Boeing is starting certification flight testing of the higher thrust Rolls-Royce Trent 895 turbofan on the 777-200ER, and is preparing to start tests of the General Electric GE90-94B by the middle of next year.

Tests of the R-R engine, rated at 93,400lb (415kN) thrust, have focused on the effects of the more powerful engine on stability and control, as well as on the powerplant's initial performance.

"The engine has been doing really well," says Roger Houck, chief engineer of 777 test programmes. "Now we are just about to get into certification testing, which is centred on the engine itself," he adds.

The test effort, which is expected to accumulate about 40 flight hours, will be stretched over several months to accommodate additional test work on an updated aircraft information management system (AIMS). The revised Honeywell avionics system, called the "AIMS '99 programme" includes updated database and functionality features, such as an electronic checklist and a flight data recorder with 256 words capability.

Final tests on the revised engine and upgraded AIMS-equipped 777 will be completed in December, says Houck, who expects initial deliveries to begin to British Airways in January.

The GE90-94B test effort will be "a slightly larger programme and will involve a lot more engine testing", says Houck. The GE90 test programme is expected to start on the 777 in mid-May next year, with completion following at the end of July before first delivery to Air France in November next year.


The engine, which incorporates three-dimensional aerodynamic improvements to the high pressure compressor (HPC), completed its test programme on GE's 747 testbed on 3 September. GE says the programme, involving 19 flights and 90 flight hours, demonstrated "specific fuel consumption, operability and airstart performance, which met all technical objectives for the combined 94B and 3D aero HPC programmes".

Based on data from the flight test effort, GE says the engine is projected to "realise a 17¼C improvement in EGT [exhaust gas temperature] margin at thrust relative to the current production engine". Cruise specific fuel consumption is also projected to be 1.4% better than current production units. The company adds that compressor stability margin was demonstrated at all flight conditions, including cold rotor burst take-off.

Source: Flight International