Design and Development
The GE90 was launched in 1990 GE Aviation associated with Snecma (France), IHI (Japan) and Avio (Italy). Developed from the 1970s NASA Energy Efficient Engine, the 10-stage high pressure compressor develops a pressure ratio of 23:1 (an industry record) and is driven by a 2-stage, air-cooled, HP turbine. A 3-stage intermediate pressure compressor, situated directly behind the fan, supercharges the core. The fan/IPC is driven by a 6-stage low pressure turbine.
The higher-thrust variants, GE90-110B1 and -115B, have a different architecture from the earlier marks of GE90, with one stage removed from the HP compressor (probably from the rear, to increase core size), with an extra stage added to the IP compressor to maintain/increase overall pressure ratio to achieve a net increase in core flow. General Electric did a similar re-staging exercise when they upgraded the CF6 from the -6 to the higher thrust -50. However, this thrust growth route is expensive, since all the downstream components (e.g. turbines) have to be larger (in flow capacity). As a result GE sought (and received) sole engine supplier status with the -115B on the Boeing 777-300ER. The fan is an advanced, larger diameter unit made from composite materials and is the first production engine to feature swept rotor blades. Although the larger fan in itself would produce a higher static thrust, an increase in core size and, thereby core power, was required to improve the net thrust at normal flight speeds.
In October 2003, a Boeing 777-300ER broke the ETOPS record by being able to fly five and a half hours (330 minutes) with one engine shut down. The aircraft, with GE90-115B engines, flew from Seattle to Taiwan as part of the ETOPS certification programme.
The GE90 series are physically the largest engines in aviation history, the fan diameter of the original series being 312 cm (123 in). The largest variant, the GE90-115B, has a fan diameter of 325 cm (128 in). As a result, GE90 engines can only be airfreighted in assembled form by outsize cargo aircraft such as the Antonov An-124 Condor, presenting unique problems if, due to emergency diversions, a 777 were stranded in a place without the proper spare parts. If the fan is removed from the core, then the engines may be shipped on a 747 Freighter. Apart from its size, the GE90-115B is powerful enough to fully operate GE's Boeing 747 testbed on its own power during a maximum thrust low speed flight testing on board the aircraft
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