A retrofit effort to return an undisclosed number of grounded Bell-Boeing V-22 Ospreys to flight is over halfway complete, but the root cause of a so-called “hard clutch engagement” (HCE) issue remains elusive. In February, the Pentagon barred an unclear number of tiltrotors from flying until each were able to replace their input quill assembly (IQA).
Replacing the IQA mitigates the issue with the aircraft’s clutch, where power can rapidly shift between the tiltrotor’s two engines and force aircrews to land immediately if the clutch slips. Boeing’s vice president for tiltrotor programs Shane Openshaw said the process of putting the appropriate fix onto the effected aircraft within the fleet is well underway and the customer is satisfied with the progress that’s being made. The V-22 program is replacing all the input quills that are in excess of that time, but the root cause of what's wearing out the quill assembly is still not fully understood.
Besides the IQA replacements, the program is pursuing other mitigation efforts, such as a $13 million contract to design a new IQA along with the refreshed clutch, and a $54 million contract to design a new system that will alert the ground crew of abnormal vibrations in the drive system and enable condition-based maintenance. The Air Force, Marines, and Navy each fly variants of the Osprey, as well as the Japanese military.
In March, a US official told media that the Japanese Ospreys are young enough that they have not needed to be retrofitted with the new parts, but acknowledged that they may need the fix in the future. The V-22's "subtle" differences mainly materialize in different mission equipment for the Air Force, with the Navy's variant focused mainly on range and fuel capacity. Japan's variants feature a specialized communications package.