[derstosstrupp]

Just to be clear, it’s a common misconception that the rudder and hydroplanes were controlled hydraulically on German submarines. This was only the case later with the XXI. I think the misconception might stem from the fact that US fleet submarines operated this way, but the Germans didn’t do so until much later. The control surfaces were operated electrically, using electric motors, with dynamic braking to stop the control surface relatively quickly (the case for all types except II, which was hand-powered, and XXI as mentioned, although hydraulic steering was attempted as a test on at least 1 VII as we have a Skizze of such a system for one boat). I might add as an aside that on the Type II there was no hydraulic system at all, even for the periscopes. All electric, and also the case for VIIA.

Inch for inch, moving a control surface electrically is noisier than hydraulically (assuming sufficient fluid pressure and the hydraulic pumps don’t need to recharge the hydraulic accumulators), so this suggestion still holds, and is good, just wanted to point out the misconception. The electric motors themselves made noise, as well as the magnetic controller relays that alternately switched in the control and dynamic braking circuits.