French submarine Perle (1935)

The French submarine Perle was a built for the French Navy in the mid-1930s. Laid down in 1931, it was launched in July 1935 and commissioned in March 1937. In November 1942, after Operation Torch, Perle joined the Allied fleet. While returning from refitting in the United States, Perle was mistaken for a U-boat by Allied aircraft and sunk in position 55.45°N, -30.83333°W.

Design
66 m long, with a beam of 7.2 m and a draught of 4.3 m, Saphir-class submarines could dive up to 80 m. The submarine had a surfaced displacement of 670 t and a submerged displacement of 925 t. Propulsion while surfaced was provided by one 1300 hp diesel motor and two 1100 hp electric motors. The submarines' electrical propulsion allowed it to attain speeds of 9 kn while submerged. Their surfaced range was 7000 nmi at 7.5 kn, and 4000 nmi at 12 kn, with a submerged range of 80 nmi at 4 kn.

The Saphir-class submarines were constructed to be able to launch torpedoes and lay mines without surfacing. The moored contact mines they used contained 220 kg of TNT and operated at up to 200 m of depth. They were attached to the submarine's exterior under a hydrodynamic protection and were jettisoned with compressed air. The Saphir-class submarines also featured an automatic depth regulator that automatically flooded ballast tanks after mines were dropped to prevent the risk of the submarine surfacing in the middle of enemy waters.

Service history
Laid down in 1931, Perle was launched in July 1935 and commissioned in March 1937. It was not scuttled with the French fleet in Toulon and in November 1942, after Operation Torch, Perle joined the Allied fleet and was assigned to Dakar. After taking part in several operations, Perle sailed to the United States for refitting. On 26 June 1944, it left port and, after stopping in Newfoundland, Perle set sail for the sea port of Dundee in Scotland to participate in operations in Norway. In the middle of the Atlantic Ocean, Perle, flying a French flag, was mistaken for a U-boat by Allied aircraft and sunk in position 55.45°N, -30.83333°W.