So it's not like cycling the vents to release trapped air in the ballast tanks after the dive. I was wondering along those lines but couldn't remember ever hearing an order to "Cycle the tubes." Not that it didn't happen, I just never heard it.
Come to think of it, it was the poppet valve's job, I think, to scavenge off the air following a torpedo shot so that the left-over impulse air wouldn't bubble to the surface and give the boat's position away. But then again I wasn't a TM and they might well have been cycling the tubes regularly and not telling anybody
.
At any rate, thanks to this thread, I now know what the "W" key really does. And that's a help. One more piece of the puzzle.
Thanks