Pratt & Whitney's rivals have been content to mostly watch from the sidelines during the past year as the geared turbofan concept garnered headlines and its first two customers.

But the General Electric/Snecma joint venture, CFM International, is poised to break a year-long silence on its two-pronged response to the emerging need for a next-generation engine to serve the narrowbody market.

Duelling press conferences hosted by P&W and CFM at the Farnborough air show this month will set the stage for a decade-long debate within the industry about the future of narrowbody propulsion.

CFM's strategy, last updated in May 2007, is to introduce the LEAP56 advanced turbofan in 2015 and perhaps follow up with open-rotor technology after 2017.

The LEAP56 has a 15% higher-loaded single high-pressure turbine stage and an eight-stage high-pressure compressor, with 10-15% lower specific fuel consumption, up to 15dB less noise and 25% longer life on wing.

Both the GTF and LEAP56 technology would essentially transfer the ultra-high bypass ratio technology already powering widebody jets to the narrowbody market. Narrowbody engines have remained stuck in the same bypass range since turbofans were introduced in the 1970s.

A 1.8m (70in) class blade was scheduled to enter stress tests by the end of 2007, and should run on a CFM56-5C some time this year.

Meanwhile, CFM's more radical open-rotor concept still faces the same questions that appeared when the concept was reintroduced by CFM last year.

It will be at least another 18 months before GE can validate that the noise generated by unshrouded, counter-rotating blades can be counteracted by other design techniques, such as blade design.

Rolls-Royce, meanwhile, is continuing to pursue both advanced turbofans and open-rotor technology, but have yet to clarify their strategy.

P&W's strategy is now well-known and focused on the GTF, but also faces questions.

The PW6000 is being adapted for the GTF demonstrator engine, which is scheduled to fly in July.

But P&W plans to introduce an all-new core for the production GTF engine - the company's first new centreline project in more than a decade.

Source: Flight International