Guy Norris and Andrew Doyle/PARIS

Airbus Industrie is battling to overcome weight problems threatening a payload/ range shortfall on its A340-500 and -600 models with a weight-reduction programme and the possible introduction of higher operating weights and uprated engines.

Separately, Pratt & Whitney is expected to decide by the end of this year whether to pursue development of a geared-fan engine to offer as an alternative to the Trent 500 on the new Airbus models.

Airbus declines to comment on the performance shortfall, but sources close to the programme say the maximum take-off weight (MTOW) of the A340-500/600 may have to be increased by around 6.8t to meet range guarantees given to early customers. In their current 365t-MTOW configuration, the -500 and -600 fall around 740km (400nm) short of their target ranges, say the sources.

The A340-600 is due to enter service in 2002. Initial subassemblies are in production.

Rolls-Royce says it can meet any increase in thrust that might be required with the Trent 500, but is believed to have accelerated studies on applying its "swept fan" technology to this engine. Use of the swept fan would provide extra thrust without increasing weight, and reduce fuel consumption.

Among options under consideration to save weight is the removal of the outboard thrust reversers. An earlier plan to shed another 500kg by removing the over-wing exits on the A340-600 has been dropped due to certification issues.

DaimlerChrysler Aerospace Airbus president Gustav Humbert says the weight issue is "not such a big problem. It does not worry us too much", he adds.

Airbus says the aircraft will be delivered "to specification, to guaranteed performance or better, and to our customers' satisfaction".

Meanwhile, P&W's studies of a 60,000lb-thrust (270kN) geared-fan engine, internally designated the PW8160, could lead to the US manufacturer joining the A340-500/600 programme as an alternative powerplant supplier by around 2006. R-R's exclusive engine deal with Airbus on the -500/600 will expire by then.

P&W will decide this year on whether the PW8160 studies are worth pursuing, say industry sources. The engine, based on a scaled-up PW6000 core with a re-designed fan and low-pressure turbine, would take around five years to develop and could be available as early as 2004, possibly as a 767 powerplant, the sources add. P&W believes geared-fan technology offers the prospect of significantly reduced fuel consumption, compared with conventional turbofans.

Although Airbus has encouraged P&W to look at the technical feasibility of a geared-fan engine for the A340, no talks have taken place at a commercial level.

P&W has scaled back earlier plans to develop a geared fan engine for the A320 family and is working on a higher-thrust version of the V2500 with its International Aero Engines partners.

Source: Flight International