Photo/Illutration An SH60K patrol helicopter on the Maritime Self-Defense Force’s Izumo destroyer off Darwin, Australia, on Aug. 15, 2023 (Asahi Shimbun file photo)

An airborne system to prevent mid-air collisions apparently malfunctioned, leading to the crash of two Maritime Self-Defense Force helicopters operating over the Pacific Ocean, according to government sources.

The SH-60K patrol helicopters apparently collided off the Izu island chain, south of Tokyo, during late-night anti-submarine training on April 20.

Four crew members were aboard each helicopter. One member was recovered in the search operation and confirmed dead, and seven others remain missing.

The two helicopters were equipped with an airborne collision avoidance system that shares their positions and issues warnings when they get too close to other aircraft.

Investigators so far have not found any records of the collision avoidance alarm being activated on either helicopter, leading them to suspect a malfunction in the system's communication between the aircraft.

This type of position-sharing system is often used in anti-submarine warfare maneuvers as it also allows aircraft to share the data on detected targets.

The MSDF is continuing to analyze the recovered flight data recorders and communication records from the other aircraft and vessels involved in the training.

(This article was written by Daisuke Yajima and Nen Satomi.)

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