Significant concerns as nuclear sub and ferry nearly collide

The Marine Accident Investigation Branch (MAIB) has released its report into the near collision of Stena Superfast VII and a Royal Navy submarine.

A statement from the Chief Inspector of Marine Accidents calls the incident a “matter of serious concern”, as it was the third accident or incident between a dived Royal Navy submarine and a surface vessel in four years.

The report says the vessels came within 50-100m of one another in the North Channel, as the submarine underestimated the ferry’s speed.

The Stena Superfast VII ferry, travelling from Belfast to Cairnryan, spotted the periscope and turned to avoid a collision.

It happened in November 2018 with 215 passengers and 67 crew on board the ferry.

The Royal Navy submarine, based in Faslane, had been patrolling an area south of the ferry route.

The investigation found the near miss happened because the submarine’s control room team had underestimated the ferry’s speed and overestimated its range, resulting in an unsafe situation developing, says the report. However, the submarine’s control room electronic tactical display presented a picture of a safer situation than reality; this meant that safety-critical decisions made on board the submarine may have appeared rational at the time.

When the submarine’s control room team initially detected the ferry visually, they estimated it to be at a range of 9,000-10,000 yards.

At a speed of 21 knots, Stena Superfast VII would cover 6,000 yards in eight minutes and 34 seconds, which was an estimate of the time available for the submarine’s officer of the watch (OOW) to take avoiding action.

However, the report found the OOW had estimated the ferry’s speed as 15 knots, so would have “incorrectly calculated” it would take the ferry 12 minutes to travel 6,000 yards and “almost certainly assessed that there was significantly more time to take avoiding action than was actually the case”.

A number of key safety issues were identified in the report such as passage planning and identifying potential hazards.

“The Royal Navy co-operated with the MAIB’s investigation into this near miss and has taken a series of actions, intended to prevent recurrence, in response to this, and the other similar incidents. However, I have today recommended that the Royal Navy undertakes an independent review of the actions that have been taken, in order to ensure that the risk of similar collisions has been reduced to as low as possible,” says the chief inspector.