The US Air Force has awarded two five-year development contracts to GE Aviation and Pratt & Whitney worth up to $1 billion each to continue development of a next-generation military jet engine and prepare for an anticipated competition in the early 2020s for the chance to power a new combat aircraft and possibly re-engine the Lockheed Martin F-35.

The awards of the Adaptive Engine Transition Programme (AETP) contracts to GE and P&W on 30 June extends a nearly 10-year effort to introduce a fuel-saving cruise mode into an engine intended for a supersonic fighter. Both contractors will develop and test multiple new centreline engines sized at a 45,000lb-thrust level.

“We believe GE is best positioned to integrate the adaptive suite of technologies into existing and next-generation combat aircraft,” says Dan McCormick, general manager of GE Aviation's Advanced Combat Engine programmes.

P&W senior director of advanced programmes and technology Jimmy Kenyon says the company can leverage experience as the propulsion supplier for the F-22 and F-35 to "provided a highly capable adaptive engine with the ability to power a wide range of future and legacy aircraft applications".

The USAF is developing concepts for replacing the Lockheed F-22 after 2030, which includes updating existing designs with new technology. Re-engining the F-35 with an adaptive cycle, 45,000lb-thrust engine is also under study.

An adaptive-cycle engine is intended to address a design limitation in modern powerplants. An engine optimised for subsonic speed is more fuel-efficient, but cannot easily exceed the speed of sound. A supersonic engine, however, can accelerate over Mach 1.0 but is limited in range because it guzzles fuel.

The AETP programme continues development of a technology that could make supersonic engines 25% more fuel-efficient, thus extending the range of a fighter by as much as 30%, according to GE.

There are two kinds of airflow in modern engines. One airflow enters the engine core, mixes with fuel, combusts and generates energy to power the gas turbine machinery and create thrust. Another portion of the airflow enters the inlet and then bypasses the core, generating thrust without the need to consume any fuel directly. An adaptive cycle engine proposes to add a secondary stream of bypass airflow in cruise speed conditions. This secondary duct can be shut off when it’s necessary to accelerate rapidly.

The USAF launched the technology development programme in 2007 with adaptive versatile engine technology programme with GE. P&W and GE then participated in the adaptive engine technology demonstration (AETD) programme that began in 2012. AETD is expected to end later this year.

[UPDATE: The article has been updated with P&W's comments.]