The fatal V-22 Osprey crash in Japan in November 2023 was partly the result of a pilot’s poor instinct and decision-making, a US Air Force investigation has concluded.
The pilot, Maj. Jeff Hoernemann, reportedly decided to keep flying despite multiple cockpit warnings of a mechanical failure involving the aircraft’s proprotor gearbox.
The investigation said several cracks were found in the toothed piece called a pinion gear, which transmits the engine’s power to turn the Osprey’s masts and rotor blades.
The crew received the first “left-hand proprotor gearbox (PRGB) chip burn” warning as soon as they took off, but the pilot continued flying, as service regulations indicate they should land as soon as possible if they receive the warning three times during a flight.
The aircraft received at least five PRGB chip burn warnings before crashing, according to the report.
“The [crew] continued their planned mission with limited discussion of divert considerations or the changing dynamics of the situation. [They] never discussed or considered landing to rendezvous with G23,” it noted, referring to a maintenance crew.
‘A Causal Factor’
The American V-22 Osprey was participating in a military exercise off the coast of Japan when the incident happened, killing all eight crew on board.
They were just 10 miles (16 kilometers) from an airfield when the third warning occurred, telling the pilot to “land as soon as practical.”
However, Hoernemann and the crew tried to look for secondary indications of the problem but saw none. The pilot then directed his co-pilot to keep monitoring the situation while they continued with the 300-nautical-mile (345 miles/555 kilometers) flight.
“Decision-making was causal, prolonging the mishap sequence,” investigators said. But “it doesn’t mean blame. It doesn’t mean liability. It simply means that these were the circumstances that led and caused the incident.”
Lead investigator Lt. Gen. Michael Conley argued that Hoernemann was likely balancing split priorities in his decision-making, as he was leading the airborne portion of the military exercise and reportedly spent months planning for it.