I have noticed, at PD moving at 1-2 knots the sonar man wont follow contacts beyond 3500 yards. I go as far as to manually place the hydrophone in the direction of the contact, see on the notepad what it is and still the sonar man can track the contact, give range. The only odd thing is he says, no sound contact at bearing XXX that the actual contact is at visually (and locked on)
at PD or even deeper depths, at slow turns of the screws, sound contacts should be picked up by the sonarman.
Otherwise, maybe its the crew member...or not?