Guy Norris/LOS ANGELES
General Electric hopes to win US Federal Aviation Administration approval for the 94,000lb-thrust (420kN) GE90-94B in early April, pending the successful conclusion of icing tests now entering the final stages of completion at the company's Peeble test site in Ohio.
The GE90-94B is aimed at higher gross weight Boeing 777-200ERs and will enter service in November with launch customer Air France. Just as importantly to GE, the growth engine is also a strategic stepping stone to the more powerful GE90-115B in development as the exclusive powerplant for Boeing's proposed 777X family. The two share virtually identical new high-pressure compressors (HPC). Tests on the three-dimensional aerodynamically designed unit and other configuration changes to the -94B have gone "as smooth as silk", says Dick Ostrom, manager of GE90 advanced programme integration.
The original -94B test core has been reconfigured to -115B standard for tests starting at Evendale, Ohio, this month that will run to late May. To increase flow through the core to match the higher requirements of the 115,000lb-thrust powerplant, it will be reduced to nine HPC stages, compared to the 10 in the -94B. Detailed design of the full-up engine is expected to begin around June, assuming that no major issues are uncovered with either the reconfigured HPC, or the other major elements of the design.
These include swept high-flow blades which GE recently settled on. Scale tests of the fan are set to begin at a Boeing test site in April and will run until mid-June. "We will run multiple configurations against the current radial blade as a reference," says Ostrom, who adds that tests will also "look for a slight acoustic advantage", as well as check for baseline operability and aero-mechanical stresses.
The 325cm (128in) diameter fan will be made up of composite blades 128cm long, around 6cm longer than those in the current GE90. Meanwhile, GE has opted against the use of "z" pins that had been studied as a means of strengthening the extended blade.
"We ran a series of tests and didn't see enough value in them to consider them for the design stage," says Ostrom. GE believes "the geometry of the current composite system can be maintained and, because of the more robust dimensions of the bigger blade, we feel we can handle the larger energy levels and bird ingestion events".
Prototype forgings of the midshaft using new material that will take the higher torque loads of the bigger engine have been manufactured and tests on them will be completed by June. More tests have been undertaken on a revised low-pressure turbine design which incorporates between 10% and 20% fewer blades and vanes. The new unit, which will be theoretically lighter, cheaper and easier to maintain, is called the "low solidity aerofoil" design, with most of the blades and vanes being removed from the forward stages.
Testing of the first GE90-115B is to begin in September next year, with FAA certification targeted for August 2002 and entry into service on the first 777-300X expected in September 2003 after a year-long flight test effort.
Source: Flight International
