Japan grounds its V-22 Osprey fleet again

Japan has grounded its fleet of V-22 Osprey aircraft again after an incident where one of the hybrid helicopter-aircraft tilted unexpectedly and hit the ground while trying to take off.

A week ago the V-22 was taking part in the joint US military exercise Keen Sword and carrying 16 passengers, including three US service members.

During takeoff it "became unstable as it swayed from side to side, and the left wing, the lower part of the aircraft came into contact with the ground and part of the aircraft was damaged, so the flight was aborted," Japan's Ground Self Defense Forces said in a statement on Sunday.

It was the first major incident for Japan's V-22 fleet since an Osprey crash off the Japanese coast last November killed eight Air Force Special Operations Command service members and led to a months long grounding of the entire fleet in both Japan and the US.

The aircraft resumed flight operations earlier this year, but the Osprey's use remains controversial particularly in Okinawa, where residents have questioned its safety record.

The Osprey in last Sunday's incident was able to land and no one was injured, however Japan will keep its fleet of more than a dozen V-22s grounded while it investigates the incident, Defence Minister General Nakatani told reporters last week.

"We believe there is no safety problem with Ospreys, although ensuring flight safety is a prerequisite for aircraft operations," Nakatani said.

The Pentagon's V-22 joint program office is supporting Japan's investigation into the incident, spokesman Neil Lobeda said on Saturday.

The V-22 was operating on the Japanese island of Yonaguni during the joint exercise Keen Sword. Yonaguni is only 100km east of Taiwan.