Marine Corps Suspected Part Causing Osprey Clutch Failures in 2010

MV-22B Osprey arrive at Marine Corps Air Station Futenma
MV-22B Osprey arrive at Marine Corps Air Station Futenma, Oct 1, 2012. (U.S. Marine Corps photo by Cpl. John Kennicutt)

The Marine Corps identified the MV-22 Osprey part that was failing and causing dangerous hard clutch mishaps in 2010 -- more than a decade before the mechanical problem resulted in the deaths of five Marines, according to a document obtained by

The document, drafted by the service, also reveals that the Marines and the manufacturer made several efforts to fix the problem years before the deadly 2022 Osprey crash in the California desert.

Ever since the clutch issue became public in August 2022, the Marines have made it clear that their experience with the problem went back to 2010, but the document reveals the service was also focused on a component called the input quill assembly -- the part it would point to much later as the key to its attempted fix -- in the same time period.

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The document says that, after the very first incident of a hard clutch engagement on the Osprey, the input quills were identified as the failing component. It would be 13 years until the military would publicly say that.

The persistent mechanical issue -- a hard clutch engagement, often referred to as HCE -- is capable of shredding the components responsible for powering the Osprey's propellers and enabling it, in the event of a single engine failure, to keep flying.

The issue only became public after the Air Force abruptly grounded its Osprey fleet last August over a cluster of such incidents. Yet the Marine Corps, which operates the lion's share of the military's Osprey fleet, said the very next day that it didn't need to ground its aircraft.

Officials who spoke with reporters at the time stressed that the issue largely occurred "within seconds after takeoff" and that "in every incident, the aircraft landed safely."

Months later, though, would exclusively report on a 2017 HCE incident with an Air Force Osprey that happened mid-flight and forced the aircraft to perform an emergency landing with a single engine.

In June 2022, a Marine Corps Osprey -- call sign Swift 11 -- would crash in southern California, claiming the lives of five Marines. In March, the Marine Corps investigation would find that they were the first deaths stemming from the problem. The branch wouldn't tell the victim's families or the public until July.

In February, when the military announced that replacing the input quills would be a mitigation measure put in place to stop the issue from happening, officials wouldn't say how often the replacement would need to take place or how many Ospreys would be down as a result.

When the Swift 11 investigation was released, it became known that the quills were being replaced every 800 flight hours. However, that investigation also revealed that the Marine Corps does not know the definitive cause of the issue. The document reviewed by says that the entire "in-reporting" Osprey fleet has now been retrofitted.

Despite the absence of an understanding of what causes the issue, the Marine Corps says replacing the quills is a near-perfect, 99% fix. A widow of a Marine killed in the Swift 11 incident, as well as aviation experts, told they were skeptical of this claim.

Amid this back and forth, the Marines and the Osprey's manufacturer, Bell/Boeing, were apparently working on a fix for years, according to the document shown to

An effort to redesign the input quills first kicked off in 2017 though it would fail three years later in 2020, the document explained. Another redesign effort began in 2022 and continues to this day. However, neither effort included an actual fix, and the cause of HCEs is still unknown.

Complicating these efforts is the fact that, according to the Marine Corps document, the service hasn't been successful in recreating an HCE in a lab environment where they could document the exact chain of events that causes the problem.

A double HCE -- the kind of incident that downed Swift 11 -- is even harder to duplicate. In fact, the document makes clear that at the time Swift 11 went down, the Corps wasn't aware that such a thing was even possible. The service hadn't seen any models or simulations that suggested that both of the aircraft's clutch assemblies failing simultaneously was feasible.

Despite that, between data within the document and other Marine Corps sources, it appears that out of all 16 known instances of hard clutch engagements in the military, two incidents -- Swift 11 and one other incident -- involved a double HCE.

Media representatives for Bell/Boeing referred questions to Naval Air Systems Command.

Additionally, the Air Force and Navy did not provide comment on the latest information provided in the documents.

The Marine Corps and Air Force officially started flying the Osprey in 2007 and 2009, respectively. The Navy got its first operational aircraft more recently, in 2021, according to fact sheets from all the services.

Fast-forward to when the fiscal 2024 budget documents came out for all the services earlier this year, and something becomes clear: The military is done buying the flawed aircraft.

The latest budget documents, released in March by the Navy, say that the military services ultimately want 464 aircraft -- 360 for the Marines, 48 for the Navy, and 56 for Special Operations Command and the Air Force.

-- Konstantin Toropin can be reached at Follow him on Twitter @ktoropin.

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