Pratt & Whitney was awarded a $437 million contract modification by the US Air Force to further develop its adaptive jet engine design, a propulsion system for a future sixth-generation fighter.

The contract comes after the United Technologies-owned manufacturer’s competition for developing the new engine, GE Aviation, was awarded a $437 million contract modification on 29 June by the USAF. The two companies are competing in the Adaptive Engine Transition programme, an effort to develop a sixth-generation fighter propulsion system, which might also be used to replace the Pratt & Whitney F135 engine in the F-35 in the mid-2020s.

An adaptive turbine jet engine can change the volume of air that flows to its core or bypass by opening and channeling air from a third stream. The USAF believes such a design can improve fuel consumption of an engine by 25%, increasing range and reducing in-flight refueling requirements. It also could deliver additional air flow through the core for higher thrust and cooling air.

"In addition to providing a seamless transition between high thrust and fuel efficiency, adaptive propulsion can enable an unprecedented range of capability growth in mission systems and heat dissipation capacity at the air vehicle level," says Chris Flynn, vice president of military development programmes at Pratt & Whitney.

The USAF has been developing the technology behind the adaptive engine concept since 2007 when it launched its Adaptive Versatile Engine Technology programme. Pratt & Whitney said it is using knowledge gained from design and test activities completed as part of that programme to push forward its current efforts.