convoy surface attacks can work,
I've done it in GWX as late as december 1940 I did the same sort of approach I normally do, go in from one of the forward corners, keep an eye on the nearest escorts, usually the lead and 1 of the flankers, you can start your run when the lead escort moves away from you on a sweep in front of the convoy, Ideally you should also have the flank escort moving away from the convoy in one of its periodic sweeps. if there's more than one flanking escort, don't try it'll give you 3 escorts to keep track of...that's real tough
Important note, I
never try this in anything less than light fog, overcast, no moon and at least 7meters/sec of windspeed also do not use any sort of timecompression, you wont have enough response time
go in at 4 to 6 knts, decks awash, once you're in a position about 4km away from the flank escort, which ideally should be around your 120 to 180 position (and he hasn't detected you (obviously)) and about 2.5km away from the lead merchant start picking your targets, ignore the lead escort he should be well away by now...
fire at your targets and then make a sharp turn towards the rear of the convoy, go parallel to the convoy and increase speed, lots! you want to be at least 2km away from the point you fired at, ideally it should be 5km or more, if you succeed in getting this far, head away from the convoy and also away from the nearest escorts, still decks awash and about 8knts
once your torpedoes hit the nearest 1 or 2 escorts to the impact point will immediately head towards the firing point, ideally they are now moving away from your sub so you can just sort of sneak away, do not get caught in a searchlight or you're toast. If at any point the escort looks like coming closer than 4km try to match his speed and keep a narrow profile towards him
if detected at any point I'd suggest crash-diving, turning into and under the convoy and getting religious real quick
also I've never tried this when I've detected any sort of warship in the middle of the convoy on hydrophones, these are usually some sort of cruiser or possibly worse, even a humble auxiliary cruiser packs enough punch to ruin your entire day in one salvo
so yes, it can be done, it's bad for the nerves, I had to pause the game afterwards and step outside for a quiet smoke and cooldown but what a rush
Good luck mate
