 Torpedo bombers were modified Heinkel He 111 and Junkers Ju 88 aircraft, but the Focke-Wulf Fw 190 fighter aircraft was successfully tested as a delivery system.Deficiencies in German-designed torpedoes after the capitulation of Italy in September 1943 were addressed just over a year before, through the "yanagi" visit of Japanese submarine "I-30" in August 1942, to supply the Wehrmacht with the Type 91 torpedo's technology and blueprints, to be made in Germany itself as the Lufttorpedo LT 850.The Mark 13 torpedo was the main American aerial torpedo, yet it was not perfected until after 1943 when tests showed that it failed in 70 percent of the drops made from aircraft traveling faster than .