Editing U-boat (section)

===Torpedo developments===
The U-boats' main weapon was the [[torpedo]], though [[sea mine|mines]] and [[deck gun]]s (while surfaced) were also used.  Early German World War II torpedoes were fitted with one of two types of pistol triggers&nbsp;– impact, which detonated the warhead upon contact with a solid object, and [[Magnetic pistol|magnetic]], which detonated upon sensing a change in the magnetic field within a few meters. Initially, the depth-keeping equipment and magnetic and contact exploders were notoriously unreliable. During the first eight months of the war, torpedoes often ran at an improper depth, detonated prematurely, or failed to explode altogether{{snd}}sometimes bouncing harmlessly off the hull of the target ship. This was most evident in [[Operation Weserübung]], the invasion of Norway, where various skilled U-boat commanders failed to inflict damage on British transports and warships because of faulty torpedoes. The faults were largely due to a lack of testing. The magnetic detonator was sensitive to mechanical oscillations during the torpedo run, and to fluctuations in the Earth's magnetic field at high latitudes. These early magnetic detonators were eventually phased out. The depth-keeping problem remained problematic, not until January 1942 was the last fault discovered by accident: when ventilating the onboard torpedoes during maintenance, it was possible that the excess internal air-pressure in the U-boat offset the depth setting mechanism in the balance chamber of the torpedo.{{Sfn|Dönitz||p=482}}{{Sfn|Blair||p=485}}[[File:Flachenabsuchender Torpedo type I-firing positions.svg|thumb|The pattern running of a FAT torpedo]]
In order to give U-boats better opportunities against well-defended convoys, several types of "pattern-running" torpedoes were developed. The FAT ('''Flächen-Absuch-Torpedo''' or '''Federapparat-Torpedo''') and LUT ('''LageUnabhängiger''' Torpedo) was an electric torpedo which ran straight out to a preset distance, then traveled in either a circular or ladder-like pattern through the convoy lanes. This increased the probability of a hit. The torpedo had one setting to regulate the length of the prerun, after which one of four other possible settings kicked in and made the torpedo zigzag towards either left or right and either on short (1200&nbsp;m; {{frac|2|3}}&nbsp;nmi) or long (1900&nbsp;m; 1 [[nautical mile]]) legs. When fired, the firing U-boat sent out a warning to the other U-boats in the vicinity so these could dive to avoid being hit by the random running torpedo. The FAT torpedo became available end of 1942 and was in regular use during the convoy battles of March 1943.{{Sfn|Middlebrook||pp=170–171}}{{Sfn|Brennecke|1984|pp=389–391}}

Germany also developed acoustic homing torpedoes. In February 1943, the first acoustic torpedo, the T4 "Falke", was tested on a small scale with moderate success, but this torpedo could only be used against large, slow ships. The acoustic torpedo ran straight to an arming distance of 1000 m and then turned toward the loudest noise detected. Its successor, the [[G7es torpedo|T5 "Zaunkönig]]", was designed to combat small and fast warships, and entered service in September 1943.{{Sfn|Brennecke|1984|pp=391–394}}