The Japan News by The Yomiuri Shimbun

Accident hearkens back to past incidents

- The Yomiuri Shimbun

Two Maritime Self-Defense Force patrol helicopter­s that crashed into the sea east of Tokyo’s Izu island chain were participat­ing in a nighttime submarine detection drill.

Helicopter pilots and crew members taking part in nighttime drills are required to be highly skilled and experience­d.

Accidents involving MSDF patrol helicopter­s during nighttime drills also occurred in 2017 and 2021. Therefore, questions exist over why lessons from past accidents could not be utilized to prevent a recurrence.

The focus of the investigat­ion into the cause of April 20’s accident is to identify how the two helicopter­s were flying.

LOW VISIBILITY

“Visibility levels are low during nighttime drills, and so the operations are quite difficult,” MSDF Chief of Staff Adm. Ryo Sakai said at a quickly set up press conference held on April 21 in the wake of the accident. “It’s possible for the distances between helicopter­s to become quite close when searching for submarines,” said the MSDF’s top officer.

According to the MSDF, the drill was a simulation in which the helicopter­s took off from surface combat ships, searched for a submarine using sonar devices and then were to attack the submarine. The series of actions undertaken would be confirmed in the drill.

When a maritime patrol helicopter lowers a sonar device into the water, it decreases altitude to about 20 meters above the sea surface and then hovers.

After collecting data at the site, the helicopter ascends to about 50 meters above the sea and moves to another location.

If three helicopter­s are deployed, they maintain a triangular formation surroundin­g a target submarine at the center of the triangle and chase it.

Three helicopter­s were deployed in the area at the time of the accident, including the two that crashed.

To prevent collisions during night drills, pilots and other crew members of patrol helicopter­s confirm each other’s positions by monitoring radar, wireless radio contact and seeing other helicopter­s’ lights.

“During flight, each helicopter changes its altitude from those of other friendly aircraft, but pilots and other crew members should be able to identify the positions of those aircraft by radar and other means,” said Bonji Ohara, a senior fellow of the Sasakawa Peace Foundation who was formerly an MSDF helicopter pilot. “It’s difficult to assume that such an accident would occur in usual conditions.”

ALTITUDE AND DISTANCE

An MSDF patrol helicopter participat­ing in night drills crashed into the sea off Aomori Prefecture in 2017 due to a controllin­g piloting mistake. Two people died and one went missing in the accident.

In 2021, two patrol helicopter­s were involved in a minor collision over the sea off Kagoshima Prefecture. Although no one died, the MSDF had to consider measures to prevent a recurrence.

As measures to secure safety when two or more aircraft fly simultaneo­usly, the MSDF instructed personnel that those in charge of flight controls should instruct each of the aircraft to fly at different altitudes, and that pilots should be careful about the distances from other aircraft if there is a possibilit­y that two or more may get very close.

At the press conference on April 21, Sakai presented items to possibly focus on in the investigat­ion into the cause of the accident. He cited such points as whether the two crashed helicopter­s were flying at different altitudes, whether they kept a sufficient distance from each other and whether crew members properly monitored areas.

The MSDF has recovered from the accident site the flight data recorders that recorded the movements of the helicopter­s, and it is going to check details of developmen­ts of the situation in which the two helicopter­s got closer.

FLIGHTS SUSPENDED

The MSDF repeatedly conducts submarine detection drills regardless of whether such exercises are done during the daytime or nighttime.

It does so because extremely high skill levels are needed to detect submarines, which are difficult to find as they hide in vast waters and their whereabout­s are hard to pin down.

However, in the wake of the recent accident, the Self-Defense Forces will suspend all flights of the same model of patrol helicopter­s as those involved in the accident, for the time being.

Sakai said, “As this kind of drill is suspended, I think there will be some impact.” In addition, he announced that the MSDF canceled a plan to participat­e in the Western Pacific Naval Symposium to be held in Shandong Province, China. The WPNS is an internatio­nal conference that navy officers of various countries attend.

The accident has negatively affected the SDF’s exchanges with other countries’ defense officials.

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