People's Liberation Army Air Force (formed in 1949) used the Ki-44 until the early 1950s. Surviving aircraft No complete surviving examples of the Ki-44 exist today. However, a wing center section is preserved at the Northwestern Polytechnical University Aviation Museum, at Xi'an in China. Variants Ki-44 First prototype (s/n 4401) with Ha-41 engine with a complex cooling system, unique for the first prototype. Ki-44 Nine pre-production aircraft (s/n 4402-4410), the first of which were quite different than the later ones. These aircraft were used for combat evaluation with the 47th Independent Fighter Chutai at the start of the Pacific War. Their armament consisted of two 7.7 mm (.303 in) Type 89 machine guns in the nose and two 12.7 mm (.50 in) Ho-103 machine guns in the wings. Type 89 telescopic gunsight protruding through the windscreen. Provision for a single drop tank under the fuselage centre line or two drop tanks under the wings. Recognisable by their pointed spinner caps. Ki-44-I Powered by a 930 kW (1,250 hp) Nakajima Ha-41 engine with annular oil cooler, with a maximum speed of 580 km/h (363 mph). Armament and gunsight were unchanged from the pre-production models. Provision for two drop tanks under the wings. Rounded spinner caps with provision for Hucks starter. Late models had external fuel coolers. Forty produced (s/n 111-150). Ki-44-II Ko (Ki-44-IIa) Powered by a 1,074 kW (1,440 hp) Nakajima Ha-109 engine with external oil cooler and a top speed of 604 km/h (378 mph). Armament, gunsight and drop tank provision as for Ki-44-I. Rectangular cockpit access doors replaced the rounded version of earlier models. 355 produced (s/n 1001-1355). Ki-44-II Otsu (Ki-44-IIb)Standard armament reduced to just two 12.7 mm (.50 in) Ho-103 machine guns in the nose. Optional provision for two 40 mm (1.57 in) Ho-301 cannons in the wings. These were not always installed due to disappointing combat results and were sometimes replaced with two 12.7 mm (.50 in) Ho-103 machine guns. This variant retained the Type 89 telescopic gunsight as standard. 394 produced (s/n 1356-1749). Ki-44-II Hei (Ki-44-IIc)Standard armament of four 12.7 mm (.50 in) Ho-103 machine guns, two in the nose and two in the wings. Type 100 reflector gunsight mounted as standard. 427 produced (s/n 1750-2176). Ki-44-III A single prototype built, powered by a Ha-145 two-row 18-cylinder engine of 1,491 kW (2,000 hp). Ki-44-III Ko (Ki-44-IIIa) Proposed variant with an armament of four 20 mm Ho-5