Given the brilliant response to my Schnee Organ question, I venture another one (hope as a new user to the forum this doesn't tax the patience of the experts unduly).

Again given my experience with the Silent Hunter III submarine simulator, I am wondering about the various drivers of the depth level decision facing a commander under destroyer attack.

It would seem that most everything points towards going as deep as possible:

* More difficult tracking (though appreciate late-war ASDIC etc. was very effective)

* More time for evasive manouvering between DC/ Hedgehog launch and impact (this would be a straight linear relationship - @10 feet/second descend depth, a u-boat at a depth of 270m (900 feet) and sailing @8 knots (4m/sec) would be able to cover 360m before impact, easily enough to get out of harms way except if the destroyer captain was a psychic. At 90m depth, the uboat would cover only 120m, rather less comfortable, particularly with a Hedgehog attack thrown forwards from the destroyer

* Lesser effectiveness of DCs at depth[???], i.e. need to be closer to the hull to kill than the near-to-the-surface ~5 meters DC lethal distance(though this may reflect on my poor understanding of fluid dynamics and clearly does not apply to Hedgehogs)

The main countervailing factors would obviously be:

* the risk of reaching (and exceeding) crush depth
(Was this in effect a predictably quantity for the commander, given general design parameters, and specific maintenance status of the boat/ specific experience from training dives?)

* the lower probability of being able to conduct an emergency surface, should damage occur

* the larger probability of a leak being catastrophic, the deeper you are

* the difficulty of getting into a decent firing position from great depth (though I guess surviving was generally of greater concern)


Given the above, I think the purely rational (ignoring the terror of crunching-like sounds on the hull at great depth), would have been to go the edge of the depth envelope, particularly in late war scenarios and/or with a consistent hunter/killer team above you.

Any comments on above, and on following specific questions:

1) What was the greatest depth reached by U-boats during combat, and how did it relate to their theoretical max depths? Any known examples of uboats going below 300m? [obviously, diving depth differs between types, believe late-war VIICs the deepest divers]

2) How many times were uboats sunk through "pure" crushing, i.e. without being hit, at that moment, by DCs, Hedgehogs etc?. Assuming attacking destroyers would be able to hear crushing noises, and relate to their own attack, to generate these statistics.


3) How much warning (through creaking, leaking valves etc.) would a captain get that his boat was nearing crushing depth? Would just ascending 5m take him out of danger (the way you can get out of ear discomfort, as a diver, just by ascending a little)

4) What were the weakest points, from a crush depth perspective?

5) What German measures were taken towards the end of the war, to increase max diving depth, and how effective were they? (my impression would be that allied bombing campaigns would if anything decrease build quality, and hence diving depth) towards 44/45?

6) Believe the relatively recent Alpha class Soviet sub was able to go to 500m or below. Is this true, and what US tactical countermeasures did this lead to?

Thanks in advance for any/ all reflections on above.