I have had success steaming at high speed parallel to the convoy course at 7-10 miles away to a point where I can turn in to be at 90 degrees to the convoy course about 15-20 miles ahead of the lead escort. When I am confident of the convoy's course, I close to ~1000 yards at 90 degrees and check torpedo settings (10 ft depth, Contact/Influence setting and Fast or Slow speed depending on how I want to shoot them if a selection is available)
When the convoy reaches 6-8 mi range, I submerge to 200 ft, silent running and battle stations. When the lead escort moves to about 15 degrees off the bow, I come up to 150 ft, and as the escort passes the bow and I am out of their prime sonar detection zone I continue to periscope depth, opening the outer doors as I pass through 100 ft.
After deciding which merchants to target, I up set and take the shots, then immediately submerge to maximum depth. After passing the thermocline, I begin zig zagging while creeping at 2-3 kt toward the transports to mask my sub's noise among the merchants and set up another shot if the opportunity presents itself, jogging at least five miles away before surfacing if no firing opportunity arises...
Every so often a superman sonar operator will display uncanny skill and dog my boat unerringly with only shreds of information, at which time I scrub the mission, go deep, go quiet and get out of Dodge.
