By 1937, it became apparent to the Imperial Japanese Army (IJA) that a more modern replacement for the Nakajima Ki-27 was needed. The Ki-27 (Allied codename of "Nate") began a private venture design by Hideo Nakajima himself, after an invitation by the IJA to supply a modern fighter in 1935 with all-metal stressed skin. The type was of a monoplane design with an enclosed cockpit and lightweight yet was fielded with a fixed undercarriage and a tail skid, no pilot armoring nor self-sealing fuel tanks and required an external unit for starting. At the time of its inception, the Ki-27 became the first Japanese monoplane to achieve operational service with the military. While fighting on until the end of the war in 1945, Nates were quickly withdrawn from direct contact against the more modern Western fighters as they were wholly outclassed.
The IJA went straight to the Nakajima Aircraft Company once more and Mr. Nakajima took on the new requirement and delivered a promising prototype. As in the Ki-27 "Nate" before it, the new design was kept lightweight to make for a more maneuverable mount. As such, important facets such as pilot armor and self-sealing fuel tanks were once again dropped from the equation. Armament consisted of just a pairing of 2 x 7.7mm Type 97 machine guns firing from the upper engine cowl and synchronized to fire through the spinning propeller blades. 250 rounds of ammunition were afforded to a machine gun. Flight tests of the new fighter began in 1939 but soon proved the overall design something of a disappointment, forcing a halt to all further development for the time being. It was not until 1941 that the design was revisited and revised to make up for the inherent deficiencies. The wing surface area was enlarged and the addition of combat flaps helped in maneuverability to the point that the modified airframe proved to have excellent turning capabilities, promising to content with the best Allied fighters that could be fielded. The fighter was formally designated as the Ki-43 "Hayabusa" (meaning "Peregrine Falcon") and accepted into service with the IJA. Serial production of the new mount occurred in June of 1941 and the type entered service shortly thereafter as the Ki-43-Ia.
Outwardly, the Ki-43 was a highly conventional aircraft and, in some ways, decidedly Japanese in origin. She sported fine contoured lines making for an elegant design. The engine was fitted well-forward in the thin fuselage and covered over in a nicely rounded cowling. The spinner was noticeably protruding from the engine compartment and powered a three-bladed propeller system. The cockpit sat just behind the engine and just ahead of amidships. The fuselage tapered off to a point and the empennage was highly conventional in its use of a single vertical tail fin and applicable horizontal planes - all well-rounded at the edges. Wings were set ahead of amidships and initially rounded at the tips. The undercarriage was wholly retractable and featured two main landing gear legs and a diminutive tail wheel (the tail wheel remained exposed in flight). The main legs retracted inwards towards centerline under each wing near the wing roots and were exposed to the elements along one side (the main legs were not covered over by door panels in flight).
It was only after more modern Allied fighters appeared that the Ki-43 design was addressed once more. This time, Nakajima saw fit to add the all-important self-sealing fuel tanks as well as armor near the cockpit - two standard design features to be found on Allied warplanes. A more powerful engine was also eventually added to help increase the lethality of the Ki-43 series and the wings were now noticeably clipped. All these changes went on to produce the much improved Ki-43-II series in the family line.
The Ki-43-IIa sported provisions for the carrying of 2 x 551lb bombs under the wings. The Ki-43-IIb had radio equipment installed in the cockpit and was powered by a Nakajima Ha-115 14-cylinder, air-cooled radial piston engine delivering 1,150 horsepower. This supplied the airframe with a top speed of 329 miles per hour (cruise speed = 273mph), a range of 1,095 miles and a service ceiling of 36,750 feet. The Ki-43-KAI was given ejector exhaust stacks.
The final important mark became the Ki-43-III series. Prototypes were given the Nakajima Ha-115-II series engine of 1,230 horsepower and increased their operational range by the addition of 2 x 45 gallon drop tanks. The Ki-43-IIIa was the main production mark and was followed by the Ki-43-IIIb that was armed with 20mm cannons over the original machine gun suite.
One other notable Ki-43 variant became the Ki-62 "Project" which was nothing more than a highly modified Ki-43 for the dedicated interceptor role. This version sported and even more powerful engine and could be armed with either 30mm or 40mm cannons as required.
The Ki-43 proved her worth throughout all of World War 2. After her service in the active Pacific Theater was limited to the area around the Japanese islands, the aircraft was utilized as an interceptor for homeland defense, particularly of the national capital of Tokyo. Some Ki-43 airframes were also set aside for use in the lethal, yet suicidal, kamikaze runs against Allied ships in the Pacific.
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Nakajima - Imperial Japan Manufacturer(s)
China; France; Indonesia; Imperial Japan; Manchukuo; Thailand; North Korea Operators
2 x 7.7mm Type 97 machine guns (Ki-43-Ia)
1 x 12.7mm Ho-103 and 1 x 7.7mm Type 97 machine gun (Ki-43Ib).
2 x 12.7mm Ho-103 machine guns (Ki-43-Ic)
2 x 20mm cannons (Ki-43-IIIb)
2 x 550lb bombs (Ki-43-IIa)
Ki-43 - Designation for prototypes and evaluation models.
Ki-43-Ia - Fitted with 2 x 7.7mm Type 97 machine guns.
Ki-43-Ib - Fitted with 1 x 12.7mm Ho-103 machine gun and 1 x 7.7mm Type 97 machine gun.
Ki-43-Ic - Fitted with 2 x 12.7mm Ho-103 machine guns.
Ki-43-II - Designation used for improved prototype and developmental models.
Ki-43-IIa - Provision added for 500kg of external ordnance.
Ki-43-IIb - Equipped with Radio Communications Capability.
Ki-43-II-KAI - Modified Ki-43-II series with ejector exhaust stacks.
Ki-43-III - Prototype Models fitted with Nakajima Ha-115-II powerplants of 1,230 horsepower.
Ki-43-IIIa - Main Production Designation
Ki-43-IIIb - Fitted with 20mm cannons
Ki-62 (Project) - Advanced Interceptor Model; improved powerplant; 40mm cannons.
Mark I - Japanese Army Designation of Ki-43-Ia model series.
Mark Ib - Japanese Army Designation of Ki-43-Ib model series.
Mark Ic - Japanese Army Designation of Ki-43-Ic model series.
Mark 2a - Japanese Army Designation of Ki-43-IIa model series.
Mark 2b - Japanese Army Designation of Ki-43-IIb model series.
Mark 3a - Japanese Army Designation of Ki-43-III model series.
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Left side view of the Nakajima Ki-43 Hayabusa / Oscar fighter at rest
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