NAHA, OKINAWA PREF. – The United States military has concluded that pilot error led one of its Ospreys to ditch off Okinawa Prefecture last December and denied that mechanical problems had anything to do with the accident, the Japanese government said Monday.
The finding was part of a final report released after a series of accidents involving the tilt-rotor MV-22 in Japan and abroad that stirred safety concerns in Okinawa, which hosts the bulk of U.S. military facilities in Japan.
In its final report on the Dec. 13 accident, the first major accident involving the aircraft in Japan, the U.S. military said, “There were no indications that a mechanical malfunction or maintenance malpractice were contributing factors to this mishap.”
The report also said the MV-22 Osprey “made an intentional water landing under controlled, powered flight.”
Okinawa Deputy Gov. Moritake Tomikawa visited Camp Foster on Monday to hear the outcome of the investigation directly from Lt. Gen. Lawrence Nicholson, top commander of U.S. forces in Okinawa.
Tomikawa urged Nicholson during their talks to give the people of Okinawa a “convincing” explanation about the safety of the MV-22 Osprey, such as by citing data on its accident rates.
According to the report, the accident occurred during a nighttime refueling drill when the Osprey’s right rotor hit a fuel hose extended by a U.S. Air Force MC-130 refueling plane about 15 km southeast of the airport on Yoron Island, Kagoshima Prefecture.
The rotor struck the refueling line at 9:18 p.m. because the pilot increased the engine output too much. The pilot immediately removed the power input, but found it was difficult “to maintain balanced flight due to high vibrations,” the report said.
Upon reaching Okinawa, the Osprey “followed the coastline in order to avoid flying over people and property,” but the crew found it difficult to maintain altitude and fly the aircraft safely, leading them to execute an emergency water landing at 9:29 p.m., it said.
The aircraft broke apart as it landed in shallow waters off the coast of Nago on Okinawa’s main island, and two of the five crew members were injured.
The report noted that the U.S. military had initially judged flight risks to be low on the day, though the refueling exercise itself was conducted in difficult weather conditions.
Even before the Dec. 13 accident, Ospreys, which usually take off and land like helicopters but cruise like standard planes, were already unpopular in Okinawa because of their noise and record of fatal accidents overseas.
The U.S. military has deployed more than 20 MV-22s at U.S. Marine Corps Air Station Futenma in Okinawa.
In August, three U.S. Marines were killed when an Osprey crashed off Australia during training. Another Osprey made an emergency landing at a commercial airport in Oita Prefecture the same month after experiencing engine trouble.