German submarine U-31 (1936)

	U-33, a typical Type VIIA boat
History
Nazi Germany
Name	U-31
Ordered	1 April 1935
Builder	AG Weser, Bremen
Cost	4,189,000 Reichsmark
Yard number	912
Laid down	1 March 1936
Launched	25 September 1936
Commissioned	28 December 1936
Recommissioned	30 July 1940
Decommissioned	24 March 1940
Fate	Sunk, 11 March 1940, raised; sunk again 2 November 1940;
General characteristics
Class & type	Type VIIA submarine
Displacement	626 t (616 long tons) surfaced; 745 t (733 long tons) submerged;
Length	64.51 m (211 ft 8 in) o/a; 45.50 m (149 ft 3 in) pressure hull;
Beam	5.85 m (19 ft 2 in) o/a; 4.70 m (15 ft 5 in) pressure hull;
Height	9.50 m (31 ft 2 in)
Draught	4.37 m (14 ft 4 in)
Installed power	2,100–2,310 PS (1,540–1,700 kW; 2,070–2,280 bhp) (diesels); 750 PS (550 kW; 740 shp) (electric);
Propulsion	2 shafts; 2 × diesel engines; 2 × electric motors;
Speed	17 knots (31 km/h; 20 mph) surfaced; 8 knots (15 km/h; 9.2 mph) submerged;
Range	6,200 nmi (11,500 km; 7,100 mi) at 10 knots (19 km/h; 12 mph) surfaced; 73–94 nmi (135–174 km; 84–108 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged;
Test depth	220 m (720 ft); Crush depth: 230–250 m (750–820 ft);
Complement	4 officers, 40–56 enlisted
Sensors &; processing systems	Gruppenhorchgerät
Armament	5 × 53.3 cm (21 in) torpedo tubes (four bow, one stern); 11 × torpedoes or 22 TMA mines; 1 × 8.8 cm (3.46 in) deck gun (220 rounds); 1 × 2 cm (0.79 in) AA gun;
Service record
Part of:	2nd U-boat Flotilla; 28 December 1936 – 12 March 1940; 30 July – 2 November 1940;
Identification codes:	M 28 961
Commanders:	Kptlt. Rolf Dau; 28 December 1936 – 8 November 1938; Kptlt. Johannes Habekost; 8 November 1938 – 11 March 1940; Kptlt. Wilfried Prellberg; 30 July 1940 – 2 November 1940;
Operations:	7 patrols:; 1st patrol:; 27 August – 2 September 1939; 2nd patrol:; 9 September – 2 October 1939; 3rd patrol:; 21 – 31 October 1939; 4th patrol:; 19 November – 11 December 1939; 5th patrol:; 15 January – 4 February 1940; 6th patrol:; 16 September – 8 October 1940; 7th patrol:; 19 October – 2 November 1940;
Victories:	11 merchant ships sunk ; (27,751 GRT); 2 auxiliary warships sunk ; (160 GRT); 1 warship damaged ; (33,950 tons);

German submarine U-31 was a Type VIIA U-boat of Nazi Germany's Kriegsmarine during World War II. She was laid down on 1 March 1936 as yard number 912, launched on 25 September and commissioned on 28 December 1936.

History
U-33, a typical Type VIIA boat
Nazi Germany
Name	U-31
Ordered	1 April 1935
Builder	AG Weser, Bremen
Cost	4,189,000 Reichsmark
Yard number	912
Laid down	1 March 1936
Launched	25 September 1936
Commissioned	28 December 1936
Recommissioned	30 July 1940
Decommissioned	24 March 1940
Fate	Sunk, 11 March 1940, raised sunk again 2 November 1940
General characteristics
Class & type	Type VIIA submarine
Displacement	626 t (616 long tons) surfaced 745 t (733 long tons) submerged
Length	64.51 m (211 ft 8 in) o/a 45.50 m (149 ft 3 in) pressure hull
Beam	5.85 m (19 ft 2 in) o/a 4.70 m (15 ft 5 in) pressure hull
Height	9.50 m (31 ft 2 in)
Draught	4.37 m (14 ft 4 in)
Installed power	2,100–2,310 PS (1,540–1,700 kW; 2,070–2,280 bhp) (diesels) 750 PS (550 kW; 740 shp) (electric)
Propulsion	2 shafts 2 × diesel engines 2 × electric motors
Speed	17 knots (31 km/h; 20 mph) surfaced 8 knots (15 km/h; 9.2 mph) submerged
Range	6,200 nmi (11,500 km; 7,100 mi) at 10 knots (19 km/h; 12 mph) surfaced 73–94 nmi (135–174 km; 84–108 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth	220 m (720 ft) Crush depth: 230–250 m (750–820 ft)
Complement	4 officers, 40–56 enlisted
Sensors & processing systems	Gruppenhorchgerät
Armament	5 × 53.3 cm (21 in) torpedo tubes (four bow, one stern) 11 × torpedoes or 22 TMA mines 1 × 8.8 cm (3.46 in) deck gun (220 rounds) 1 × 2 cm (0.79 in) AA gun
Service record
Part of:	2nd U-boat Flotilla 28 December 1936 – 12 March 1940 30 July – 2 November 1940
Identification codes:	M 28 961
Commanders:	Kptlt. Rolf Dau 28 December 1936 – 8 November 1938 Kptlt. Johannes Habekost 8 November 1938 – 11 March 1940 Kptlt. Wilfried Prellberg 30 July 1940 – 2 November 1940
Operations:	7 patrols: 1st patrol: 27 August – 2 September 1939 2nd patrol: 9 September – 2 October 1939 3rd patrol: 21 – 31 October 1939 4th patrol: 19 November – 11 December 1939 5th patrol: 15 January – 4 February 1940 6th patrol: 16 September – 8 October 1940 7th patrol: 19 October – 2 November 1940
Victories:	11 merchant ships sunk (27,751 GRT) 2 auxiliary warships sunk (160 GRT) 1 warship damaged (33,950 tons)