The investigation into the cause of the Marine Medium Tiltrotor Squadron 364, 3rd Marine Aircraft Wing MV-22B Osprey mishap in Glamis, California, on June 8, 2022, is complete. We have provided the results of the investigation to the families of our fallen Marines and provided all available resources to them during this difficult time.

The loss of Capt. Nicholas P. Losapio, Capt. John J. Sax, Cpl. Nathan E. Carlson, Cpl. Seth D. Rasmuson, and Lance Cpl. Evan A. Strickland continues to be felt across the Marine Corps.

The investigation revealed the cause of the mishap was a dual hard clutch engagement (HCE) which created a Single Engine and Interconnect Drive System (Single Engine/ICDS) failure; the failure resulted in a catastrophic loss of thrust on the right-hand (RH) proprotor. The degraded drivetrain caused by the dual HCE event and subsequent Single Engine/ICDS failure created an unrecoverable departure from controlled flight, resulting in the tragic crash that occurred on June 8, 2022.

It is clear from the investigation that there was no error on the part of the pilots and aircrew and nothing they could have done to anticipate or prevent this mishap. They were conducting routine flight operations in accordance with applicable regulations when this catastrophic and unanticipated mechanical failure occurred. The investigation also found there was no maintenance error on the part of the team whose job it was to prepare the aircraft to fly on the day of the flight.

The Marine Corps has taken the following actions in coordination with the original equipment manufacturer: design and field a new Proprotor Gearbox Input Quill Assembly that mitigates unintentional clutch disengagements and hard clutch engagement events; improve MV-22B drivetrain and flight control system software, drivetrain component material strength, and inspection requirements; and integrate a crash survivable, high-temperature, fire-resistant flight data recorder into all MV-22B aircraft. All USMC MV-22B commands will also present this investigation to pilots and aircrew to discuss the hazards of hard clutch engagements and its potential to cause a Single Engine/Interconnect Drive System failure compound emergency.

On February 3, 2023, the Marine Corps, Navy, and Air Force Special Operations Command issued Dynamic Component Bulletin 63 which directed the replacement of all input quill assemblies over a predetermined flight hour threshold at the recommendation of the V-22 Joint Program Office. Replacing the input quill assembly at this threshold significantly reduces the likelihood of a Hard Clutch Engagement occurring by 99 percent, based on the data.

We will never forget Capt. Nicholas P. Losapio, Capt. John J. Sax, Cpl. Nathan E. Carlson, Cpl. Seth D. Rasmuson, and Lance Cpl. Evan A. Strickland, and their loved ones, as we continue with our quest to provide the safest, most lethal platforms to the men and women who fly them.

The redacted command investigation is available to the public via the Marine Corps Freedom of Information Act website: https://www.hqmc.marines.mil/Agencies/USMC-FOIA/FRR/