U.S. Army, Japanese Forces Ground CV-22 Osprey Fleet After Precautionary Landing

The U.S. Army and the Japanese Ground Self-Defense Force (GSDF) temporarily grounded their Osprey transport aircraft this month following a precautionary landing by a U.S. Osprey in November.

According to the U.S. Naval Air Systems Command (NAVAIR), which is in charge of safety measures for Ospreys, an Air Force CV-22 Osprey made a precautionary landing in New Mexico on Nov. 20 this year.

The details about the landing are not known, but the grounding of the fleet raises concerns over the safety issues that have plagued the Osprey fleet, Japan Times reported.

Quoting sources in the Japanese and U.S. governments, the CV-22 Osprey may have experienced an issue with its propulsion system after the takeoff. U.S. media has cited the possibility of metal fatigue.

An official of the Air Force Special Operations Command was quoted as saying in the U.S. media that an initial investigation of the incident pointed to a possible flaw in the aircraft's equipment, suggesting that lessons from the November 2023 crash off Yakushima helped the CV-22 Osprey land safely in the New Mexico case.

Yakushima CV-22 Osprey crash

A CV-22 Osprey from the U.S. Air Force's Yokota Air Base in Tokyo crashed off the island of Yakushima in Kagoshima Prefecture in November 2023, killing all eight crew members. This was followed by more issues, such as a GSDF Osprey being damaged during takeoff in October this year.

In the crash off Yakushima last year, a gear transmitting power from the engine cracked and ruptured. Part of the debris then got stuck in another gear. The gear was worn out as a result, leading to the loss of power and the crash of the aircraft.

Rotor blades relatively short compared to aircraft weight

Referring to sources in the Japanese Self-Defense Forces, Japan Times said that the Ospreys have the functions of both helicopters and fixed-wing aircraft, but their rotor blades are short relative to their weight. This feature requires Ospreys to increase engine output during takeoff and landing.

This has raised concerns about rapid metal fatigue and abrasion due to a heavy burden on the power transmission system.

The U.S. side is considering additional safety measures after temporarily suspending flights of its Ospreys deployed at the Yokota base, the Marine Corps' Futenma air base in Okinawa Prefecture and the Iwakuni base in Yamaguchi Prefecture in stages from Dec. 6 following NAVAIR's recommendations.