TYPE: Twin-engined high-altitude fighter

ACCOMMODATION: Pilot in pressure cabin

POWER PLANT: Two Mitsubishi Ha-112-II Ru radial engines, rated at 1,500 hp each

PERFORMANCE: 360 mph at 32,810 ft

COMMENT: In early 1943 intelligence reports concerning progress in the USA with the B-29 Superfortress recognized the Imperial Army Air Service that itself might eventually find confronted by bombers cruising above the effective combat ceiling of its existing fighters. So a requirement was prepared for a specialized heavy interceptor fighter capable of operating at extreme altitudes. Kawasaki proposed a derivative of its Ki-102, work on which just had commenced, featuring a pressure cabin for the pilot. As work proceeded the project was assigned the designation Ki-108. Two prototypes were ordered and flight trials began in mid 1944. Concerning the pressure cabin, it was calculated than an equivalent pressure of 9,845 ft could be maintained up to an altitude of 32,810 ft, but there were serious misgivings concerning the vulnerability of such a cabin to battle damage. These were answered in somewhat unexpected fashion, for, during early flight tests, an insecure lock resulted in the entry hatch blowing out at an altitude of some 33,000 ft with an immediate loss of pressure in consequence. The pilot immediately dived the aircraft and landed safely, indicating that the effect of a bullet penetration the pressure cabin would not be particularly hazardous. Further modifications resulted in the Kawasaki Ki-108-KAI (Ref.: 5).

TYPE: Twin engine heavy fighter

ACCOMMODATION: Pilot only

POWER PLANT: Two Mitsubishi Ha-12-11 radial engine, rated at 1,500 hp

PERFORMANCE: 391 mph at 31,170 ft

COMMENT: The great success of the Kawasaki Ki-45-KAI “Toryu” (“Dragon Slayer”, Allied code “Nick”) encouraged the Kawasaki Company to initiate work on a refined, more powerful derivative of the Ki-45. Compared with its forerunner an aerodynamically improved fuselage, a larger square-tipped vertical tail surface, and more powerful engines were provided. In 1943 work on the Ki-96 gained tempo and in September that year the first prototype was completed. In the meantime it became obvious that a second crew member was superfluous in a high-performance twin-engined fighter. So the second cockpit of the first prototype was faired over and the two other prototypes under construction were finished as single-seater. Flight test were most satisfactory, the Ki-96 combining good handling characteristics with performance exceeding design estimates. However, the Army’s interest in the potential of single-seat twin-engined fighters was to prove short-lived and consequently the Ki-96 had only a brief live as an aerodynamically prototype for the two-seat Kawasaki Ki-102 which supplanted it (Ref.: 1, 5).

TYPE: High-speed research aircraft

ACCOMMODATION: Pilot only

POWER PLANT: One Daimler-Benz DB 601A liquid-cooled piston engine, rated at 1,155 hp with Water/Methanol injection                  

PERFORMANCE: 435 mph at 11,500 ft

COMMENT: The Ki-78, designed at the Aeronautical Research Institute and built at Kawasaki Kokuki Kogyo K.K. to investigate flying behaviour at very high speed, featured a streamlined minimum cross-section fuselage fitted with a licence-built Daimler-Benz DB 601A engine. For short duration power boost methanol/water injection was used, and cooling was improved by a 60 hp turbine driven cooling fan for the radiators. By the outbreak of the war, the whole project was taken over by the Imperial Japanese Army who gave it the military type designation Ki-78. Kawasaki received the order to build two prototypes of the Ki-78, construction of which was started in September 1941. The first prototype was completed more than a year later and was flown for the first time on 26 December 1942. A feasibility study to improve the KI-78 flight performance showed that extensive airframe modifications were needed and consequently the project was officially terminated after the 32nd flight on 11 January 1944; the second Ki-78 was never completed (Ref.: 23).

TYPE: Interceptor fighter

ACCOMODATION: Pilot only

POWER PLANT: : One Daimler-Benz DB 601 liquid-cooled inverted V-12 engine, rated at 1,175 hp

PERFORMANCE: 348 mph at 14,800 ft

COMMENT: The Kawasaki Ki-60 was an experimental fighter that used a license-built German Daimler-Benz (Kawasaki) DB 601 liquid-cooled engine. This was at that time an unusual choice because the majority of Japanese aircraft used air-cooled radial engines. The Ki-60 was designed by Kawasaki Aircraft Industries in response to a 1939 Imperial Japanese Army Aviation Bureau requirement for a heavily armed specialised 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. A requirement was issued at the same time for a lighter, less heavily armed, general-purpose fighter which was to be designed almost in parallel with the Ki-60; this became the Kawasaki Ki-61 Hien. Priority was to be given to the Ki-60, design of which started in February 1940. The first prototype of the Ki-60 emerged in March 1941 as a compact monoplane with a relatively deep fuselage and tapered wings with rounded tips built around a system of three spars. The pilot’s seat was mounted high over the rear spar, giving the fuselage a distinctive “humped” profile; the hood featured a framed, rear sliding canopy and an elongated rear transparent section. The main coolant radiator was housed in a long ventral bath under the wing center-section and central fuselage, while the oil cooler was mounted under the engine with a long air intake. The prototype was powered by an imported Daimler-Benz DB 601A as production of the Ha-40 had not yet started. Although a top speed of 370 mph had been projected the Ki-60 was only able to achieve 341 mph. By this time the Nakajima Ki-44 Hajabusa, which had also been designed as a dedicated interceptor, was beginning to show some promise and the Koku Hombu selected this in fulfilment of its requirements. From early 1941 the full attention was focused on the Kawasaki Ki-61 Hien, but the Ki-60 became important in that the Ki-61 design was able to be improved using the lessons learned from the poor characteristics of the Ki-60. Plans for production were cancelled in late 1941 after three airplanes had been built. (Ref.: 23)

TYPE: Interceptor fighter

ACCOMMODATION: Pilot only

POWER PLANT: One Nakajima Ha-109 radial engine, rated at 1,520 hp

PERFORMANCE: 367 mph at 17,060 ft

COMMENT: The Ki-44-IIc variant of the Nakajima Shoki aircraft was armed with wing-mounted 20 mm Ho-3 cannon that proved particular effective against the B-29’s attacking Japan. But in December 1944, Shoki production terminated as the aircraft was replaced on Nakajima’s assembly-lines by the Nakajima Ki-84 Hayate and, when the war ended, only three Sentais were still equipped with them. In total 1, 225 Ki-44’s were built (Ref.: 1, 6)

TYPE: Interceptor fighter

ACCOMMODATION: Pilot only

POWER PLANT: One Nakajima Ha-45-21 radial engine, rated at 1,990 hp

PERFORMANCE: 385 mph at 21.325 ft

COMMENT: Although the Nakajima Ki-84 Hayate was one of the most successful Japanese aircraft a modified version seemed to be necessary due to the increasingly critical light alloy supply situation as the war progressed. In late 1943 Tachikawa Hikoki K.K. were entrusted by the Ministry of Munitions with the task of designing an all-wood version of the Ki-84. Work on three airframes, designated Ki-106, began in autumn 1944, but various factors delayed the programme and the first of these prototypes was not to be completed and flown until July 1945. The Ki-106 was heavier than the standard Ki-84 what exerted an adverse effect on maneuverability and climb rate, but maximum level speed was virtually unchanged. The end of the war brought the Ki-106 project to a halt. (Ref.: 1., 6.)