Boeing's demands for efficiency and affordability are causing companies offering engines for the 7E7 to be cautious about the technologies they incorporate. General Electric, Pratt & Whitney and Rolls-Royce say technologies will have to "buy their way" on to the engine because of Boeing's emphasis on low maintenance cost.

The three manufacturers submitted a second round of engine data packages to Boeing on the eve of the show. A third "best and final" round of offers is expected before one or two engines are selected later this year to power the ultra-efficient airliner. A sole-source deal is possible.

GE's offering has a 60-70%-scaled, improved GE90 core with the low-NOx twin annular pre-swirl combustor demonstrated under the Tech56 technology programme. Pressure ratio will be close to 50. Bypass ratio will probably be around 11:1. Compared with today's Boeing 767 engines, NOx emissions will be reduced by around 65% and fuel consumption by 13-15%.

R-R's proposed Trent 7E7 is based on a scaled Trent 900, with increased bypass ratio, potentially incorporating technologies from the company's Vision 10 initiative, including the European-funded ANTLE low-emissions demonstrator due to run early next year. Features include an improved hollow swept fan, contra-rotating spools and, potentially, a direct injection, lean burn, single annular combustor.

P&W's PW-EXX is the only new centreline engine on offer, although the low-pressure system is derived from that of the PW4000. The new core has a 10-stage high-pressure compressor, Talon low-NOx combustor and two-stage high-pressure turbine. The advanced titanium fan has the same 2.84m (112in) diameter as the PW4000 powering the Boeing 777, giving a bypass ratio of around 10.

Source: Flight International