General Electric has begun detailed design work on the GE90-115B growth engine which will exclusively power Boeing's 777-200LR and -300ER long-range widebody twins.

The first engine is due to be bench-tested in October 2001, followed by a first flight on the company's 747 testbed at Mojave, California, by the end of that year, with certification to FAR 33 standards planned for October 2002. The 777-300ER is set to enter service in September 2003, followed by the -200LR around six months later.

GE says the engine design hinges on several key "enabling" technology efforts that are either completed, in final test, or well into definition. These include 227hr of rig tests on a 9-stage, 40:1 pressure ratio, high pressure compressor, which were completed in June.

The test results "met all the requirements to deliver the performance we committed to on the 777X programme", says GE manager for GE90 integration Dick Ostrom. "We got the flow we needed for the -115B and we got significant stall margin, or in other words, very good operability."

Rig tests on a 0.76m (2.5ft) scaled version of the 3.25m diameter fan planned for the -115B are under way in a low-speed, aero-acoustic site at Boeing. "We are pretty much done with the performance parts of the test and preliminary data from the acoustic tests show no degradation of acoustics, and maybe even a small improvement," says Ostrom.

The revised blade design is 120mm longer than the current GE90 unit, and is swept, with a higher degree of three dimensional shaping. "It is designed for greater efficiencies in mid-span," he says, adding that initial bird strike tests on a 1.1kg (2.4lb) bird are due to begin in the fourth quarter of this year.

Another key area is the development of a high torsional strength alloy for the engine's mid-shaft. The GE1014 material has been put through 30,000 torque cycles at 120% of the in-production GE90-94B's take off thrust level in tests at Ishikawajima Harima Heavy Industries in Japan.

Meanwhile, GE is claiming leadership in the 777 engine market for the first time following 39 firm orders for the -200LR/300ER versions. The manufacturer says the latest batch of orders for the 777X, as it is still officially called by Boeing, takes the number of GE90-powered 777s firmly-ordered to 185 of the 521 total announced. Rolls-Royce, which has held pole position in the 777 market since 1998, holds 35% with 181 firm orders. Pratt & Whitney has 155 firm orders.

Source: Flight International