ASDIC modelling in game

[stellaferox]

Thanks for this post. I don't know if this was the case in the beginning after the war. Anyway if you read up on how Scheppke could be sunk and Kretschmer was invisible on the surface until the dive alarm was (falsely) given. Then he showed up on ASDIC. Read the numbers in there somewhere.
Anyway ASDIC didn't work on surfaced U-boats of at periscope depth.

[AKD]

ASDIC (searchlight type developed before war) could detect subs at periscope depth. It could also detect surface ships in particular conditions, although a surfaced U-Boat would be a small target, especially if bow-on.

ASDIC maximum range was against a submarine at periscope depth, typically given as 2,000-2,500 yards (in ideal conditions, perhaps out to 3,000-4,000 yards), although average detection range during the war was more like 1,300 yards. For a periscope depth target, contact could be maintained down to 250 yards or so, depending on signal-echo merge. Contact on deeper submarines would be lost at greater distances, which was countered with additional mid- to late-war tech like "Q" and "Sword" in illustration above that allowed ASDIC operators to maintain contact with deep subs down to the signal merge. However, ocean conditions could alter detection ranges based on depth significantly.

For the anecdote given, ASDIC performance varied hugely depending on ocean conditions and operator skill. Conditions can also alter radically during the course of a engagement due to depth charges and wakes.