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F-35 Lightning II Joint Strike Fighter.

Defense Dept. Ends F-35 Future Engine Project

March 15, 2023
By cancelling its seven-year-long Adaptive Engine Transition Program for the Joint Strike Fighter, the Pentagon is keeping the jets’ propulsion system in the hands of its current and sole contractor, Pratt & Whitney.

In a victory for Pratt & Whitney, the U.S. Air Force is abandoning the Adaptive Engine Transition Program underway since 2016 to define a new engine for the F-35 Joint Strike Fighter. The decision confirms that Pratt will remain the sole supplier of the F135 engine that powers those single-engine jets.

Among other factors working against the AETP was the availability of Pratt’s Engine Core Upgrade to the current F135, which service officials now determine is the most cost-effective way to achieve all the F-35 program’s objectives.

The F-35 is a series of three different, single-engine aircraft with Stealth capability and designed for ground attack and combat. It's deployed by the U.S Air Force, U.S. Marine Corps, and U.S. Navy, and the defense forces of multiple allied nations.

The AETP effort was initiated seven years ago in the expectation that adaptive engine technology could provide more fuel efficiency, greater thrust, and better thermal management for the propulsion systems powering the fighter aircraft. According to the USAF, nearly $2.7 billion was obligated to the AETP program since 2016.

Prototype AETP engines were developed by Pratt & Whitney as well as GE Aerospace, but those offerings failed to address the various objectives required by the F-35 program. There were specific concerns about the AETP engines’ ability to safely power the F-35B and F-35C models, which are designed for aircraft carrier takeoff and landing.

According to U.S. Air Force Secretary Frank Kendall, the choice to proceed with the updated version of the F135 rested in “the combination of affordability and the fact that the Air Force, with the F-35A variant, was the only service that was really seriously interested in AETP.”

The Pentagon recently settled a purchase agreement for over 500 more F-135 engines to cover three more production rounds of the F-35. Those engines are expected to incorporate updates to address some existing maintenance concerns for the engines, as well as improvements developed as part of the Engine Core Upgrade Pratt has developed to advance the capabilities of the engines.

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