POWER PLANT: One Kawasaki Ha-140 liquid-cooled engine, rated at 1,500 hp
PERFORMANCE: 373 mph at 19,685 ft
COMMENT: The Kawasaki Ki 88 was designed as a fighter aircraft and inspired by the Bell P-39 Airacobra. Work on the design began in 1942 and by 1943 a full-scale mock-up was completed. The engine was mounted behind the cockpit, driving a tractor propeller via an extension shaft. Proposed armament comprised a 37 mm cannon in the propeller shaft and two 20 mm cannon in the lower section of the nose. Calculation suggested no great improvement on that of the Kawasaki Ki-61 Hien already in production, and so the project was abandoned during 1943 (Ref.: 1).
POWER PLANT: One Kawasaki Ha-40 liquid-cooled engine, rated at 1,175 hp
PERFORMANCE: 370 mph at 15,950 ft (estimated)
COMMENT: The Nakajima Ki-62 was a light fighter designed in 1941 to compete with the Kawasaki Ki-61 “Hien”. Although this design appeared to be promising, its development was discontinued to enable Nakajima to concentrate on production of their Ki-63 “Hayabusa” and Ki-44 “Shoki” fighters. Later, the Ki-62’s data and design features were incorporated in the Nakajima Ki-84 “Hayate” design (Ref.: 1).
POWER PLANT: One Nakajima Ha-44 radial engine, rated at 2,200 hp
PERFORMANCE: 439 mph at 36,090 ft (estimated)
COMMENT: The Nakajima Ki-87 was developed in response to American Boeing B-29 “Superfortress” raids on the Home Islands. It followed up on earlier research by Nakajima and the Technical Division of Imperial Army Headquarters into boosting a large radial engine with an exhaust-driven turbo-supercharger, which had begun in 1942, well before the B-29 raids began. The efforts of the Technical Division of Imperial Army Headquarters eventually culminated into the Tachikawa Ki-94-I, while the Nakajima Ki-87 was developed as a fall-back project, using less stringent requirements. Nakajima started in July 1943 with the construction of three prototypes, to be completed between November 1944 and January 1945, and seven pre-production aircraft, to be delivered by April 1945. The Technical Division of Imperial Army Headquarters made itself felt during the development of the Ki-87 prototype when they insisted upon placing the turbo-supercharger in the rear-fuselage, and from the sixth prototype the Nakajima fighter was to have that arrangement. The Ki-87 had a rearward folding undercarriage to accommodate the storage of ammunition for the cannons, which were mounted in the wing.
Construction was delayed due to problems with the electrical undercarriage and the turbo-supercharger, and the first prototype was not completed until February 1945; it first flew in April, but only five test flights were completed, all with the undercarriage in the extended position. Production of 500 aircraft was planned, but the war ended before any more than the single prototype was built.
A further variant, the Nakajima Ki-87-II, powered by a 3,000 hp Nakajima Ha-217 (Ha-46) engine and with the turbo-supercharger in the same position as the USAAF Republic P-47 “Thunderbolt”, never went further than the drawing board (Ref.: 24).
POWER PLANT: Two Mitsubishi Ha 211 Ru (Ha-43) radial engines, rated at 2,070 hp each
PERFORMANCE: 438 mph at 32,180 ft
COMMENT: The Mitsubishi Ki-83 was designed as a long-range heavy fighter. The design was a response to a 1943 specification for a new heavy fighter with great range. The first of four prototypes flew on 18 November 1944. The machines displayed remarkable maneuverability for aircraft of their size and carried a powerful armament of two 30 mm and two 20 mm cannon in its nose. Despite the bomb-ravaged Japanese manufacturing sector, plans for the Ki-83 to enter production within were underway when Japan surrendered on 15 August 1945.
Both the existence and performance of the Ki-83 were little known during the war, even in Japan. It was completely unknown in Allied military aviation circles – as demonstrated by the fact that the Ki-83 had not been given a reporting name. Most early photographs of the type were taken during the post-war occupation of Japan, when the four prototypes were seized by the USAAF and re-painted with USAAF insignia. When they were evaluated by US aeronautical engineers and other experts, a Ki-83 using high-octane fuel reached a speed of 473 mph at an altitude of 23,000 ft (Ref.: 24).
POWER PLANT: One Kawasaki Ha-201 coupled liquid-cooled engines, rated at 2,350 hp
PERFORMANCE: 430 mph at 16.000 ft
COMMENT: The Kawasaki Ki-64, Allied code name “Rob”, was a one-off prototype of an experimental heavy, single seat, fighter. It had two unusual design features. First; it had two Kawasaki Ha-40 engines in tandem; one in the aircraft nose, the other behind the cockpit, both being connected by a drive shaft. This combination, called the Kawasaki Ha-201, drove two, three-bladed, contra-rotating propellers. The second feature was the use of the wing surface as a radiator for the water-cooled engines. The aircraft first flew in December 1943. During the fifth flight, the rear engine caught fire; and while the aircraft made an emergency landing, it was damaged. The aircraft was subsequently abandoned in mid-1944 in favour of more promising projects. The airframe survived the war, and parts of the unique cooling system were sent to Wright Field in the US for examination (Ref.: 24).
POWER PLANT: One Nakajima Ha-44 radial engine, rated at 2,450 hp
PERFORMANCE: 442 mph at 39,370 ft (estimated)
COMMENT: In mid-1942, the Imperial Japanese Army Air Force wanted to obtain a high-altitude fighter fitted with a pressure cabin and capable of reaching a top speed of 497 mph and having a maximum range of 1,850 miles. As these performance requirements were rather stringent, the Koku Hombu decided to instruct Tachikawa to proceed with the design of the aircraft designated Ki- 94 while they placed a contract with Nakajima for another high-altitude fighter, the Ki- 87, with less stringent range requirements.
The initial aircraft was a large twin-boom monoplane with two engines mounted in tandem driving four-blade tractor and pusher propellers. But it was judged that the design was too complex and in 1943 Tachikawa submitted a new proposal to meet the same requirements as the competitive Nakajima Ki-87. The new aircraft was a single-engine high-altitude fighter of conventional design with laminar-flow wing and featuring a pressure cabin mounted in the fuselage behind the wing trailing edges. The aircraft was to be powered by a fan-cooled turbo-supercharged 2,400 hp Nakajima radial engine driving a six-blade propeller. This design was approved by the Koku Hombu, and the aircraft was designated Ki-94-II (the scrapped earlier Ki-94 design was named the Ki-94-I). An order was placed for one static test airframe, three prototypes, and eighteen pre-production aircraft. Only two prototypes were built in the event; the first was equipped with a single 2,541 hp Nakajima Ha-219 (Ha-44) engine, driving a four-blade propeller because the six-blade one was not ready. The second prototype was to be fitted with a six-blade propeller. The war’s end however stopped the construction of the second prototype and also found the first prototype still being readied for its intended maiden flight, the Ki-94-II never taking to the air (Ref.: 1, 24).