General Electric has decided to replace the aluminium-hybrid fan platforms on the GE90 turbofan with advanced composite structures produced by Dow-United Technologies Composite Products (Dow-UT).

The 22 platforms provide a flowpath surface between the fan blades and, in their original form, were responsible for some of the delays to the GE90 programme in 1995. The platforms were responsible for the engine's failure to pass a 4.5kg birdstrike test during certification runs for the 409kN (92,000lb)-thrust rating.

As a result, the edges of the platforms, which had sliced into the base of the blades during the test, were made more frangible to absorb energy instead of transferring it. The new units will be made using the advanced resin-transfer molding (AdvRTM) techniques developed by Connecticut-based Dow-UT, and replace the aluminium-hybrid spacers which were developed in the interim.

"This validates the coming of age of AdvRTM," says Dow-UT engineering director, Lawrence Varholak. "This is the first use of a composite part as a rotating, flight critical piece of hardware, as well as being a fatigue-loaded component." The $9.7 million award was made after the platforms passed initial risk-reduction tests by GE, which adds that the change to composites produces "-weight and cost savings for the GE90". The first units are due to be shipped to GE in August, with retrofits to existing engines planned for 1998.

Dow-UT, which produces similar AdvRTM fan spacers for the Pratt & Whitney PW4090/98, also announced a five-year contract, worth up to $8 million, to deliver up to 15,000 AdvRTM-made bypass vanes to Allison Engine for the AE3007. The first deliveries are due to begin in mid-October. Dow-UT is also believed to be in final negotiations with Rolls-Royce over the supply of AdvRTM-made exit guide vanes for the Trent engine family.

Source: Flight International