British Royal Navy sub in near-miss with passenger ferry

A British nuclear-powered submarine narrowly avoided crashing into a passenger ferry between Northern Ireland and Scotland, with disaster averted only because an officer spotted its periscope, a report revealed Thursday.

The government's Marine Accident Investigations Branch called for an independent review into the incident on November 6, 2018, saying it was the third such near-miss involving a Royal Navy sub in four years.

The Stena Superfast VII ferry, carrying 215 passengers and 67 crew, was travelling between Belfast and Cairnryan on the west coast of Scotland when a lookout spotted the submarine's periscope close by. "The officer of the watch then took immediate and effective action, turning the ferry to avoid a genuine risk of collision with a submerged submarine," said the chief inspector of marine accidents, Andrew Moll.

The submarine, from the Faslane naval base west of Glasgow, was conducting pre-deployment safety training at the time, and detected and tracked the ferry including with sonar data. But its crew miscalculated how close it was and instead of turning away from the ferry, turned towards it and at one point it passed just 250 yards (metres) away.

"The incident happened because the submarine's control room team had underestimated the ferry's speed and overestimated its range, resulting in safety-critical decisions being made based on inaccurate information," Moll said in a statement. "Although there was no collision, this was the third accident or incident between a dived Royal Navy submarine and a surface vessel in four years, which is a matter of significant concern."

He said the Royal Navy had taken actions to prevent a recurrence but said it should conduct an independent review to ensure the risk of similar near-misses was reduced as much as possible. Further details about the sub were not given in the report for security reasons.