The Senate Appropriations Committee’s version of the fiscal 2022 defense funding bill recommends adding $460 million for the U.S. Air Force’s Adaptive Engine Transition Program (AETP) for the Lockheed Martin [LMT] F-35A and future Next Generation Air Dominance (NGAD) family of systems.

The Air Force had requested just $13.5 million in fiscal 2022 for AETP, down from more than $214 million appropriated by Congress in fiscal 2021 and nearly $527 million in fiscal 2020.

Launched in 2016, AETP followed Air Force engine developments in the Adaptive Versatile Engine Technology (ADVENT) program, begun in 2007, and the Adaptive Engine Technology Development (AETD) program, started in 2012.

The Air Force has said that its focus for AETP has been on NGAD, not the F-35A, due to what the service has said are significant costs for retrofitting AETP engines on the F-35A, the only F-35 version that will accomodate an AETP.

Last month, General Electric [GE] said that the company has begun testing the second prototype of the company’s XA100 adaptive cycle engine as part of AETP, and the House Armed Services Committee (HASC) advised accelerating AETP in the committee’s version of the fiscal 2022 defense authorization bill (Defense Daily, Sept. 8).

In May, after a six-month run, GE said that it had finished testing the first prototype of the XA100, which is to provide significant fuel cost savings, performance improvements, and less wear and tear on airframes. The company said that XA100 will provide a 10 percent increase in thrust, 25 percent better fuel efficiency, and significantly enhanced heat dissipation capacity. GE said that testing on the second XA100 had begun on Aug. 26 at GE’s Evendale, Ohio, altitude test facility.

Pratt & Whitney [RTX], the builder of the F-35’s F135 engine, has also participated in AETP with the company’s XA101 engine.

GE said it plans to test the XA100 at the Air Force’s Arnold Engineering Development Complex (AEDC) in Tennessee to complete AETP testing once the company finishes the first phase XA100 testing.

The HASC version of the fiscal 2022 defense authorization bill would require the Air Force to submit an acquisition strategy to integrate AETP into future F-35A aircraft and retrofit them on existing F-35As starting in 2027. The submission of that acquisition strategy is to come no later than two weeks after the submission of the president’s fiscal 2023 budget next year.

Among sustainment cost problems for the F-35 has been a shortage of working F135 engines for the fifth generation fighter (Defense Daily, Apr. 23).