Flight Home

Guy Norris/LOS ANGELES

General Electric is to upgrade its GE90 compressor design to reduce fuel consumption by 1.5-2%. Although the move is aimed at the Boeing 777-200IGW (increased gross-weight), the company is preparing for the possibility that a substantial market will develop for future growth versions.

The US engine manufacturer is focusing its improvement drive on advanced three-dimensional aerodynamic design of the ten-stage high-pressure compressor, already based on a scaled version of the GE/NASA energy-efficient-engine compressor design. Software has "-evolved to new levels" since the GE90 was designed, when more ambitious codes were not used because of GE's "risk-abatement" policy, says Dick Ostrom, manager of GE90 integration. The results of the application of the software to the CFM International CFM56-5BP compressor have been encouraging, however, says Ostrom.

Other improvements will include "optimised" blade clearances in the low-pressure compressor (LPC), which were increased after a fourth-stage LPC blade failure in flight tests in 1994. The failure was traced to a "dynamic response problem", which resulted in rubbing. Clearances will also be slightly altered in the fan and the low and high-pressure turbines.

The first improved core will begin test runs at GE's Evendale, Ohio, test site in April, while the first complete-engine test is scheduled for mid-year. Tests on the company's 747 testbed will begin in Mojave, California, "towards the end of the third quarter", says Chuck Chadwell, GE commercial engines operation vice-president.

A higher exhaust-gas temperature margin will enable GE to offer the engine with either a life improvement of 7,000-10,000h on wing, a higher flat-rating or a thrust "bump" up to 418kN (94,000lb)-thrust, says GE. Chadwell says that GE has held off on growth and waited for the market to "sort itself out", but "-if a market for a bigger engine develops, I don't want to do incremental developments - I'd rather have something ready".