GUY NORRIS/ LOS ANGELES
Revised schedule gives more scope to make changes ahead of 2005 approval for A380
The General Electric-Pratt & Whitney Engine Alliance has brought forward the planned first full GP7200 engine test by two months to mid-February next year. It wants to give more margin for "lessons learned" before the scheduled certification of the turbofan in 2005 and entry into service on the Airbus A380 in 2006.
In the build-up to the critical full-scale runs, P&W has begun tests in Florida of a 94%-scale hollow titanium swept fan-blade design for the GP7200. "It is a boomerang with a reverse sweep at the tip," says Bob Saia, P&W GP7200 programme vice-president. "The shape gives it efficiency and reduces the shock loss as the flow goes from supersonic to subsonic at the tip," he adds.
In particular, swept aerodynamics reduce the shock strength and its interaction with the viscous boundary layer, he says.
Based on tests conducted in April 2001 on a 42%-scale version of the fan on the Advanced Technology Fan Integrator, P&W expects fan efficiency will be improved by at least 2% relative to conventional radial fan blades at the same airflow. The final configuration for the blades, which at 2.9m (9.6ft) fan diameter will be the largest hollow titanium units made by P&W, was selected over an alternative composite design in March 2002 after a decision in late 2001 to increase fan size to meet noise requirements.The 94%-scale blade set, mounted on a PW4098, will be used initially to conduct stress, fan performance, flutter and operability tests. In the second quarter, identical blades in a whirl rig will be tested against 1.1kg (2.4lb), 2.5kg and 3.8kg birds before the damaged blades from the smaller and larger bird tests are replaced for performance tests on the engine. Further operability tests, including crosswind performance and crucial noise tests, are also planned for the third quarter of 2003. "The main objective is to finish 2003 with a fully validated blade," says Saia.
Containment tests of the full-scale blade will be conducted in a fan module test rig with a 3.8kg bird strike event in the first quarter of 2004. Further ingestion tests of the 2.5kg and 3.8kg birds will be conducted with a full engine before a final blade-out test in mid-September 2004.
In 2005, the GP7200 will be certificated concurrently at take-off thrust ratings of 76,600lb (340kN) and 81,500lb, although the basic architecture is able to accommodate future A380 growth with ratings up to 84,000lb. The initial variants include the GP7270 rated at 70,000lb for the passenger A380-800, and the GP7277 rated at 76,500lb for the A380-800F.
Source: Flight International
