The US Naval Air Systems Command (NAVAIR) announced that the US military has grounded a subset of V-22 Osprey aircraft due to hard clutch engagement issue.

A time limit was issued through the fleet bulletin on the V-22 input quill assembly by the US Navy, Marine Corps and Air Force Special Operations Command. It came into effect from 3 February 2023.

The imposed time limit was based on the recommendations from V-22 Joint Programme Office to address the gradual increase in the hard clutch engagement issues and to support the ongoing engineering analysis.

Following this announcement, all the flight operations of the V-22 fleet have been restricted until the associated input quill assembly repair and replacement activities are complete. The latest order will further ensure the safety of the aircrew.

Input quill assembly is a crucial element of proprotor gearbox, which carries the aircraft clutch.

According to NAVAIR, the hard clutch engagement issue is primarily due to the sudden reengagement of clutch, driven by the engine, which sends an impulse via the drive train after being released from the rotor system, resulting in potential damage.

The fleet bulletin allows the service to identify aircraft with input quill assemblies over a pre-determined flight hour threshold to eventually replace the damaged component.

NAVAIR said that the services have not released the specific input quill assembly flight-hour threshold as well as the number of affected aircraft due to different operational security reasons.

As soon as the replacement work is complete, the aircraft will resume its flight operations.

Meanwhile, the V-22 joint programme office is currently exploring around 24 initiatives as part of the ‘analyse, identify, mitigate, eliminate’ efforts.

The latest announcement to improve V-22’s safety is also a result of these efforts.