General Electric [GE] said on Sept. 7 that the company has begun testing the second prototype of the XA100 adaptive cycle engine as part of the U.S. Air Force’s Adaptive Engine Transition Program (AETP) for the Lockheed Martin [LMT] F-35A and future fighter aircraft, as the House Armed Services Committee (HASC) advises accelerating AETP in the committee’s version of the fiscal 2022 defense authorization bill.

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] has also participated in AETP with the company’s XA101 engine.

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 U.S. Air Force and Congress have invested more than $4 billion in adaptive cycle engine development over the past 14 years to mature its associated technologies,” David Tweedie, GE Edison Works’ General Manager for Advanced Combat Engines, said in a Sept. 7 statement. “We’re confident this phase of the program will significantly reduce risk and prepare GE for a low-risk engineering and manufacturing development program, consistent with Air Force objectives…Getting our second prototype engine into the test cell means we’re one step closer to getting this transformational technology into the hands of the warfighter.”

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.

The Air Force has said that its focus for AETP has been on the Next Generation Air Dominance (NGAD) program, not the F-35, due to what the service has said are significant costs for retrofitting AETP engines on the F-35.

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