A Mysterious Osprey Clutch Issue Caused the Deaths of 5 Marines. But V-22s Remain Flying.

Five Marines who took off on training flight on June 8, 2022, died when their Osprey suffered a catastrophic clutch issue, the Marine Corps revealed in an investigation report Friday.

Despite the findings -- and earlier concerns over the possibility of a deadly crash caused by the clutch -- the military continues to fly the V-22 with no firm understanding of the cause or any definitive mechanical fix for the problem in sight.

The five Marines are the first known casualties of a persistent mechanical issue -- a hard clutch engagement, referred to as HCE -- that shredded the components responsible for powering the aircraft's propellers. The issue has plagued the Osprey platform for years, but it was not acknowledged publicly until a month after their aircraft crashed in southern California.

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Amber Sax, the wife of John Sax, one of the pilots who died on that Osprey, told Military.com on Friday after the new revelation from the Marine Corps that a tragedy like her husband's death is not something she wants others to experience.

"The aviation community is our family. John loved being a Marine; John loved flying the Osprey," she said. "This is a difficult day for so many. We just want to make sure this doesn't happen to anyone else."

The report and accompanying letters from Marine Corps leaders lay bare the scope of the problem. Despite a history of at least 15 such incidents between March 2010 and August 2022, "the root cause of HCE remains unknown," Maj. Gen. Bradford Gering wrote in a March letter accepting the investigation results.

Gering wrote that the fix the Pentagon touted in February -- replacing a part of the drivetrain called an input quill assembly -- serves only to reduce the chance of this costly, and now deadly, issue from happening again.

"Once the root cause of HCE is understood, then and only then, can improvements to flight control system software, drivetrain component material strength, and robust inspection requirements be developed where applicable," Gering wrote.

Despite no clear understanding of what causes the problem, the office that runs the Osprey program for the Pentagon claimed in a statement released Friday that, "through a combination of efforts, including the recent input quill assembly replacement bulletin in February 2023, the risk of a HCE event occurring was reduced by greater than 99%."

The office's statement added that the results of this investigation "have further driven efforts to mitigate the HCE phenomenon, identify root cause and prevent it from occurring."

'Nothing Seemed Strange About That'

The massive, 400-page report released by the Marine Corps on Friday reveals that the Marines of Swift 11 -- the call sign of the doomed Osprey -- had little indication that anything was wrong in the moments leading up to their crash.

The Osprey left Camp Pendleton that morning with a wingman headed for an aerial gun range near the California and Arizona border. The training flight was going normally until 12:12 p.m., when the Osprey told its wingman that its gearboxes were getting too hot.

However, one of the enlisted crew in the accompanying Osprey later told investigators "that's pretty normal" for the maneuvers they were doing because of the heat in the summer of southern California. "Nothing seemed strange about that," he added.

The procedure was for the Osprey to climb to a higher altitude to help cool the oil in the gearboxes.

Investigators say Swift 11 began its climb at 12:14 p.m. Seconds later, it would slam into the ground from a height of around 500 feet.

The crash was so sudden that the crew of the accompanying Osprey -- Swift 12 -- didn't realize what happened at first. Investigators said that the doomed Osprey made no radio calls and no one witnessed the crash. When Marines in the wingman Osprey spotted the smoke from the crash, the same enlisted crew member told investigators he thought it was an oil or tire fire.

"I did not think for a second that it was our wingman," he said in written testimony.

After they weren't able to raise Swift 11 on the radio, they flew in for a closer look, and reality dawned on them. Despite the thick, black smoke, one of the pilots on Swift 12 told investigators that "you could tell it was an Osprey."

Investigators determined that Swift 11 crashed so violently that its fuel cells ruptured and caught fire. The ensuing fire was so fierce that it destroyed the Osprey's black box. When the crew from a nearby Navy helicopter landed nearby and tried to put out the flames, they found that their fire extinguishers did nothing.

The remains of all five Marines -- Capt. Nicholas Losapio, Capt. John Sax, Cpl. Nathan Carlson, Cpl. Seth Rasmuson, and Lance Cpl. Evan Strickland -- were found at their stations, the report said.

The oldest Marine, Sax, was 33. The youngest, Strickland, was only 19.

Two months later, on Aug. 18, the Marine Corps, responding to the Air Force's grounding of its own Osprey fleet over HCE concerns, would tell reporters that its pilots could handle the issue.

"Hard clutch issue has been known to the Marine Corps since 2010, and as such, we have trained our pilots to react with the appropriate emergency control measures should the issue arise during flight," Maj. Jim Stenger, a spokesman for the Marines, said at the time.

According to the documents included in the report on the crash, the crew of Swift 11 were some of the best the Corps had to offer.

The squadron that the Osprey belonged to -- Marine Medium Tiltrotor Squadron 364, known as the Purple Foxes -- had recently been named the Marine medium tiltrotor squadron of the year. The citation specifically noted the squadron surpassed 10,000 mishap-free hours and "managed risk across a wide spectrum of desert and littoral combat operations."

Furthermore, the lead pilot of Swift 11, Losapio, was widely regarded as an excellent aviator.

His commanding officer told investigators that he was a "phenomenal" officer and pilot who was "leaps and bounds ahead of his peers in terms of capability and stick control."

Friday, however, the office that manages the Osprey program for all the services called the incident "unpreventable and unanticipated."

'A Christmas Tree of Lights'

While the Air Force was more cautious and grounded its aircraft in August as the Marines continued to take to the skies, the pause was short-lived.

That same month of August would see one of the Air Force's CV-22 Ospreys get stuck on a remote nature reserve in Norway after the crew experienced a hard clutch engagement, forcing an emergency landing. There were no fatalities, but retrieving the aircraft began an intense ordeal involving international cooperation.

By September, just two weeks after grounding its Ospreys, the Air Force announced it had cleared them to fly once more, saying that, despite not having a mechanical fix for the issue, "the focus is on mitigating operations in flight regimes where HCEs are more prevalent and ensuring our aircrews are trained as best as possible to handle HCEs when they do occur," a spokesperson said at the time.

Lt. Gen. Jim Slife, then the head of Air Force Special Operations Command, told reporters at the Air Force Association's Air, Space & Cyber Conference in September that he was frustrated by the lack of a mechanical fix to the problem and said he was grateful there hadn't been any deadly incidents with his command.

"In AFSOC, we haven't had a catastrophic mishap," Slife said at the conference. "Each one of them results in a kind of a Christmas tree of lights, caution lights in the cockpit. ... I'm really, really proud of our crews and the way they've been able to safely land these airplanes, but I'd rather they not have to demonstrate their superior skill because we put superior controls in place to prevent them from having to do that."

That same month, Military.com exclusively reported the details of a 2017 Air Force Osprey mid-flight incident in Arizona that was caused by a clutch issue similar to the one that downed Swift 11.

That incident caused more than $5 million in damage to the aircraft, according to the Air Force report. Both engines and five gearboxes needed to be replaced, as well as nearly a dozen other components. It took a team of six, working 12-hour days, 45 days to repair the aircraft, according to the report.

It wasn't until February that the issue resurfaced again when the military announced that the services that fly the aircraft had grounded an unknown number of Ospreys. Officials wouldn't disclose the exact number, citing "operational security concerns."

A defense official, who spoke with reporters on the condition of anonymity at that time, pointed to the input quill assembly, saying it wears out more quickly than previously thought and would need to be replaced.

Lt. Col. Rebecca Heyse, an Air Force Special Operations Command spokeswoman, told Military.com on Friday that the service has been flying the Osprey since the February grounding. The command did not comment on the revelation that a hard clutch engagement led to the deaths of the five Marines.

The released Marine Corps investigation did manage to fill in one detail of the current approach to flying the Osprey that the military wouldn't discuss in February: how many hours it takes to wear out that assembly.

Both the report and Gering's letter mention that an analysis determined that the input quills should be replaced after 800 flight hours. Both of Swift 11's quills had more than 2,000 hours of flight time.

It's not clear what portion of the Marine or Air Force fleet is above the 800-hour threshold.

Meanwhile, when fiscal 2024 budget documents came out for all the services earlier this year, something became clear: The military was done buying the flawed aircraft.

The Navy, Marine Corps and Air Force all say that they don't need any new aircraft and that the end of the buy is simply the end of the contract for the services. But Liz Mildenstein, a spokeswoman for the office that oversees the program, told Military.com in March that they were dedicated to the aircraft "for decades to come."

Japan is the only other country that currently flies the Osprey, and other countries such as Israel and Indonesia have reportedly been interested over the last decade.

Jeremiah Gertler, a senior associate with the Center for Strategic and International Studies think tank in Washington, D.C., who specializes in aviation, told Military.com in an interview Friday that, while the U.S. military is done buying it, that doesn't mean they're done flying it in the future, if there's a fix.

But other countries who are weighing additional or new buys have and will be paying attention to the V-22 track record.

"Those countries are the ones who are going to have to make the judgment about suitability for their use," Gertler said. "Everybody knows the V-22's record, for both good and ill. The countries that are considering buying are keeping their eyes open."

The Families Grieve

Meanwhile, many of the families of the five Marines have grieved publicly, and the Marine Corps said that it would "never forget" them "as we continue with our quest to provide the safest, most lethal platforms to the men and women who fly them."

Amber Sax, who was pregnant with her second child at the time of the mishap, has started a foundation in her late husband's name to provide scholarships to "bolster the aspirations of current and future aviators."

Avery Rasmuson has made many posts on Instagram talking about her late husband and posted photos of the various memorials the Purple Foxes have put together for the crew of Swift 11.

The family of Evan Strickland has started a podcast talking about his life and service.

Kelsie Hancock was set to marry Losapio just shy of two months after the crash. She has since spoken on social media about what it was like to learn about his death and how she has tried to move forward with her life.

"Two Marines and a chaplain were at my door," Hancock recalled in a YouTube interview. "I remember getting the knock and I knew. I knew what it was. And that whole walk down the hallway I was like, 'Please God, please let it not be this.'"

-- Konstantin Toropin can be reached at konstantin.toropin@military.com. Follow him on Twitter @ktoropin.

-- Thomas Novelly can be reached at thomas.novelly@military.com. Follow him on Twitter @TomNovelly.

Related: Military Grounds Some Ospreys While a 'Complete Redesign' Is Underway on Troubled Clutch System