The Pentagon has modified all F-35 Lightning II fighters, but still has not found the cause of the "harmonic resonance" in the F135 engines

At the end of last year, the Pentagon stopped flights and deliveries of fifth-generation F-35 fighters, as well as

The cause was the so-called "harmonic resonance", which caused the plane to crash during landingF-35 near the Lockheed Martin plant in Texas.Six months later, all American fighters have been modified, but the cause of the "harmonic resonance" has not yet been determined.

What is known

In simple words, "harmonic"resonance" is the vibration that destroys the fuel pipe of the engine. The downing of the F-35 in Texas is not the first manifestation of the problem. Due to vibration, the fighter was disabled back in March 2020, i.e. almost three years before the incident near the Lockheed Martin plant.

The F-35 program office and Pratt & Whitney have found a temporary solution.The F135's powertrains have been given a "hole" that "reduces the likelihood of losing engine control" in the event of a broken fuel pipe due to vibration.Despite this, until now, the U.S. Department of Defense has not been able to figure out what exactly is causing the "harmonic resonance."


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By the beginning of May, all American F-35s received"updated" engines. The government and industry team are continuing to work to hand over all fighter jets whose deliveries have been delayed due to an engine vibration problem.


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On February 17, 2023, Pratt & Whitney received permission to resume deliveries of F135 power units.Lockheed Martin was able to resume deliveries of the F-35 Lightning II in about a month.It is expected that the backlog will be completely eliminated by the beginning of the summer.


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As the Pentagon continues to investigateengine problems, the number of US F-35s ready for service remains below the target of 70% for the F-35A and below 75% for the B/C models. In April, the combat capability of all US F-35s was 56%.