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Have emailed U-boat site for more source info on U-242 downing of Russian aircraft. Meanwhile: Of some considerable interest: "The concept of the "U-flak" or "Flak Trap" originated the previous year, on 31 August 1942, when U-256 was seriously damaged by aircraft. Rather than scrap the boat, it was decided to refit her as a heavily armed anti-aircraft boat intended to combat the losses being inflicted by Allied aircraft in the Bay of Biscay. Two 20 mm quadruple Flakvierling mounts and an experimental 37 mm automatic gun were installed on the U-flaks' decks. A battery of 86 mm line-carrying anti-aircraft rockets was tested (similar to a device used by the British in the defense of airfields), but this idea proved unworkable. At times, two additional single 20 mm guns were also mounted. The submarines' limited fuel capacities restricted them to operations only within the Bay of Biscay. Only five torpedoes were carried, preloaded in the tubes, to free up space needed for additional gun crew.
Four VIIC boats were modified for use as surface escorts for U-boats departing and returning to French Atlantic bases. These "U-flak" boats were U-441, U-256, U-621, and U-951. Conversion began on three others (U-211, U-263, and U-271) but none was completed and they were eventually returned to duty as standard VIIC attack boats.
The modified boats became operational in June 1943 and at first appeared to be successful against a surprised Royal Air Force. Hoping that the extra firepower might allow the boats to survive relentless British air attacks in the Bay of Biscay and reach their operational areas, Donitz ordered the boats to cross the bay in groups at maximum speed. The effort earned the Germans about two more months of relatively limited freedom, until the RAF modified their tactics. When a pilot saw that a U-boat was going to fight on the surface, he held off attacking and called in reinforcements. When several aircraft had arrived, they all attacked at once. If the U-boat dived, surface vessels were called to the scene to scour the area with sonar and drop depth charges. The British also began equipping some aircraft with rockets that could sink a U-boat with a single hit, finally making it too dangerous for a U-boat to attempt to fight it out on the surface regardless of its armament. In November 1943, less than six months after the experiment began, it was discontinued. All U-flaks were converted back to standard attack boats and fitted with Turm 4, the standard anti-aircraft armament for U-boats at the time. (According to German sources, only six aircraft had been shot down by the U-flaks in six missions, three by U-441, and one each by U-256, U-621, and U-953.)"<CASE in point: "U-441 was rebuilt as U-flak 1, the first of three U-flak boats. Perhaps the most noticeable change in appearance was a greatly expanded Wintergarten (bridge) which had an additional gun platform erected in front of the conning tower. As the boat was to act as an aircraft trap she received greatly increased fire-power in the form of 2cm quadruple anti-aircraft machine-guns, 1 3.7cm machine-gun
and additional MG 42 machine-guns (which were mostly effective in boosting morale). " The flak boat was strafed by three British Beaufighters from 248 Sqdn RAF in the Bay of Biscay. 10 men died and 13 more were wounded, including all officers other than the ship's doctor. Dr Paul Pfaffinger took over command from Kplt Hartmann, treated the wounded and brought the boat back to Brest. He was subsequently awarded the German Cross in Gold. This action led to the abandonment of the flak boat experiment, and all the boats involved were returned to their original armament configuration." IN SHORT: just dive ASAP! http://www.uboat.net/boats/u441.htm