I have had a great deal of success using them against escorts. I plot a normal solution and fire. It is best not to fire from close range as I think the homing device needs some time to activate. On occasion I have made desperation shots while being chased at 500m but that is really pushing it. If the torp misses, it will reacquire the target and often will take it out on a second attempt (they will alter course big time). If you are too close there are no second chances. There will be no time to reaquire.
It is important that your target is louder than you are. I usually order all stop after firing and the torp will chase the escort only. It is a waste of a torp to use one on a merchant. You can easily hit them with a standard load.
I will load one homing torpedo in the bow and two in the stern.
I like to sneak up to the head of the convoy (silent running) and take out the lead escort with a homing torp. (Possibly another escort on the flank of the convoy using the stern tube as well if they are close enough) After the lead escort is hit, come out of silent running mode so you can reload any tubes. You probably won't be heard if you took out the lead escort. You now have a bit of time to insinuate yourself into the convoy and do some damage and then dive deep in the middle of the convoy (escorts will have to go around shipping to get to you) after your attack. Remember, it is later in the war. That means more escorts, better detection. So, one attack on a juicy target and dive, dive, dive.
I have fired a few blindly into a convoy and they did lock onto a merchant and take them out. You can't be sure what merchant will be hit even if you lock onto it. It will lock onto the loudest ship. That's why they are so accurate against escorts - they are loud and they are usually isolated.
Happy hunting.
