[UKönig]

I know this might be a bit off topic, but maybe only a little left-of-center.

Apart from machine guns, the normal ballistic armament of a U-boat was one 1-pounder AA gun on the conning tower, and one 8.8cm cannon mounted on the forward casing. During the course of 1943, starting with boats that were operating in the Mediterranean (where the need was greatest), these guns were replaced by more effective automatic weapons, namely four 20mm AA guns, mostly paired but sometimes mounted together, one of the excellent German-pattern 3.7cm AA guns, and the latest type of machine guns. To accommodate them, the tower superstructure was extended aft to include a lower gun platform, while the tower itself was provided with light armor plating to provide some kind of protection against machine gunning from the air.
When sighted by aircraft, U-boats were now expected to slug it out on the surface. At first, while the element of surprise lasted, the U-boats did achieve some success and in the summer of 1943, U-boats extracted a heavy toll against the RAF squadrons of Coastal Command. However, the enemy soon changed those tactics. As soon as the enemy pilot could see, from the men still standing on the bridge, that the boat was not going to dive, he would hold back or fly off until reinforcements arrived, and then they would all attack in force. BdU tried to counter this by sending boats through the Bay in groups and when this plan proved inadequate, they attempted to turn some of them into 'flak traps', that is, redoubling the AA armament in the hopes that the enemy would take it as typical and treat *all* U-boats in future, with greater respect. This idea was also not amazing, as the following experience will show...
In July 1943, on her second patrol, the U-441 was sighted by a beaufighter. Before committing to attack, the pilot called up two more beaufighters, so their combined firepower was no less than 3, 40mms, 12, 20mms, and a dozen lesser machine guns. Staying out of range of the U-boat's return fire, they proceeded to make a clean sweep of the superstructure, disabling every single AA gun, detonating two ammunition boxes and killing or severely wounding all 24 officers and crew on the bridge and fore-casing. Luckily, the aircraft carried no bombs that day, and their shells did not penetrate the pressure hull, the boat, still able to dive, did submerge and finally, under the command of the ship's doctor, limp back to base.
This was the last experiment with the 'flak trap'. Since the previous May, some British aircraft had been fitted with a rocket projectile system, which had sunk a U-boat on the very first time it was used. Introduction of the rocket projectiles had made if far too dangerous for a U-boat to stay on the surface and invite air attack, and by the autumn of that year, U-441, along with all the other 'flak traps' was reconverted back to normal use.