German submarine U-821 was a short-lived Type VIIC U-boat of Nazi Germany's Kriegsmarine, built by Oderwerke in Stettin during World War II for service in the Battle of the Atlantic. She only participated in two brief combat patrols, one of which ended after four days when she was sunk by allied aircraft. U-821 was built in Stettin at a small shipyard, and thus took eighteen months to complete, being ready by October 1943. The boat was of the VIIC Type, which possessed long range cruising capabilities as well as five torpedo tubes.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-821 had a displacement of 769t when at the surface and 871t while submerged. She had a total length of 67.1m (220.1feet), a pressure hull length of 50.5m (165.7feet), a beam of 6.2m (20.3feet), a height of 9.6m (31.5feet), and a draught of 4.74m (15.55feet). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of NaNPS for use while surfaced, two Brown, Boveri & Cie GG UB 720/8 double-acting electric motors producing a total of 750PS for use while submerged. She had two shafts and two 1.23abbr=onNaNabbr=on propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-821 was fitted with five 53.30NaN0 torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.82NaN2 SK C/35 naval gun, (220 rounds), one 3.7cm (01.5inches) Flak M42 and two twin 2sp=usNaNsp=us C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.
Following her sea trials and warming-up period, U-821 departed Bergen, Norway on 19 March 1944 for her first war patrol, during which she spent 24 fruitless days in the North Atlantic before returning to Brest, France for resupply. Her second patrol was more eventful, as just four days out from Brest and not far from Ushant, Royal Air Force aircraft spotted and attacked the U-boat on the surface. Her captain made the decision to battle it out rather than dive, and engaged in a running firefight with three Mosquito aircraft of 248 Squadron and a large Consolidated Liberator bomber of 206 Squadron. One Mosquito was shot down in the clash, but rockets and depth charges took their toll on the submarine which soon sank, taking with her 50 sailors, in position 48.5167°N -16°W. One survivor was pulled from the sea by small German naval units a few hours later.
The sinking was filmed by gun camera footage on board the attacking aircraft.[1]