Well, like said it depends on the year/how many escorts/weather etc. But mainly I run an attack like this (which may not be successful). :
Once I receive a convoy contact, or on the rare occasion stumble into one, I will then plot an intercept course that will put me in front of the convoy, giving me time to assess whats in the convoy/ get into a firing position - usually 60 to 90 degrees AoB to the convoy.
Whilst doing this I will dive on several occasions to plot its course through hydrophone soundings, and get an idea of it size/number of escorts.
Once im in a good position I choose my targets (usually the biggest ships i.e tankers), get into firing position and start the attack run - if I can get past the destroyer screen this makes this much easier. Immediately I order a crash dive and go to around 120m, as the escorts will be looking for you!
I then spend time evading the escorts and in most cases getting past them so I can re-acquire the convoy for another attack. This way I can make at least 3 attack runs, before I slip away leaving much confused escorts.
This would work upto late '43 (especially of the US coast), but after that forget stuff lie this - If you can make a convoy attack, do so, but it will be VERY difficult to escape let alone survive.
Hope this all helps, and good hunting
