Albrecht Heilmann, Helmsman aboard the UB-77 reports, that at the time when the transport Tuscania was attacked, the impact of the torpedo was felt aboard the u-boat. The concussion from the blast rolled the submarine.

 2005 INFORMATION SOURCE:

Wisconsin Newspaper

5th Feb. 1936 - Sheboygan Press, "History of the Tuscania Destruction," Page 4, 5, 6, 8.