NAHA, Japan — The U.S. military has concluded pilot error caused one of its Osprey aircraft to crash-land in waters off Okinawa last December, while denying any mechanical malfunction in the aircraft itself, the Japanese government said Monday.
The findings were announced as safety concerns over the aircraft remain strong in the southern island prefecture where the bulk of U.S. military facilities in the country are based. In August alone, one Osprey crashed off Australia, resulting in the death of three U.S. Marines, while another made an emergency landing at a commercial airport in Oita Prefecture, southwestern Japan.
In the final report on the Dec. 13 crash-landing, which was 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 that the MV-22 Osprey “made an intentional water landing under controlled, powered flight.”
Okinawa Deputy Gov. Moritake Tomikawa visited Camp Foster in the prefecture on Monday to hear the outcome of the investigation report from Lt. Gen. Lawrence Nicholson, the top commander of U.S. forces in Okinawa.
Tomikawa said after the talks that he urged Nicholson to offer a “convincing” explanation to the people of Okinawa on the safety of the aircraft, such as by referring to data on accident rates.
According to the report, the accident occurred during a nighttime refueling drill, with the Osprey’s propeller hitting a hose extended from an Air Force MC-130 refueling plane in the air, about 15 kilometers southeast of an airport on Yoron Island, Kagoshima Prefecture.
The right propeller struck the refueling line at 9:18 p.m. as the pilot increased the engine output too much. The pilot immediately removed the power input, but 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 continue to 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, with two of the five crew members injured.
The report noted that the U.S. military had initially judged flight risks to be “low” on the day, while the refueling exercise was conducted in difficult weather conditions.
Even before the accident, Ospreys, which take off and land like helicopters but cruise like planes, were already unpopular in Okinawa due to their noise and record of accidents overseas.
The U.S. military has deployed more than 20 of the MV-22s at the U.S. Marine Corps Air Station Futenma in Okinawa.