorities did not require it when it approved the new variant in December 2002.

The manufacturer is redesigning the fuel jettison system so the RCT automatically empties first if a fully fuelled aircraft has to return for landing soon after take-off. The Kevlar-lined tanks will be certificated as a major modification by the JAA on behalf of the FAA.

With JAA approval expected by year-end, A340-500s rolled out before January will have the RCT lining retrofitted, and subsequent aircraft will have the modification during production, says Airbus.

Airbus's policy is to standardise aircraft with any modifications required by the JAA or FAA so they are transferable between countries. Although the manufacturer says the unlined RCT satisfied JAA crashworthiness requirements, the FAA, keen to improve fuel tank safety in many types, required the linings, which Airbus says "use similar technology to those developed for Concorde". The company says the weight penalty involved is "minor".

Source: Flight International