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Nakajima Ki-43 Hayabusa



Design work began on the Ki-43 in late 1937 with the Army instructing Nakajima to supersede the Type 97 Fighter Ki-27. The specifications were precise and within one year the first prototype was complete. Departing from the previous practice of selecting a suitable design by calling for competitive projects from two or more aircraft firms, the specification was issued only to Nakajima, and required a fighter capable of reaching a maximum 500 km/h (311 mph), climbing to 5000 m (16 400 It) in five minutes, and having a range of at least 800 km (500 miles). At the same time the Ki-43 was to match Ki-27 in manoeuvrability. Two further 925-hp Nakajima Ha-25 radial-engined prototypes were completed and test flown in 1939 and were ready for service trials. To meet the performance requirements further changes were still required to reduce the overall weight and improve maneuverability. The unique combat flaps were designed and handling of the aircraft was well reported on. To reduce the weight the retractable undercarriage was made from ground aluminum and the frame material changed to Alclad 24, a lighter alloy. It possessed neither armour nor self-sealing fuel tanks.

They met the army's speed and climb requirements, but were heavy on the controls and in no way compared with the Ki-27 in manoeuvrability. Ten service test aircraft were accordingly built with various modifications incorporated in each. The development programme was successful and led to the first Ki-43-I production order. The fuselage had been redesigned with a reduced diameter, and changes were made to the tailplane and wings. Specially designed butterfly-type combat flaps, tested on the service test machines, gave exceptional manoeuvrability, making the Ki-43 a formidable dogfight opponent - a worthy successor to the Ki-27 - with an exceptional rate of turn. Two service trials aircraft had been tested with the 1100-hp Ha-105 radial, but initial production aircraft retained the Ha-25. Named Hayabusa (Pere-grine Falcon) the Ki-43 went into service as the Army Type 1 Fighter. Some were produced as the Ki-43a with twin 7.7-mrn (0.303-in) Type 89 machine-guns. Others, which were designated Ki-43-Ib, had a 12.7-mm (0.54in) Ho 103 gun in place of one of the 7.7-mm weapons.




Very little paint was applied to keep weight at a minimum and later on this was to see a large variety of colour schemes, as most Ki-43’s were sent to combat in bare aluminium, the individual units producing their own schemes of camouflage. Basic factory paint included internal corrosion protection, Hinomaru on the wings - after 1942 it became standard also on the fuselage - and the antiglare forward of the canopy. Most propellers were left bare or in dark brown prime. Individual units often colour coded the spinner and propeller to their unit colours.
In Spring 1940 the two bladed wooden propeller was replaced with a metal two bladed propeller, similar to a Hamilton Standard.

Production commenced in 1941 at Nakajimas Ota plant and the Ki-43-Ia reached fighter units some six months later. The first Sentais re-equipped with Ki-43s, from August 1941, were the 59th and 64th. From the first day of the Pacific war against Britain and the United States, they were in action over Malaya and Burma, in support of invading Japanese land forces, and were codenamed Oscar by the Allies. Like its navy counterpart, the Mitsubishi A6M Zero, the Ki-43 acquired a reputation of supremacy in the first months of combat.

Some 40 army Ki-43 pilots claimed each to have destroyed at least ten enemy aircraft, and even discounting a proportion of these figures, this was a formidable score. In one encounter on December 22, 1941, aircraft of the 2nd Chutai, 64th Sentai, destroyed five Australian Brewster Buffaloes for the loss of one of their own number. Allied fighters caught in dogfights with experienced Japan-ese pilots had little chance. Early on, the Ki-43-Ic went into production, with two 12.7-mm Ho 103 machine-guns, but production of the Ic was terminated after 716 aircraft had appeared.

Five prototypes of the Ki-43-II (codenamed 'Oscar' by the Allies) flew in early 1942, and production began in November 1942 at Nakajima's Ota factory. The weak wing structure of early aircraft had caused a number of crashes, and the new version had a strengthened wing of slightly reduced span. The new 858kW / 1150-hp Nakajima Ha-115 engine was installed, enclosed in a longer-chord cowling incorporating the supercharger air intake, which increased the top speed to 530km/h. The armament of the Ki-43-1c was retained. The Ki-43-I was vulnerable once it was in an enemy's sights, and to provide some protection the Ki-43-II had fuel tanks enclosed in rubber while 13-mm (0.51-in) armour protected the pilot's head and back. The reinforced wings had racks for two 250-kg (550-1b) bombs or 200-litre (44-Imp gal) drop tanks. Maximum speed was greatly improved without detriment to the aircraft's flying qualities. Range with maximum internal fuel rose from 1200 km (750 miles) to 1620 km (1000 miles) in the Ki-43- II. With drop tanks, range rose to a remarkable 3000 km (1860 miles) at 400 km/h (248 mph) cruise speed. Further modifications in the Ki-43-IIb model were only minor. Three Ki-43-II Kai prototypes had ejector-type engine exhaust stubs in place of the conventional collector ring of Ki-43-II. Deliveries to operational Sentais began in mid-1943.

The armament consisted of 2 x 7.7 mm Type 80 machine guns initially, later to be improved to 1 x 7.7mm and 1 x 12.7mm, each with 250 rounds. The Type 2 Ki-43 saw the armament with 2 x 12.7mm and the Type 3 with 2 x 20mm Ho-5 cannons replac-ing the 12.7mm. Racks for two bombs of 250 kg each were found on the wings, however this fighter’s main disadvantage throughout combat was to be the inadequate armament.

The Ki-43-IIb entered mass production in November 1942, first with Nakajima and six months later with Tachikawa.

The 14 cylinder double row radial engine, with a round shaped oil cooler, was one of the superior engines created by Nakajima, namely Ha-25 Type 99 rated at 980 h.p and the later improved Ha-115 power plant with a two speed super-charger and driving a three bladed propeller. The later Ha-il 5 air intake was moved from under the cowling to its upper lip.

Final variant was the Ki-43-III with 917kW engine and a top speed of 576km/h, but relatively few examples reached operational units. Ten Ki-43-III prototypes were followed by production Ki-43-IIIa machines from Tachikawa, who had already joined the pro-duction programme of Ki-43-IIs, allowing Nakajima to switch entirely to production of the Ki-84 Hayate. The Ki-43-III differed mainly in its 1230-hp Ha-115-II engine. The armament was still two 12.7-mm guns.

A captured Ki-43-II had been thoroughly tested and examined in Australia, and Allied pilots were given much valuable guidance on the aircraft's weak points. This helped to alter the balance in favour of Allied aircraft. Early on, the 50th Sentai, flying over Burma, produced outstanding Ki-43 pilots, notably Sergeant Satoshi Anabuki who scored 50 kills in 18 months, and pilots Isamu Sasaki and Yukio Shimokawa who claimed 32 and 15 victories respectively. But as the war moved against Japan, Ki-43 losses began to soar as they were confronted by improved Allied fighters and better trained pilots. Tachikawa continued to produce the Ki-43 until the end of the war. Production of all versions from all manufacturers totalled 5919. Many Ki-43s remained in first-line service until August 1945. Some Sentais operated them as fighter-bombers, while a number were expended in kamikaze attacks.


The final version was the Tachikawa-developed Ki.43-IIIb, the first and only version to include 20mm cannon in its armament, but only two of these had been completed by VJ day.

Second only in numbers to the Navy Zero, a total of 5,919 Ki-43s including 33 prototypes and trials aircraft, code named Oscar, were manufactured between 1938 and 1945. Tachikawa built 2529.


Ki-43 prototype
Engine: 925-hp Nakajima Ha-25

Ki-43 service trials
Engine: 1100-hp Ha-105 radial

Ki-43-I / Army Type 1
Engine: 925-hp Nakajima Ha-25

Engine: 925-hp Nakajima Ha-25
Armament:  twin 7.7-mrn (0.303-in) Type 89 machine-guns. each with 250 rounds
Range internal fuel: 1200 km (750 miles)

Engine: Nakajima Ha-25, 990 hp.
Max speed: 495 km/h at 4,000m
Cruise: 320 km/h at 2,500m
Max range: 745 miles
Armament: 2 x 12.7mm mg

Engine: Nakajima Ha-25, 990 hp.
Range internal fuel: 1200 km (750 miles)
Armament:  1 x 7.7-mrn (0.303-in) Type 89 machine-gun, 1 x 12.7-mm (0.54in) Ho 103 gun

Engine: Nakajima Ha-25, 990 hp.
Span: 11.44 m (37 ft 6 in)
Length: 8.83 m (29 ft)
Gross weight: 2048 kg (4515 lb)
Maximum speed: 492 km/h (306 mph)
Range internal fuel: 1200 km (750 miles)
Armament:  two 12.7-mm Ho 103 machine-guns


Engine: 858kW / 1150-hp Nakajima Ha-115
Top speed: 530km/h
Range internal fuel: 1200 km (750 miles)
Armament two 12.7-mm Ho 103 machine-guns

Engine: 858kW / 1150-hp Nakajima Ha-115
External load: two 250-kg (550-1b) bombs or 200-litre (44-Imp gal) drop tanks
Range internal fuel: 1620 km (1000 miles)
Range w/drop tanks: 3000 km (1860 miles) at 400 km/h (248 mph)

Ki 43 IIb
Engine: 1 x Nakajima Ha-115, 858kW / 1130 hp
Span: 10.84 m (35 ft 7 in)
Length: 8.92 m (29 ft 3 in)
Height: 3.27 m / 10 ft 9 in
Wing area: 21.4 sq.m / 230.35 sq ft
Max take-off weight: 2590 kg / 5710 lb
Empty weight: 1910 kg / 4211 lb
Ceiling: 11200 m / 36750 ft
Range w/max.fuel: 3200 km / 1988 miles
Maximum speed: 530 km/h (329 mph) at 19,680 ft
Crew: 1
Armament: 2 x 12.7mm machine-guns, 2 x 250-kg bombs


Ki-43-II Kai


Engine 917kW / 1230-hp Sakae Ha-115-II
External: two 250 kg bombs
Top speed: 576km/h
Armament: 2 x 20mm Ho-5 cannons

Engine 917kW / 1230-hp Sakae Ha-115-II
Armament: two 12.7-mm guns.
Max speed: 358 mph.


Nakajima Ki-43 Hayabusa / Oscar



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