German submarine U-311

German submarine U-311 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 21 March 1942 at the Flender Werke yard at Lübeck as yard number 311, launched on 20 January 1943 and commissioned on 23 March under the command of Kapitänleutnant Joachim Zander.

During her short career, the U-boat sailed on two combat patrols, sinking a single ship, before she was sunk on 22 April 1944.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-311 had a displacement of 769 t when at the surface and 871 t while submerged. She had a total length of 67.10 m, a pressure hull length of 50.50 m, a beam of 6.20 m, a height of 9.60 m, and a draught of 4.74 m. The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of 2800 to 3200 PS for use while surfaced, two Garbe, Lahmeyer & Co. RP 137/c double-acting electric motors producing a total of 750 PS for use while submerged. She had two shafts and two 1.23 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 17.7 kn and a maximum submerged speed of 7.6 kn. When submerged, the boat could operate for 80 nmi at 4 kn; when surfaced, she could travel 8500 nmi at 10 kn. U-311 was fitted with five 53.3 cm torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.8 cm SK C/35 naval gun, 220 rounds, and two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.

First patrol
After training with the 8th U-boat Flotilla at Kiel, U-311 was transferred to the 1st U-boat Flotilla based at Brest in France, for front-line service on 25 November 1943. On that day she departed Kiel and sailed out into the middle of the Atlantic, via the North Sea and the gap between Iceland and the Faroe Islands. She operated as part of 8 wolfpacks before arriving at Brest on 26 January 1944.

Second patrol and loss
U-311 sailed from Brest on 7 March 1944. On the 19th, she sank the Seakay 375 nmi west of Fastnet. On 22 April, she was sunk by depth charges dropped by the Canadian frigates HMCS Matane (K444) and HMCS Swansea (K328).

Previously recorded fate
The boat was previously thought to have been sunk southwest of Ireland on 24 April 1944 by a Canadian Sunderland flying boat of 423 Squadron, RCAF.

Wolfpacks
U-311 took part in eight wolfpacks, namely:
 * Coronel (7 – 8 December 1943)
 * Coronel 1 (8 – 14 December 1943)
 * Coronel 2 (14 – 17 December 1943)
 * Amrum (18 – 23 December 1943)
 * Rügen 5 (23 December 1943 – 2 January 1944)
 * Rügen 4 (2 – 7 January 1944)
 * Rügen (7 – 19 January 1944)
 * Wolfpack_Preussen (19 – 22 March 1944)