Nakajima Ki-27 Nate

All three contestants were single-seaters with open cockpits and two-wheel fixed landing gear with tail skids. Each was armed with two 7.7-mm machine guns housed in the fuselage, the standard Japanese fighter armament until the early ‘40s. Also, all embodied the strutted parasol wing layout as per the requirements of Koku Hombu. The direct cause of this requirement was the most recent trend in European fighter designs, particularly with regard to German and French constructions, of which a few had been bought for testing by the IJAAF, making a very strong impression on the Japanese military.
After the first factory tests, the prototypes of the three competitors were delivered to the IJAAF research establishment at Tokorozawa in the Saitama prefecture for comparison tests. However, flight tests were abandoned after the first Mitsubishi Hayabusa prototype literally fell apart in a diving attempt to exceed 400 kph. Ground testing on all the aircraft continued for some time. As a result, it was concluded that the strutted parasol layout was impractical and did not ensure the required strength of the construction, especially in the case of the heavy loadings experienced by fighter aircraft. In addition – even though the competition was largely inconclusive, given that none of the fighters met the requirements of Koku Hombu – the NC from Nakajima was found to be the best design. The Kawasaki KDA-3 was runner up, whereas the unfortunate Mitsubishi 1MF2 Hayabusa-go was abandoned.
Nakajima Type 91 monoplane
Despite the inconclusiveness of the ‘fly-off’, the Koku Hombu would not entirely give up the idea of a parasol fighter monoplane, and Nakajima was instructed to develop the basic NC design. The airframe was significantly stengthened and five more prototypes were built in 1929-1931. After the introduction of final modifications dictated by the results of flight tests, the aircraft was eventually approved by Koku Hombu in the fall of 1931 as capable of operational service; intended to replace the Ko 4, the fighter entered volume production under the designation Kyuichi-Shiki Sentoki, Army Type 91 Fighter (the 91 standing for the second part of the design year number according to the Japanese calendar – 2591). The production Type 91s were different from the original NCs chiefly in that they featured a redesigned wing of a smaller lifting surface, a redesigned fuselage, tail unit and wing struts, and a Jupiter VII engine of 450/520 hp enclosed by the Townend ring. In total, by September 1934 the Nakajima factory built 320 such aircraft, designated Type 91-1, plus 22 aircraft of the Type 91-2 version. These were powered by Nakajima Kotobuki 2 engines of 460/580 hp. Additionally, from September 1932 till March 1934 a further 101 (or 115 according to other sources) Type 91-1s were manufactured under license by Ishika­wajima.

arado 3

It should also be mentioned that in 1930, after the NC’s first failure but prior to its redesign, Nakajima purchased a license from Bristol in Britain for the production of the Bulldog Mk II fighter. This classic biplane was being considered as a potential replacement for the Ko 4 in the case of Koku Hombu’s definitive withdrawal from the development of a redesigned NC monoplane. However, upon the approval of the latter for production as the Type 91, further work on the Japanese Bulldog was abandoned after the construction of only two prototypes.
Kawasaki Type 92 biplane
Kawasaki was not discouraged by the lack of success of its KDA-3, and no later than June 1929 Dr Ing. Richard Vogt and Takeo Doi began working on the design of a new aircraft designated KDA-5. This was a light all-metal biplane with fabric-covered wings, open cockpit, and fixed two-wheel landing gear and a tail skid, powered by a BMW VI 6.3 rated at 500/630 hp and manufactured under license by Kawasaki. The aircraft was armed with two 7.7-mm machine guns. Assembled in July 1930, the first prototype attained a maximum speed of 320 kph and a ceiling of 10,000 m in tests. These results exceeded anything achieved by Japanese fighters of the time, and potentially placed the KDA-5 among the best fighter aircraft in the world. Built in January 1931, the second KDA-5 prototype achieved an even higher top speed of 335 kph. Impressed by this performance, Koku Hombu showed much interest in the new Kawasaki fighter and ordered volume production of the machine in January 1932 under the designation Kyuni-Shiki Sentoki, Army Type 92 Fighter. This decision was ratified not only on the basis of the fighter’s high performance (better than that of the only recently approved Nakajima Type 91) but also as a direct result of the military conflict with China developing in Manchuria, which called for a greater involvement on the part of the IJAAF.