Hull Integrity? the same, didn't get detected so far, but you've gotta pick your moment.
my trick:
<lecture>
a: a moonless night, I don't try otherwise
b: NO FOG, in fog you won't be able to see more than 4km, Escorts that close and you not knowing where they are is bad!
c: seas not too rough, but not flat calm either say 7 m/s wind
d: approach convoy from forward corner, stay at least 5 km away from leading escort
(also don't time compress, have coffee or other stimulants at hand and remember to pause once in a while, unless your going full realism, but then, real Kaleuns would have officers and such so the pause button represents my XO taking over for a bit)
now there's 2 options:
You can match course and speed with convoy and try to find one of the side escorts once you do this wait for it to go outbound from the convoy for a scan. at this moment you turn to intercept and go in about 7 knots max speed set depth for 7 meters.
Once your at 2 km from the leading outer merchant the escorts should be well away, the lead about 8km the flanker about 6, then pick your target, pick a juicy one, don't go for more than 2 (although I tend to get greedy).
Shoot at 1 or 1.5 km out, no closer or they definitely searchlight you, the flanking escort should be past or right behind you at least 5km out, now turn parallel to the convoy, towards their rear, go to 9 or 10 knots still decks awash, and get the hell away from your firing point (clear datun?)
try to stay at least 5km away from the inbound escorts, mainly the flanker. As soon as he has reached your firing point he'll begin searching for you, going around in circles and whatnot, if he hasn't detected you by now, he won't.
Your next worry is any trailing escorts or worst case scenario, that big honking Auxiliary Cruiser you mistook for a merchant.
In case a you can now start angling away from the convoy, don't go to sharply or you'll present a big profile to the searching flanker, just angle away from the convoys course about 20 degrees. The trailing escort probably won't get close to you unless it was really close to that side of the convoy when the torpedos hit.
In case B or when otherwise detected, crash dive, make a sharp turn into the convoy,deploy decoys if available, 2 at 50 meters, then go silent, and do the usual evasive routine.
The other option is to map out the convoy with your hydrophones and periscope from well away and at silent running, especially good if it's light out or your waiting for the moon to set.
Once you have a good idea about how many escorts there are, and where they are in relation to the convoy and especially the merchants you intend to attack you can go about 10km out, do an end around and end up in front of the convoy again, then proceed with option 1. Problem here is convoy changing course, because it takes longer to set this up, very annoying, especially if your just about to attack.
My other suggestion would be to only do this sort of thing in very deep water, you want to be able to go below 200 meters if you get detected
</lecture>
Night Surface attacks are possibly the tensest ride SH3 has to offer, well worth it IMO
other than that, if you mess up there'll be carousing in Valhalla, and you get a seat of honor because of extraordinary bravery in the face of certain doom
