An unspecified number of V-22 Ospreys will be grounded to address a hard clutch engagement issue until the component linked to the engine is replaced. The problem was first brought to light in summer 2022.
The fault lies in the input quill assembly that connects the Osprey's engine to the proprotor gear box. On Saturday, the V-22 Joint Program Office announced the grounding after data analytics showed the link of fault between the age of input quill assemblies and hard clutch engagement.
The Defense Department has not stated the flight hour limit or how many of the approximately 400 total V-22 Ospreys across all services would need repairs.
To a group of reporters, a defense official said Navy, Marine Corps, and Air Force Special Operations Command squadrons would continue training and operations with V-22s that have not reached the time threshold.
The official said, "the aircraft that have input quills under the time limit are ready to go and ready to train and ready to fight tonight."
According to the Marine Corps' spring 2022 aviation plan, it has 296 V-22s, while Air Force Special Operations Command has 52, and the Navy is in the process of receiving 44.
The Defense Department's decision to ground for repairs came after an analysis by the V-22 Joint Program Office into the hard clutch engagement problem, which has increased in the number of occurrences.
"This recommendation was based on the progressive increase in these hard clutch engagement events," the official said. "From that, and looking at the totality of the data, we in recent weeks have been able to determine that this time limit was an appropriate step for us to take."
Previously, when hard clutch engagement problems occurred, V-22s would require gear box and engine replacement, costing millions of dollars.
Sources familiar with the topic have said these problems have been more persistent.
The engagement occurs when the clutch connecting the propeller's rotator gear box to the engine slips. The aircraft is designed to shift the power load from the engine to the other engine when this malfunction happens, allowing single-engine use.
Still, that transfer of torque causes the Osprey to dip and sway which has alerted Air Force Special Operations Command leadership in the summer of 2022.
The Air Force and Marine Corps both responded differently.
AFSOC commander Lt. Gen. Jim Slife ordered 52 CV-22 Ospreys to be grounded after two incidents in 2022 and two in 2017. The Air Force said no one was injured, but it was necessary for the airmen's safety.
That grounding was later lifted two and a half weeks later.
The Marine Corps said it had known the problem since 2010 and had trained pilots accordingly, so it did not ground the Ospreys.
The Navy did not encounter these issues with the new CMV-22 variants.
The use of the MV-22 may play a role in the different branches' decisions. The Marine Corps fly the MV-22s over water from amphibious vessels. It also has pilots briefly hover after takeoff to check that the clutch is not slipping.
According to the defense official, the study into the V-22 clutch issue started in 2010, ramping up significantly after 2022's grounding by the Air Force.
The official said they are working on redesigning the clutch assembly and on better understanding through data mining.
A temporary solution will be to replace the input quill assembly on V-22s that are affected. The new input quills are to last for "years" before servicing, said the defense official.
The joint program office and industry-leading teams will be working on a long-term fix, the official said.
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