Osprey Crash Report: Structural Defects Are Evident

The Osprey's structural flaws are evident. The defective aircraft should be withdrawn and retired from military service, in order to protect the lives of crew members and residents living near the flight paths.

The U.S. Air Force has released the accident investigation report stemming from last November's CV-22 Osprey crash off the coast of Kagoshima Prefecture's Yakushima Island, which killed all eight crew members.

The cause of the crash was a broken gear in a “prop-rotor gearbox” on the left side of the fuselage, and fragments from the broken gear wore down another gear, impeding transmission of power to the rotor.

Furthermore, the report also pointed out that the pilot who continued flying despite the fact that an alarm indicating the condition of the gearbox had been triggered multiple times made an error in judgment.

The report concluded that the two main causes of the crash were the fractured gear in the gearbox and pilot error, but the more serious problem is the broken gear. Previous discussion about the defective gearbox pointed to structural problems.

A U.S. Marine Corps investigation into an Osprey crash in June 2022 in southern California that killed five people concluded that a “catastrophic, unpreventable and unanticipated” mechanical failure occurred due to a malfunctioning clutch in the gearbox. This MV-22 was the same type of aircraft used at the Futenma Air Base.

We can’t overlook the fact that a specific root cause for the broken gear in this latest crash has not been identified. As long as the cause of the gear fracture is unknown, then the crash essentially unexplained, and a nother similar crash is still possible.. Normally, flights would not be permitted.

In addition to the fractured gear, pilot error identified in the report is also extremely serious.

Before the plane that crashed took off from the Iwakuni Air Base in Yamaguchi Prefecture, an alarm sounded five times warning of metal fragments in the gearbox. By regulation, if the alarm goes off three times, the pilot should immediately land the plane, yet the pilot proceeded. Fifty minutes passed between the first warning and the crash, during which time an emergency landing was possible on certain islands. Yet, there was no evidence the crew considered landing.

This error in judgment is baffling. Disregarding an alarm like this would be unthinkable in a private aircraft, so we can only surmise that the crew was not aware of any crisis. It is likely indicative of inconsistent troop training and deficient safety measures for the Osprey across the entire military. This is also a problem that must be explained.

The Japanese government's approval of Osprey flights is also questionable. In an interview on Aug. 2, Japanese Chief Cabinet Secretary Yoshimasa Hayashi said, “it is possible to prevent similar accidents by taking various safety measures in response to the causes,” but this perception is too naive. If there are doubts about the cause of the accident or measures to prevent it from happening again, the U.S. should be required to once again suspend the flights.