The following is the June 6, 2024, U.S. Air Force Aircraft Accident Investigation Board report on the Nov. 29, 2023 crash of an Air Force CV-22B off the coast of Yakushima Island, Japan.
From the report
Executive Summary
On 29 November 2023, at approximately 1440 local time (L), mishap aircraft (MA), a CV-22B aircraft, tail number (TIN) 10-0054, impacted the water approximately one-half mile off the coast of Yakushima Island, Japan, while participating in a joint inter-operability exercise. The MA was operated by the 21st Special Operations Squadron (21 SOS), 353rd Special Operations Wing
(353 SOW), Yokota Air Base (AB), Japan. The eight-member Mishap Crew (MC) included five CV-22B aircrew members from the 21 SOS, one Direct Support Operator (DSO) from the 43rd Intelligence Squadron, Detachment 1, Yokota AB, Japan, and two medical personnel from the 1st Special Operations Squadron (1 SOS), Kadena AB, Japan. The MA was destroyed and all crewmembers sustained fatal injuries upon impact. The remains of seven crewmembers were recovered in the subsequent search and recovery. The remains of the eighth crewmember were not recovered, despite an extensive 43-day, multi-national search.
The MC aborted their planned mission after multiple advisories and a caution displayed in the MA cockpit, indicating a “Land as Soon as Possible” condition. The MC diverted towards Yakushima Airport (RJFC) located approximately 60 miles east of the MA’s position. While on final approach to the runway, at approximately 800 feet above ground level (AGL), the MA experienced a sudden materiel failure that put the MA into an immediate left roll, resulting in the MA rolling twice and impacting the water.
The Accident Investigation Board (AIB) President (BP) found, by a preponderance of the evidence, the mishap was caused by a catastrophic failure of the left-hand Proprotor Gearbox that created a rapidly cascading failure of the MA’s drive system, resulting in an instantaneous asymmetric lift condition that was unrecoverable by the MC. The BP further found, by the preponderance of evidence, Mishap Pilot’s (MP) decisions were causal, as they prolonged the mishap sequence and removed any consideration of an earlier landing at a different divert location.
In addition, the BP found, by the preponderance of the evidence, the following factors substantially contributed to the mishap: ( 1) Inadequate Risk Management; and (2) Ineffective Crew Resource Management. These factors, when considered together, substantially contributed to an insufficient sense of urgency throughout the entire mishap sequence, beginning with the first PRGB cockpit advisory approximately 49 minutes prior to aircraft impact.
Accident Summary
On 29 November 2023, at approximately 1440 local time (L), while participating in a joint interoperability exercise, the MA, a CV-22B aircraft, TIN 10-0054, crashed in the water approximately one-half mile off the coast ofYakushima Island, Japan (Tab EE-9). The aircraft was operated by 21 SOS, 353 SOW, Yokota AB, Japan {Tab EE-17, and EE-104). The eight members of the mishap crew (MC) consisted of five CV-22B aircrew members from the 21 SOS, including the Mishap Pilot (MP), Mishap Co-pilot (MCP), Mishap Additional Pilot (MAP), Mishap Special\ Mission Aviator Flight Engineer (MSMAFE), and Mishap Special Mission Aviator Tail Scanner (MSMA TS), along with two medical personnel from the 1st Special Operations Squadron (1 SOS), 353 SOW, Kadena AB, Japan, including the Mishap Special Operations Forces Medical Element I (MSOFMEI) and Mishap Special Operations Forces Medical Element 2 (MSOFME2), and one member from the 43rd Intelligence Squadron, Detachment I (43 IS, Det 1), Yokota AB, Japan, Mishap Direct Support Operator (MDSO) (Tab EE-85 to EE-95). The MA was destroyed and all eight crewmembers sustained fatal injuries upon impact (Tabs P-3, and X-3 to X-9). The remains of seven crewmembers were recovered in the subsequent search and recovery (Tab EE-81 ). The eighth crewmember was not recovered, despite an extensive 43-day, multi-national search effort (Tab EE-81 ). After impact, most of the aircraft wreckage sank to the sea floor in approximately I 00 feet of water (Tab EE-37). Extensive salvage operations were able to recover many key components of the MA; however, due to the extensive damage from impact, duration of time underwater, and strong sea cunents, recovery of all components of the MA was not possible
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