There is an online manual to the real submarines,
The Fleet Type Submarine, Navpers 16160, published just after WWII at
http://www.maritime.org/fleetsub . There is much more there than meets the eye. I was captivated for about an hour reading the specific instructions for the sonar operator. I think I learned some things that will apply to Silent Hunter.
This is a collection of online manuals including:
1. The Fleet Type Submarine NavPers 16160
2. Submarine Main Propulsion Diesels NavPers 16161
3. Submarine Electrical Installations NavPers 16162
4. Submarine Refrigerating and Air-Conditioning Systems NavPers 16163
5. Submarine Distilling Systems Navpers 16163A
6. Submarine Air Systems NavPers 16164
7. Submarine Periscope Manual NavPers 16165
8. Submarine Trim and Drain Systems NavPers 16166
9. Submarine Sonar Operator's Manual NavPers 16167
10. Submarine Underwater Log Systems NavPers 16168
11. Submarine Hydraulic Systems NavPers 16169
12. Torpedo Tubes, 21-Inch submerged, Mks 32 to 39 O.P. 1085
Hey look! Links to all the individual manuals. I'm accidentally very good there!
(lost the table format though, dock me some renown for that)
edit: Fixed the table, I want my renown back! The first link in my post is the first item on the list. See ya! I have to spend some serious time in the periscope manual!
Moderators, you might want to sticky this one! This is one great link.