V-22 Ospreys grounded over hard clutch issue

The U.S. military has halted flight operations for an undisclosed amount of its V-22 Osprey fleet. The issue is a hard clutch engagement issue that caused several mishaps in 2022. V-22s with the U.S. Marine Corps, Navy and Air Force Special Operations Command are grounded until a part of the engine is replaced.

It’s the latest trouble for the tiltrotor aircraft and comes after the military previously implemented workarounds to get the V-22 flying again following a stand down. The military is not disclosing how many Ospreys are affected.

The indefinite grounding will allow maintenance crews to replace the input quill assembly in each craft. The assembly houses the clutch. This will be done for any V-22 that has reached a certain flight time threshold; the military is also not disclosing what that threshold is. 

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The move “only impacts a subset of aircraft,” a U.S. defense official speaking on the condition of anonymity told a group of reporters. The official stressed that V-22 operations are not halting entirely, and training and operations for unaffected aircraft will continue. The defense official said that the hard clutch engagement issue has been something the military has been looking into prior to the summer’s mishaps, and in fact since 2010.

In a hard clutch engagement mishap, the clutch slips, causing the craft to distribute power from the V-22’s other engine. When the slipped engine reengages, that can cause a sudden spike on one side, throwing it off balance.

In August 2022, AFSOC grounded its fleet of CV-22s for more than two weeks after a pair of mishaps related to the mechanical issue. They were the first to affect the command’s aircraft since 2017. In one instance, an AFSOC CV-22 Osprey suffered a hard clutch engagement mishap and ended up making an emergency landing on a wildlife refuge on a Norwegian island. It took weeks to recover the aircraft, as American and Norwegian officials developed a strategy to retrieve it without disturbing the preserve. 

After these mishaps, AFSOC implemented temporary measures, such as adding training for hard clutch engagements in simulations, as well as an interim guidance that said to pause for two-seconds at takeoff before boosting power. At the time, AFSOC said that those measures were necessary until a “root cause is identified, and solution implemented.” 

The Marine Corps — which has its own history of fatal V-22 mishaps — chose not to ground its V-22s at the time, saying it was aware of the issue and trained its pilots with the “appropriate emergency control measures.”

The input quill replacement is a part of routine procedures and can be done at a squadron level for each aircraft, the defense official told reporters. The input quills being put in aren’t a newer design, but simply fresh ones that have not hit a limit. 

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