Dornier Do 11

The Dornier Do 11 was a German heavy bomber developed in secret in the early 1930s, originally called the Dornier F before the Reichsluftfahrtministerium renamed it in 1933. It entered service in 1932 under the guise of a freight transport used with the German railway and Deutsche Luft Hansa, while in fact training crews for the still secret Luftwaffe. It was the first of its line to have two large engines, in place of the three or four of the Do Y and Do P. Wing vibration and gear problems made it unpopular, and it was withdrawn by 1936. Bulgaria also operated it.