|Ordered:||15 August 1940|
|Builder:||Blohm & Voss, Hamburg|
|Laid down:||15 July 1941|
|Launched:||31 March 1942|
|Commissioned:||21 May 1942|
|Fate:||Sunk 21 February 1943 in the North Atlantic in position Coordinates: , by depth charges from a RAF Liberator.|
|Class and type:||Type VIIC submarine|
|Draught:||4.74 m (15 ft 7 in)|
|Complement:||4 officers, 40–56 enlisted|
German submarine U-623 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 15 July 1941 by Blohm & Voss, Hamburg as yard number 599, launched on 31 March 1942 and commissioned on 21 May 1942 under Oberleutnant zur See Hermann Schrüder.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-623 had a displacement of 769 tonnes (757 long tons) when at the surface and 871 tonnes (857 long tons) while submerged. She had a total length of 67.10 m (220 ft 2 in), a pressure hull length of 50.50 m (165 ft 8 in), a beam of 6.20 m (20 ft 4 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.74 m (15 ft 7 in). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2,800 to 3,200 metric horsepower (2,060 to 2,350 kW; 2,760 to 3,160 shp) for use while surfaced, two Brown, Boveri & Cie GG UB 720/8 double-acting electric motors producing a total of 750 metric horsepower (550 kW; 740 shp) for use while submerged. She had two shafts and two 1.23 m (4 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).
The submarine had a maximum surface speed of 17.7 knots (32.8 km/h; 20.4 mph) and a maximum submerged speed of 7.6 knots (14.1 km/h; 8.7 mph). When submerged, the boat could operate for 80 nautical miles (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 8,500 nautical miles (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph). U-623 was fitted with five 53.3 cm (21 in) torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm (3.46 in) SK C/35 naval gun, 220 rounds, and a 2 cm (0.79 in) C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.
In two patrols she sank no ships.
U-623 took part in five wolfpacks, namely
- Drachen (22 November – 3 December 1942)
- Panzer (3–9 December 1942)
- Ungestüm (11–13 December 1942)
- Raufbold (13–18 December 1942)
- Ritter (11–21 February 1943)
U-623 was caught while hurrying on the surface to join the attack against Convoy ON 166 and sunk on 21 February 1943 in the North Atlantic, at the position , by depth charges from a RAF Liberator of 120 Squadron. All hands were lost.
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