TRENT XWB
Rolls-Royce’s latest big fan is aimed at aiding shop work while further reducing MRO costs.
ready change of modules if required. A 15 percent reduction of blades and vanes across the engine reduces MRO work and consequently the associated costs. These advances have stemmed from computer modelling and design improvements, including 3D fluid dynamics. Engine health monitoring/ Prognostics was another, designed-in feature of the XWB, with the greatest number of sensors ever on a Trent to predict maintenance issues and further reduce down-times. “As a philosophy we try to maximize the amount of work that an airline can do on-wing (like core washing or boro- blending) to restore the engine to health and keep it running well,” Boddy told Aviation Maintenance, “but we offer a range of services, while off-wing MRO work on the Trent XWB is covered by our TotalCare support service package (under which Trent operators are either partnered or have a joint venture agreement with Rolls-Royce).”
“With the Smart design the XWB has the most efficient compressor system of any in the series, with a low aspect ratio for the compressor entrance, which is angled to reduce the likelihood of foreign object debris entering the core. There are two sets of blisks (bladed disks) within the HP compressor, which, while large and expensive components, they reduce the number of blades needed overall and consequently reduce maintenance time. In passing, we’re looking closely at the repair technology of blisks at the moment as we do a lot of blisk work in military applications. We are commercializing that technology with the XWB because it is a critical component in the performance of the engine, as the blisks not only reduce weight but provide laminar flow through the engine to deliver greater efficiency.”
Other items of note which had been given close attention,
Boddy related, was the design of the fancase-mounted units, to provide ease of access and removal, while the larger fancase allowed the engine to cool quicker, thus providing faster access to the engine after arrival at the gate. To add to these features has been the measures taken to deal with the bird-strike issue. For many airline operators this can be a serious problem, with the FAA reporting that there were 7,666 bird strikes in 2007, an increase of 6.5 percent over 2006, the annual cost of this to the industry being assessed by ICAO as $1 billion. With this remaining a greatly intractable problem amongst aero engine makers, Rolls-Royce has designed into the XWB boroscope access to all compressor stages to allow its latest boroblend techniques to be fully deployed should any FOD affect the compressor. Quick on-wing changes are facilitated by bolted-in fan track liners.
by Roy Allen
Advanced materials All engine makers are looking at new materials for tomorrow and Rolls-Royce is seriously into this work. “We spend $1 billion a year on research and new technology and you have to invest strongly in this business to stay ahead,” Tim Boddy responded to AM’s question. “We have a lot of different technologies and materials under study as a part of what we call our Continuous Improvement programme, and composites is one such area. We’ve just signed a joint venture contract with GKN for fan blade development, while studies are under way on materials such as ceramics. Ceramics are really all about weight reduction while they do have high-temperature capability. We would argue that until now Rolls-Royce has led the world in blade technology but you do have to continue to look ahead. Our standpoint is that if it can be done in an economic way and is to the benefit of our customers, that it reduces maintenance costs or vastly improves specific fuel consumption then that would be exactly where we would want to go. Its all about being customer-aligned.” Towards the Fall the Trent XWB engine was well into its test flying period and on track for certification by the end of 2012 — or well ahead of the A350 aircraft’s planned maiden flight in 2013. This engine testing program has been meeting all objectives, with one XWB engine fitted to an Airbus A380, and on one occasion it was demonstrated that the single Trent XWB could enable the big aircraft to maintain level flight with all other engines at idle. Testing has taken place at Rolls-Royce’s civil aerospace HQ in Derby, UK; at Spain’s aerospace technical centre in Madrid; at the GLACIER aerospace centre for icing and environmental research in Manitoba; at the Rolls-Royce facility in Mississippi, and at Edwards Air Force Base in California. To date, the Trent XWB has proved to be 16 percent more efficient than the first-generation Trent engines that first entered service, including a 35 percent increase in the overall pressure ratio and a 25 percent improvement in internal aerodynamics, with 15 percent fewer blades and five percent lower weight per pound of thrust. According to Rolls, these factors mean the XWB engine can save airlines around $2.6 million per aircraft per year compared to the first generation Trents. “As it has been run today the Trent XWB is the most fuel-efficient engine in the world,” proclaimed Robert Nuttall, Rolls-Royce vice-president for strategic marketing. Nudging the 600 mark, orders for the XWB-powered Airbus A350 include 25 for QANTAS and 80 for Qatar Airways, which will be the first operator of the aircraft in 2014. AM
Aviation Maintenance |
avm-mag.com | August / September 2012 63
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