The Aichi Experimental Type 15-Ko Reconnaissance Seaplane (Mi-go) was designed to replace the Type Hansa Reconnaisance Seaplane but wasn't a success and didn't enter production.
After the end of the First World War Japan received a Hansa-Brandeburg W 33 reconnaissance seaplane as part of their war reparations (effectively booty from Germany). This was a twin-float low wing monoplane with open cockpits and a very distinctive tail, with the vertical surfaces below the horizontal tail plane, the reverse of the normal arrangement. The W 33 had been designed by Dr Ernst Heinkel. In 1922 it was adopted by the Japanese Navy as their new reconnaissance seaplane, replacing the Navy Type Yokosho Ro-go Ko-gata Reconnaissance Seaplane. The Type Hansa was produced by Aichi and Nakajima, and was used in front line service until 1927-28.
The Type Hansa wasn't popular with its pilots due to its poor handling and limited visibility while on the water. In 1924 the Imperial Japanese Navy decided to order a replacement for the aircraft, and asked Aichi, Nakajima and Yokosho to produce designs.
The Aichi design was effectively a modified Type Hansa, with a new wing, new floats and a different arrangement of struts, with the floats connected to the wings rather than to the fuselage as they had been on the earlier aircraft. The aircraft had a wooden framework, with a plywood covered fuselage and fabric covered wings. It was almost the same size as the older aircraft, but was lighter (both loaded and empty). Despite this it was only 8mph faster, and had a lower service ceiling, although its rate of climb was better.
The first prototype used Dornier bench-type aileron balances, but tests showed it to be unstable in flight. Aichi attempted to solve this problem by moving the centre of gravity, altering the positions of the seats and making a number of other changes. Despite all of their efforts Aichi were unable to improve the aircraft, and the Nakajima design was accepted for production as the Nakajima Type 15 Reconnaissance Seaplane.
Engine: Mitsubishi Type Hi (Hispano) vee water-cooled engine
Span: 44ft 9in
Length: 31ft 1.5in
Height: 10ft 9in
Empty weight: 2,645.5lb
Loaded weight: 3,748lb
Max speed: 112mph
Climb Rate: 18min 10sec to 9,843ft
Service ceiling: 15,748ft
Armament: One dorsal mounted 7.7mm machine-gun