What happened
On 29 November 2023, a CV-22B Osprey, tail number 10-0054, crashed into the water approximately half a mile off the coast of Yakushima Island, Japan. The aircraft, operated by the 21st Special Operations Squadron, 353rd Special Operations Wing, was participating in a joint inter-operability exercise at the time of the accident.
Prior to the impact, the crew received multiple cockpit advisories and a caution indicating a "Land as Soon as Possible" condition. In response, the crew diverted toward Yakushima Airport, located roughly 60 miles east of their position. During the final approach to the runway, at an altitude of approximately 800 feet AGL, the aircraft suffered a sudden mechanical failure that induced an immediate left roll. The aircraft rolled twice before impacting the sea. All eight crewmembers were killed in the accident; while seven remains were recovered during a multi-national search, one crewmember remained missing following a 43-day operation.
The investigation
The Accident Investigation Board examined the mechanical state of the aircraft's drive system and the decision-making processes of the flight crew. Investigators analyzed the sequence of events following the initial gearbox advisories, specifically looking at the diversion to Yakushima Airport and the flight path chosen during the emergency.
Technical evaluations focused on the left-hand Proprotor Gearbox (PRGB) and its interaction with the wider drive system. The board also reviewed cockpit communications, maintenance records, and the crew's use of resource management protocols during the period between the first advisory and the final impact.