As third test phase for XA100 adaptive engine wraps, GE mutes F-35 pitch

WASHINGTON — When GE Aerospace invited a small group of reporters and analysts to its facilities in Evendale, Ohio in May, the company revealed that it launched a new phase of testing for its XA100 adaptive engine for the F-35, pushing to collect more data that could not only improve the prototype powerplant, but lay the groundwork for next-gen engines that will follow.

That phase of testing is complete, David Tweedie, GE Aerospace vice president and general manager for advanced defense products, told Breaking Defense in a recent interview — while providing a sign that the company is moving its focus for the engine away from its long standing F-35 target. 

“We had a good asset,” Tweedie said of the XA100, which completed its original objectives last year. “So in collaboration with the Air Force, we decided: Let’s go get some more runtime on it.”

According to Tweedie, GE’s third XA100 test phase, conducted in the company’s Evendale test cell, ran between April and June 2023. Through it, GE engineers collected reams of new data and pursued some new approaches. For example, the company tested different elements of the flight envelope, and Tweedie said that “there’s ways to reconfigure the engine to go exercise it in different ways to understand performance derivatives, and other things.”

Additionally, “there were some small pieces of hardware that we were able to take empirical learnings from phase 2 of testing, quickly redesign, and through some rapid prototyping efforts get some new hardware made and get that replaced on the engine and then validate some of our design methods and tools that we’re using.”

GE hopes this data gleaned from the third round of testing will bolster its efforts to mature adaptive engine technology — cutting edge propulsion that can offer capability improvements like greater fuel efficiency and more thrust over legacy engines. Adaptive engines work by adjusting a powerplant’s bypass ratio in flight, enabling jets to switch between fuel-efficient cruising and high-thrust performance. 

Both GE and Pratt & Whitney are competing to build an engine for the Air Force’s Next Generation Air Dominance (NGAD) fighter through a program known as Next Generation Adaptive Propulsion (NGAP), building off the two engine primes’ previous work in the Adaptive Engine Transition Program (AETP). The companies’ pitches are now expected to be carried through the prototyping phase, with the Air Force set to award a contract to a single airframe vendor for the NGAD aircraft next year.

Shifting Focus From F-35

Notably, GE’s press release discussing the completion of the recent test phase makes no mention of the F-35 — the aircraft the XA100 was designed to fit into, and for which GE lobbied hard to re-engine through a competition against Pratt. The rival engine maker strongly backed its Engine Core Upgrade (ECU) proposal, a modular enhancement to its incumbent F135 engine that would maintain the company’s lock on powering the tri-variant stealth fighter. 

As part of the May tour of its facilities, GE executives emphasized that the company was urging lawmakers to keep AETP going following the Air Force’s move to end the program in its fiscal 2024 budget request. Continuing AETP was critical, company executives said, so that a new, adaptive engine could be integrated in the F-35 and to help mature adaptive engine technology for future programs like NGAD.

The emphasis was primarily on F-35, with Tweedie saying then: “We truly believe that to keep the F-35 relevant — and not only the F-35 — but to continue this technology forward into other future platforms that adaptive cycle engines are the way to go.”

But in his recent talk with Breaking Defense, Tweedie seemed to emphasize the primary need to keep funding the company’s XA100 engine is to support development on next-generation jets, even backing Senate language that would provide hundreds of millions of dollars for next-generation engine work, but explicitly furnishes zero funding for AETP. 

“What I would say is adaptive engines have always been much bigger than any single platform,” Tweedie said when asked why the company is still advertising its XA100 prototype engine – in ads featuring the F-35 – despite seemingly little appetite from the Pentagon or Capitol Hill to pursue a new powerplant for the Joint Strike Fighter.

“There’s been over $4 billion invested by the government and that was not for any singular platform, but to bring about a whole new generation of adaptive cycle engine technology. So we think there’s been great support over the years for investing in that and the data that we are getting from the XA100 will set the foundation for all the adaptive cycle engines that come next,” he added.

In the time since GE’s May lobbying push, key defense congressional committees have weighed in on the engine debate through markups of FY24 spending and policy bills, where only the House Armed Services Committee seems supportive of keeping a new engine for the F-35 in play. 

In a June interview with Breaking Defense, House defense appropriations subcommittee Chairman Rep. Ken Calvert, R-Calif., along with fellow California Republican and House defense appropriator Rep. Mike Garcia, seemed open to keeping an adaptive engine option as a backup in case Pratt’s ECU experienced a “catastrophic failure.” But, Calvert emphasized he didn’t “foresee” that occurring, reasoning that “Pratt & Whitney will continue to have that engine.” 

Asked about lawmakers’ various proposals, Tweedie pointed to legislation proposed by Senate appropriators, indicating that GE is largely supportive of the lawmakers’ position. But the Senate appropriations defense subcommittee’s (SAC-D) proposed legislation, according to draft text of the committee’s markup, would disburse $280 million “only to develop advanced engine technologies for integration into future engine development programs” and “maintain a robust industrial base” — with no mention of a new engine for the F-35.

Asked whether the proposed legislation would be sufficient to achieve GE’s objectives, Tweedie replied by saying “our objectives really are continuing to mature adaptive engine technology for a variety of platforms to continue to keep the industrial base healthy and strong.

“And so we see that the SAC-D approach of what they’ve put in their bill, would be sufficient for the Air Force to keep those efforts going in a way that they best saw fit, aligned with congressional intent,” he continued.

He then added, “And the fact that there is looking to be a transition point to wrap up AETP and transition towards a broader advanced engine development activity set, which we’re fully supportive of.”

Those comments stand in contrast to the company’s position when the Air Force first announced in March that it intended to axe AETP and abandon the possibility that the new engine could power the F-35. At the time, GE responded by emphasizing the service’s proposed budget “fails to consider rising geopolitical tensions and the need for revolutionary capabilities that only the XA100 engine can provide by 2028.” The XA100 was designed to be specifically tailored to the Air Force’s F-35A, though the engine could be a potential option for the Navy’s carrier-launched F-35C.

In May, GE was also asking Congress, at least in the immediate term, to carry AETP roughly to critical design review. Asked this week what funding might be needed to make that happen, he said, “Certainly I think the SAC-D position would offer that opportunity.”

GE’s seemingly muted support for a new F-35 engine may help put to rest a contentious debate that has at times turned bitter, such as when F-35 prime Lockheed Martin, during the Paris Air Show, backed an adaptive engine competition for the fighter in an interview with Breaking Defense. The company’s position drew an extraordinary and swift rebuke from Pratt, prompting Lockheed Chief Executive Officer Jim Taiclet to later tamp down the controversy.

Though GE may now support SAC-D’s funding for adaptive engine technology, the company may be waiting some time since lawmakers have yet to approve a budget. House Republican leadership is currently proposing a continuing resolution for the Pentagon that would stretch to Feb. 2 — that is, if they can wrangle the support of hardline conservatives.

Still, once a budget does get approved, lawmakers appear poised to fully grant the Air Force’s requested $595 million for NGAP, where either GE or Pratt will emerge victorious in their quests to power the world’s first sixth-generation fighter.