The United States military has grounded its worldwide fleet of V-22 Osprey aircraft after a crash off the coast of Japan last week that killed eight service personnel.
The US air force special operations command (AFSOC) said: “Preliminary investigation information indicates a potential materiel failure caused the mishap, but the underlying cause of the failure is unknown at this time.”
Japan, the only other country that uses the hybrid tilt-rotor aircraft, which can land and take off vertically and fly horizontally, suspended flights for its 14 Ospreys immediately after the crash.
Last week’s crash happened during a training flight off the island of Yakushima, about 1,000km (620 miles) southwest of Tokyo. Witnesses said that the aircraft had flipped over and was on fire before it fell into the ocean. The bodies of two of the eight people on board have yet to be recovered.
The Osprey was travelling between a US Marine Corps base on Honshu island and the Kadena air base on the island of Okinawa.
Tony Bauernfeind, commander of the AFSOC, said: “The honourable service of these eight airmen to this great nation will never be forgotten, as they are now among the giants who shape our history.”
Residents of Okinawa, which hosts most of the American military in Japan, have expressed opposition to the deployment of the aircraft on the island because of its safety record. The Japanese Self-Defence Forces deployed Osprey in the Okinawa islands for the first time in October, for joint drills with American troops, prompting a protest from the island’s governor.
More than 50 people have died in crashes involving Ospreys, which are developed by Boeing and Bell Helicopter. Four military personnel were killed in a crash in northern Norway last year, and three US Marines died and 20 more were injured in August this year in a
crash in northern Australia during a routine training exercise.
More than 400 of the aircraft are in service across the US air force, navy and Marine Corps.
The Osprey was the first tilt-rotor aircraft put into production. The aircraft have Rolls-Royce engines and can switch from vertical to horizontal flight in about 12 seconds.
The original development costs of $2.5 billion announced in 1986 had ballooned to about $30 billion two years later.
Minoru Kihara, the Japanese defence minister, said today that the country’s Ospreys would remain grounded until further notice, and that he expected the US to “share as much detailed information as possible” about the investigation into the aircraft.