Photo/Illutration A Maritime Self-Defense Force SH-60K patrol helicopter (Asahi Shimbun file photo)

Two Maritime Self-Defense Force helicopters that crashed over the Pacific Ocean in April likely collided on their way to the site of a surprise training drill after being scrambled, Defense Ministry sources said.

The SH-60K patrol helicopters crashed east of the Izu island chain, south of Tokyo, during nighttime training to detect and track a submarine around 10:38 p.m. on April 20.

One crew member was killed, while the other seven remain missing.

The commander of the MSDF Fleet Escort Force was inspecting the training to assess the proficiency of Escort Flotilla Four, which is based in Kure, Hiroshima Prefecture.

Three helicopters took off from the destroyers where they were based to participate in the anti-submarine training, which was held without advance notice.

An MSDF investigation determined that the two aircraft collided mid-flight en route to the training site, the sources said.

The Defense Ministry suspects that they were not fully aware of each other’s proximity, the sources said.

“When an anti-submarine warfare scenario is presented out of the blue, both the vessels and helicopters spring into action with a frenzy of activity,” a source said. “We have found little evidence that the two aircraft attempted to avoid a collision.”

The exercise was conducted based on a scenario that a transport vessel had been torpedoed by an enemy submarine.

The helicopters were expected to rush to the sea area where the submarine was navigating and deploy dipping sonar systems to identify the vessel’s location.

At the time of the accident, the two helicopters were not connected to a communications system that allows aircraft to share their locations and the information they obtained.

But a senior ministry official said that the lack of a connection was not directly responsible for the accident.

“The system only plays a supplementary role as a safety measure,” the official said. “First and foremost, confirmation should be made visually and by radar.”

The Defense Ministry plans to replace Rear Adm. Makoto Nakaoji, commander of Escort Flotilla Four, in early June, at the earliest, sources said.

Nakaoji is expected to exclusively participate in the investigation into the accident and handle issues related to the families of the crew members, both deceased and missing, the sources said.

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