[AVGWarhawk]

I also use the 90 degree approach. I go deep to avoid the escort. Once he has passed I make my run to the merchants. I exit out the back of convoy. Sometimes I can submerge into the track of the convoy and wait. That usually works. Your best bet is attack at night. Wait at some distance at 90 degrees of the convoy track. Once the patrol craft pass, make a high speed run at the convoy, let all you available tubes go and the stern tube if you can, dive deep and exit the back of convoy. Repeat as neccessary.