Rolls-Royce is expected to complete design work on the 454kN (102,000lb)-thrust Trent 8104 by the start of June and is still "on track" to run the first engine in December, despite the slowdown of the Boeing 777-200X/300X derivative programme for which the powerplant is being developed.

Although R-R plans to stick to the overall test schedule laid out for the engine under its original agreement with Boeing, the remainder of the test programme is being restructured to reflect the proposed -200X delayed entry into service. "Boeing has slid this until mid-2002, so we're taking advantage of that," says R-R Trent technical director Phil Hopton.

Pratt & Whitney has signed a similar agreement with Boeing on development of a growth PW4000 engine. General Electric, for the moment, is not pursuing further growth versions of its GE90.

A key element of the Trent 8104 test programme will be the performance of newly designed swept fan blades. "We will use the aerodynamics of the swept fan to achieve higher thrust without increasing the diameter," says Hopton, who expects the 2.79m-diameter fan to have increased resistance to bird strikes.

The efficiency of the blades, which like the current Trent family will be superplastically formed, diffusion bonded, hollow wide chord units, is expected to be boosted by the scimitar-like curvature of the leading edge. "The sweep has the same effect as on a wing. The tip is travelling at supersonic speeds, so instead of shock waves aligning and causing the blade to lose efficiency, the shock waves are staggered,"Hopton says. Inflowing air entering the engine across the span of the blade will be smoothly decelerated, rather than abruptly slowed.

The Trent 800-powered 777 fleet now totals 33 aircraft, with the delivery of the first -300 to Cathay Pacific on 20 May, and is expected to rise to 48 by the end of 1998. The fleet will virtually double to 87 by the end of 1999 as the first 777s begin entering service with American Airlines and Delta Air Lines. To keep pace, production of Trents is being almost doubled, to 90 engines in 1999.

Current Trent 800 fleet dispatch reliability is now at over 99.96%, says Hopton, who adds that the company "bit the bullet" following the Emirates compressor blade failure and "-changed to the 892 blade as standard to avoid any repeats". The only other recorded unplanned removal, at Malaysia Airlines, was caused by a "rogue vibration indicator", he adds.

Thai Airways International, the Trent 777 launch customer which now has eight aircraft in service, has run at a 100%dispatch reliability rate for the past three months, according to R-R.

Singapore Airlines, with six in service, "has over 17,000h of operation with zero aborts or in-flight shut downs, and only one precautionary removal", says the engine maker.

Source: Flight International