A few years ago when Hurricane Harvey was dumping millions of gallons of water on my roof I spent the inside time doing a couple of videos explaining how the basic firing angle is a simple trigonometry problem revolving around the ratio of the target speed to the torpedo speed.
The TDC in SH4 was not the easiest thing to get to work correctly so I rarely used it and developed this method (actually stole it directly from the guys who did all this for real). A "discussion" with another member who disagreed with this method prompted the videos
I have only fired three torpedoes in Wolfpack but I can see the theory behind this and learning the rules of thumb and having the prepared tables or calculator ready will make an excellent backup method for a quick shot or to confirm TDC setup.
Of course, one has to know torpedo speed as well as target speed or none of this works.
http://www.subsim.com/radioroom/showthread.php?t=233175
The original thread where I got my motivation to develop the two videos.
http://www.subsim.com/radioroom/showthread.php?t=232987
I am very excited about Wolfpack because I love the math behind plotting and executing an attack.