In 1939 the Imperial Japanese Army imported a Kellet KD-1A single-engined two-seat autogyro as an artillery spotter. Powered by a 225hp Jacobs L-4M4 seven-cylinder air-cooled radial, the KD-1A featured an advanced version of the Kellet direct control rotor system. Shortly after its arrival in Japan, the aircraft was seriously damaged during flight trials at low speeds. The Kellet KD-1A had been damaged beyond repair, but the Japanese Army delivered the wreck to K.K. Kayaba Seisakusho (Kayaba Industrial Co Ltd), a small company doing autogyro research, with instructions to develop a similar machine. The Kayaba engineering team developed a two-seat observation autogyro based on the Kellet KD-1A but modified to Japanese production standards, designated Ka-1. The Ka-1 was powered by a 240hp Kobe eight-cylinder inverted-vee air-cooled (licence version of the German Argus Argus As 10c) engine driving a two-blade propeller, and had a three-blade rotor. Completed in May 1941 at the Sendai (Miyagi Prefecture) plant of Kayaba, the first Ka-1 made its maiden flight at Tamagawa on 26 May, 1941. During its flight test programme the Ka-1 performed remarkably well, demonstrating its ability to take-off after running only 30m in still air. By running the engine at full power and holding the nose 15 deg up, the Ka-1 could hover and could also execute a full 360 deg turn while hovering. As maintenance in the field appeared to present less difficulty than anticipated the aircraft was placed in production for service with artillery units. Eventually some two hundred and forty aircraft of this type were built.
A small number of Ka-ls were modified for operation from naval craft as anti-submarine patrol aircraft. As the load-carrying capability of the standard two-seat Ka-1 was too limited, the carrier-borne Ka-ls were operated as single-seaters and carried two 60kg bombs or depth-charges. In this role the Ka-ls operated over Japanese coastal waters and particularly over the Tsugara and Korean channels. The Kayaba Ka-1 autogyro was the first armed autogyro/helicopter to have been used operationally.
At least one of these aircraft, the Ka-1 KAI, was tested with powder rockets on the rotor tips in an attempt to improve its load-carrying capability while another aircraft was fitted with a 240hp Jacobs L-4MA-7 seven-cylinder air-cooled radial. With Jacobs engine the type became the Ka-2.
Kayaba Ka-1 Engine: 1 x Kobe/Argus As 10c, 180kW / 240 hp Main rotor diameter: 12.2m Max take-off weight: 1170kg Empty weight: 775kg Max speed: 165km/h Cruising speed: 115km/h Ceiling: 3500m Range: 280km Armament: 2 x 60kg depth charges
Japan In 1939 a U.S.-built Kellett KD-1A autogiro was exported to Japan. K. K. Kayaba Seisakusho developed Ka-1 along similar lines for Japanese Navy; used for observation, antisubmarine patrol (incl. shipbome), and for testing rocket augmented rotors. Ka-2 was re-engined.
The Kawasaki Ki-108 pressurised high-altitude fighter was developed from the Ki-102 in 1943. Four were completed; two modified from Ki.102b.
Ki-108 KAI Engines: 2 x Mitsubishi Ha-112-II Ru, 1125kW Wingspan: 15.67 m / 51 ft 5 in Length: 11.71 m / 38 ft 5 in Height: 3.7 m / 12 ft 2 in Wing area: 34 sq.m / 365.97 sq ft Max take-off weight: 7200 kg / 15873 lb Empty weight: 5300 kg / 11685 lb Max. speed: 580 km/h / 360 mph Ceiling: 13500 m / 44300 ft Range: 1800 km / 1118 miles Armament: 1 x 37mm cannon, 2 x 20mm cannons Crew: 1
Derived from the Ki-96 twin-engine single-seat fighter, the Kawasaki Ki-102b was intended as a two-seat attack fighter. Some assemblies of the Ki-96 prototypes were incorporated into the three Ki-102 prototypes, the first completed in March 1944.
A cantilever mid-wing monoplane with a conventional tail unit, retractable tailwheel landing gear and two Mitsubishi Ha-112-11 radial engines, the Ki-102 carried a two-man crew in separate enclosed cockpits in tandem.
The prototypes were followed by the construction of 20 pre-production aircraft and in October 1944 the type was ordered into production.
Kawasaki modified six of the preproduction Ki-102s to serve as prototypes of a twin-engine high-altitude fighter for the Imperial Japanese Army. This differed from the attack fighter by having improved two-seat accommodation, a revised tail unit and Mitsubishi Ha-112-IIru engines with turbochargers. Successful testing of this version in mid-1944 resulted in a high-priority production order, but problems with the turbocharged engine resulted in only about 15 being delivered to the army before the war ended.
The design had also been revised to produce a night-fighter version under the designation Ki-102c, but only two examples were completed. These had increased wing span, a lengthened fuselage, redesigned tail surfaces, primitive AI radar, and armament of two 30mm Ho-105 cannon in the underfuselage and two 20mm Ho-5 cannon mounted obliquely in the fuselage to fire forward and upward.
Twenty Ki.102b were built with one 57mm and two 20mm cannon, one 12.7mm machine gun and provision for 1100 lb of bombs. Maximum range was 1243 miles and ceiling just over 36,000 ft.
Ki-102b aircraft, which were allocated the Allied codename ‘Randy’, saw comparatively little service, some being used in action over Okinawa, but the majority were held in reserve in Japan.
Ki-102b Engines: 2 x Mitsubishi Ha-112-II, 1125kW Wingspan: 15.57 m / 51 ft 1 in Length: 11.45 m / 37 ft 7 in Height: 3.7 m / 12 ft 2 in Wing area: 34 sq.m / 365.97 sq ft Max take-off weight: 7300 kg / 16094 lb Empty weight: 4950 kg / 10913 lb Max. speed: 580 km/h / 360 mph Ceiling: 13500 m / 44300 ft Range: 2000 km / 1243 miles Armament: 1 x 57mm cannon, 1 x 12.7mm machine-guns Crew: 2
The Japanese Army was faced with the prospect of having 270 Ki-61-II airframes sitting around waiting for installation of their Ha-140 liquid-cooled engines.
The Ha-140 engine had proven to be totally unreliable, and, to make matters worse, the Akashi factory manufacturing the Ha-140 had been destroyed in a B-29 raid. Since Japan desperately needed aircraft capable of intercepting the B-29, in November of 1944 the Ministry of Munitions instructed Kawasaki to install a different powerplant in the 275 Ki-61-II airframes gathering dust in the Kagamigahara factory in an attempt to get as many aircraft in the air as possible.
Kawasaki settled on the 1500 hp Mitsubishi Ha-112-II fourteen-cylinder double-row radial engine. This engine had established a standard of easy maintenance and reliable service, however, the Ha-112 was a radial engine, and, with a diameter of four feet, the installation of this engine in a fuselage only 33 inches wide provided a major challenge. The Kawasaki concern was guided in its work by being able to study the engine mount in an imported Focke-Wulf Fw 190A, an example in which a wide radial engine had been successfully installed in an airframe with a narrow width. In addition, the same Mitsubishi Ha-112 radial engine had been successfully installed in the Aichi-built D4Y3 (Allied code name JUDY) dive bomber, earlier versions of which had been powered by a liquid-cooled engine.
Kawasaki’s design team converted three airframes to serve as prototypes, installing a Mitsubishi Ha-112-II engine which had the same power output as the unreliable Ha-140. The new project was sufficiently different from the Ki-61 Hien that it was assigned a new Kitai number: Ki-100.
The first Ki-100 prototype aircraft made its first flight on February 1, 1945. The results of the flight testing exceeded everyone’s expectations. The Ki-100 was about 600 pounds lighter than its Ki-61-II predecessor. Maneuverability and handling were markedly improved due to the lower wing and power loading.
Although the maximum speed of the Ki-100 was slightly lower than that of the Ki-61-II because of the higher drag exerted by the radial engine, this performance could be reliably attained because of the better reliability of the Ha-112 engine. The design was ordered into immediate production as the Army Type 5 Fighter Model 1A (Ki-100-Ia). The first Type 5 fighters (Ki-100-Ia) were direct conversions of existing Ki-61-II airframes. 271 airframes were converted between March and May 1945, and were immediately delivered to operational units.
The Ki.100 also had provision for carrying two 550 lb bombs externally.
In combat, the Ki-100-Ia proved to be an excellent fighter, especially at low altitudes. It possessed a definite ascendancy over the Grumman F6F Hellcat. In one encounter over Okinawa, a Ki-100-equipped unit destroyed 14 F6F Hellcat fighters without loss to themselves. When the Ki-100 encountered the P-51D Mustang at low or medium altitudes over Japan, it was able to meet the American fighter on more or less equal terms. The outcome of P-51D vs Ki-100 battles was usually determined by piloting skill or by numerical advantage rather than by the relative merits of the two fighter types. However, at altitudes above 26,000 feet, the maneuverability of the Ki-100 began to fall off rather severely and the fighter was at a relative disadvantage in intercepting the high-flying B-29. With the Ki-100 proving such a success, it was decided to initiate production of this aircraft, the resulting Ki-100-Ib differing only by having the cutdown rear fuselage and all-round-view canopy that had been designed for the proposed Ki-61-III.
The first Ki-100-Ib fighters were built at the Kagamigahara and Ichinomiya Kawasaki factories in May of 1945, but production was severely hampered by the continual Allied bombing. Plans had been made to produce 200 fighters per month, but the Ichinomiya plant was forced to shut down in July 1945 after having built only 12 aircraft, and the Kagamigahara plant had its production severely curtailed by aerial attacks. By the time of the Japanese surrender, only 118 Ki-100-Ib aircraft had been delivered.
Ki.100-1b
In an attempt to improve the high-altitude performance, the Ki-100-II version was evolved. It was powered by a 1500 hp Mitsubishi Ha-112-II Ru with a turbosupercharger and water-methanol injection to boost power for short intervals. Because of a lack of space, the turbosupercharger had to be mounted underneath the engine without provision for an intercooler and its associated ducting, with air being ducted directly from the compressor to the carburetor. It first flew in May 1945. The lack of an intercooler limited the high-altitude performance of the Ki-100-II, and the turbosupercharger added 600 pounds to the weight, which reduced maximum speed by 15 mph at 10,000 feet. However, the boosted high-altitude power enabled a maximum speed of 367 mph to be be reached at 32,800 feet (the cruising altitude of the B-29 during daylight operations). It had been planned to begin production of the Ki-100-II in September of 1945, but only three prototypes of this high-altitude interceptor had been produced by the time of the Japanese surrender.
A total of 396 Ki-100s were built, including 275 Ki-61-II conversions, 118 Ki-100-Ib production aircraft built from scratch, and three Ki-100-II prototypes. Most of them were assigned to the defense of the home islands, operating from Chofu and Yokkaichi from the spring of 1945. At the end of the war, two Ki-100-Ibs were shipped to the USA for evaluation. The Ki-100 never had a separate Allied code name assigned to it.
Ki-100-I Engine: 1 x Mitsubishi Ha-112-II, 1125kW Max take-off weight: 3495 kg / 7705 lb Empty weight: 2525 kg / 5567 lb Wingspan: 12 m / 39 ft 4 in Length: 8.82 m / 28 ft 11 in Height: 3.75 m / 12 ft 4 in Wing area: 20 sq.m / 215.28 sq ft Max. speed: 580 km/h / 360 mph Cruise speed: 400 km/h / 249 mph Ceiling: 11000 m / 36100 ft Range w/max.fuel: 2200 km / 1367 miles Range w/max.payload: 1400 km / 870 miles Armament: 2 x 20mm cannons, 2 x 12.7mm machine-guns Crew: 1
Kawasaki Ki-100-Ia Army Type 5 Fighter Model 1a Engine: 1 x Mitsubishi [Ha-33] 62 or Ha-112-II, 1500 hp Takeoff, 1350 hp at 6560 ft, 1250 hp at 19,030 ft Wingspan: 34 ft 4 7/16 in Length: 28 feet 11 1/4 in Height: 12 feet 3 5/8 in Wing area: 215.3 sq.ft Empty weight: 5567 lb Loaded weight: 7705 pounds. Max speed: 360 mph at 19,685 ft / 332 mph at 32,810 ft. Time to 16,405 ft: 6 min. Service ceiling: 36,090 ft. Maximum range: 1367 miles. Armament: Two fuselage-mounted 20-mm Ho 5 cannon and two wing- mounted 12.7 mm machine guns.
Ki 100 1b Engine: 1,500 hp Mitsubishi Ha.112 11. Wing span: 39 ft 4.25 in (12m). Length: 28 ft 11.25 in (8.82 m). Height: 12 ft 3.75 in (3.75 m). Wing area, 215.278 sq.ft (20 sq.m). Empty wt: 5,567 lb (2 525 kg). Loaded wt: 7,705 lb (3 495 kg). Max speeds of 317 mph (510 kph) at 3,280 ft (1 000 m), 352 mph (567 kph) at 16,400 ft (5 000 m), 360 mph (580 kph) at 19,685 ft (6 000 m), and 332 mph (535 kph) at 32,800 ft (10000 m). Climb to 16,400 ft (5 000 m): in 6 min, 26,250 ft (8 000 m): 11.5 min, 32,800 ft (10 000 m): 20 min. Service ceiling: 36,090 ft (11000 m). Cruising speed: 248 mph (400 kph) at 13,123 ft (4 000 m). Armament: two 20 mm Ho.5 cannon and two 12.7¬mm Type 103 machine guns.
Ki-78 Engine: 1 x Deimler-Benz DB-601A, 880kW Wingspan: 8 m / 26 ft 3 in Length: 8.1 m / 26 ft 7 in Height: 3.07 m / 10 ft 1 in Wing area: 11 sq.m / 118.40 sq ft Max take-off weight: 2300 kg / 5071 lb Empty weight: 1930 kg / 4255 lb Max. speed: 700 km/h / 435 mph Ceiling: 8000 m / 26250 ft Range: 600 km / 373 miles Crew: 1
The first Ki 66 dive bomber prototype flew in October 1942. Did not entered production.
Ki-66 Engines: 2 x Nakajima Ha-115, 850kW Wingspan: 15.5 m / 50 ft 10 in Length: 11.2 m / 36 ft 9 in Height: 3.7 m / 12 ft 2 in Wing area: 34.0 sq.m / 365.97 sq ft Max take-off weight: 5750 kg / 12677 lb Empty weight: 4100 kg / 9039 lb Max. speed: 535 km/h / 332 mph Ceiling: 10000 m / 32800 ft Range: 2000 km / 1243 miles Armament: 2 x 12.7mm machine-guns, 2 x 7.7mm machine-guns, 300-500kg of bombs Crew: 2
The Kawasaki Ki 64 experimental fighter had two engines in tandem driving separate propellers. The first prototype flew in December 1943.
The type did not entered production.
The Allied code name was ‘Rob’.
Ki-64 Engine: 1 x Kawasaki Ha-201, 1760kW Wingspan: 13.5 m / 44 ft 3 in Length: 11.03 m / 36 ft 2 in Height: 4.25 m / 13 ft 11 in Wing area: 28 sq.m / 301.39 sq ft Max take-off weight: 5100 kg / 11244 lb Empty weight: 4050 kg / 8929 lb Max. Speed: 690 km/h / 429 mph Ceiling: 12000 m / 39350 ft Range: 1000 km / 621 miles Armament: 4 x 20mm cannons Crew: 1
The Ki-61’s designers, Takeo Doi and Shin Owada, had worked under the German Richard Vogt, and in December 1940 they were instructed to go ahead with the Ki-61, and one year later the prototype was flown. Powered by an inverted V-12 inline engine, the Kawasaki Ha-40 being in effect a lightweight Daimler-Benz DB 601A built under licence.
The first of 12 Ki.61 prototypes was flown in December 1941 and went into production shortly afterwards.
The first production Ki-61-I fighters were deployed operationally in April 1943 when the 68th and 78th Sentais arrived in New Guinea. Named Hien (Swallow) in service (and codenamed ‘Tony’ by the Allies), the new aircraft proved popular with its pilots. Being well-armed and armoured, the type was a match for opposing American fighters. Its armament (of four 12.7-mm machine-guns) proved inadequate to knock down enemy bombers, and the Ki-61 I-hei(c) was introduced with a pair of Mauser MG151 20-mm cannon in the nose, these being replaced in a small number of Ki-61 I-tei(d) fighters by two Japanese built 30-mm cannon. The Ki-61-I and Ki-61-I KAI remained in production until 1945, but in 1944 they were joined in service by the Ki-61-II with more powerful Kawasaki Ha- 140 engine (producing 1500 hp / 1119-kW); with a top speed of 610km/h this would have been an excellent fighter but for constant engine problems; yet when fully serviceable the Ki-61-II was one of the few Japanese fighters fully able to combat the Boeing B-29 at its normal operating altitude, particularly when armed with four 20-mm cannon. The Ki-61-II featured a larger wing and modified cockpit canopy. Engine difficulties limited the number completed to eight.
A complete redisgn was undertaken for the Ki.61-IIKai, and 99 of these were built as Ki.61-IIa and –IIb.
The Ki-61-III project, featuring a cut-down rear fuselage with an all-round visin cockpit canopy, did not achieve production, being superseded by the Ki.100.
Excluding prototypes and development aircraft, production totalled 1,380 Ki-61-Is, 1,274 Ki- 61-I KAIs and 374 Ki-61-Ils.
Subtypes:
Ki61I-ko(a) 2X7.7mm 2X12.7mm Ki61I-otsu(b) 4X12.7mm Ki61I-hei(c) 2X12.7mm (nose) 2X20mm (MG151/20 imported by submarine from Germany) Ki61I-tei(d) 2X20mm Ho-5 nose guns 2X12.7mm wing guns (also called Ki61I-kai, this had a longer fuselage and additional fuselage tank).
Ki.61-Ic Engine: Kawasaki Ha.40 Type 2, 1175 hp Wingspan: 39 ft 4 in Length: 29 ft 4 in Height: 12 ft 1.75 in Empty weight: 5798 lb Loaded weight: 7650 lb Max speed: 348 mph at 16,400 ft Service ceiling: 32,800 ft Max range: 1185 mi Armament: 2 x 20 mm cannon, 2 x 12.5mm mg Bomb load: 2 x 550 lb Crew: 1
Ki-61-II KAIa Crew: 1 Engine: 1 x Kawasaki Ha-140, 1125kW Max take-off weight: 3780-3825 kg / 8334 – 8433 lb Empty weight: 2840 kg / 6261 lb Wingspan: 12 m / 39 ft 4 in Length: 9.16 m / 30 ft 1 in Height: 3.7 m / 12 ft 2 in Wing area: 20 sq.m / 215.28 sq ft Max. speed: 610 km/h / 379 mph Cruise speed: 400 km/h / 249 mph Ceiling: 11000 m / 36100 ft Range w/max.fuel: 1600 km / 994 miles Range w/max.payload: 1100 km / 684 miles Armament: 2 x 20mm cannons, 2 x 12.7mm machine-guns, 2 x 250kg bombs
Ki-61-II Max speed: 423 mph @ 28,000 ft Initial climb: 3,425 fpm Time to 20,000 ft: 6.6 minutes Max range: 2,120 miles
In February 1940 Kawasaki were instructed to commence work on a heavy intercepter fighter design using the German Daimler Benz DB 601A in¬line liquid cooled engine, for which the firm had already obtained manufacturing rights. The specification for the Ki 60 was issued at the same time as that for the Ki 61, but was given priority as it was intended to be superior in speed, climb rate and armament. At that time the army’s standard fighter was the radial engined Nakajima Ki 27 which had good manoeuvrability rather than speed and was thus the antithesis of the Ki 60 concept. The Ki 60 was developed by a design partnership of Takeo Doi and Sin Owada, the first prototype flying in March 1941. It was a low wing all metal cantilever monoplane with a short fuselage of rather humped appearance. The main wheels retracted inwards to lie entirely within the wing profile, and the tail wheel was also retractable. The wings and horizontal tailplane had straight taper. With the 1100 hp DB 601A engine a top speed of 550 km/h (342 mph) was attained, less than the designers’ estimates. Armament was four 20 mm (0.79 in) cannon, two in the wings and two fuselage mounted.
The second prototype was modified to have increased wing area, a cleaner engine cowling and a slightly lighter structure. The increase in speed of only 10 km/h (6 mph) was disappointing, but the landing speed was reduced. A third and final prototype was built, with a smoother cowling, but only another 10 km/h in top speed was gained and Ki 60 development was cancelled in favour of the Ki 61.
Ki-60 Engine: 1 x Deimler-Benz DB 601A, 860kW Wingspan: 10.5 m / 34 ft 5 in Length: 8.47 m / 27 ft 9 in Height: 3.7 m / 12 ft 2 in Wing area: 16.2 sq.m / 174.38 sq ft Empty weight: 2150 kg / 4740 lb Max take-off weight: 2750 kg / 6063 lb Max. speed: 560 km/h / 348 mph Ceiling: 10000 m / 32800 ft Armament: 2 x 12.7mm machine-guns, 2 x 20mm cannons Crew: 1
All Aero 