Pratt & Whitney is planning a new family of hybrid PW4000 engines to meet the thrust requirements of widebodies under study by Airbus Industrie and Boeing. News of the development emerged as the company gave its long-awaited commitment to develop a 454kN (102,000lb)- thrust engine for Boeing's proposed ultra-long-range 777-200X.

Work on the new derivative PW4000s will begin in 1998, pending the outcome of "business discussions" with Airbus and Boeing, says P&W programmes and senior vice-president Bob Leduc. Two main developments are planned, a 320-334kN engine for a higher-gross-weight A330, and a 290-298kN engine for the proposed 747-400IGW and the recently launched 767-400. As with the similar derivative philosophy adopted by Rolls-Royce with the Trent family, P&W's new engines will use the core of the higher thrust 2.84m fan engine combined with the smaller low pressure system for the 2.54m and 2.38m fan engines.

Leduc says that Airbus has always wanted to develop a higher-gross-weight A330 in the 240 -250t range, and " we want to be in a position to go on that". He adds that some customers for the 230t A330 would like more capability, so P&W is designing a programme. The new variant, to be called the PW4172/75, will offer a thrust specific fuel consumption (TSFC ) "1-1.5% better than the current 2.54m engine", predicts Leduc.

"We're also going to take the 2.84m core and match it with the 2.38m low-pressure system [of the PW4056/58] to make a 298kN engine for the 747-400IGW and, possibly, the 767-400," adds Leduc. The new engine would offer an estimated 1.5% TSFC improvement over the current 2.38m-fan engine and will be a head-on competitor with the Trent 600 and General Electric CF6-80C2B7/8F variant launched on the newly stretched 767.

Leduc adds that the joint venture GP7000 engine project with General Electric is not threatened by the initiative. "The GP7000 is still the engine we are offering for the A3XX and, if Boeing launches the 454,000kg 747, we will still be offering that engine. The weight, noise and range criteria are still such for those aircraft that you still need an all-new engine," he says.

P&W's formal commitment to develop a 454kN version of the 777 engine does, however, put paid to any ideas of extending the joint venture with GE to the higher-thrust range, as tentatively mooted by P&W president Karl Krapek at the 1997 Paris air show. The decision to sign a memorandum of understanding was taken after the company successfully passed several critical certification tests on the PW4098 engine for the 777-300.

P&W's growing confidence in the engine's ability to reach 454kN levels, and pressure from loyal customers pushed it into the move, says Leduc. "We owe it to the airlines like All Nippon Airways, Japan Airlines and Korean not to leave them stranded," he adds.

P&W believes that the higher thrust will be achievable with only a throttle push.

Source: Flight International