German submarine U-243

German submarine U-243 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.

An order was placed for U-243 on 10 April 1941 and construction began on 28 October 1942 at Friedrich Krupp Germaniawerft, Kiel, as yard number 677. She was launched the following year on 2 September 1943 and commissioned on 2 October 1943 under the command of Oberleutnant zur See Hans Märtens. Three days into her only patrol, she shot a German aircraft down.

She was sunk in the Bay of Biscay on 8 July 1944.

Design
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-243 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 AEG GU 460/8–27 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-243 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), one 3.7 cm Flak M42 and two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of between forty-four and sixty.

Service history
Her only patrol was preceded by a short voyage from Kiel to Flekkefjord in southern Norway in May 1944. On 11 June 1944, she mistakenly shot down a German Junkers Ju 88 aircraft 40 nmi southwest of Bergen while making for that city.

She passed through the gap between Iceland and the Faroe Islands and steamed south, heading for the French Atlantic ports.

She was attacked and sunk by a Sunderland flying boat of No. 10 Squadron RAAF in the Bay of Biscay on 8 July 1944. Eleven men died; there were 38 survivors.