House Bill Keeps Alternate F-35 Engine Afloat, but Only for Research Purposes

Flames shoot out of the back of a dimly lit fighter jet

A 61st FS F-35 accelerates through the evening sky propelled by the force of its afterburner. – U.S. Air Force

The House’s recent version of the FY24 defense appropriations bill provided a lifeline for the alternate engine being developed for the F-35, but the legislation doesn’t foresee actually using the engine in the aircraft. Rather, the program would be used to help inform future engine development efforts.

The FY24 budget request included $254.7 million for work on upgrading the existing F135 engine used in the F-35, as well as $595.4 million for the Next Generation Adaptive Propulsion (NGAP) program, which is being developed for the Next Generation Air Dominance fighter. However, the Air Force canceled the Adaptive Engine Transition Program (AETP), a program to develop a competitive engine that was seen as an alternative to upgrading the existing F135 engine on the F-35. The Air Force said that fielding the AETP only on the F-35A would place a significant financial strain on the service, which the House Appropriations Committee agreed with. However, the committee also says a business case analysis completed by the Joint Program Office failed to fully assess if an upgraded F135 engine would be able to meet F-35 power needs over the life of the aircraft, and the issue will continue to be assessed.

For now, the committee sees a benefit in continuing multiple engine development paths, which lawmakers say will only strengthen the industrial base. The bill therefore adds $150 million to keep the AETP alive, but that doesn’t mean lawmakers support full development of an F-35 alternate engine. In fact, the bill specifically states that the funding increase is not intended to incentivize the Air Force, or the other services, to establish an alternate engine program for the F-35. The legislation includes a provision that prohibits the use of funds to integrate an alternative engine on any F-35 aircraft. Rather, the committee says continued AETP development will help serve a risk mitigation for adaptive cycle and future engine development programs.

Lockheed Martin recently expressed public support for an alternate engine for the F-35, to the consternation of Pratt & Whitney, which is working on improving the existing engine.

About Shaun McDougall

As editor of International Military Markets, North America, Shaun has cultivated a deep understanding of the vast defense markets in the United States and Canada. Shaun's perspective on defense procurement and budget issues has been cited in a variety of defense periodicals, including Defense News and National Defense Magazine. Further, Shaun played an integral role in the development of Forecast International's U.S. Defense Budget Forecast product, which offers an unprecedented level of insight into the Pentagon's acquisition budget. In addition to providing original analytical content for the U.S. Defense Budget Forecast, Shaun oversees an internal defense budget forecasting process involving Forecast International's team of skilled systems analysts following release of the DoD's annual budget request. Shaun is also in charge of managing Forecast International's Weapons Inventory database.

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