Pentagon grounds ‘subset’ of Osprey fleet over safety concerns

WASHINGTON — Months after declaring the V-22 Osprey safe for use, the Pentagon is standing down “a subset” of the fleet over safety concerns that will require the installation of a replacement part.

However, the department is being cagey about exactly how many rotorcraft will be grounded and how long it will take to get them flying again.

The stand down of the multi-mission tiltrotor aircraft used by international allies and three US military services — the Marine Corps, Navy and Air Force — comes months after Air Force Special Operations Command grounded its own Osprey fleet in August following an “increased number of safety incidents” involving an issue with the clutch, as first reported by Breaking Defense. The Air Force later lifted that grounding in early September.

However, investigators have since concluded that when the aircraft reaches a certain number of flight hours, the “input quill assembly” must be replaced in order to continue safely flying the Osprey, a defense official told reporters in a Saturday briefing. The input quill assembly connects the aircraft’s engine to the drive system, and inside of that assembly resides the clutch.

“This recommendation is based on a progressive increase in hard clutch engagements and ongoing engineering analysis,” the official said. “The fleet bulletin identifies aircraft with input quill assemblies above a predetermined flight hour threshold and the requirement to replace that component. Once replaced, aircraft will return to flight status.”

Despite being pressed by multiple reporters, the defense official declined to provide any characterization of how many V-22s have been impacted by the new fleet bulletin, declaring only that it was a “subset” — a wide-open statement that could mean anything from a small handful to a large majority of the rotorcraft are impacted.  The official also declined to provide how many flight hours trigger the replacement.

In terms of fixing the issue, the defense official said replacing the input quill assembly can be done at the squadron level and that relevant units will be able to start that process immediately. The services are also working with V-22 prime contractor Bell-Boeing to conduct laboratory testing and data analysis. There is also an ongoing effort to redesign the clutch as part of a long-term solution, they said.

“Bell-Boeing, the prime for this aircraft, is very much involved in all of these lines of effort,” the defense official said. “Once the IQA is replaced, the aircraft can return to flight and a replacement will not be required for years. Timelines to hit that threshold are based on overall flight time on the asset and will vary.”

The Osprey variants include the Air Force’s CV-22, the Marine Corps’ MV-22 and the Navy’s CMV-22B; the Japanese military also flies its own V-22 variant. The US official said Japanese officials overseeing that country’s V-22 fleet are being provided the same support and information as the US military services.

While the Air Force shut its V-22 fleet down for safety inspections over the summer, the Marine Corps did not, instead insisting their pilots could compensate for the issue and had been doing so for some time.

When asked about what had changed since last summer the defense official referenced the “progressive increase” in hard clutch events.

“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 and so we decisively made the decision to implement this life limit,” the official said.