The commander of the Marine Corps’ MV-22 Osprey test squadron has canceled all flight operations due to recurring problems with a key gearbox component.
In recent months, four of the service’s 14 tilt-rotor aircraft were forced to land when a warning light indicated that metal shavings were running through lubricant in the system that drives the aircraft’s powerful rotors.
The excess metal shavings stemmed from faulty manufacturing of bearings in the “input quill” — the junction between the engine drive shaft and the gearbox — though officials say the problem could not have caused the aircraft to crash.
The commander of Marine Tiltrotor Test and Evaluation Squadron 22, Col. Glenn Walters, ordered the “operational pause” Jan. 13 to allow engineers at Patuxent River Naval Air Station, Md., to develop a fix. A limited stock of spare gearbox parts and an already packed schedule of aircraft modifications to prepare the fleet for operational evaluation tests this spring prompted the flight cancellation.
“So I said, ‘Let’s give them time to fix this problem and in the meantime, while we’re down, we’ll turn to and do all the aircraft mods that we’re going to have to do before the start of [operational evaluation],’” Walters said in a Jan. 19 telephone interview from the squadron’s headquarters at Marine Corps Air Station New River, N.C.
The squadron was due to begin operational evaluation in late February or early March, the final exam before the Osprey is formally declared fleet ready and deploys for the first time for real-world operations in 2007. This latest snag could delay the start of the tests, officials said.
“We will not begin OpEval until this problem is resolved,” said Ward Carroll, a program spokesman at Patuxent River.
Program officials say bearings were manufactured with too much chrome coating; that extra metal — about .003 inches — was shaving off during flight. In each instance, detectors identified the metal shavings — a potential indicator of more catastrophic problems — forcing a landing as soon as possible each time.
Walters said program engineers were to brief him on potential fixes Jan. 21 and he hoped to restart flight operations soon after.
It is unclear how many Ospreys contain the faulty bearings, Carroll said, and all Ospreys are being checked for the problem, including those still at the Bell-Boeing plant in Amarillo, Texas.
Testing has been relatively smooth since officials gave the Osprey the go-ahead to resume flights in May 2002 after a grounding of nearly 18 months, but manufacturing flaws in the tilt-rotor transport’s delicate parts have been discovered.
In March 2003, for example, the Navy grounded six Ospreys after testers discovered titanium hydraulic fluid tubes that were too thin. The problem was the result of poor manufacturing, so program officials changed tubing suppliers.
A December 2000 crash that killed four leathernecks near Marine Corps Air Station New River, N.C., was blamed on failed hydraulic lines in the Osprey’s engine. A wire bundle in the aircraft’s nacelle — the compartment at the end of each wing that houses the aircraft’s engine components — chafed the thin titanium tubing enough to cause the line to rupture, Marine investigators found. Engineering changes are being made to existing and future MV-22s to avoid such problems.
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