The General Electric Pratt & Whitney Engine Alliance is testing a redesigned high-pressure (HP) turbine blade design to counter cracks which halted tests of the second GP7200 turbofan in May.
Engine Alliance president Lloyd Thompson says problems were found when the test engine was decelerated and "we noticed a vibration shift. We shut it down and found bits of metal in the tailpipe, and then found we had lost the outer third of one blade."
The trailing edges of the HP turbine blades are being "trimmed off" to stiffen them, explains Thompson, who says the programme remains on schedule for engine certification in July 2005 despite the delay. "We had built contingency time into the programme, and fortunately we found these sorts of things early." The second engine is being rebuilt to incorporate the fixes and "will become our first endurance engine", he adds.
In initial runs, the engine has demonstrated better performance than predicted, with an exhaust gas temperature 10°C lower than expected and cruise specific fuel consumption some 0.5% better. "The fan efficiency is 0.5 to 1 points better than predicted," adds Thompson.
First flight of the GP7200 is due in October on GE's Boeing 747 flying testbed, while the initial flight on the Airbus A380 is due in November 2005. The engine is "on track" to enter service with Emirates in October 2006.
Source: Flight International
