For starters, the final "lesson" starts you off too close to the convoy.
In Career Mode you will have had more distance and time to make decisions on your attack run. I wasn't too impressed with starting off being sighted either. That's poor planning and the "lesson" should be adjusted.. unless it was a lesson in evading which I doubt.
The biggest points about manual TDC that I'd mention is..
1) Speed, AoB, and Range in order of importance
2) Before firing, resubmit range to TDC to update your bearing to target
3) Only use the Slow and Contact settings on the fish
4) The W and Q hotkeys are your friend in firing a fanshot of multiple torpedoes in a
semi-quick way. Use Q to open your first tube, after firing it hit W and Q to switch to the next and open the tube all while you adjust any settings (most notably contact detonator). Do the same for each extra you fire at the same target.
5) When learning manual TDC, use the pause key during certain time-consuming
parts.. such as after locking the target in the scope and opening the ID manual. You can still use certain things (such as flipping through the ID manual) while the game is paused. It helps you get the process down at a fair pace of your own while learning and gradually getting to the speedy and efficient killer you know you'll become.
Hopefully someone here will create a "Beginner's Guide" as they have for many of the previously featured sub sims on this board. I'm sure it's just a matter of time. Be patient and ask all the questions you can.
We were all new to this at some point.
