Report: Insufficient Sonar Analysis Behind 2021 Msdf Submarine Collision
Japan's transport investigators say the accident of a Maritime Self-Defense Force submarine colliding with a commercial vessel in February last year was caused by the sub failing to detect the vessel with its sonar.
The Japan Transport Safety Board released the results of its probe into the accident on Thursday.
The accident involving the MSDF sub Soryu occurred off the coast of Kochi Prefecture, western Japan. It collided with a cargo vessel as it was surfacing. Three of the sub's crew suffered minor injuries.
The report says the analysis of sonar data by the submarine crew was insufficient, which determined there was no surface vessel nearby when it was ascending.
The report also says the sub's crew recognized a container vessel, but failed to spot the cargo ship positioned in the same direction as the container vessel.
It also says the sonar crew noticed a change in the sonar data, which should have provided them with information to spot the cargo ship, but the crew did not report it to the captain.
To prevent a recurrence, investigators are calling on the MSDF to establish a system where multiple crew members reexamine all data gathered using sonar and other measures.
The board also says the MSDF should conduct training based on the lessons learned from the accident.