Emphasis up to 1939 had always been on manoeuvrability, but in that year a specification was issued calling for a fighter which could reach 600 km/h (373 mph) at 4000 m (13100 ft), climbing to that height in no more than five minutes and armed with at least four machine-guns. Nakujima's design team, led by engineer Yasumi Koyama, had the first Ki-44 prototype in the air during August 1940.
A low-wing all-metal cantilever monoplane, it had a deep forward fuselage tapering sharply to the tailplane, which had the fin and rudder set further back than the horizontal tail surfaces. The wing was built in three sections, with a broad centre section integral with the fuselage. The undercarriage retracted inwards and the tail wheel was fully retractable. Metal stressed-skin covering was employed on fuselage and wings. The combat flap intro-duced in the Ki-43 was used on all Ki-44s built. Power was provided by a 14-cylinder two-row 1250-hp Nakajima Ha-41 radial engine. Test flights were successful, although the small wing resulted in a high wing loading and a high landing speed. The Ki-44 prototypes incorporated the manoeuvring flaps that had been introduced on the Ki-43, and carried an armament of two 7.7mm and two 12.7mm machine-guns.
The first prototype was soon followed by two more, but the top speed and rate of climb were not up to specification. The super-charger intake and cowl flaps were revised several times and every effort was made to reduce drag. Maximum speed rose to 616 km/h (383 mph) in a prototype flown without armament by chief test pilot Hayashi.
Seven service test aircraft were built and issued in September 1941 to a special operational evaluation unit, the 47th Dokuritsu Chutai (independent squadron), which flew the Ki-44 Shoki (Dragon Slayer), against the Chinese over Canton. The Ki-44 was involved in a series of comparative trials against Kawasaki's Ki-60 prototype, based on use of the Daimler-Benz DB 601 engine, and an imported Messerschmitt Bf 109E. The Ki-44 was accepted for service in September 1942 as the Army Type 2 Single-seat Fighter, which carried the same armament as the prototypes.
A total of 40 Ki-44-Is were built, including small numbers of the Ki-44-Ib, and the similar KI-44-Ic with some minor refinements. Closely resembling the preproduction aircraft, but with armament increased from two fuselage mounted 7.7-mm (0.303-in) Type 89 machine-guns and two wing-mounted 12.7-mm (0.5-in) Ho 103 machine-guns to four 12.7-mm weapons.
Pre-production and early production aircraft were designated Model 1. Model 2 prototype and preproduction aircraft (eight in all) were built and tested during summer and autumn 1942. Powered by the 1520-hp Naka-jima Ha-109 radial, they had limited pilot armour and fuel tank protection. There was provision for two drop tanks each with 125 litres (27.5 Imp gal) of fuel. Only small numbers of the Ki- 44-IIa were built, the variant being followed by the major production Ki-44-IIb.
A number of the Ki-44-IIc version armed with four 20-mm (0.79-in) Ho 3 cannon in place of the 12.7-mm wing guns went into service later in the war. Only in late 1943 did Tojo (the Allied codename for the Ki-44) appear in quantity on the war fronts. Its impressive rate of dive and climb - 5000 m (16 400 ft) was reached in just over four minutes - made them especially suitable for target defence. The 85th and 87th Sentais for example, defended the strategically important oil refineries on Surnatra. Other Sentais were deployed in the Philippines in a vain attempt to stem the US tide, or based at home where they had some success against Boeing B-29 Superfortress attacks.
The final variant, Ki-44-III had ejector-type thrust-augmented exhaust stacks (fitted also to a few earlier machines) and was powered by a 1491kW / 2000-hp Nakajima Ha-145 18-cylinder engine, an increased wing area and enlarged vertical tail surfaces. Armament was either four 20-mm Ho 5 cannon or two Ho 5s and two 37-mm (1.46-in) Ho 203s. Only evaluation aircraft were completed, and snags with the new engine caused development of the Ki-44-III to be abandoned.
When Japan surrendered, Ki-44s still equipped three Sentais and had established a fine reputation with pilots able to exploit their good qualities, while avoiding old-style dogfights in which their inferior manoeuvra-bility became apparent. Among a number of army air force aces who made their marks flying the Ki-44, perhaps the most outstand-ing was Colonel Yukiyoshi Wakamatsu of the 85th Sentai. He had achieved at least 18 victories before he was shot down and killed in December 1944.
A total of 1225 aircraft, including prototypes, were built up to December 1944 when production was phased out in favour of the Ki-84.
Span: 9.45 m (31 ft)
Length: 8.75 m (28 ft 9 in)
Gross weight: 2550 kg (5622 lb)
Maxi-mum speed: 580 km/h (360 mph).
Span: 9.45 m (31 ft)
Length: 8.78 m (28 ft 10 in)
Gross weight: 2764 kg (6093 lb)
Maxi-mum speed: 605 km/h (376 mph).
Engine: 1 x Nakajima Ha-109, 1133kW
Max take-off weight: 2995 kg / 6603 lb
Empty weight: 2105 kg / 4641 lb
Wingspan: 9.45 m / 31 ft 0 in
Length: 8.8 m / 28 ft 10 in
Height: 3.25 m / 10 ft 8 in
Wing area: 15 sq.m / 161.46 sq ft
Max. speed: 605 km/h / 376 mph
Ceiling: 11200 m / 36750 ft
Range w/max.fuel: 1700 km / 1056 miles
Armament: 4 x 12.7mm machine-guns
Nakajima Ki-44 Shoki / Tojo