The UK Marine Accident Investigation Branch (MAIB) has confirmed that the 200-m long, 30,235 gt passenger ferry Stena Superfast VII and a UK Royal Navy (RN) nuclear-powered submarine narrowly avoided collision in the Irish Sea in November 2018.
Following the incident, the master of the ferry notified the coastguard that a submarine’s periscope had passed down the starboard side of the vessel at a range of 50–100 m.
MAIB investigators found that the submarine, which was patrolling an area south of the ferry route between Belfast, Northern Ireland, and Cairnryan, Scotland, did in fact sail within that range of the vessel putting the lives of the 215 Stena passengers and 67 submarine crew in ‘immediate danger’.
According to the MAIB report, upon detecting the ferry visually, the submarine’s control room team estimated it to be at a range of 8–9 km. They also grossly underestimated the ferry’s speed, estimating it to be 15 kt. This means that the officer of the watch (OOW) assumed that it would take the ferry 12 minutes to travel 5 km. However, the ferry’s actual speed was 21 kt, meaning that it would cover 5 km in 8 minutes and 34 seconds.
Therefore, the submarine’s OOW believed he had more time to move out of the path of the ferry. The collision was only avoided when the submarine’s OOW took immediate action to turn the vessel and avoid collision, the report confirmed.
The report stated, “This combination meant the submarine’s commanding officer and its OOW made safety-critical decisions that might have appeared rational to them at the time but were actually based on inaccurate information.”
This incident was the third near-miss in four years involving a UK RN submarine and surface vessel, sparking the MAIB to call for an independent review to be conducted by the UK Navy to ensure that the risk of similar collisions is reduced to as low as possible. The UK Department for Transport also echoed that the repetition of similar incidents is “a matter of significant concern”.
Numerous key safety issues were identified in the MAIB report, including inadequate passage planning and identification of potential hazards.