Aircraft

Rolls-Royce expects to freeze the design of the baseline Trent XWB turbofan by the end of July and sees no significant implications from Airbus's recent decision to increase operating weights for all three members of the A350 XWB.

"We put a big fan on [the Trent XWB] deliberately because if the weight goes up, that's what constrains the noise," says Colin Smith, R-R's director of engineering and technology.

He adds that Airbus is "actually freezing the baseline design now and I don't think we quite know where the aircraft's going to be. There's a long way to go on the programme, but broadly we have a common bill of material throughout the power range."

The first three-shaft Trent XWB is scheduled to undergo bench testing in early 2010 and the engine is due to be certificated by the end of 2011 following a flight-test programme using the Airbus-owned A380 prototype MSN001. The baseline A350-900 is due to fly in early 2012 and enter service in mid-2013.

"We will start producing components this time next year for the first test of the Trent XWB," says R-R president, civil aerospace, Mark King. "This is not a long way in the future - this is becoming more and more real."

Airbus is having to increase maximum take-off weights for the three A350 models by around 3t each to maintain payload range performance, resulting in a fuel-burn penalty of around 1% for a typical mission.

"An increase in the operating weight of any aircraft has an impact on the engine," says Smith. "One of the advantages of the three shafts is we do scale each bit inside the design tools. The biggest parameter we set is the fan diameter. We set quite a conservative fan diameter and we are working on an optimised core size."

The Trent XWB will be the first of the family to feature blisks in the compressor, but otherwise represents an "iteration" of the Boeing 787's Trent 1000, says Smith.

"There's incremental technology all over the place," he says. "We've taken a bit more weight out of the system because we can optimise it with our computer tools. There's nothing there that you would say is a step change in technology."