Thanks for all answers, now I'll tell you how it went.
I decided to attack during the day, I was afraid that convoy may change it's course (we were pretty close to Ireland), the air support would be too strong (last time not far away from my attack spot 3 planes were all over me 15 minutes after I sunk a merchant), finally - I don't know how SH3 works, I wasn't willing to risk that convoy would just dissapear. (in stock SH3 v. 1.4b, how close to shores AI ships are vanishing? do they enter some harbor or just dissapear?)
It was early in the morning when I attacked for the first time. I decided not to engage escorts - we'll go for tonnage, I said to myself, and if the weather holds we can still find some small merchants later to sink with our deck gun. For my first attack I decided to go for T2 and T3. Sybmerged for a long time I waited 'till ships arrived, luckilly (and just luckilly, pure luck
) DD was circling in the oposite direction. Submerged with 2 knots I placed myself inside a convoy, between 1st and 2nd line. Merchants were blocking my view on tankers, not cool
I was afraid my scope would be spotted. Anywho, I sent two torps for T2 and two for T3. T2 was easy, AOB 90 at scope angle 0, distance ca. 900m. 4 torpedoes shot, first one - kaboom, T2 got it in what will be remembered as a 'perfect spot', immediately 'she's going down'. Second torp. for that vessel was unnecessary, and probably missed his aft by inches.
T3 - two torps, no luck. I have no idea how big my mistake was, as I was already diving and changing course. DD was all over me in a matter of minutes, soon corvette joined, I was depth charged several times, it took me two hours to escape. Result of attack nr 1 - sunk T2, minor damage of AA gun, HI 100%.
I took another shot after 3 hours, still during the day. To rebuild my confidence I went after C2/3. Turned out there were some C3's (all American) and 5 C2 (British). This time I positioned myself on their port side.
I was between 5th and 4th lane, attacking on 4th. I prepared a solution - AOB 90 at scope angle 0, distance 550m. I shot 2 torps (depth 3,5 m, contact trigger) willing to sink two C2 cargo. First one - no problem, hit just below the stack, a sure kill. Second one... miss!
I was already going deeper when I heard explosion and my WO told me 'torpedo missed'. I didn't get intended C2, that's for sure. Maybe my electric torpedo just exploded or maybe I hit another target.
This time escorts couldn't even find me. I'm still in the hydro zone of the convoy.
I must say I'm a little dissapointed with my performance - 6 shots, 2 one-hit kills but also 4 misses. I was wondering - how could I miss another C2 if the first one was hit
precisly where I aimed? Both ships had same speed, my speed was dead zero, AOB at 0 was 90. Later I fiddled with TDC and - to my astonishment, I overlook this earlier - when distance, bearing, AOB and speed are fixed on TDC, changing bearing results only in changing AOB. Distance stays the same. So, I hit first one when it was 550 from my bow, but same solution was applied to second C2, which was few hundred meters behind the first one.
I know why I missed, and realized it may be difficult to attack several targets at once - when they are travelling on the same lane (we're assuming they won't have a chance for ziggzagging) one has to prepare solution for first one, fire, than put scope on second, measure distance, with scope on second target input new distance to TDC and fire immediately.
Is my thinking correct on this one?
I will make one last run at a T3. However I only have one bow torp. left - I don't know when and how but I incidentally fired my aft torp. Possibly when I was hitting pause I pushed 'enter' with my palm. It happened before.
So -
where should I aim to sink T3 with one shot? I think if T2 went down after one, it can be done with T3 also. Should I aim below the stack? I hit T2 under small conning tower, not the one with stack.
Anyway, it was a very entertaining experience. I hope you enjoyed reading this, despite English errors