Hello, Alan,

I seem to recall, from books such as The Cruel Sea, that a u-boat could turn within a destroyer's turning circle. Bear in mind, though, that such things as the skill of both Captains could come into play, and that by increasing propeller revolutions on the outboard screw and decreasing them on the inboard one, under certain circumstances this did not become an issue. I think, however, that not all RN ships were twin screw, and this applies in particular to those brave little Flower class corvettes, with a single boiler, a triple-expansion reciprocating engine, and only one screw.

Handling characteristics are, therefore, a function of the skill of the commanding officer and what he had to work with.

As for maximum rate of descent under control, I can't answer that directly. I spent four years serving on Daphne submarines, and we could angle the boat as much as thirty degrees in perfect safety. These steep diving angles were never carried out at speed because of the noise factor, and I don't think we ever exceeded about four knots under those circumstances.

Further questions are welcome, and I think better posted in this forum, because I am sure that there are better qualified persons than me, and such subjects are of interest to all of us who tread here.

Best of luck

Garth