Ospreys had safety issues long before they were grounded. A look at the aircraft's history

abcnews.go.com:

When the U.S. military took the extraordinary step of grounding its fleet of V-22 Ospreys this week, it wasn't reacting just to the recent deadly crash of the aircraft off the coast of Japan

WASHINGTON — When the U.S. military took the extraordinary step of grounding its entire fleet of V-22 Ospreys this week, it wasn’t reacting just to the recent deadly crash of the aircraft off the coast of Japan. The aircraft has had a long list of problems in its short history.

The Osprey takes off and lands like a helicopter but can tilt its propellers horizontally to fly like an airplane. That unique and complex design has allowed the Osprey to speed troops to the battlefield. The U.S. Marine Corps, which operates the vast majority of the Ospreys in service, calls it a “game-changing assault support platform."

But on Wednesday, the Air Force, Navy and Marine Corps grounded all Ospreys after a preliminary investigation of last week’s crash indicated that a materiel failure — that something went wrong with the aircraft — and not a mistake by the crew led to the deaths.

And it's not the first time. There have been persistent questions about a mechanical problem with the clutch that has troubled the program for more than a decade. There also have been questions as to whether all parts of the Osprey have been manufactured according to safety specifications and, as those parts age, whether they remain strong enough to withstand the significant forces created by the Osprey's unique structure and dynamics of tiltrotor flight.

The government of Japan, which is the only international partner flying the Osprey, had already grounded its aircraft after the Nov. 29 crash, which killed all eight Air Force Special Operations Command service