[Jimbuna]

Originally Posted by maillemaker

What was it about the fjords that caused a magnetic field disruption?

Steve

The magnetic detonator anomoly:

The magnetic detonator however proved to be immune to simple fixes. It was supposed to detonate when it passed underneath a ship’s keel, as it was triggered by a sudden change in magnetic fields. This did not work as intended as the British had found a way to reduce a ship’s magnetic field by degaussing. Additionally, the earth’s magnetic fields also varied at different geographical locations and were influenced by iron ore deposits beneath the sea bed. Only when the completely redesigned Pi2 detonator had been introduced in December 1942, the problems of magnetic detonator continued to plague the U-boat Force.
But even if the detonators had been working flawlessly, problems with depth keeping meant that torpedoes were running two to three meters too deep. The depth keeping device worked by using an atmospheric chamber which controlled running depth. The Torpedo Directorate conducted new tests and could not discover any flaws. This occurred because the test torpedoes were launched from normal atmospheric conditions. But since atmospheric pressure inside a U-boat varied greatly, especially after prolonged submerged activity, air would leak into the torpedo chamber, effectively recalibrating the depth sensor.