It was a conventional single-bay biplane with staggered wings braced by N-type interplane struts.

Aichi Tokei Denki requested a design for a reconnaissance seaplane from Heinkel to enter in an IJN competition.

The Heinkel design was announced the winner in 1931, on the condition that Aichi would address some shortcomings, particularly a lack of range.

Modifications to the HD 56 by Aichi included reductions in length and span, the replacement of the prototype's Wright Whirlwind with a locally-built Hitachi Tempu, and numerous detail changes.

Flight tests were carried out at Nagoya in August 1931, and the type was accepted into service the following year.