Spooling Up

For Rolls-Royce, the next six months will be critical for the development of the Trent 900 high-bypass turbofan engine as the program moves toward numerous milestones.

Up to now, it has been a case of so far, so good: The development and test phase is broadly on track. There have been few surprises, and engine performance is in line with, or better than, predictions.

The Trent 900 shipped to Toulouse, France, will be run on Airbus' A340-300 testbed on the No. 2 engine station, with a first flight around mid-May. Certification is penciled in for the end of October, well in time for the A380's first flight in January 2005.

Rob Savidge, the chief engineer on the Trent 900, said key targets over the next half-year include icing type tests, the 51/2-lb. bird strike test, completion of the 3,000-cycle run, and the fan-blade-off test.

Rolls-Royce last month shipped the first Trent 900 engine to Airbus in Toulouse. Initial engine flight test is expected by mid-May.Credit: ROLLS-ROYCE

The engine will be the first to undergo the so-called flocking-bird engine-strike test. The 21/2-lb. bird strike test has already been carried out on the engine, Savidge said. A rig test for the heavier bird strike has also been conducted with satisfactory results. The use of a heavier weight is to simulate impact by a goose-size bird.

"We've done a 51/2-lb. rig test with a blade. There was a small nick in it, and this was in line with our modeling predictions," he said. The results provided the company with enough confidence to move directly to the full engine test, without any further rig testing.

A total of seven Trent 900s will be used in the development and test program. The first of these powerplants was run in March 2003, and the final test engine will be used for the fan-blade-off test now slated for midyear. A further 20 engines will be manufactured during the course of 2005 to meet the needs of the A380 flight test program.

Initial testing has been aimed at proving the mechanical integrity of the engine, examining the gas pathway, stresses and casings. Savidge says so far the program has generated "very few problems."

With an eye on certification, a type-test engine has been built and run more than 115 hr., which he says has provided "pretty good results; we learned a lot from these tests. . . . With regard to specific fuel consumption, we are within a half-percent of what our model says." He is optimistic that the performance guarantees will be met as the program moves ahead over the coming months.

Initial performance figures gained from sea-level altitude runs have been followed by test-cell work at altitude. Savidge said these results have also been good. He's also confident the high standard of results is not simply the outcome of a handcrafted powerplant. "It doesn't appear to be a one-off--we've got a good sample size of engines." The altitude simulation is being carried out at the Arnold Engineering Development Center near Tullahoma, Tenn., at heights up to 38,000 ft.

The Trent 900 has a 116-in.-dia. fan featuring swept blades, a design approach Savidge suggests will likely become a standard for commercial high-bypass turbofan engines. He points to "performance and noise benefits" as the drivers for this.

The fan was one area of risk on the Trent 900, but Savidge views this as a success story. Tests to ensure the engine meets noise targets are underway, and these should culminate in August. So far, the engine is on track to meet those objectives.

Discussing modifications that have resulted from the test program so far, Savidge identified small adjustments to the turbine blade cooling, as well as beefing up a seal on the high-pressure turbine air system.

"EARLY IN THE PROGRAM we had a seal vibration problem on engine number one; it needed strengthening," he explained. Given the importance of minimizing weight, he noted that "we initially pared it [the seal] down too much."

The engine will be cleared at certification up to 81,000 lb. thrust, though the initial requirement is for 70,000 lb. Test runs up to 88,000 lb. have already been carried out, however.

Rolls-Royce has so far secured just under half of firm and option orders on the A380. Malaysian Airlines, Korean Air and Qatar Airways, which have all opted for the aircraft, are expected to make engine decisions this year. Singapore Airlines, Qantas, Virgin Atlantic and Lufthansa have already opted for the Trent 900 on their A380s.