Airbus's brand-new A350 XWB widebody twin may be disappointingly absent from this year's Le Bourget flying display, but UK engine manufacturer Rolls-Royce is still making an impact at the show thanks to the presence of the first Trent 900-powered A380 superjumbo destined for British Airways.

It is perhaps appropriate that the UK flag-carrier's first ever Airbus widebody is a star of the show, as together with its R-R engines and Broughton-built wings, the aircraft is approximately 50% British by value.

Thanks to its position as sole-source powerplant supplier to the A350 programme with its latest and greatest turbofan - the Trent XWB - R-R is poised to become the dominant force in Airbus widebody propulsion. This feat is all the more surprising given that R-R had not powered a single Airbus type until 1995, when the Trent 700 debuted as the third engine option for the A330 widebody twin.

The exclusively Trent 500-powered A340-500/600 quadjet programme followed, although production ended after only around 130 aircraft were sold. A two-way battle against Engine Alliance for A380 business began with the launch of the A380 in 2000, with R-R pitching the Trent 900, and the spoils have been split relatively evenly. Meanwhile, R-R's share of A330 deals has steadily grown.

On the Boeing side, Trent 800 production for the 777 has effectively ended after the US manufacturer decided growth versions of its biggest twins would be exclusively GE-powered, but the Trent 1000 is firmly entrenched in the contest for orders to power the 787, against its US rival's GEnx.

All in all, around 2,000 Trent engines have been delivered during the 18 years since the Trent 700 entered service, but R-R is set to deliver the next 2,000 in just five years.

"That gives you some view of how the business is ramping up," says Simon Carlisle, R-R executive vice-president strategy and future programmes for civil large engines.

"With the Trent 700 we were third onto the A330, and now we enjoy 70% of that market," he says. "First is not always best - sometimes being able to look at what the competition is doing and being able to deliver a product that is significantly better can serve you in the long run."

To cope with unprecedented Trent production rates, R-R has brought on line an additional production facility at Seletar in Singapore. The first Singapore-assembled Trent 900 was delivered in November 2012, and the first locally built Trent 1000 is due to emerge next year.

"We've got a lot to do over the next five years. We've got to double the number of [Trent] engines that we've delivered. The focus on delivery is absolutely imperative for us, and making sure that we execute.

"The plan is that Derby will make XWBs and Singapore will take up the load on the Trent 900 and 1000," says Carlisle.

Over the course of the 18-year Trent production run, technological advances have been progressively introduced, yielding efficiency improvements of roughly 1% per year. The Trent 900, for example, offers a 16% efficiency improvement compared with the original Trent 700. This trend has continued with the arrival of the Trent 1000, which entered service in 2012, and the Trent XWB, which is due to begin powering revenue flights in 2014.

"If you were to look at a Trent XWB and compare it to a Trent 700, the differences in technology are enormous, even down to the architecture of the engine, with the Trent XWB having three stages of core turbine which separates it from the rest of the family," says Carlisle.

With the airline industry consuming around 65 billion US gallons of fuel - worth nearly $200 billion - every year, "using fuel efficiently is massively important to the industry, and hence why that 1%-per-year improvement in efficiency becomes an imperative for the business".

He adds: "We keep demonstrating technology by running rigs and engines and doing testing and modelling. All of that is designed not only to ensure that we are positioned strongly for the future, but that we can also feed that technology back into our existing products and take benefits where we can.

"We've used that in the past to help us push temperatures up to generate more thrust and incorporate SFC (specific fuel consumption) improvements. The Trent 900EP (enhanced performance) is a good example of something where we've taken technology that has been developed for Trent 1000 and XWB and adapted it and re-inserted it back into the Trent 900."

The latest 3D geometry design and manufacturing methods have been employed on the XWB, so the sweep and angle of fan blade is "completely different", says Carlisle.

"On a [Trent] 700 I absolutely know which way the blade goes in. On an XWB I think it's actually quite challenging to know which way round the blade goes because when you pick it up it isn't immediately obvious, because of the twist in the blade at the top. That's how far the design has come on the titanium blade."

Despite sticking with titanium blades for the Trent XWB fan, R-R is preparing to make the switch to lighter composite materials as the technology matures. It has set up a joint venture with GKN to develop and test composite blades and associated production systems, and plans to test a composite fan using the ground-based ALPS (advanced low-pressure system) demonstrator.

A350 XWB 


"We are manufacturing it using a different method to blades that are currently made," says Carlisle. "This is a more automated, tape lay-up approach. The blades made by our competition are more traditional hand lay-up. We believe that will give us an advantage for our future product."

The principal driver behind the pending Trent production ramp-up is the A350 XWB programme, which has accumulated a firm order backlog of well over 600 aircraft prior to first flight.

The Trent XWB test programme has so far accumulated more than 4,000h, says programme director Chris Young. Three engines are being used for cyclic maturity testing and a further two are in endurance testing. Also being carried out is a third phase of flight tests using a Trent XWB mounted on Airbus's A380 flying testbed, to investigate natural icing characteristics.

"It's had some exciting times in the clouds, trying to find the right icing conditions," says Young.

The flight test programme for the baseline A350-900 will utilise five aircraft, and is due to get underway imminently.

"There is lots of material coming down the line. Everything is on time and in plan to meet Airbus's [schedule for the] next aircraft," says Young.

Another element of Trent XWB testing involves the transportation system that will support the TotalCare maintenance programme.

The XWB is the first R-R engine that needs to be split into a fan module and propulsor for transport in a 747 or 777 freighter. The projected Trent XWB in-service fleet will generate up to 1,200 shop visits per year, "so we'll actually be transporting these engines three or four times a day", says Young. "Making sure we get the transportation and logistics right is critically important."

Initial trials of splitting an engine and loading into a 747 have been completed. It has been determined that up to three engine shipsets can be accommodated in a single 747, and it takes a five-person crew eight hours to disassemble an engine for air transportation, and the same time to reassemble it.

"It's one of these things that not many people really think about. When we're designing these things, you've not just got to get the product right in terms of its specific fuel consumption. It's got to be completely transportable, and that sets some of the dimensions for the engine. If you can't transport it by air, then you have to do it by ship and the turnaround times are enormous," says Young.

Also being demonstrated is a laser repair capability for the XWB's blisks (single-piece compressor disks and blades) to avoid unscheduled shop visits.

"Previously if you had a nick on one compressor blade, it was not a very expensive thing to throw it in the bin. If you've got a nick on a blisk, you've got to be able to repair it. Repair technology has become quite critical," says Young.

R-R and Airbus have agreed that the A380 testbed will be used to demonstrate the 97,000lb-thrust growth version of the Trent XWB prior to the first flight of the stretched A350-1000, which is due to enter service in 2017.

"We think it's the right thing to do for overall maturity of the powerplant," says Young.

The A350-1000's engine has the same fan diameter as the baseline, 84,000lb-thrust Trent XWB-84, but a slightly increased core size.

"Now it's about growing its margins and making sure its time on wing is what it needs to be," says Young.

The bigger core means a slightly reduced bypass ratio, but Young says a business case for increasing the fan diameter could not be made.

"As soon as you change the fan diameter, you lose huge amounts of commonality. So the good thing about this is that the interfaces through to the aircraft are identical," says Young. "All the things that really matter for the airlines' day to day operations, we've kept common. The airline only needs to buy one set of tooling and one set of line-replaceable units (LRU). It's only the stuff that we'll look after in shop visits that are bits that will really change.

"We decided along with Airbus that actually the benefit of commonality for the airlines means that we have the optimum fan diameter."

Around 80% of LRUs will be common between the baseline and growth engines. R-R is preparing to run prototype demonstrations using a Trent XWB-84 with some of the XWB-97 technologies incorporated, but without the core change. The first full-specification growth engine is due to be run in mid-2014.

"We're on track to hit all of the targets we set out to achieve," says Young. "We will carry on looking at a programme of continuous improvement over time, but to make it even more competitive rather than to meet our [service-entry] targets."

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Source: Flight Daily News