GE/P&W team's GP7200 engine will not fly until late November but remains on target for July 2005 certification

The General Electric Pratt & Whitney Engine Alliance team has delayed flight tests of the GP7200 until late November, but says the Airbus A380 powerplant is on schedule for July 2005 certification.

Originally scheduled for September, flight tests on GE's Boeing 747 testbed are now expected to start around the US Thanksgiving holiday on 25 November. As recently as July, the Engine Alliance planned to get the powerplant flying in October, but has opted for the later time to ensure adequate margin for checking out the flight test engine, No 4, with a revised compressor and turbine configuration. The changes to the high-pressure (HP) turbine, in particular, will be validated within weeks on test engine No 2, which is expected to begin a 150h endurance test at GE's Peebles, Ohio site at the end of September.

"We're still on schedule, and still planning to have six engines and a core engine running in the test programme before the end of the year," says Engine Alliance president Lloyd Thompson. "We are also expanding a rapid ramp-up in the number of engines we are introducing into the programme." The No 2 engine will be run consistently at high thrust levels "above at least the [A380] Freighter rating [76,500lb (340kN) thrust] or maybe even higher," he adds, saying the engine is expected to rack up about 750 cycles.

The revised configuration includes changes to the second-stage HP turbine blade trailing-edge design to counter vibration problems found during earlier tests, plus minor changes to the first few stages of the compressor (Flight International, 27 July-2 August). Issues with the baseline design included unexpected surges in the cruise condition during tests. "This is 100% behind us, and was related to mis-matched aerofoils in the front end of the compressor where the twist angle changed from the cold configuration to the running configuration," says Thompson. "They were running a bit too far open."

The programme has, however, received good news from the results of the high-altitude tests on engine No 1 conducted at the US Air Force's altitude test facility at Tullahoma, Tennessee, where the performance of the rematched compressor proved the overall design was optimum. "We have a very good low-pressure compressor. We had planned to go back and do touch-ups to the aero-mechanics, so now we don't have to go and touch that," says Thompson.



Source: Flight International