German submarine U-631

History
Nazi Germany
Name:	U-631
Ordered:	15 August 1940
Builder:	Blohm & Voss, Hamburg
Yard number:	607
Laid down:	5 September 1941
Launched:	27 May 1942
Commissioned:	16 July 1942
Fate:	Sunk 17 October 1943 in the North Atlantic in position , by depth charges from HMS Sunflower.
General characteristics
Class & type:	Type VIIC submarine
Displacement:	769 tonnes (757 long tons) surfaced 871 t (857 long tons) submerged
Length:	67.10 m (220 ft 2 in) o/a 50.50 m (165 ft 8 in) pressure hull
Beam:	6.20 m (20 ft 4 in) o/a 4.70 m (15 ft 5 in) pressure hull
Draught:	4.74 m (15 ft 7 in)
Installed power:	2,800–3,200 PS (2,100–2,400 kW; 2,800–3,200 bhp) (diesels) 750 PS (550 kW; 740 shp) (electric)
Propulsion:	2 shafts 2 × diesel engines 2 × electric motors
Speed:	17.7 knots (32.8 km/h; 20.4 mph) surfaced 7.6 knots (14.1 km/h; 8.7 mph) submerged
Range:	8,500 nmi (15,700 km; 9,800 mi) at 10 knots (19 km/h; 12 mph) surfaced 80 nmi (150 km; 92 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth:	230 m (750 ft) Crush depth: 250–295 m (820–968 ft)
Complement:	4 officers, 40–56 enlisted
Armament:	5 × 53.3 cm (21 in) torpedo tubes (four bow, one stern) 14 × torpedoes or 26 TMA mines 1 × 8.8 cm (3.46 in) deck gun (220 rounds) various AA guns
Service record
Part of:	5th U-boat Flotilla 16 July 1942 – 31 December 1942 - Training 9th U-boat Flotilla 1 January 1943 – 17 October 1943
Commanders:	Oblt.z.S. Jürgen Krüger 16 July 1942 – 17 October 1943
Operations:	1st patrol: 19 December 1942 – 4 February 1943 2nd patrol: 6 March – 11 May 1943 3rd patrol: 18 September – 17 October 1943
Victories:	2 merchant ships sunk (9,136 GRT)

German submarine U-631 was a Type VIIC U-boat built for Nazi Germany's Kriegsmarine for service during World War II. She was laid down on 5 September 1941 by Blohm & Voss, Hamburg as yard number 607, launched on 27 May 1942 and commissioned on 16 July 1942 under Oberleutnant zur See Jürgen Krüger.

Design

German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-631 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 BBC 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-631 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 an anti-aircraft gun. The boat had a complement of between forty-four and sixty.

Service history

The boat's career began with training at 5th U-boat Flotilla on 16 July 1942, followed by active service on 1 January 1943 as part of the 9th Flotilla for the remainder of her service. In three patrols she sank two merchant ships, for a total of 9,136 gross register tons (GRT).

Wolfpacks

U-631 took part in seven wolfpacks, namely

• Falke (28 December 1942 – 19 January 1943)
• Landsknecht (19–28 January 1943)
• Stürmer (11–20 March 1943)
• Seewolf 2 (21–30 March 1943)
• Meise (11–27 April 1943)
• Rossbach (27 September – 9 October 1943)
• Schlieffen (14–17 October 1943)

Fate

U-631 was sunk on 17 October 1943 in the North Atlantic SE of Cape Farewell, Greenland, in position , by depth charges from British corvette HMS Sunflower. All crew members died.

Summary of raiding history

Date	Name	Nationality	Tonnage (GRT)	Fate
29 December 1942	Ingerfem	Norway	3,978	Sunk
17 March 1943	Terkoelei	Netherlands	5,158	Sunk