FARNBOROUGH: Airbus outlines A330neo engineering demands

Farnborough
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Airbus believes it can almost fully negate the weight increase of the new A330neo by implementing a reduction exercise to trim structure across the entire A330 airframe.

It intends to shed 800kg of weight as it develops the re-engined aircraft, to offset the modifications required to accommodate the larger Rolls-Royce Trent 7000 powerplants.

“We’re trying to head back to an almost neutral [weight] position,” said Airbus executive vice-president for programmes Tom Williams during the Farnborough air show.

The sole-sourcing of the engines will ease some of the design work, he says, because Airbus will not have to come up with a compromise pylon to handle two engine options, as with the A320neo.

Pylon design is one of the critical Airbus tasks for the A330neo. The airframer is planning to maintain the current powerplant ground clearance – just under 0.9m for the Trent 700 – on the A330neo.

This means that, owing to the larger engine diameter, the powerplant must be mounted higher.

“The pylon has to be more carefully thought through,” says Williams. He points out that Airbus must consider the temperature consequences, particularly on leading-edge systems, of installing a hot engine closer to the wing.

Williams adds that the engine-nacelle interface will also be “critical” to the design effort. “You can easily lose 1-1.5% [efficiency] between a well-optimised and a poorly-optimised configuration,” he says.

Airbus and Rolls-Royce have already sealed a partnership with Safran Group’s Aircelle division covering development of the A330neo nacelle.

Williams says that the engineering needs to consider not just the turbine but complex issues relating to configuration of the gearbox and other peripheral equipment, all within the tight deadline to enable late-2017 service entry.

“That’s more or less tomorrow in aircraft development terms,” he adds.

While the Trent 7000 is based on the Trent 1000, it will have an electronically-controlled bleed-air system and Airbus has started the process of selecting a bleed-air supplier. Initial discussions have taken place with Liebherr.

Reinforcement of the wing will be “quite extensive”, says Williams, and involve some material improvements, such as alloy changes, to optimise the loading capabilities. But the architecture of the high-lift devices and spoilers will stay unchanged.

Airbus considered several winglet designs before settling on the swept tips similar to those on the A350. Williams says they provide a “clean extension” of the wing, with a better loading of the centre wing-box which will avoid substantial modification.

The landing-gear, which is already being designed to handle the higher-weight 242t version of the A330, will remain unchanged.

Airbus will also keep any cockpit changes minimal beyond the upgrades necessary to cope with the new engines, in order to stay within the demanding schedule.

Flight test and integration chief Fernando Alonso says that Airbus engineers will have to resist the temptation to suggest improvements, adding: “If you start pulling the thread, it will keep going.”

Airbus A350 project pilot Frank Chapman says that the airframer will not want to deviate from the handling qualities of the current A330. He says the development effort will already “take plenty of time”, and says: “We don’t want to go too much further.”

Although the A330 secured certification two decades ago, Williams points out that the A330neo will face a tougher regime including criteria that were not previously included. He says the aircraft will have to demonstrate, for example, that it can cope with flying several hours with the vibration from sustained engine imbalance.