Japan has sent its own assessment team to check out the V-22 Osprey in advance of the U.S. Marine Corps going operational with the tiltrotor in the Asian country.

“They sent an assessment team over here and they went through the simulators and they flew in the V-22,” says Lt. Gen. Robert E. Schmidle Jr., deputy commandant for Marine Corps aviation.

The Japanese have been wary of the Osprey deployment there given recent high-profile crashes with the aircraft, including an April 11 accident that killed two Marines. Schmidle says he briefed the Japanese assessment team members on the results of the Corps’ investigation of that fatal crash.

The investigation determined that the aircraft did not suffer from any mechanical or material failures and that there were no issues with the safety of the aircraft, Schmidle told reporters at the Pentagon last week.

Instead, Schmidle says, there was a series of events that led to the crash. “This aircraft was flying from an airfield in Morocco [Africa] and transporting Marines to the landing zone,” he told reporters.

“The wind [was] blowing into the face of the airplane. It lifts off the deck and normally we would depart into the wind, but there were people and vehicles and structures in the landing zone. So the pilots made a decision to turn and take off with a tail wind so that they wouldn’t endanger any of the folks that were in the rest of the landing zone. The aircraft lifted to a hover about 25 ft. above the ground and the pilot pedal-turned the Osprey so that the wind was going to be behind the aircraft.

“The wind is at his tail,” Schmidle says. “He now begins to rotate the nacelle. As he rolls the nacelles forward, [the Osprey] begins to pitch forward. The wind catches the tail, exacerbates the motion and pitches the nose down.”

At the same time, Schmidle says, “The control stick doesn’t have enough movement at this point to move the horizontal stabilizer on the tail up enough to get the nose position to come up. The aircraft now is committed and it flies into the ground.”

If “instead of moving the nacelles down quickly, they’d left them up until they had enough forward speed to ... override the tail wind, and then [they could have] flown the airplane away,” he says. “Unfortunately, the pilots didn’t recognize that at the time.”

He says, “It’s an extraordinarily complex set of circumstances that caused this to happen. And it could be something that might depend on how quickly you move the nacelle. The wind was gusting that day. It was gusting between 15 and 27 knots. It’s a pretty big span of wind. And 20, 25 knots of wind is a pretty significant. It’s a pretty strong wind.”

There are some limitations to the aircraft, he says, “to the speed with which you can move the nacelles or to the angle that you can move them depending on the air speed. In this particular case, this is in an area where the rate at which the nacelles can move is slowed down considerably, but it is ... not an area that currently precludes you from being able to move them at all. You just have to move them more slowly.”

The Marine Corps is looking to change the way it teaches its pilots and uses simulators to avoid similar crashes in the future.

While the Corps want to emphasize the aircraft’s safety as it deploys Ospreys to Japan, Schmidle says the bigger issue is protecting Marines.