Pratt & Whitney has lost out in a three-way contest to demonstrate technology for the next generation of US combat aircraft engines.

General Electric and Rolls-Royce's US arm have each won contracts under the US Air Force Research Laboratory's Adaptive Versatile Engine Technology (ADVENT) programme to demonstrate variable-cycle engines that combine high thrust for supersonic dash with fuel efficiency for subsonic loiter.

P&W builds the F119 engine powering the Lockheed Martin F-22 and is developing a derivative, the F135, to power the F-35 Joint Strike Fighter. GE and R-R are teamed on development of the F136 alternative engine for the F-35, but the programme has been threatened with cancellation.

ADVENT contracts worth $231 million have been awarded to Cincinatti-based GE Aviation and $296 million to R-R's Liberty Works in Indianapolis. Ground demonstrator engines are scheduled to run in 2012.GE and R-R decided to bid separately for ADVENT, but agreed that if either or both won contracts the technology developed would be available for insertion into the F136. Losing the competition is therefore a double blow to P&W and its plans for the F135.

Part of the larger national Versatile Affordable Advanced Turbine Engines (VAATE) programme, ADVENT is focused on developing and demonstrating the ability to vary the engine cycle between the low bypass ratio and high thrust required for supersonic dash and the high bypass ratio and low fuel burn required for subsonic loiter.

Such an engine could power a future combat aircraft requiring high speed and long endurance for long-range, persistent strike and surveillance missions. But AFRL has said that ADVENT technology will not be ready in time for the US Air Force's next-generation bomber if it sticks to its 2018 deadline for initial operational capability.