First of all, you should preface you enquiry with the sea state you are attacking in. If it is glassy smooth seas, you might never shake them. If there is some chop to the waves, much better luck in that regard. If it is stormy, all the better. It is best to pick when to attack by the sea state and time of day.
First of all, your avoidance methodology somewhat depends upon how far away you are shooting from, and where the escorts are to begin with. If you are off to the side of the convoy, and inside the screen, you can sometimes use Ahead Flank and go deep, but do so in a straight line. You'll get down faster. If you hear "Passing thermal layer", note the depth and go no more than 50 foot below that. Then cut the motors and turn. If you know where the escorts all were to begin with, you could turn toward or away from them so that you present the smallest sized part of your boat to them that you can. Do that based upon which escort is where. Plan, man, before the attack... If they are close to you, go immediately to Run Silent. If instead, they were like 5000 yards away, you have a little bit before they close and can hear you. You want to get away from that spot you shot from though, because that will be where they look first, unless they hear you before that. Once they are relatively close to you, go to the Knot Gauge by clicking that "hamburger" menu button by the telegraph gauge. Once on that screen, click near the 1 knot mark on that gauge. You should then see the rpm gauge drop to about 50rpm. Those gauges are found by the helmsman's station in the Control Room toward the bow end.
Every once in a while after that, change your direction every once in a while, and alter your depth down another 50 or so feet. Do NOT come above 50 feet below where you heard the "Passing thermal layer". The game acts like it can "hear" your shears if you do... You might also notice, especially if you use the external camera, that the ocassional boat will pass directly overhead and drop a few depth charges, no matter how far away you are... in theory, those are just "scare tactic" drops, designed to get you to panic and go Ahead Full to get out from underneath the drops... then again, maybe they heard Bernard in the engine room drop that sledge hammer...
- Patience is required though, and you might take damages, and you might still be heard and have to do more to avoid, with greater use of speed changes, depth changes, and course changes...
