The first production model of the Ki-100 was Ki-100-I-Ko, based around the airframe of the earlier Kawasaki Ki-61 Hien. As an interceptor, the Ki-100 had a rate of climb of 500 metres per minute and a service ceiling of 10,700 metres. Operational range was
The first and only variant of the Ki-100 was a modified Ki-100-ko or Ki-100-I, designated the Ki-100-otsu or Ki-100-Ib. This version had parts of the fuselage located just behind the cockpit cut down so that the vehicle had increased vision for the pilot. An improved version, the Ki-100-II was also planned but never saw production due to the shortage of time at which the series was produced. The Ki-100-II sported an improved engine with a now added turbocharger to increase performance at the high altitudes where the Ki-100 operated.
The Ki-100 was developed in late 1944 to fit the gaps and replace aging Japanese designs of aircraft. It took the base of the Kawasaki Ki-61, one of the more successful aircraft of the IJAAF, and installed a radial engine. The original plan was to utilise the entire engine/nacelle installation from the Kawassaki Ki 102, but this was soon abandoned due to predictions of severe turbulence, and replaced with an exhaust and mount design based on that of the Focke Wulf Fw 190. This led to the removal of the coolant and lubrication pipes, and the associated ventral radiator and fairing, which initially made the aircraft excessively tail heavy. The design team were thus faced with two undesirable choices: extend the engine mount, or fit a counter weight to the nose. At this point senior designer Takeo Doe remembered that, due to the increasing weight of the Ki-61's Ha 140 engine, the airframe had lead weights placed in the tail. When the weights were removed, the new centre of gravity was almost exactly where it was supposed to be.[N 1]
The design itself was also heavily influenced upon the German Focke Wulf Fw 190. The engine choice in fact was more of a requirement of the times as the Ha-40 engines needed to make the traditional Ki-61s were out of supply to bombing raids. the entire engine/nacelle installation from the Kawassaki Ki 102
The first combat operation executed by Ki-100s was in March 1945 in use by numerous bomber interceptor units such as the 244th Sentai against B-29s. Results were conclusive, the Ki-100 far exceeded any expectations set for it. Arguably, it was one of the best interceptors that had ever been created. Even though maneuverability was not at the center of the design for the Ki-100, it still managed to outmaneuver anything the Allies had sent to protect their bombing raids. In total, approximately 400 units had been produced during the war.
- Doe later referred to this realisation as 'the providence of God'.
- Aeroplane Magazine Database section November 2005 - Ki-100. Page 64
- Aeroplane Database November 2005 - Ki-100. Page 66