Rolls-Royce Building First XWB-97 For Flight Tests

Core and fan for flying testbed A350-1000 engine will be mated at Rolls-Royce this month
Flying Engine

Rolls-Royce is assembling the first flight-test version of the Trent XWB-97 A350-1000 engine, the highest-thrust production engine ever made by the manufacturer.

The fan case for the first flight engine, No. 26001, is nearing completion and vertical stacking of the core is progressing quickly at the manufacturer’s Derby, England, facility after getting underway toward the end of April. “The engine will be moving to Toulouse around mid-year and is due to fly in the beginning of the fourth quarter,” says Simon Burr,  Rolls-Royce’s chief operating officer for Civil Large Engines.

The 97,000-lb.-thrust engine is the first of two units destined for initial evaluation flights on the Airbus A380 flying testbed MSN001, and will be used for evaluating engine operability, relights and handling. Beyond engine- specific testing, Airbus also intends to use the XWB-97 on the A380 for integrated nacelle tests. “It will do this to take credit for A350 certification and flights will run well into 2016, so it is not a short program,” says Burr. The first A350-1000 is due to fly in mid-2016 and is scheduled to enter service in 2017, two years after the Trent XWB-84-powered A350-900.


Fan case (left) and core (below) for first flight-test XWB-97 come together in Derby, England.



Unlike the -84, which first flew on the A380 in February 2012, the higher- thrust engine will not have undergone simulated altitude evaluation in a test cell before it takes to the air on the flying testbed. “On the -84 we did altitude work in North America (at the Arnold Engineering Development Center in Tennessee), whereas on the -97 we are using the A380 for flight-test data at altitude,” says Burr. “We’ve already proved the basics from the -84 and we can get useful data off that,” he adds.

Since making the first run of the XWB-97 in July 2014, Rolls has focused ground testing on the newer design features of the engine. These were introduced to generate 13,000 lb. of additional thrust over the baseline XWB while maintaining the same fuel-burn efficiency, 118-in. dia. fan and external nacelle packaging. The higher-flow fan turns 6% faster than the -84 and pumps more air. The XWB-97 is also designed with a 5% larger core and higher temperature capability as well as unshrouded high-pressure turbine blades.

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As part of the biggest shake-up to its production system since the start of the big-fan era, Rolls-Royce is transitioning to a pulsed system assembly and test facility to handle the growing volume of mainly Trent XWB engines for the Airbus A350.
Burr adds that while Rolls was “very pleased with the first engine, which ran for 150 hours,” the company has made some design modifications to improve durability as a result of inspections following a teardown. Chief among these was an adjustment to the gas temperatures generated across the width, or traverse, of the combustor exit. “At the exit point you set up a particular profile in terms of temperature and you match the materials to that. Our first runs showed that profile was flatter than desirable, which would mean the high-pressure turbine blades and nozzle guide vanes would end up seeing a higher temperature than [designed]” explains Burr. Changes were made and tested on a combustor rig and “we have got a really nice match to the design now. Those changes are going into the next two engines on build right now and will feed into certification.”

“In terms of clearing the XWB-97 for flight, the icing work is complete and the first phase of type testing has been done. We have to do the medium bird-strike test, and we will be doing that over the next few weeks,” Burr says. The first flight-test engine is “very close to production standard, in fact much closer than the first -84 was. The only differences are just in terms of the external dressing and various small design changes,” he adds, referring to aspects such as the configuration of the systems and wiring harnessing, which is “as close as possible to the final standard.”

“When we built the first engines we used a different harness technology to experiment with it, but here we have aligned it so it will feel the same to a mechanic servicing either the -84 or the -97,” says Burr. The two engines already share 80% of the same line replaceable units, but Rolls is refining the configuration to increase the “feel” of commonality. “It’s about things like where things will be positioned. We’ve done a lot of design changes to align it to the first A350-900 in service in terms of the -84 engine,” he adds.