German submarine U - 441 German submarine " U - 441 was a Type VIIC U - boat of the Nazi German " Kriegsmarine " during World War II , which served for a short time as an anti - aircraft submarine under the designation U - flak 1 " . The submarine was laid down on 15 October 1940 at the Schichau - Werke in Danzig as ' werk ' 1462 , launched on 13 December 1941 and commissioned on 21 February 1942 , under the command of " Kapitänleutnant " Klaus Hartmann . " U - 441 " first served with the 5th U - boat Flotilla , a training unit , and then operationally with the 1st flotilla from 1 October 1942 . Service history . 1st and 2nd patrols . Her first patrol took her from Kiel , Germany to Brest in occupied France , via Trondheim in Norway and the mid - Atlantic , between 17 September and 7 November 1942 , spending 38 days at sea . Her second patrol , sailing from Brest ( where she was based for the rest of her career ) , on 7 December 1942 , again took her out into the mid - Atlantic where on 27 December she sank the Dutch 7 , 051 ton cargo ship " Soekaboemi " , part of Convoy ON 154 . The ship had been wrecked and abandoned after being struck by a torpedo from hours before . The U - boat returned to Brest on 22 January 1943 . 3rd patrol , conversion and 4th patrol . " U - 441 " departed on 27 February 1943 for another Atlantic patrol , but had no success . On 20 March the boat was attacked by a Sunderland aircraft west of Ireland and slightly damaged . She returned to Brest on 11 April after 44 days at sea . In April – May 1943 , in recognition of the air threat , " U - 441 " was converted into the first of four U - flak boats , which were designed to be surface escorts for attack U - boats operating from the French Atlantic bases and intended to lure unsuspecting aircraft into a deadly trap . The U - flak boats had greatly increased anti - aircraft firepower , " U - 441 " was fitted with additional gun platforms forward and aft of the conning tower , which served as a base for two four - barrelled " Flakvierling " 20 mm flak guns and one 3 . 7 cm weapon , as well as a number of MG 42 machine guns . " U - 441 " was redesignated " U - flak 1 " . The increased anti - aircraft capability required additional personnel , so crew numbers were increased from 44 - 48 men to 67 . As " Kptlt " . Klaus Hartmann was seriously ill , " U - flak 1 " sailed from Brest on 22 May 1943 under the command of " Kptlt " . Götz von Hartmann , formerly of . It was not long before the new configuration was put to the test . At 20 : 50 on the 24th , the flak boat was attacked by a Sunderland of 228 squadron RAF in the Bay of Biscay . Despite being hit by heavy anti - aircraft fire , the aircraft managed to drop five depth charge s before it crashed into the sea ; the attack wounded one crewman and extensively damaged " U - Flak 1 " which returned to base the next day . 5th patrol . Her second patrol as a U - flak boat began on 8 July 1943 . On the 12th the boat was strafed by three Beaufighter aircraft from No . 248 Squadron RAF . Ten men were killed and thirteen others wounded , including all of the officers . " Marine - Stabsarzt " Dr . Paul Pfaffinger , an experienced U - boat doctor took command , and brought the boat safely back to Brest , subsequently being awarded the " Deutsche Kreuz " in Gold . By this time the U - flak boats were considered a failure and " U - flak 1 " was converted back to her original configuration and reverted to " U - 441 " . 6th , 7th and 8th patrols . With " Kptlt " . Klaus Hartmann returning to command the " U - 441 " , she made three unsuccessful patrols between October 1943 and May 1944 . The only incident of note was when she was unsuccessfully attacked by an unknown aircraft on 2 March 1944 . 9th patrol and sinking . " U - 441 " sailed from Brest for the final time on 6 June 1944 , ( " D - Day " ) , and headed into the English Channel . There , on 7 June she was involved in the shooting down of a Canadian Vickers Wellington , although other U - boats , such as " U - 413 or U - 740 " , are also mentioned in the sources . On 8 June she was sunk with all hands , 30 miles off Ushant , in the approximate position , by depth charges dropped from a Liberator of 224 squadron , RAF .