The Aichi E12A was a two-seat twin-float reconnaissance floatplane designed in response to a Japanese Navy 12-Shi specification issued in 1937 for an aircraft to replace the Kawanishi E7K2 three-seat reconnaissance seaplane. The specification was issued to Aichi, Kawanishi and Nakajima, but before the prototypes had been completed a second 12-Shi specification was issued, calling for a three-seat floatplane, to be developed alongside the two seat model.
Only Aichi decided to develop both aircraft, producing prototypes of both the E12A and E13A. Kawanishi concentrated on the three seat version, producing the E13K, while Nakajima focused on their two-seat E12N.
The E12A was a single engined monoplane floatplane, powered by a 870hp Mitsubishi Zuisei radial engine. The two crewmen sat in tandem in a single cockpit. The aircraft was very similar to the E13A, which was simply a larger version of the same design, with a more powerful engine.
The prototype E12As and E13As were both ready at the end of 1938. Aichi’s own tests showed that the larger but more powerful aircraft was faster and more stable in flight. By 1939 the Japanese Navy had also decided that it preferred the three seat designs, and so work on the E12A (and on the E12N) was suspended. Competitive tests of the Aichi E13A and Kawanishi E13K followed, and in December 1940 the Aichi design was declared the winner, entering production as the Navy Type 0 Reconnaissance Seaplane Model 1.