Design work on the Ki-12 was a collaboration between engineers Roger Robert and Jean Beziaud from the French Dewoitine firm and Shigenobu Mori, a Nakajima engineer, and was heavily influenced by the Dewoitine D.510 design.[1][2] Nakajima wanted the new design to be the most technically advanced in Japan.[2] Based on the Ki-11 airframe, the engine was replaced by a liquid-cooled 454 kW (610 hp) Hispano-Suiza 12Xcrs V engine. The landing gear were fully retractable (the first Japanese design to have this feature),[2] and the design introduced the use of slotted flaps. Proposed armament consisted of a 20 mm cannons firing from between the engine cylinders and twin 7.7 mm (.303 in) machine guns.
The Ki-12 was tested against the Mitsubishi Ki-18. Although technically advanced and with advantages in speed, range and firepower over the other contemporary Japanese fighter designs, the Ki-12 was deemed too heavy and complex by the Imperial Japanese Army Air Force. The IJAAF also felt that the design was lacking in maneuverability, and would not want to rely on the manufacturing licence for the Hispano-Suiza engine.[2]
Although the Army declined to pursue the project, Nakajima continued to refine the design, introducing a simpler version styled the Nakajima Type P.E., which evolved into the successful Ki-27 "Nate" several years later.
