http://www.subsim.com/radioroom/show...98#post1619698--start at the beginning of the thread.
http://www.subsim.com/radioroom/show...98&postcount=8--the eigth post in the thread deals with reading the Aob dials on a UBoat.
I have not played the German side for awhile. The links above will help you figure out how to set set the TDC for the German side. There is no position keeper for UBoats. The thread discusses a UBoat attack. The post, which is at the end of the thread, discussed the Aob dials and settings for a broadside using the German TDC.
A good mod set up is in the ATO forum. It is OM/OMEGU/KIUB. Learning the UBoat side takes awhile.