Mitsubishi Ha-43

The Mitsubishi Ha-43 was a Japanese 18-cylinder, twin-row air-cooled radial engine developed during World War II. The Army air force knew it as the Ha-211 and the Navy air service as the MK9, and Mitsubishi itself designated it the A20. It was a more powerful derivative of the 14-cylinder Kinsei and was Mitsubishi's answer to the Nakajima Ha-45. The engine was planned to produce 2,200 hp (1,600 kW) while keeping high reliability and a superior power-to-weight ratio, and its frontal area per horsepower was meant to be the smallest in the world. Development was delayed because Mitsubishi gave priority to the Ha-42, an 18-cylinder derivative of the Kasei. Aircraft such as the Kyushu J7W interceptor and Mitsubishi's own A7M Reppu fighter were planned to use it, but only prototypes were built and neither the aircraft nor the engine saw combat.