Programme officials rush to fix bearing fault in proprotor gearbox caused by flaking chrome

A critical operational evaluation (Opeval) starting in March for the Bell Boeing V-22 Osprey tiltrotor could be delayed by a new glitch found in a component inside the aircraft's proprotor gearbox. Programme officials are rushing to design a fix and install it on the test fleet to allow the tiltrotor's final evaluation phase to begin on schedule.

The glitch is caused by faulty chrome plating on ball bearings in a gearbox component called a quill, which is the initial point at which the engine transmits power to the rotor system. The "thin-dense" chrome material is flaking off the ball bearings, injecting tiny metal chips into the oil flow. This triggers a warning light in the cockpit, forcing the crew to abandon a test mission and land quickly.

Officials believe the flaking problem is not a safety of flight issue, and no aircraft have been grounded. However, the glitch still requires precautionary landings after warning lights appear, which could disrupt the Opeval flight schedule. The Bell Boeing team has a "very aggressive" schedule in place to resolve the issue before the Opeval phase starts, says Bob Ellithorpe, Bell's executive director of the V-22 programme. Programme officials are working with suppliers to design an acceptable thin-dense chrome plating for the quill ball bearings, which will then have to be manufactured and installed on the V-22 Opeval fleet of eight aircraft.

The Opeval is the final series of tests before the V-22 programme can enter full-rate production. The evaluation begins with a four-week training period. Six aircraft will then be deployed to a base in Yuma, Arizona for analysis of assault support capability and operational tactics. This will be followed by three weeks at China Lake, California for survivability tests and tactics development, while a one-week environmental assessment is also conducted in Bridgeport, Connecticut. Finally, all eight aircraft will be undergo shipboard compatibility testing.


Source: Flight International