It is appropriate to begin our account of Japanese army fighters in World War II with some remarks about the Ki-27 Army type 97 (allied codename “Night”) aircraft manufactured by the Nakajima firm. Although production had been discontinued in Japan by 1940, the fighter saw action throughout the duration of the war. It was subsequently used as a training craft in the People’s Republic of China up to 1954 , after which it was obtained by the Vietnamese.
Being used in Indo-China and South-East Asia by the Japanese rather restrictedly, the Ki-27 was not able to play a significant role in the course of WWII. Yet, it remained a formidable threat to Allied forces operating in those regions.
Of most importance to this account is the fact that the Night served as an impetus for the production of a new generation of Japanese fighters. Moreover, the incorporation of this aircraft and its “elder brother,” the A5M Naval type 96, into the Japanese armed forces signaled the end of Japanese dependence on Western developments in aircraft manufacturing.
The Kawasaki Ki-10 type 95 (Perry), the principal Japanese army fighter until 1937. Seized by Soviet troops near Halhin-Gol river
Prototype of the new army fighter Nakajima Ki-11, first manufactured according to the monoplane scheme. Service test of the fourth prototype with a closable cockpit, 1935.
Mitsubishi A5M1 type 96 “Kiuroku-Sen” (“Claude”), first Japanese marine fighter manufactured according to the monoplane scheme. 1937.
Mitsubishi Ki-18, prototype of the army variant of A5M. It never went into serial production. 1935.
It all began in 1935 with the announcement of a competition to create a prospective high-speed monoplane fighter capable of serving both the army and the navy. Entries were submitted by the three leading Japanese aircraft manufacturing firms—Kawasaki, Mitsubishi and Nakajima. This development followed the outcome of a struggle within engineering circles and the Air Force High Command between supporters of the “maneuverability” scheme and supporters of the “speed” scheme. The former contended that a biplane should be adopted as the principal fighter, whereas their opponents preferred to gamble on the construction of a monoplane. Supporters of the “maneuverability” scheme won, and the Military Air Force Command arranged a contract with Kawasaki for the manufacture of the biplane Ki-10 type 95, which subsequently served as the main army fighter until 1937. Meanwhile, aircraft Ki-11, manufactured by Nakajima firm in accordance with the monoplane scheme, was rejected by the Army Command and not included in the series.
The prototype of the Kawasaki fighter Ki-28 entered in the competition. 1936.
The main army Nakajima fighter Ki-27 type 97 (Night). China, 1939.
However, prototype Ka-14, manufactured by Mitsubishi, went into serial production and entered the Imperial fleet arms in the middle of 1937 under the marking A5M1 fleet type96. This aircraft, subsequently known as «Claude» to the Allies, so impressed the Army Command that a decision was made to create an army variant, the Ki-18. Test-flights of Ki-18 were conducted up to the end of 1937. The aircraft participated in training combats with biplane Ki-10 and always lost. However, despite these unsatisfactory results, test-flights ultimately shook the Army Command’s faith in the “maneuverability” scheme and Mitsubishi received the go-ahead to prepare specifications for the new prospective army fighter Ki-33. It was this aircraft that Mitsubishi submitted in the competition.
But Mitsubishi’s competitors were busy as well. After the failure of Ki-11, Nakajima introduced the Ki-12, the result of collaboration with engineers of the French Devoitine firm and an aircraft which aspired to become the most advanced in Japan. Powered by a liquid-cooled Hispano-Suisa 12Ycrs, it could carry a gun in the vee of the engine and sported retractable landing gear and slotted flaps. These advanced features made the aircraft a very promising machine, but the army leaders considered the project too complicated to implement. A “simpler” project with fixed landing gear, named “Type P.E.” and a direct successor to the Ki-11, was regarded a better prospect. Later, Type P.E. received the standard army designation “Ki-27”. Thus, by mid-1937, the Japanese army had acquired its first new-generation monoplane fighter.
Ki-27 was the first model in the history of Japanese aircraft production to feature such innovations as a closable canopy, armored rear, and radio station (transceivers on commanders’ aircraft and receivers on the others). It was added to the arsenal, and appeared in the sky over China in March 1938.
In late 1937, the army leaders, mindful of the constant need to upgrade their aircraft, resolved to find a successor to the Ki-27. This decision initiates the history of the Ki-43 type 1 “Hayabusa”, one of the best fighters of its time. Immediately after Ki-27 entered the arsenal in December 1937, Nakajima received an order for a new aircraft destined to replace the Ki-27. However, so outstanding was the Ki-27 that the Air Force HQ was unable to formulate their requirements in definite terms—the military authorities simply could not specify what else they might ask for. As a result, no competition was announced and an order was issued to Nakajima with the vague instruction to “make us another Ki-27, only bigger and better.” However, such indefiniteness presented many opportunities for Hideo Itokawa, the “father” of the Ki-27. Unconstrained by the conservatism of the army leaders, Itokawa enthusiastically took up the design of Ki-27’s “little brother.” All the advanced ideas that had been discarded in the development of the Ki-27 were realized in the Hayabusa. Special attention was devoted to reduction in weight and drag coefficient. Itokawa was the first Japanese aircraft engineer to implement fully retractable landing gear. Of course, the engine, a 975-hp Nakajima Ha.25 Sakai, was much more powerful than that of its predecessor.
But fortune did not always favor the new fighter. The first Ki-43 prototype emerged from the Nakajima hangar in Ota, northwest of Tokyo, on December 12, 1938, and it passed the factory tests in January 1939. Two other prototypes were delivered to the aviation center in Tachikawa. Testing by army pilots recorded discouraging results. Ki-43 was no better than its predecessor, and even inferior in horizontal maneuverability. Even more distressing, the new aircraft was heavier and more difficult to handle. The verdict of the army pilots, accustomed to flying maneuverable and light aircraft, led the army HQ to doubt the expediency of further development. But Professor Itokawa managed to convince the test pilots that the flaws could be easily removed, with attainment of the required characteristics only a matter of time. As a result, Nakajima received an order to build ten more pre-series aircraft.
The last pre-series aircraft produced in September 1940 was free of all the prototype’s “childhood ailments.” Most important, the aircraft was equipped with “Fowler” - type combat flaps, which enabled it to surpass Ki-27 in maneuverability. With the aid of the more powerful experimental Nakajima Ha.105 1150-hp engine with a two-stage supercharger, the new aircraft could fly at a top speed 45 km/h greater that that of its predecessor. The plane featured a two-bladed metallic variable pitch propeller and a canopy with 360-degree field of view, something not found on any comparable foreign model. The enhanced weaponry included two Ho.103 12.7mm machineguns in place of the two type 89 synchronous rifle-caliber machineguns. The plane was equipped with a transceiver.
After joining the arsenal as an “army fighter”-interceptor type 1 model 1A on January 9, 1941, the Ki-43 went into mass production under the formidable name “Hayabusa” (“Peregrine”). But the serial planes were somewhat different. First of all, it was impossible to install the experimental engines on a conveyor, so the engineers reverted to using the Ha.25 Sakai. Instead of experimental Ho.103 machineguns, serial 7.7mm type 89 ones were installed. From the summer of 1941 on, the Ki-43-Ia gradually replaced the Ki-27 in combat divisions.
Main army fighter Nakajima Ki-43-I type 1 model 1 Hayabusa (“Jim”, “Oscar”) at the factory airfield. An exemplar of the first series with two-bladed propeller.