HMS Affray

1951

English Channel, the snort mast, seventy-five Location: English Channel, off Start Point, Devon · Coordinates: 50.12°N 3.60°W · Casualties: 75 · Survivors: 0 · Depth: 85 m · Cause: flooded · mechanical failure — Failed to surface from an exercise dive on the night of 16 April 1951. Located on the seabed at 85 metres on 14 June after two months of Royal Navy search. The most probable cause, based on the position of her snort mast, was a structural failure of the mast itself that flooded the boat while submerged. · Fate: war grave · protected · Type: submarine · A class · Tonnage: 1,120 tons · Crew: 75 · Flag: United Kingdom · Launched: 1945 Royal Navy A-class submarine, on a training exercise out of Portsmouth. Failed to surface from a dive on the night of 16 April 1951 somewhere between Start Point and the Channel Islands. Seventy-five dead, no survivors. Located two months later on the continental shelf at 85 metres; the probable cause was a structural failure of the snort mast that flooded her while submerged. The Vessel HMS Affray (P421) was a British A-class submarine of the Royal Navy, commissioned at the Cammell Laird yard at Birkenhead on 25 November 1945. She was 87 metres long, 1,120 tons surfaced displacement, 1,620 tons submerged, armed with ten 21-inch torpedo tubes (six forward, four aft) and a single 4-inch gun. Her designed operational depth was 150 metres; her test depth was 180 metres. The A-class was the Royal Navy's last generation of conventional diesel-electric submarine built during the Second World War, commissioned between 1945 and 1948. Sixteen A-class submarines were built at various British yards; Affray was the eighth of the class. Her peacetime service had been primarily in the Mediterranean Fleet and the Home Fleet, with periodic operational deployments through the late 1940s. By 1951 she had been in Royal Navy service for five and a half years. She had recently completed a refit at HM Dockyard Portsmouth that had modernised her electrical switchboard, replaced some of her older Vickers electrical components, and upgraded her snorkel system (an equipment that allowed her to run her diesel engines at periscope depth rather than on the surface). Her commanding officer from January 1951 was Lieutenant John Blackburn, 27 years old, a career Royal Navy submarine officer on his first submarine command. The Disaster At 12:00 on 17 April 1951 HMS Affray did not surface as scheduled. The Portsmouth submarine command initiated the standard overdue-submarine alert at 12:30 on 17 April. The Royal Navy's subsequent search operation was one of the most extensive peacetime submarine searches ever mounted. Over 50 surface ships, 4 submarines, and continuous RAF Coastal Command maritime patrol aircraft operations searched the Affray's expected operating area for 60 days between 17 April and 14 June 1951. HMS Affray was located on 14 June 1951 by the submarine search vessel HMS Loch Fada using an experimental Type 193 sonar that the Royal Navy had been developing specifically for submarine-location operations. Her wreck was found in 86 metres of water at approximately 50°17′N 2°17′W, on the continental shelf south of Dorset, on a relatively smooth sandy bottom. Subsequent investigation of the wreck, conducted by the recovery vessel HMS Reclaim using both surface-supplied diving and the newly-developed tethered remotely-operated underwater vehicle, identified the immediate cause of Affray's loss. Her snorkel mast, a 6-metre vertical pipe that allowed air intake when she operated at periscope depth, had failed structurally at the base. The failure had admitted the sea into the submarine's upper ventilation system, which then flooded through the open ventilation valve of the control room. The flooding had occurred rapidly; the crew had no time to reach their escape positions. 75 of Affray's 75 crew an