Rolls-Royce's Big Trent XWB Entering Production Phase
Ahead of an initial engine run in the second quarter of this year, Rolls-Royce (Booth N23) has started to assemble the 97,000-pound thrust Trent XWB-97 powerplant that will power the heavier, 308-metric-ton (680,000-pound) max takeoff weight Airbus A350-1000 stretch variant of the new twin-aisle twinjet that has been flying since last June. The first items for the powerplant were arriving in the Rolls-Royce (RR) finished parts stores during January, according to program director Chris Young.
The move follows last year’s Trent XWB-97 critical design review and prototype demonstration runs. Progress since last November’s Dubai Airshow has included fabrication of early components, welding of the stator-vane assembly and completion of the intermediate-pressure compressor stage 1 “blisk” (bladed disc).
To ensure manufacturing fluency while the new variant is introduced, RR will build initial flight-test engines in a preproduction “factory,” not on current Trent assembly lines. As production begins to accelerate, the manufacturer will integrate the XWB-97 into the assembly flow line. The XWB-84 and -97 are essentially “very similar” and have “common tooling,” which will allow the models to be mixed in final assembly.
Asked if RR has the scope to advance the XWB-97 if Airbus brings A350-1000 development forward, Young said the company has an agreed program with the airframe manufacturer and is working to deliver engines in line with that schedule. Active preproduction engine testing is slated to begin in the first half of next year.
RR expects to be build at least eight flight-test Trent XWB-97s–and possibly more–during the preproduction phase. The focus of such work is to meet what RR calls “exit criteria,” which means understanding the requirements for each work station “before engine assembly really begins to flow.”
Seven complete ground-test units will be produced, along with additional modules and cores, said Young. The predominant proportion of future Trent XWB-84 manufacturing is to be performed at Rolls-Royce’s Seletar production center in Singapore, releasing capacity at the Derby factory in the UK, where existing assembly capacity will be extended to accommodate the larger -97 engine.
Rolls-Royce says the Trent XWB program is “on target,” with only minor tuning of scheduled plans; the company is “happy [with performance, which is] on track, exactly where we expect to be.” By January, it had completed some 6,000 hours and 11,250 real and simulated flight-cycles of running with 13 Trent XWB-84 development engines, of which four were currently on test.
Two were being used for cyclic tests at Rolls-Royce North America’s outdoor jet engine testing facility at the NASA John C. Stennis Space Center in Mississippi. One “endurance” engine had another 150 hours to run as RR sought to expand the design’s temperature margins, while the fourth unit was one of a pair devoted to proving the Trent XWB’s robustness.
Among remaining development examples, three are earmarked for use on the Airbus A380 flying testbed and two will be for mechanical tests. Others are being (or have been) used for performance, low-pressure system and integration trials.
Of the two Trent XWBs at Stennis, engine serial number (ESN) 20002/4 has completed 1,610 simulated flight cycles, including 3,000 thrust-reverser deployments, on the center’s 59 Bed. Meanwhile, on 60 Bed ESN 20011/1 is being used to clear the design for Airbus’s targeted 350-minute ETOPS approval before entry into service by year-end.
Reliability has been demonstrated during 4,250 simulated cycles, with the unit also being used for on-wing maintenance and inspection routines. Both engines are scheduled to provide Target 1 shop-visit demonstrations, said Young. Low-temperature testing also has been conducted with ESN 20003/4 on RR’s 58 Bed at Derby, where liquid oxygen is used to cool the powerplant, which must demonstrate 10 starts at -40C (-40F) to represent winter operations.
Passenger Flight Planned
The second A350-900, manufacturer’s serial number (MSN) 002 and the first with an airline cabin interior, was rolled out in early January sporting a so-called “carbon” livery. In early February, it was being prepared for a first flight before month’s end and is intended to carry the initial (non-flight test) passengers on planned “early long flights” later this year. After A350 MSNs 001 and 003, which both flew last year, the next development aircraft (MSN 004) is scheduled to fly soon after MSN002.
Rolls-Royce expected to deliver the Trent XWBs for MSN 005–the final flight-test machine, and the second with an airline interior, which should fly in May–before this week’s airshow began. Dispatch of MSN 005’s engines from Derby to Toulouse marks the transition from powerplant preproduction into the Trent XWB’s production phase.
The engine manufacturer expected to begin assembly in early February of Trent XWB ESN 20019, which is destined to power the first Qatar Airways A350 (MSN 006). This will be followed by the second Qatar engine (ESN20020), which is scheduled for delivery to Airbus in mid-year, and another unit earmarked to be available as a spare at the time of A350 entry into service, according to RR information. As of mid-January, RR had not finalized overall 2014 Trent XWB production plans
Overall, Trent XWB performance aboard the first two flying A350-900s has gone extremely well, the engines demonstrating “good operability and reliability” and having undergone only routine inspection and maintenance, according to Young. By mid-January, the four Trent XWBs had accumulated around 1,750 flight-hours during about 180 A350 flights (more than 50 flights with MSN 003, including a 12-hour 48-minute transatlantic flight to Bolivia in South America for hot-and-high testing).
Young said the altitude- and temperature-related engine and aircraft performance trials involved genuine tests in temperatures of up to ISA +21C (ISA +38F) at Cochabamba (about 8,300 feet above sea level). Engine starts, and aircraft takeoffs, automatic landings and touch-and-gos flown at La Paz’s 13,300-foot-altitude airport were said to have been performed “immaculately with no flaws, no nothing.”
The trials, which also featured simulated engine failures, were to collect data on operating characteristics and to validate the A350’s takeoff performance. From Bolivia, MSN 003 went on to tropical Martinique and, later, to Canada for cold-weather trials that included starts at temperatures as low as -40C/F.
Overall, Airbus A350 testing will involve about 2,500 flight hours (5,000 engine hours), leading to formal European Aviation Safety Agency and U.S. FAA airworthiness approval in time for service entry before the end of 2014. During last year, a “strong [one] for market activity,” RR received orders for more than 500 Trent XWBs to power 252 A350s. One of the largest orders (for 30 A350-900s) came from local carrier Singapore Airlines, while other Asian customers were Japan Airlines (31 A350-900 and -1000s) and Sri Lankan Airlines (four A350-900s).