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The recent crash of a US Air Force V-22 Osprey off Japan’s coast, resulting in the tragic loss of eight airmen, has directed attention to the aircraft’s propeller rotor gear box as a potential factor.

This incident marks the fourth fatal Osprey crash in under two years, cumulatively claiming 20 service members’ lives and prompting a sweeping grounding of the fleet across all US military branches in December.


Osprey aircraft wreckage after the crash landing off the coast in Nago, Okinawa Prefecture. This photo was taken on Dec. 14, 2016 (Asahi Shimbun file photo)

Officials familiar with the ongoing investigation have yet to pinpoint the exact cause of the November disaster but have acknowledged a “material failure” related to the aircraft’s innovative tiltrotor mechanism, which allows it to take off like a helicopter and fly like a plane. Despite this, the specific reason behind the gear box failure remains undetermined, with Air Force Special Operations Command cautioning against premature speculation.

A Mv 22 Osprey Aircraft Prepares To Land On The Flight Deck.

The Osprey’s history of “hard clutch engagement” issues, notably a June 2022 crash that resulted in five Marines’ deaths, highlights the challenges faced in diagnosing and rectifying the tiltrotor’s mechanical problems. Although military officials expressed confidence in addressing the clutch issue, the discovery of metal chips in the gear boxes of several aircraft since July 2022 has raised additional concerns about the Osprey’s reliability.

The presence of these chips has been documented in multiple hazard reports, highlighting ongoing performance issues despite the aircraft’s advanced design and capabilities. Marine and Navy pilots are trained to respond immediately to any indication of metal chips in the gear boxes, a critical component similar to a car’s transmission.


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