POWER PLANT: One Mitsubishi Ha-211 Ru radial engine, rated at 2,200 hp
PERFORMANCE: 485 mph at 32,810 ft (estimated)
COMMENT: Preliminary discussions regarding a heavily armed high-altitude fighter were held between the Koku Hombu and Tachikawa Hikoki K. K. in mid-1942. The new aircraft was to be fitted with a pressure cabin and capable of reaching a top speed of 490 mph. The aircraft proposed by Tachikawa, which received the Kita designation Ki-94, was of a highly unconventional design. The aircraft was a large twin-boom monoplane, powered by two 2,200 hp Mitsubishi Ha-211 Ru air-cooled radials which were mounted fore and aft of the pilot’s cockpit and drove four-blade tractor and pusher propellers. The very heavy armament that should have been mounted on the aircraft should have been powerful enough to make short work of most US heavy bombers of that area at that time. A full-scale wooden mock-up of the Ki-94 was ordered and built although at the same time a contract was placed with Nakajima for another high-altitude fighter, the Ki- 87, with less stringent range requirements as a fall-back design for the Tachikawa Ki-94.
Notwithstanding the outstanding prospective performance, which however was judged by the technical department of the Japanese Army Air Force as “unduly optimistic” and too complex, the design was discarded. But in mid-1943 Tachikawa submitted a new proposal to meet the same requirements as the competitive Nakajima Ki-87. In order to avoid confusion the Kitai designation the first Tachikawa design received the designation Ki-94-I, and the new design Ki-94-II (Ref.: 1, 24).
POWER PLANT: One Kawasaki Ha 40 liquid-cooled engine, rated at 1,100 hp
PERFORMANCE: No data available
COMMENT: In the summer of 1941, Rikugun Kokugijutsu Kenkyujo (Japanese Army Aerotechnical Research Institute, short named “Kogiken”) formed a design group under the leadership of Ando Sheigo. The task was to study Japanese aviation technology in terms of what was possible at present and in the near future. Additionally, some effort was to be spent on reviewing the aircraft technology of other countries. From the results the group was to assemble and draft proposals for aircraft to fill various pre-determined roles: heavy fighter, light bomber, heavy bomber and reconnaissance. For a bigger idea pool, Imperial Japanese Army (IJA) main aircraft providers, Kawasaki and Tachikawa, were invited to join the group, too. In that period projects such as Kogiken Plan III Revised light bomber and Kogiken Plan V Revised light bomber were designed and proposed to the IJA.
Among fighter designs the Kogiken Plan I Type A was a single seat heavy fighter and a Japanese adaption of the Bell P-39 “Airacobra” mid-fuselage engine concept. The aircraft was designed end 1941 and should be powered by a single Kawasaki Ha 40 liquid-cooled in-line engine, derived from the German Daimler-Benz DB 601A. The engine was installed immediately aft the cockpit driving a four-bladed puller propeller via an extension shaft. A tricycle landing gear was provided similar to the Bell P-39. Armament consisted of 37 mm Ho-203 or 20 mm Ho-5 canon firing through the propeller hub and two wing-mounted 12.5 mm Ho-103 guns. No further details are known, the project never left the drawing board (Ref.: Parts from Unicraft).
POWER PLANT: Two Mitsubishi Ha-104 radial engines, rated at 1,900 hp each
PERFORMANCE: 324 mph at 19,980 ft
COMMENT: In early 1943 the Mitsubishi Ki-67 heavy bomber then undergoing flight trials had proved that despite its size and weight it was fast and manoeuvrable. Consequently it was suggested that the Ki-67 be used as a basis for a hunter-killer aircraft. The project received the designation Ki-109 and two versions were built. The Ki-109a, nick-named “Killer”, was to mount in the rear fuselage two oblique-firing 37 mm Ho-203 cannon while the Ki-109b, the “Hunter”, was to be equipped with radar and a 40 cm search light. However, soon thereafter, the project was redirected and a standard 75 mm Type 88 anti-aircraft cannon was to be mounted in the nose. It was hoped that with this large cannon the aircraft could be able to fire on the Boeing B-29s while staying well out of range of their defensive armament. As the authorities anticipated that, initially at least, the B-29s would have to operate without fighter escort, the project was found sound and feasible and Mitsubishi were instructed in early 1944 to begin designing the aircraft which retained the Ki-109 designation.
Ground and inflight test firing of the heavy gun were sufficiently successful and an initial order of 44 aircraft was placed. Fifteen shells were carried for the 75 mm Type 88 cannon which were hand-loaded by the co-pilot, and the sole defensive armament consisted of a flexible 12.7 mm machine-gun in the tail turret. The rest of the airframe and the power plant were identical to those of the Ki-67. Despite the lack of high-altitude performance the Ki-109 was pressed into service, but, by the time enough aircrafts were on hand, the B-29s had switched to low-altitude night operations. A total of 22 Ki-109s were built by Mitsubishi Jukogyo K.K. (Ref.: 1).
POWER PLANT: One Nakajima Ha.35/21 air-cooled radial engine, rated at 1.130 hp
PERFORMANCE: 320 mph at 19,680 ft
COMMENT: Combat experiences with the Ki-43-I dictated a number of changes in the design of the aircraft that led to the development of the Nakajima Ki-43-II-KAI. It entered service in summer 1943 and served over every theatre to which the JAAF was committed. The Ki-43-II-KAI was capable to out-maneuvering every Allied fighter it encountered and its element was dog-fighting, but the Lockheed P-38 ‘Lightning’, the Republic P-47 ‘Thunderbolt’ and the north American P-51 ‘Mustang’ could all out-dive and out-zoom the Japanese fighter which could not withstand the greater firepower of the Allied types, frequently disintegrating in the air when hit. More than 5.000 Ki-43-II ‘Hayabusa’ were built by Nakajima and Tachikawa (Ref.: 13)
POWER PLANT: One Nakajima Ha.115 radial engine, rated at 1,130 hp
PERFORMANCE: 320 mph at 19,680 ft
COMMENT: The Nakajima Ki-43 ‘Hayabusa’was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in WW II. It was light and easy to fly and became legendary for its combat performance in East Asia in the early years of the war. It could outmaneuver any opponent, but did not have armor or self-sealing tanks, and its armament was poor until its final version, which was produced as late as 1945. Allied pilots often reported that the nimble Ki-43s were difficult targets but burned easily or broke apart with few hits. In spite of its drawbacks, the Ki-43 shot down more Allied aircraft than any other Japanese fighter and almost all the JAAF’s aces achieved most of their kills in it. Prototypes for the Nakajima Ki-43-II flew in February 1942. The Ha-25 engine was upgraded with the 2-stage supercharger, thus becoming the more powerful Nakajima Ha-115 engine, which was installed in a longer-chord cowling. The new engine turned a three-bladed propeller. The wing structure, which had suffered failures in the Ki-43-I, was strengthened and equipped with racks for drop tanks or bombs. The Ki-43-II was also fitted with 13 mm armor plate for the pilot’s head and back, and the aircraft’s fuel tanks were coated in rubber to form a crude self-sealing tank. Nakajima commenced production of the Ki-43-II at its Ota factory in November 1942. Production was also started at the Tachikawa Hikoki KK and the 1st Army Air Arsenal (Tachikawa Dai-Ichi Rikugun Kokusho), also at Tachikawa. Although Tachikawa Hikoki successfully managed to enter into large-scale production of the Ki-43, the 1st Army Air Arsenal was less successful – hampered by a shortage of skilled workers, it was ordered to stop production after 49 Ki-43s were built. Nakajima eventually ceased production in mid-1944 in favor of the Nakajima Ki-84 ‘Hayate’, but the Tachikawa Hikoki continued to produce the Ki-43. Total production amounted to 5,919 aircraft. Many of these were used during the last months of the war for kamikaze missions against the American fleet (Ref.: 24).
TYPE: Twin-engined heavy fighter, ground attack aircraft
ACCOMMODATION: Pilot and radio-operator/gunner
POWER PLANT: Two Mitsubishi Ha-102 radial engines, rated at 1,050 hp each
PERFORMANCE: 335 mph at 19,685 ft
COMMENT: The Kawasaki Ki-45-Kai Toryu was probably the most manoeuvrable twin-engined fighter to be employed operationally by any combatants during WW II. Although outclassed in the air-to-air combat arena by Allied single-seat fighters, the Toryu was never to be considered an “easy kill” and it was to prove capable of out-manoeuvring the Lockheed P-38 “Lightning” without difficulty. Furthermore, the Ki-45 was very effective in ground attacks. A special version, the Ki-45-KAI-Otsu, was equipped with 20-mm Ho-3 cannon, too low-firing in air combat, but, as the Imperial Army enjoyed air superiority over the areas in which the Toryu was operating, it was found to be particularly efficacious in attacks on US Navy PT boats and other smaller vessels and in ground-attack role. In late 1943 the 20-mm Ho-3 cannon was replaced by a hand loaded 37-mm Type 98 gun, making this variant even more successful for close-support duties (Ref.: 5).
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-engined heavy fighter, ground attack aircraft and night fighter
ACCOMMODATION: Pilot and radio operator/gunner
POWER PLANT: Two Mitsubishi Ha-102radial engines, rated at 1080 hp each
PERFORMANCE: 373 mph at 9,186 ft
COMMENT: The primary task of the Kawasaki Ki-45 “Toryu” , it’s design dates back to the late 1930th , was long-range escort of bombers. But it took a long time until the first pre-series aircraft were completed and flight testing initiated. Soon it became clear that the model has to be revised. This new aircraft, Ki-45-KAI (Kaizo means modified) was in fact a totally new design and performed completely satisfactory during its initial flight tests. Orders for quantity production were placed and the first aircrafts reached units by August 1942. The increasing use by the USAAF of B-24 Liberators by night called for improvisation on the part of the Imperial Army as the service possessed no specialized night fighters. The Ki-45-KAI-Ko was a choice for the nocturnal role and a field modification resulted in installation of a pair of Ho-103 machine guns or Ho-5 cannon mounted obliquely to fire upward and forward at an angle of some 70 degrees. While lacking AI radar and being forced to rely on ground guidance to intercept intruders, with searchlight illuminating the quarry, the Toryu enjoyed some success as a night fighter (Ref.: 5).
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).
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).