The static thrust requirements for the engines powering Airbus’s A350 XWB family will be lower than first estimated after the airframer established that the aircraft’s aerodynamic performance will be better than that originally forecast.

Airbus has frozen the static thrust levels at sea level/15o C for all three A350 variants for entry-into-service with Rolls-Royce, which is the XWB programme’s sole supplier with its Trent XWB engine family.

The static thrust levels are 74,000lb (329kN), 83,000lb and 92,000lb for the A350-800, -900 and 1000, respectively. These are between 1,000 and 4,000lb lower than previous estimates, says A350 XWB chief engineer Gordon McConnell.

"After windtunnel and development work on low speed performance, we’ve improved our level of prediction and believe we have better performance than anticipated at the start of the programme," says McConnell.

"We found that we were well, well inside our targets for take-off field length and so on," he adds. "We’ve also improved the braking of the aircraft which has allowed us to reduce the thrust levels."

Airbus is still the freeze the design of the A350’s tail surfaces, and McConnell says that it was important to make sure the thrust levels were well matched to the requirements of the aircraft as excess thrust could result in the fin being larger than required to cope with engine-out scenarios.

Rolls-Royce Trent XWB static thrust revisions

   Old thrust (lb)  New thrust (lb) difference 
 A350-800  75,000  74,000  1,000
 A350-900  87,000  83,000  4,000
 A350-1000  95,000  92,000  3,000