Kawasaki Ki-60. The Kawasaki Ki-60 was an experimental Japanese pre-World War II fighter aircraft that used a license-built (Kawasaki) DB 601 liquid-cooled engine. This was, at that time, an unusual choice because the majority of Japanese aircraft at that time used air-cooled radial engines. Design and Development The Ki-60 was designed by Takeo Doi and his deputy Shin Owada of Kawasaki Aircraft Industries (Kawasaki Kōkūki Kōgyō K.K.) in response to a 1939 Imperial Japanese Army Aviation Bureau requirement for a heavily-armed, specialized interceptor fighter to be powered by the liquid-cooled Daimler-Benz DB 601 inverted V12 engine, which had been selected for license production by Kawasaki as the Ha-40. The emphasis in the requirements was for a high speed and a good rate of climb, along with a cannon armament. This was a complete change from the usual IJAAF penchant for lightly armed, highly maneuverable fighters with lightweight structures, epitomized by the Nakajima Ki-27 and...