Gearbox caused deadly 2023 Osprey crash in Japan, US Air Force says

A major gearbox failure caused the crash of a US military Osprey aircraft off the coast of Japan last year that killed eight airmen, the US Air Force said, a cause similar to some previous incidents with the tilt-rotor aircraft.

An investigation by the US Air Force, released Thursday, said the crash was caused by a “catastrophic” failure of the left-hand gearbox that destabilised the aircraft. The report also said the pilots contributed to the disaster by failing to quickly divert to an emergency landing location.

The aircraft went down off of Japan’s southwest island of Yakushima on November 29, prompting the Pentagon to ground its fleet of Ospreys. Japan, the only other country to fly the aircraft, also paused its use. Both nations have since resumed flights.

After multiple cockpit warnings, the pilots attempted to land at Yakushima Airport, but on the approach, the mechanical failure sent the Osprey into a roll around 800 feet (245 metres) above the ground, according to the report.

All the crew members sustained fatal injuries upon impact, the investigation assessed.

The incident also stirred long-running concerns among the public in Japan about the use of Osprey aircraft. The CV-22 aircraft involved in the crash last year was on a routine training mission before it went down.

Gearbox problems have triggered problems with the Osprey in the past, including two emergency landings in 2022. Since 1992, 11 crashes of the aircraft have killed more than 60 US service members and other passengers.

The Osprey, a workhorse of the US military to move troops and supplies, has two propeller engines on its wings that can be tilted to make it fly like a helicopter. The design allows it to land in tight spaces.

The aircraft is made by a unit