US AFSOC Grounds CV-22B Fleet Indefinitely

[RAFEngO74to09]

US AFSOC grounds entire 52 x CV-22B fleet indefinitely due to engine hard clutch engagement problems.

Very informative video here from a retired Cdr USN aviator who worked in the V-22 program.

https://www.youtube.com/watch?v=k2WgBlBarf0

AFSOC describes the problem as a “hard clutch engagement":

”Basically, the clutch inside a gearbox that connects one of the CV-22’s two Rolls-Royce Liberty AE1107C engines to the propeller rotor is slipping for an unknown reason, When that happens, the power load transfers nearly instantaneously to the other engine — a design feature that would allow the Osprey to keep flying even if one engine fails. Then, in most cases, the initial clutch re-engages, and the power load rapidly shifts back to the original propeller rotor and engine.

As a result of the rapid movement of power across engines, however, the aircrew is forced to land the CV-22 immediately, and if the aircrew were unable to control the aircraft when the incident occurs, it could result in loss of control and uncontrolled landing of the aircraft.”

https://breakingdefense.com/2022/08/exclusive-air-force-special-operations-command-grounds-cv-22-ospreys-due-to-safety-issue/

[fdr]

Hope they resolve this quickly, the V-22 is a unique force multiplier.

[ORAC]

https://www.defensenews.com/air/2022/08/18/us-marine-corps-isnt-grounding-osprey-fleet-over-clutch-issue/

US Marine Corps isn’t grounding Osprey fleet over clutch issue

WASHINGTON — The U.S. Marine Corps said Thursday it is not grounding its MV-22 Osprey (https://www.marinecorpstimes.com/news/2022/08/14/pilot-error-the-cause-of-norway-osprey-crash-that-killed-4-marines/) fleet over a clutch problem, as the U.S. Air Force did earlier this week (https://www.defensenews.com/air/2022/08/17/us-air-force-grounds-osprey-fleet-after-dangerous-clutch-problem/).

The service has known about the issue with hard clutch engagement since 2010, and has trained its pilots how to respond when such emergencies happen, Marine Corps spokesman Maj. Jim Stenger said in a statement to reporters…..

Air Force Special Operations Command said that because it’s unsure what is behind these clutch issues, commander Lt. Gen. Jim Slife did not feel comfortable flying them, and therefore grounded them to figure out the root cause and how to stop the problem.

But the Marine Corps feels this is an issue that can be managed by training aircrews on how to respond, and that the potential for an occurrence is common knowledge among its fleet personnel. Officials said there were no injuries associated with the Corps’ hard clutch engagement incidents, although some gear boxes or engines were replaced as a result…..

The Marines have a fleet of about 296 Ospreys, and have flown them for 533,000 flight hours.

The V-22 program has experienced a total of 15 instances of hard clutch engagement, including 10 in Marine Corps Ospreys, since 2010, the defense official said.

The Navy confirmed Thursday it has not experienced this problem with its CMV-22 variant, which is the newest in the Osprey fleet and began its first deployment last August….

[Tinman74]

They were flying over the Lake District last week.

[Fonsini]

A known problem for 12 years and still not even root-caused, I confess I’m surprised by that.

[ORAC]

Seems to be a PRGB (Prop Rotor Gear Box) quill issue.

There is an ongoing budget line item to modify the quill/clutch since 2019 (60 ship sets a year), not sure it the mod is related to this issue though.

“V-22 Prop Rotor Gear Box (PRGB) Input Quill/Clutch Redesign: To eliminate resident issues with Input Quill and clutch and to Purge Fleet of Thin Densed Chrome.”

[Lonewolf_50]

“V-22 Prop Rotor Gear Box (PRGB) Input Quill/Clutch Redesign: To eliminate resident issues with Input Quill and clutch and to Purge Fleet of Thin Densed Chrome.” That last bit is semi interesting ; "purge the fleet of thin densed chrome". There has been a (roughly) 20 year long effort among DoD activities to stop using a variety of materials (sealants, primers, conversion coatings, etc) that are chrome based. I wonder if they are changing chrome plating to {some other hard material} in its place.

[212man]

A known problem for 12 years and still not even root-caused, I confess I’m surprised by that.
Yes, and one of the mitigations is a hover check!

[212man]

That last bit is semi interesting ; "purge the fleet of thin densed chrome". There has been a (roughly) 20 year long effort among DoD activities to stop using a variety of materials (sealants, primers, conversion coatings, etc) that are chrome based. I wonder if they are changing chrome plating to {some other hard material} in its place.
I am reminded of this accident when I hear the failure mode described: https://aviation-safety.net/wikibase/188940

[M609]

Apparently a CV-22B did an emmergency landing at Senja (https://goo.gl/maps/wpHPTH4aygPUS3zx8) (West of Bardufoss) on august 12. Still parked there.
No details in what happened.

CV-22B still stuck at Senja (https://www-nrk-no.translate.goog/tromsogfinnmark/amerikansk-us-osprey-matte-nodlande-pa-senja_-flere-maskiner-sette-pa-bakken-1.16077242?_x_tr_sl=no&_x_tr_tl=en&_x_tr_hl=en&_x_tr_pto=wapp)

[ORAC]

Looks like their solution to return to flight is to implement the same take-off procedure as the Marines….

https://www.defensenews.com/air/2022/09/02/us-air-force-clears-ospreys-to-fly-amid-unresolved-clutch-problem/

US Air Force clears Ospreys to fly amid unresolved clutch problem

WASHINGTON — The Air Force cleared its CV-22 Ospreys (https://www.defensenews.com/air/2022/08/17/us-air-force-grounds-osprey-fleet-after-dangerous-clutch-problem/) tiltrotor aircraft to resume flying, some two-and-a-half weeks after grounding them due to a clutch problem that remains unresolved.

Lt. Gen. Jim Slife, head of Air Force Special Operations Command, on Friday authorized the command’s fleet of 52 Ospreys to resume flying, with measures to limit the risk from “hard clutch engagement” incidents. AFSOC Spokeswoman Lt. Col. Rebecca Heyse said the aircraft are expected to start operating again this weekend…..

Heyse said AFSOC is still not sure why the Osprey clutches are slipping, but that the command has put steps in place to try to manage them for the near term. AFSOC studied the data from all 15 recorded hard clutch engagement incidents across the Osprey enterprise to figure out what was a common factor there.

One key risk mitigation step: AFSOC has instructed its Osprey pilots to take a two-second pause immediately after taking off to keep the clutch from slipping, instead of going to full power immediately, Heyse said.

Marine Corps officials told reporters last month that its Osprey pilots are instructed to hover after taking off to check instruments and ensure the clutch isn’t slipping.….

“Until a root cause is identified, and solution implemented, the focus is on mitigating operations in flight regimes where [hard clutch engagements] are more prevalent and ensuring our aircrews are trained as best as possible to handle [them] when they do occur,” Heyse said in an email.….

[megan]

Anyone have a description of the drive train? I just assumed each engine would drive its respective gearbox through a sprag clutch and the cross shafting from engine gear box to engine gear box would be continually engaged, hard wired if you like ie no clutch involved