Passengers were put in “instant threat” when a nuclear-driven submarine and a ferry practically collided off Scotland’s west coast.

The Maritime Accident Investigation Branch (MAIB) claimed the vessels came within just 50-100m of one particular another in the North Channel.

Investigators discovered the submarine underestimated the ferry’s pace.

The Stena Superfast VII ferry, travelling from Belfast to Cairnryan, turned to keep away from a collision.

It took place in November 2018 and was the third around-overlook in four several years involving a Royal Navy submarine and surface vessel.

There had been 215 passengers and 67 crew on board the ferry when the lookout spotted a submarine’s periscope near ahead.

The officer on view had to take speedy action to switch the vessel and steer clear of collision, the report stated.

• Nuclear submarine’s in close proximity to miss with ferry

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

The investigation discovered the submarine’s command space crew underestimated the ferry’s speed and overestimated its range which led to the unsafe condition.

“This mix meant that the submarine’s commanding officer and its officer of the watch produced protection-significant selections that might have appeared rational to them at the time but were being basically primarily based on inaccurate information,” the report concluded.

When the submarine’s handle room staff originally detected the ferry visually, they believed it to be at a selection of 9,000-10,000 yards.

‘Misjudged timing’

At a pace of 21 knots, Stena Superfast VII would include 6,000 yards in 8 minutes and 34 seconds, which was an estimate of the time offered for the submarine’s officer of the watch (OOW) to choose staying away from motion.

Nonetheless, the report found the OOW had believed the ferry’s speed as 15 knots, so would have “improperly calculated” it would take the ferry 12 minutes to journey 6,000 yards and “practically certainly assessed that there was significantly much more time to just take preventing motion than was really the case”.

A range of key basic safety problems were discovered in the report these kinds of as passage arranging and figuring out probable dangers.

Andrew Moll, Chief Inspector of Maritime Accidents, mentioned the Royal Navy had co-operated with the investigation and taken a sequence of steps to prevent a recurrence.

Nonetheless, he included: “I have currently suggested that the Royal Navy undertakes an independent critique of the actions that have been taken, in order to ensure that the possibility of related collisions has been decreased to as minimal as achievable.”