Kawasaki Ki-100

The roots of the Ki-100 lay in another Kawasaki aircraft the Ki-61-II which was being used as a high altitude interceptor to attack the high flying Boeing B-29 Superfortress being used at altitudes of around 30,000 ft by the United States. The Ki-61-II was only considered as a stopgap and was powered by the still in development 1,500-hp Kawasaki Ha-140 engine. However the Akashi factory which was manufacturing the engine would be destroyed as a result of an air raid meaning the engine program was cancelled.

As a result of the Kawasaki Ha-140 engine program being abandoned there were 275 Ki-61-II airframes left without engines. Kawasaki were tasked with finding another engine to be installed instead. The major issue was that the aircraft was designed for an inline engine and no alternative was available. The decision was taken to modify three of the excess airframes to take the Mitsubishi Ha-112 II radial engine which provided the same power as the Kawasaki Ha-140.

Making its maiden flight on the 1st February 1945 the aircraft impressed Kawasaki and work started on converting the remaining 272 airframes, which would be completed by the end of May, with the first aircraft entering service on the 9th March 1945. Powered by the 1,500-hp Mitsubishi Ha-112 II engine, it had a top speed of 360 mph, range of 1,367 miles with a service ceiling of 36,090 ft. Armament consisted of two 20mm Ho-5 cannons and two 0.50-in Ho-103 machine-guns. The aircraft in its new configuration would be called the Ki-100, with this variant designated Ki-100-Ia. Although when it entered service with the Imperial Japanese Army it was known as the Type 5 Fighter Model 1A.

Two more Ki-100 variants were produced before the increasing air attacks by the United States Army Air Force and the end of the Second World War (1939 - 1945) brought production to a halt. The first was the Ki-100-Ib, of which 99 were produced, which would have an all-round-view canopy installed. This had originally been designed to be fitted to the intended Ki-61-III design which never entered production. Its rear fuselage was cut down as well. The next version would see just three prototypes built for what was to be the Ki-100-II. The turbocharged Mitsubishi Ha-112-IIru which would provide better performance at high altitude was to power these aircraft.

In total 395 aircraft would be modified or built as Ki-100s.

Ki-100-Ib at the Royal Air Force Museum, Midlands