The Hopfner HA-11/33 was an amphibious flying boat built in Austria in 1933 to a specification by the Dr. Oetker company for such an aircraft. The result was a conventional, high-wing cantilever monoplane with a stepped flying boat hull and pontoons on struts under the wings at mid-span. The cabin was fully enclosed, and the twin engines were mounted tractor-fashion on struts above the wing. The first prototype, tail number A-141 took off from the surface of the lake at the end of 1933. In 1935 the boat for training purposes, they have bought the Air Force Austria, where she
A HA-11/33 was purchased by the Austrian Air Force, received a registration number OE-DGH, and was subsequently absorbed into the German Luftwaffe following the Anschluß. Deemed worthy of further development, WNF (which had absorbed Hirtenburg, which itself had taken over Hopfner) was tasked with developing it into a military training aircraft for flying boat pilots. Designated WNF Wn 11 by the RLM, testing was undertaken at Travemünde in 1940, it crashed and no further development was done. The type was not ordered into production. Development of a highly streamlined derivative with Hirth HM 508 engines, the WNF Wn 11C was also abandoned.

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