The Nakajima Ki-44 Shōki (鍾馗, "Devil Queller") was a single-seat fighter-interceptor which was designed and produced by the Japanese aviation manufacturer Nakajima Aircraft Company. Operated by the Imperial Japanese Army (IJA) from 1942 to 1945 during World War II, its official designation was Army Type 2 Single-Seat Fighter (二式単座戦闘機) and its Allied reporting name was Tojo. The name Shōki refers to Zhong Kui (鍾馗), a Taoist deity in the Chinese mythology, traditionally regarded as a vanquisher of ghosts and evil beings.Bailey 2019, p. 117.
The development of the Ki-44 was launched in 1939 as a dedicated heavy fighter aircraft. Performing its maiden flight in August 1940, the initial prototypes initially failed to attain the demanding airspeed requirement of 600 km/h (370 mph); a redesign effort centred around decreasing drag proved the aircraft could exceed this speed. The Ki-44 differed greatly from the typical Japanese fighters of the era, its design prioritising both speed and rate-of-climb in preference to maneuverability.Millman 2011, pp. 1–8. In contrast to its predecessor, the lighter and nimbler Nakajima Ki-43, the Ki-44 was far less maneuverable and, as a consequence of its use of relatively small wings giving the aircraft a relatively high wing loading, possessed a higher landing speed, which many Japanese pilots disliked. These were concerns for pilots that were more use to more agile and responsive aircraft, such as the Ki-43 and the Ki-27. As a result, the Ki-44 was first restricted to pilots with at least 1,000 hours of flying time due to its tricky handling characteristics. However, it was later found that younger pilots who had not been instilled with the extensive aerobatic training of earlier cadres could manage the aircraft perfectly well, thus this restriction was removed.
The Ki-44 was the fastest climbing Japanese fighter upon its introduction. It was the only interceptor in IJA service when the B-29 Superfortresses flown by the United States Army Air Force (USAAF) began bombing the Japanese mainland in June 1944. While there were performance restrictions at high altitude, the aircraft was superior to the Ki-43 in that it was capable of matching Allied aircraft in both climbs and dives, which gave pilots more flexibility in combat and greater confidence than the Ki-43. The basic armament of four 12.7mm machine guns or two 12.7mm guns and two 20 mm cannons (or, in a few aircraft, two Ho-301 40mm cannons of limited range) was far more powerful than the older Ki-43's twin 12.7mm machine guns.
Production of the Ki-44 was terminated in late 1944 in favour of the more advanced Nakajima Ki-84, and when the war ended, only three sentai units were still equipped with them.Francillon 1979, p. 221. Following the Surrender of Japan, several Ki-44s were captured and briefly operated by the Chinese Nationalist Air Force.
Out of all the examples produced, none survive today.
Design and development
The origins of the Ki-44 can be traced back to 1939, shortly after the Nakajima Aircraft Company received the instruction to launch quantity production of the Nakajima Ki-43 Hayabusa fighter, the company was issued with a new specification by the Koku Hombu that called for a dedicated Interceptor aircraft.Francillon 1979, p. 215. In contrast to conventional Japanese fighter performance preferences, emphasis was placed on both airspeed and rate of climb rather than maneuverability.Aircraft of the World 1996, p. 32. Specific stipulations of the specification included a maximum speed of 600 km/h (370 mph) at 4,000 m (13,130 ft), with a climb-rate to attain such altitude from ground level within five minutes. The armament was also specified to include a pair of 7.7 mm (.303 in) along with a pair of 12.7 mm (.50 in) machine guns.Francillon 1979, pp. 215-216. These criteria were the result of a need for a heavy fighter aircraft that followed a more offensive doctrine; as such, the Ki-44 has often been referred to as an Air Defence Fighter.
Recognising that the then-standard Nakajima Ha-25 engine would not provide sufficient power to meet the performance required, Nakajima's design team instead selected the Nakajima Ha-41.Francillon 1979, p. 216. However, this engine was only 27.8L in displacement and 1,000 hp, while the Ha-41 was 37.5L and produced 1,260 hp (1,440 hp in the later Ha-109 version). In any case, since the Ha-41 wasn't powerful enough, the only alternative available was the Mitsubishi Kinsei, which was slightly smaller than the Ha-41 in diameter, five liters smaller in displacement, and was less powerful. Unfortunately, this was already in demand for many other aircraft, so the Ha-41 was chosen as the best available powerplant.
In order to achieve its design goals, the wing area was relatively small leading to a high wing loading and a comparatively high landing speed that could be daunting to the average Japanese pilot, who was more used to aircraft with a low wing loading, such as the Ki-44's predecessors, the Ki-43 and Ki-27.Aircraft of the World 1996, p. 34. To improve the aircraft's suitability as a gun platform, the fuselage possessed a relatively large side area while the fin and rudder were both mounted well aft of the horizontal tail surfaces. Possessing an all-metal structure, the Ki-44 was metal-skinned except for the control surfaces, which were fabric covered. A set of Ki-43-like "butterfly" combat flaps was fitted in order to improve its maneuverability.
In August 1940, the first prototype performed its maiden flight from Ojima Airfield; it was promptly followed by two further prototypes. Despite relatively high wing loading, initial test flights were considered to be encouraging, the aircraft's handling was considered to be acceptable even with the high wing loading necessitating a relatively high landing speed. One issue identified early on was the pilot's poor forward visibility during taxiing, caused by the large radial engine, although this was not an issue during flight.Francillon 1979, pp. 216-217. The prototypes did not satisfy during performance trials, where the aircraft was only capable of attaining 550 km/h (342 mph), raising the prospects of the Ki-44 being cancelled altogether. Modifications were made to improve performance, which included a more rigid engine mounting, changes to the cowling flaps, reshaping the intake for the supercharger, redesign of the firewall for increased engine cooling, and dispensing of five cooling vents on either side of the forward fuselage. Following these modifications, which substantially decreased drag, the prototype demonstrated its new ability to exceed the speed requirement, attaining a maximum speed of 626 km/h (360 mph).Francillon 1979, p. 217.
An initial batch of seven pre-production aircraft were produced, the last of which was delivered in September 1941. These featured a revised two-section canopy, redesigned rudder, and provision for the installation of up to two underwing drop tanks. On 15 September 1941, all seven pre-production aircraft, along with two modified prototypes, were handed over to conduct service trials.Francillon 1979, pp. 217-218. Shortly thereafter, a second pre-production batch of 40 aircraft was ordered; these aircraft featured four 12.7mm machine guns, a relocated air cooler and main gear doors.Spick 2002, p. 481.Francillon 1979, pp. 218-219.
Operational history
The Nakajima Ki-44 at one point equipped 12 sentai ("groups/wings") of the Imperial Japanese Army Air Service: 9, 22, 23, 29, 47, 59, 64, 70, 85, 87, 104 and 246 Sentai. The Manchukuo Air Force also operated some Ki-44s.
In December 1941, the Ki-44 commenced operations following the delivery of nine aircraft to an experimental unit, 47th Chutai "Kawasemi Buntai" ("Kingfisher Flight, 47th Squadron"), commanded by Major Toshio Sakagawa and station at Saigon, Indochina. The Ki-44 would see significant action with 87th Sentai in the air defense role while based at Palembang, Sumatra, where oil fields considered vital to the Japanese war effort were located.Francillon 1979, p. 219. Other units equipped with the Ki-44 during the early part of the conflict were stationed in China, Burma, the Philippines and Korea.
Later in the war, the type saw action in an air defense role over the home islands – mainly around Japan's large industrial cities. 47 Chutai, after it was transferred to air defense roles in Japan, was expanded to become 47 Sentai.
The Ki-44-II Otsu (also known as the Ki-44-IIb) could be armed with a Ho-301 40 mm autocannon. While this was a relatively high-caliber weapon, it used caseless ammunition with a low muzzle velocity and short range, which was effective only in close attacks. Some of these aircraft were used against USAAF bombers by a special Shinten Seiku Tai (air superiority unit), comprising at least four aircraft, that was part of 47th Sentai, based at Narimasu airfield in Tokyo. Pilots from such units attempted to shoot down B-29 Superfortresses and, once their ammunition was expended, to ram them – effectively a suicide attack. While the concept appeared straightforward, ramming a B-29 at high altitudes was difficult to achieve in practice.
By the end of the war, Ki-44 variants were being replaced by the Nakajima Ki-84 Hayate, which was regarded as vastly superior in aspects other than maintenance and reliability.
During 1946–49, both sides in the Chinese Civil War operated Ki-44s surrendered or abandoned by Japanese units. Air units of the People's Liberation Army obtained aircraft formerly belonging to 22 and 85 Sentai, which had disbanded in Chosen. Some of these aircraft were reportedly flown by Japanese veterans. Within the Republic of China Air Force, 18th Squadron (12th Fighter Group) was equipped with Ki-44s, formerly of 9th Sentai, which had disbanded in Nanking, and 29th Sentai, which had disbanded at Formosa Following the retreat of the Nationalists, the 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 Production: Ota Aircraft PlantUSSBS Report 17, Appendix M. pp. 40-42.USSBS Report 17, Appendix N. p. 78. Year Month Aircraft Produced Government Order 1940 August 1 pre-production 1940 September 1 pre-production 1940 October 1 pre-production 1941 June 1 1941 July 4 1941 August 1 1940–1Annual Production99 1942 January 1 1942 February 4 1942 March 4 1942 April 5 1942 May 7 1942 June 5 1942 July 3 1942 August 13 1942 September 12 1942 October 13 1942 November 34 1942 December 30 1942Annual Production131168 1943 January 30 1943 February 33 1943 March 42 1943 April 37 1943 May 37 1943 June 40 1943 July 30 1943 August 51 1943 September 51 1943 October 47 1943 November 56 1943 December 65 1943Annual Production519506 1944 January 73 1944 February 54 1944 March 75 1944 April 85 1944 May 72 1944 June 65 1944 July 39 1944 August 33 1944 September 29 1944 October 22 1944 November 11 1944 December 7 1945 January 2 1944–5Annual Production567543 Total 1223 1223 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