That is why I never use, what the Uboat Commanders Handbook calls "The 90° shot".
And this is another reason, although the TDC doesn't require it, that you use the good perpendicular approach course. It makes determining range, and estimating AoB much easier in my opinion.
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U.Kdt.Hdb B. I. 28) This possibility of using the hydrophone to help in detecting surface ships should, however, be restricted to those cases where the submarine is unavoidably compelled to stay below the surface.
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