The Castle-class corvette was a stretched version of the preceding Flower class, enlarged to improve seakeeping and to accommodate modern weapons. The ships displaced at standard load and at deep load. The ships had an overall length of, a beam of and a deep draught of. They were powered by two 4-cylinder triple-expansion steam engines, each driving one propeller shaft, using steam provided by two Admiralty three-drum boilers. The engines developed a total of and gave a maximum speed of. The Castles carried a maximum of of fuel oil that gave them a range of at. The ships' complement was 99 officers and ratings. The Castle-class ships were equipped with a single QF Mk XVI gun forward, but their primary weapon was their single three-barrel Squid anti-submarine mortar. This was backed up by one depth charge rail and two throwers for 15 depth charges. The ships were fitted with two twin and a pair of single mounts for Oerlikon light AA guns. Provision was made for a further four single mounts if needed. They were equipped with Type 145Q and Type 147B ASDIC sets to detect submarines by reflections from sound waves beamed into the water. A Type 272search radar and a HF/DFradio direction finder rounded out the Castles' sensor suite.
Construction and career
Flint Castle, the only ship of her name to serve in the Royal Navy, was ordered on 19 January 1943 and laid down by Henry Robb at their shipyard in Leith, Scotland on 20 April. The ship was launched on 1 September and completed on 31 December. She arrived at Tobermory, Mull, Scotland, on 12 January 1944 to begin training at the Royal Navy's Anti-Submarine Training School, HMS Western Isles. Flint Castle ran aground while training on 18 January and was refloated. She arrived at Belfast, Northern Ireland, the following day to begin repairs that lasted until 9 February. The ship was then assigned to the 39th Escort Group and escorted one Atlantic convoy in mid-March before being transferred to the Liverpool-based Escort Group B2 to escort convoys to and from Gibraltar. In September 1944, Flint Castle was assigned to Escort Group B3, which protected convoys sailing between St. John's, Newfoundland and Labrador, Canada, and Britain. The ship was refitted in Cardiff, Wales, in January–March 1945 and rejoined her group in Liverpool in April. She was assigned to Rosyth Command in June as an anti-submarine training ship and visited ports in Norway and Germany over the next several months. Flint Castle was transferred to the Rosyth Escort Force in June 1946, which was employed as a training unit; it was redesignated as the Basic Anti-Submarine Training Flotilla in September. The unit was then transferred to Portland and used a variety of names before settling on the Second Training Squadron in January 1952. On 15 June 1953, she took part in the Fleet Review held at Spithead to celebrate the Coronation of Queen Elizabeth II. The ship was used to portray a German anti-submarine vessel in the 1955 filmThe Cockleshell Heroes. Flint Castle was taken out of service in March 1956 at Devonport Dockyard, until her demolition began, starting on 10 July 1958 at Faslane. While her service was uneventful, Flint Castle was awarded the battle honour of Atlantic 1944–45.
