Air Warfare

It’s official: The F-35 will not get a new engine anytime soon

After rancorous debate, a new engine for the stealth fighter was already in doubt, but legislation released by congressional appropriators today seemingly puts the issue to rest.

F-35 Demo Team shows appreciation for Oklahoma maintainers

U.S. Air Force Maj. Kristin “BEO” Wolfe, F-35A Lightning II Demonstration Team pilot and commander, performs for F-135 engine maintainers assigned to the Oklahoma City Air Logistics Complex, at Tinker Air Force Base, Okla., May 25, 2021. (U.S. Air Force photo by Staff Sergeant Thomas Barley)

WASHINGTON — With text of the fiscal year 2024 spending agreement finally released today, lawmakers have officially decided the future of the F-35 Joint Strike Fighter’s engine.

Spoiler alert: Pratt & Whitney’s F135 powerplant is here to stay. 

According to explanatory text accompanying the legislation, lawmakers will provide $280 million for advanced engine development work — money that will mostly go to Pratt and GE Aerospace, which have both developed prototype powerplants through the Air Force’s Adaptive Engine Transition Program (AETP) and are competing to build an engine for the service’s secretive Next Generation Air Dominance (NGAD) fighter. 

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But that $280 million is just for the engine industrial base, the text says. In fact, “[t]he agreement does not support the integration of an alternative engine on the F-35, and includes a new general provision that prohibits the use of funds to integrate an alternative engine on any F-35 aircraft.”

Instead, the money furnished by appropriators is tailored to “only” fund work to support future engine development programs like “adaptive cycle engine technologies, improved manufacturing techniques for engine components, development of novel materials, and the integration of enhanced digital design capabilities into the engine development process” the text says.

Previously, officials had been weighing whether to pursue an upgrade to the Pratt engine or to hold a competition with Pratt’s and GE’s AETP prototypes to re-engine the F-35. Reasoning that the AETP engines would not be compatible with all three variants of the stealth fighter and pose prohibitive costs, the Air Force moved to upgrade the F135 in the FY24 budget, though some lawmakers remained open to keeping a new, adaptive engine in play. 

The decision to upgrade the Pratt engine opened up an unusual rift between F-35 planemaker Lockheed Martin and Pratt, with Lockheed’s aeronautics boss telling Breaking Defense last year he preferred to see a new engine introduced. The position led to an extraordinary rebuke from Pratt, and eventually prompted Lockheed Chief Executive Officer Jim Taiclet to tamp down the controversy

Still, the outcome in the spending agreement today is not all too surprising, as the writing has been on the wall for some time. Markups released last year by Senate and House appropriators did not include funding for a new F-35 engine, and GE followed by mostly muting its pitch for its adaptive engine prototype to re-engine the stealth fighter. 

House Appropriations defense subcommittee (HAC-D) Chairman Rep. Ken Calvert, R-Calif., cast further doubt on a new engine as well, telling Breaking Defense in an interview last year that House appropriators are “not looking or seeking to change out the Pratt & Whitney engine.”

Theoretically, it’s always possible in future budgets that lawmakers could change their mind. The two companies’ respective AETP prototypes probably aren’t going to be junked anytime soon, and lawmakers might have renewed interest in a new engine if something goes awry with Pratt’s F135 upgrade plan dubbed the Engine Core Upgrade

Calvert mentioned that possibility, though he deemed it unlikely. “Unless there’s a catastrophic failure on the part of Pratt & Whitney, which I don’t foresee, I don’t see at this point that there’s going to be any change … Pratt & Whitney will continue to have that engine,” he told Breaking Defense. Rep. Mike Garcia, a fellow California Republican who also sits on HAC-D, explained in the same interview that the adaptive engine program could serve as a “backup” and provide research utility. 

Both Pratt and GE have said they are continuing to leverage their adaptive engine prototypes, whose insights could be used for the NGAD engine program known as Next Generation Adaptive Propulsion (NGAP). Both companies are expected to have their NGAP engine designs carried through a prototyping stage, an Air Force official told reporters last year. The legislation released today fully funds the Air Force’s request to carry the NGAP program out, providing $595 million in addition to the $280 million in advanced engine work.