Japan's defense minister has expressed concerns about the safety of Osprey tilt-rotor aircraft after a report blamed downwash for a crash off Australia that killed three last summer.
In a report dated March 21, investigators said the Aug. 5, 2017, incident was caused by a heavy downwash of air as the Osprey from Okinawa's Marine Medium Tiltrotor Squadron 265 attempted to land on the USS Green Bay.
"There will be a need to deal with the matter after obtaining the relevant information from the United States," Itsunori Onodera told reporters Tuesday, according to the Asahi newspaper.
The downwash was so heavy that the Osprey didn't have enough thrust to hold its hover and collided with the ship before falling into the sea, killing three and injuring 23, according to the report.
"The mission was complex, challenging, and included flying into and out of a highly congested operational area. Executing this mission required a detailed plan and superior technical performance," Maj. Gen. Thomas Weidley, 1st Marine Aircraft Wing commanding general, wrote in an endorsement of the report.
"The Marines manning the mishap aircraft were mission capable, fully-trained, and qualified. The mishap aircraft was mechanically sound," he said.
Naval Air Systems Command engineers have looked at the effects of downwash and the amount of power an Osprey needs to land safely. They have made adjustments to the amount of weight an Osprey can carry when it's approaching a ship at sea to make sure it has enough power to land, the U.S. Naval Institute reported Monday.
Twenty-four MV-22B Ospreys fly out of Marine Corps Air Station Futenma, Okinawa, and five CV-22 Ospreys -- part of a squadron that will grow to 10 aircraft -- began operating out of Yokota Air Base in western Tokyo last month.
The Japan Self-Defense Forces plan to acquire 17 of their own Ospreys this fiscal year.
Protesters have questioned the safety of the aircraft, which are capable of taking off like helicopters, then tilting their rotors to fly long distances as fixed-wing planes.
Officials blamed the December 2016 crash-landing of a Futenma-based Osprey off Okinawa on weather and human error.