Japanese F-35s Retrofitted to Fix 'Potentially Dangerous' Engine Vibration Hazard

Japan says it has fixed ‘potentially dangerous’ vibrations in its F-35 engines by installing a U.S.-supplied adjuster.

This was reported by the Japan Times citing defense ministry officials on Tuesday.

The jets are based at Japan Air Self-Defense Force’s (JASDF) Misawa base in Aomori Prefecture.

An incident occurred in December 2022 during a pre-delivery test flight of an F-35B fighter for the U.S. Marine Corps, causing the pilot to eject. During its probe, the U.S. side found that vibrations caused a fracture to a pipe between the main fuel throttle valve and a fuel pipe.

In March, U.S. authorities notified countries using F-35s to take necessary action within the next 90 days to address the risk that an engine control-related pipe may be damaged due to vibrations caused by resonance in a rare phenomenon for F-35 fighters.

Tokyo finished taking the temporary remedial measure by the end of May. The U.S. side plans to provide Japan with fuel pipes of a new design later this year in hopes of further reducing the impact of the vibrations.

“The U.S. Department of Defense conducted a risk assessment,” a ministry official said. “Even though the vibrations may damage the engine control-related pipe in rare cases, we’ve already taken action to prevent engine control difficulties and limit the risk to a point where the fighter jets would still be able to fly safely, by installing a new part.”

Through the U.S. Foreign Military Sales program, Japan plans to acquire a total of 147 F-35A and F-35B aircraft at a price of over ¥10 billion (~$70 million) per unit.

Japan currently operates 33 F-35As from the Misawa base and plans to introduce the same type at the Komatsu base in Ishikawa Prefecture in fiscal 2025.

F-35B fighters will be introduced in fiscal 2024 for deployment at the Nyutabaru base in Miyazaki Prefecture, southwestern Japan.