Chris Hanoch | Lockheed Martin
F-135 engine installed on an F-35A in service with the Royal Danish Air Force.
F-135 engine installed on an F-35A in service with the Royal Danish Air Force.
F-135 engine installed on an F-35A in service with the Royal Danish Air Force.
F-135 engine installed on an F-35A in service with the Royal Danish Air Force.
F-135 engine installed on an F-35A in service with the Royal Danish Air Force.

Pentagon Clears Pratt & Whitney to Resume F-135 Deliveries

March 2, 2023
The OEM is implementing a remedy to an engine vibration problem that caused the U.S. Dept. of Defense in January to halt deliveries of the power units for F-35 Joint Strike Fighter jets.

Pratt & Whitney has been cleared by the U.S. Dept. of Defense to resume deliveries of the F-135 engine for the F-35 Lightning II Joint Strike Fighter program, following a halt imposed to determine the cause of a high-profile F-35 crash.

In that December 15, 2022 crash, captured on a widely circulated film clip, a F-35B bounced while attempting a vertical landing in Texas, and then flipped over as the U.S. Marine Corps pilot ejected safely.

The cause of that incident was determined to be “harmonic resonance” developing in a limited number of F-135 engines, causing uncontrollable engine vibration.

The vibration issue was found to be associated with the number of flight-hours accumulated by the engines, and it is considered to be a systemic problem, not one caused by failed or defective parts.

F-135 engine-builder Pratt & Whitney has developed a remedy to address the harmonic resonance problem, and has implemented that change to its manufacturing process.

Additionally, a Pratt spokesperson explained that the same solution can be implemented without extensive time out of service for F-135 engines already in place with F-35 aircraft.

The pause in deliveries of completed F-135 engines reportedly has impacted the production schedule for Lockheed Martin, the F-35 manufacturer, with more than a dozen aircraft left waiting for their powerplants.

The Pentagon’s F-35 Joint Program Office (which coordinates activities among the numerous suppliers) stated that it is working “to ensure incorporation of mitigation measures that will fully address/resolve this rare phenomenon in impacted F135 engines.”

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