@ducimus
the japanese never really had a functional equivalent of the british q system. the type 193 was the searchlight system they started the war with, and the type 3 was basically a copy of the german s-gerat active sonar. both were searchlight systems with a limited downward angle -- couldn't find any actual info about the specific angle.
they eventually did develop a "dipping" system to calculate a subs depth, which involved changing the angle of the sonar beam and then using some kind of mechanical calculator, but the calculation system apparently took too long to be of much tactical use. i'm sure bungo pete would've used it, though.
just some added info -- i know your philosophy is gameplay first
i might go back to sh4 now that tm 1.4 is out -- thanks for your work.
an interesting aside is that the japanese often equipped their merchant ships with both active and passive sonar systems -- how effective they were is unclear.