Thanks Tore and Don, so the 3rd one of the two inclinators is identical to the one in U 995 (which comes with only one inclinator) right? The other Type VII you served on, did she had one or two inclinator gauges?
How did the mechanical hydroplane indicator displayed the angle? I don't see a gauge needle on any of the pictures. Did the
mechanical hydroplane indicators always work or only when the manual wheels were used (instead of the electric motors)?
Which raises another question, the manual wheels could be decoupled right? Or did they always rotate simultaneously when a button was pressed on the electrical "BBC" controller?
The only thing that seems to be a mystery to me is what exactly is the function of the index pointer that slides up and down on the rod on the right side of the Papenberg meter scale?
I can only guess but I believe it is a marker which can be set to quickly mark a desired depth. I think this would be useful if the attack periscope is in use. The usable height of the observation periscope was very limited (operators must bend themselves if they want to lower it). So when the observation periscope was in use then the desired depth (to keep the head just low above the surface) was basically always the same. But the attack periscope was usable at almost any extension (at least this is what I understand from the description in Harry Schlemmer's book "Vom Turmsehrohr zum Optronikmast"), hence the "periscope depth" of the boat and the extension of the attack periscope could vary which makes a quick marker useful. But this is just my first thought and I bet I am totally wrong
Something different that I absolutely don't understand:
The head of older versions of the C/2 attack periscope (till 1942) were pressure proof up to 15 bar only (equal to approx. 150m) later ones up to 25 bar (250m). I think even with a fully retracted periscope the head was still visible and had no additional protection (or is that wrong?). This would mean the older boats could dive to a maximum depth of 150 meters only because above that they would risk an ingress of water through the periscope.