German submarine U-403 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II.
In eight war patrols, she sank two ships totalling . She was sunk by a French aircraft west of Dakar on 18 August 1943 with the loss of all hands.
German Type VIIC submarines were preceded by the shorter Type VIIB submarines. U-403 had a displacement of 769t when at the surface and 871t while submerged. She had a total length of 67.1m (220.1feet), a pressure hull length of 50.5m (165.7feet), a beam of 6.2m (20.3feet), a height of 9.6m (31.5feet), and a draught of 4.74m (15.55feet). The submarine was powered by two Germaniawerft F46 four-stroke, six-cylinder supercharged diesel engines producing a total of NaNPS for use while surfaced, two Siemens-Schuckert GU 343/38–8 double-acting electric motors producing a total of 750PS for use while submerged. She had two shafts and two 1.23abbr=onNaNabbr=on propellers. The boat was capable of operating at depths of up to .
The submarine had a maximum surface speed of and a maximum submerged speed of . When submerged, the boat could operate for at ; when surfaced, she could travel at . U-403 was fitted with five 53.30NaN0 torpedo tubes (four fitted at the bow and one at the stern), fourteen torpedoes, one 8.82NaN2 SK C/35 naval gun, 220 rounds, and a 2sp=usNaNsp=us C/30 anti-aircraft gun. The boat had a complement of between forty-four and sixty.
The submarine was laid down on 20 May 1940 at the Danziger Werft at Danzig (now Gdansk, Poland) as yard number 15, launched on 26 February 1941 and commissioned on 25 June under the command of Kapitänleutnant Heinz-Ehlert Clausen.
She served with the 5th U-boat Flotilla from 25 June 1941 for training and the 7th flotilla from 1 September for operations. She was reassigned to the 11th flotilla on 1 July 1942, then the 9th flotilla on 1 March 1943.
U-359s first patrol was preceded by a move from Kiel to the German-administered island of Helgoland, (sometimes written as 'Heligoland'), on 26 February 1942. She left there on 1 March, sailing through the Norwegian Sea. She sailed as far as the Barents Sea before docking in Narvik on the 19th.
She moved to Harstad (northwest of Narvik), on 21 April 1942, before setting out on her second foray when she sank the Empire Howard southeast of Bear Island on the 16th. The ship went down in fifty-seven seconds.
Having berthed in Skjomenfjord (south of Narvik) on 27 July 1942, the boat departed on her fourth sortie on 2 April. Her route took her through the Norwegian, Greenland and Barents Seas. She returned to Skjomenfjord on 20 August.
The submarine's fifth patrol terminated in Narvik on 21 September 1942. She moved to Trondheim on the 26th.
Patrol number six started from Trondheim on 9 January 1943. The boat passed through the gap between Iceland and the Faroe Islands and headed for southeast Greenland. She then turned south and was attacked by a Canso (the Canadian version of the Catalina flying boat) off the Newfoundland coast on 6 February. Moderate damage was sustained. She subsequently sank the Greek-registered Zeus on the 19th.
U-403 was unsuccessfully attacked by a Fairey Swordfish of 811 Naval Air Squadron from on 10 May 1943 northwest of the Azores on her seventh patrol.
The submarine was on the surface accompanied by on 30 July 1943, when they were attacked by Avenger and Wildcat aircraft from the American escort carrier . U-403 escaped, U-43 was not so lucky; she was sunk.
The boat was sunk by depth charges dropped by a Vickers Wellington of No. 344 Squadron RAF, (with a French crew), on 18 August 1943 near Dakar on the west African coast.
Forty-nine men died in U-403; there were no survivors.
U-403 was originally noted as sunk, also on 18 August 1943, by a British Lockheed Hudson of 200 Squadron near Dakar.
U-403 took part in twelve wolfpacks, namely:
| Date | Ship Name | Nationality | Tonnage (GRT) | Fate[1] | |
|---|---|---|---|---|---|
| 16 April 1942 | Empire Howard |  United Kingdom | 6,985 | Sunk | |
| 19 February 1943 | Zeus |  Greece | 5,961 | Sunk |