The Nakajima Ki-43 Hayabusa

Allied codename 'Oscar'

Japan
Japan

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The Hayabusa (peregrine falcon), or Oscar as it was known to the Allies, was the most advanced fighter available to the Imperial Japanese Army Air Force in the opening phases of the Pacific War (1941- 1945). It was a very nasty shock to the Allied air forces, which had deployed into these regions only the more obsolescent of its ‘modern’ monoplane fighters in the belief, apparently confirmed by intelligence data, that the Imperial Japanese Army Air Force had not yet fielded a ‘modern’ monoplane fighter with retractable landing gear to replace the Nakajima Ki-27 with its fixed landing gear.
The origins of the type can be traced to 1937, when the Imperial Japanese Army Air Force started the process of acquiring a successor to the Ki-27. In a break with its previous practice, the service decided not to proceed via the competitive design process, but in December 1937 issued to Nakajima the requirement for an advanced monoplane fighter providing agility at least equal to that of the Ki-27 and with the same armament of 2 × 0.303 inch (7,7 mm) machine guns, but also possessing markedly improved performance that included a maximum level speed of 311 mph (500 km/h) at optimum altitude, a range of 497 miles (800 km), and a climb to 16,405 ft (5.000 m) in 5 minutes 0 minutes.
Nakajima entrusted the task of designing the new fighter to a team under the supervision of Hideo Itokawa, and this team quickly evolved a cantilever low-wing monoplane of basically all-metal construction with fabric-covered control surfaces. The core of the structure was the semi-monocoque fuselage, which changed from a circular section at the front to an oval section father to the rear in the area of the cockpit, which was raised above the line of the fuselage and provided the pilot with very good fields of vision. The fuselage supported the plain tail unit and the stressed-skin wing, which was dihedraled, tapered in thickness and chord, and carried outboard ailerons in its trailing edges. The airframe was completed by the tailwheel landing gear, which had wide-track main units that retracted inward. Construction of three prototypes proceeded as rapidly as completion of the design, and the first prototype made its maiden flight in December 1938.

Version list:

Further pictures:

Nakajima Ki-43 'Oscar' in full flight
Nakajima Ki-43 'Oscar' in full flight

Nakajima Ki-43 'Oscar' in full flight, showing a beautiful profile
Nakajima Ki-43 'Oscar' in full flight, showing a beautiful profile

Nakajima Ki-43 'Oscar' in a museum
Nakajima Ki-43 'Oscar' in a museum

 

Technical data on the Nakajima Ki-43-Ia Hayabusa
Powerplant 1 × Nakajima Ha-25 Army Type 99 fourteen-cylinder air-cooled radial, rated at 980 hp (730.58 kW) Role during war
  • Air superiority Fighter
  • Fighter
  • Fighter-bomber
Length 28 ft 11.75 inch Height 10 ft 8.75 inch
Empty weight 3483 lb Operational weight 4515 lb typical,
5695 lb max
Wing Span 37 ft 6.28 inch Wing Aspect ratio 5.95
Wing Area 236.805 sq ft Service ceiling 38500 ft
Maximum speed 308 mph at 13125 ft Cruising speed 199 mph at 8200 ft
Initial climb rate Climb to 16,405 ft in 5 min 30 sec Range 745 miles max
Fuel capacity internal 124 Imp gal (149 US gal) Fuel capacity external Up to 88 Imp gal (106 US gal) in two 44 Imp gal (53 US gal) drop tanks
Machine guns
  • 2 × 0.303 inch Type 89 fixed forward-firing in the upper nose
Cannons -
Bomb load Up to 66 lb, carried on two underwing hardpoints, rated at 33 lb each. General disposables load consisted of:
  • 2 × 33 lb bombs
Torpedoes/rockets -
Crew 1Naval or ground based Ground
First flight (prototype) Early Januari 1939 Operational Service Fall 1941 - Late 1940's
Manufacturer Nakajima Hikoki K.K. Number produced 5,919 total, 716 Ki-43-I's
Metric system
Length 8.83 m Height 3.27 m
Empty weight 1580 kg Operational weight 2048 kg typical,
2583 kg max
Wing Span 11.44 m Wing Aspect ratio 5.95
Wing Area 22 m² Service ceiling 11735 m
Maximum speed 496 km/h at 4000 m Cruising speed 320 km/h at 2499 m
Initial climb rate Climb to 5.000 m in 5 min 30 sec Range 1199 km max
Fuel capacity internal 565 liters Fuel capacity external Up to 400 liters in two 200 liters drop tanks
Machine guns
  • 2 × 7,7 mm Type 89 fixed forward-firing in the upper nose
Cannons -
Bomb load Up to 30 kg, carried on two underwing hardpoints, rated at 15 kg each. General disposables load consisted of:
  • 2 × 15 kg bombs
Torpedoes/rockets -

Technical data on the Nakajima Ki-43-IIb Hayabusa
Powerplant 1 × Nakajima Ha-115 Army Type 1 fourteen-cylinder air-cooled radial, rated at 1150 hp (857.31 kW) Role during war
  • Air superiority Fighter
  • Fighter
  • Fighter-bomber
Length 29 ft 3.31 inch Height 10 ft 8.75 inch
Empty weight 4211 lb Operational weight 5710 lb typical,
6450 lb max
Wing Span 35 ft 6.75 inch Wing Aspect ratio 5.49
Wing Area 230.367 sq ft Service ceiling 36750 ft
Maximum speed 329 mph at 13125 ft Cruising speed 273 mph at optimum altitude
Initial climb rate Climb to 16,405 ft in 5 min 49 sec Range 1095 miles typical,
1990 miles max
Fuel capacity internal 120 Imp gal (144 US gal) Fuel capacity external Up to 88 Imp gal (106 US gal) in two 44 Imp gal (53 US gal) drop tanks
Machine guns
  • 2 × 0.50 inch Type 1 fixed forward-firing in the upper nose
Cannons -
Bomb load Up to 1,102 lb, carried on two underwing hardpoints, rated at 551 lb each. General disposables load consisted of:
  • 2 × 132 lb or 551 lb bombs
Torpedoes/rockets -
Crew 1Naval or ground based Ground
First flight (prototype) Early Januari 1939 Operational Service Fall 1941 - Late 1940's
Manufacturer Nakajima Hikoki K.K. Number produced 5,919 total, 2.500 plus unknown amount out of 2.629 Ki-43-II's and Ki-43-III's
Metric system
Length 8.92 m Height 3.27 m
Empty weight 1910 kg Operational weight 2590 kg typical,
2926 kg max
Wing Span 10.84 m Wing Aspect ratio 5.49
Wing Area 21.4 m² Service ceiling 11201 m
Maximum speed 529 km/h at 4000 m Cruising speed 439 km/h at optimum altitude
Initial climb rate Climb to 5.000 m in 5 min 49 sec Range 1762 km typical,
3203 km max
Fuel capacity internal 545 liters Fuel capacity external Up to 400 liters in two 200 liters drop tanks
Machine guns
  • 2 × 12,7 mm Type 1 fixed forward-firing in the upper nose
Cannons -
Bomb load Up to 500 kg, carried on two underwing hardpoints, rated at 250 kg each. General disposables load consisted of:
  • 2 × 60 kg or 250 kg bombs
Torpedoes/rockets -

Technical data on the Nakajima Ki-43-IIIa Hayabusa
Powerplant 1 × Nakajima Ha-115-II Army Type 1 fourteen-cylinder air-cooled radial, rated at 1230 hp (916.95 kW) Role during war
  • Air superiority Fighter
  • Fighter
  • Fighter-bomber
Length 29 ft 3.31 inch Height 10 ft 8.75 inch
Empty weight 4233 lb Operational weight 5644 lb typical,
6746 lb max
Wing Span 35 ft 6.75 inch Wing Aspect ratio 5.49
Wing Area 230.367 sq ft Service ceiling 37400 ft
Maximum speed 358 mph at 21920 ft Cruising speed 275 mph at optimum altitude
Initial climb rate Climb to 16,405 ft in 5 min 19 sec Range 1320 miles typical,
1990 miles max
Fuel capacity internal 144 Imp gal (173 US gal) Fuel capacity external Up to 92 Imp gal (111 US gal) in two 46 Imp gal (55 US gal) drop tanks
Machine guns
  • 2 × 0.50 inch Type 1 fixed forward-firing in the upper nose
Cannons -
Bomb load Up to 1,102 lb, carried on two underwing hardpoints, rated at 551 lb each. General disposables load consisted of:
  • 2 × 132 lb or 551 lb bombs
Torpedoes/rockets -
Crew 1Naval or ground based Ground
First flight (prototype) Early Januari 1939 Operational Service Fall 1941 - Late 1940's
Manufacturer Nakajima Hikoki K.K. Number produced 5,919 total, 10 prototypes plus unknown amount out of 2.629 Ki-43-II's and Ki-43-III's
Metric system
Length 8.92 m Height 3.27 m
Empty weight 1920 kg Operational weight 2560 kg typical,
3060 kg max
Wing Span 10.84 m Wing Aspect ratio 5.49
Wing Area 21.4 m² Service ceiling 11400 m
Maximum speed 576 km/h at 6681 m Cruising speed 443 km/h at optimum altitude
Initial climb rate Climb to 5.000 m in 5 min 19 sec Range 2124 km typical,
3203 km max
Fuel capacity internal 655 liters Fuel capacity external Up to 420 liters in two 210 liters drop tanks
Machine guns
  • 2 × 12,7 mm Type 1 fixed forward-firing in the upper nose
Cannons -
Bomb load Up to 500 kg, carried on two underwing hardpoints, rated at 250 kg each. General disposables load consisted of:
  • 2 × 60 kg or 250 kg bombs
Torpedoes/rockets -

Here is a quick overview of all different versions, without the full technical specifications:

Different versions of the Nakajima Ki-43  Hayabusa
Nakajima Ki-43 The designation ki-43 was used for the three prototypes and ten service trials pre-production aircraft.
The three prototypes were quickly built and completed during December 1938 and februari and March 1939. All three were powered by 1 × Nakajima Ha-25 double-row fourteen-cylinder radial with single-speed supercharger, rated at 980 hp (731 kW). The propeller was a wooden fixed-pitch two-blade type.
Initial flight trials were OK, except that the test pilots were unhappy with the maneuverability of the aircraft. Also, Army pilots thought that the retractable landing gear was purely a luxury, adding unnecessary weight to the aircraft. After these misgivings the future of the Ki-43 was in doubt, until the Imperial Japanese Army Air Force decided to conduct further testing with ten service trials aircraft. These aircraft were similar to the prototypes, except for minor equipment changes and the fitting of an all-round-vision cockpit canopy. The second Service trials aircraft was also fitted with an experimental Nakajima Ha-105 radial with two-speed supercharger, while the seventh example was fitted with 2 × 0.50 inch (12,7 mm) Ho-103 machine guns. The eighth example of this batch was also fitted with butterfly combat flaps, and these improved handling and maneuverability to such a degree that the Service pilots commented favourably on the aircraft.
Number built: 13
Nakajima Ki-43-Ia Hayabusa This version was the initial production version, and closely related to the prototypes. During the prototype trials several improvements were made to increase maneuverability and performance including butterfly combat flaps. This model was still fitted with a wooden fixed-pitch two-blade propeller, but soon after productiostarted this was replaced by a two-pitch two-blade metal propeller. Armament consisted of 2 × 0.303 inch (7,7 mm) guns in the upper nose
Number built: unknown out of 713 Ki-43-I's
Nakajima Ki-43-Ib Hayabusa This version was identical to the Nakajima Ki-43-Ia Hayabusa, except for it's armament. This version was armed with 1 × 0.303 inch (7,7 mm) Type 89 gun, and 1 × 0.50 inch (12,7 mm) type 1 (Ho-103) gun.
Number built: unknown out of 713 Ki-43-I's
Nakajima Ki-43-Ic Hayabusa This version was identical to the Nakajima Ki-43-Ia Hayabusa, except for it's armament. This version was armed with 2 × 0.50 inch (12,7 mm) type 1 (Ho-103) gun.
Number built: unknown out of 713 Ki-43-I's
Nakajima Ki-43-IIa Hayabusa Soon after the Ki-43-I's entered service, 5 airframes were modified to mount the Nakajima Ha-115 Army Type 1 radial with a two-speed supercharger, rated 1,150 hp (857 kW). Aditionally, the propeller was changed to a constant-speed three-blade metal propeller.
These five aircraft were first flown in Februari 1942, and were quickly followed by three identical pre-production aircraft. Flight testing was satisfactory, except for some engine teething problems, and the new version entered production in November 1942
More than only the powerplant were changed, also the supercharger air intake was moved from under the cowling to the upper lip. The wing span was reduced by 1 ft 11.625 inch (0,6 m)and wing area by 6.46 sq ft (0,6 m²) to improve speed at low and medium altitude. the cockpit windscreen and canopy were heightened, and a new reflector gunsight (as opposed to a telescopic gunsight through the windshield) was fitted as well. Pilot's protection was provided in the way of a 0.51 inch (13 mm) head and back armor plating, and a rudimentary form of self sealing fuel tanks were incorporated in the wings.
Number built: unknown out of 2.549 Ki-43-II's plus unknown out of 2.629 Ki-43-II's and -IIIa's
Nakajima Ki-43-IIb Hayabusa This version was the mass produced version, and was based on the Ki-43-IIa. Changes include minor equipment changes, and a different carburettor intake. The ring-shaped oil cooler was replaced with a honey-comb unit incorporated in a deeper carburettor intake. Later aircraft had their wing attachment points (hardpoints) moved outboard of the main landing gear to prevent bombs dropped during a steep dive-bombing from crashing into the propeller.. Even later the oil-cooler was replaced from the carburettor intake to a place under the center fuselage.
Number built: unknown out of 2.549 Ki-43-II's plus unknown out of 2.629 Ki-43-II's and -IIIa's
Nakajima Ki-43-II KAI Hayabusa All changes that were introduced during the production of the Ki-43-IIb were standardised in the Ki-43-II KAI. Additionally this version was also fitted with individual exhaust stacks that offered a little extra thrust, and thus improved speed and range a little. Some airframe modifications were introduced as well to ease production and maintenance.
Number built: unknown out of 2.549 Ki-43-II's plus unknown out of 2.629 Ki-43-II's and -IIIa's
Nakajima Ki-43-IIIa Hayabusa This was the final (operational) version of the Hayabusa. Nakajima built 10 prototypes, starting in May 1944. The main difference from the Ki-43-II KAI was the powerplant, which was 1 × Nakajima Ha-115-II radial, rated 1,230 hp (917 kW) at 9,185 ft (2.800 m). All subsequent production aircraft were built by Tachikawa Hikoki K.K.
Number built: 10 plus unknown out of 2.629 Ki-43-II's and -IIIa's
Nakajima Ki-43-IIIb Hayabusa This version only reached prototype status. Two aircraft were built by Tachikawa Hikoki K.K. The Ki-43-IIIb was a specialised interceptor fighter, that was still being tested when the War ended. It's powerplant consisted of 1 × Mitsubishi [Ha-33] 42 (Ha-112) radial. Armament consisted of 2 × 20 mm Ho-5 cannon.
Number built: 2
Army Type 1 Fighter Model 1A Hayabusa Official Imperial Japanese Army Air Force designation for the ki-43-Ia Hayabusa 'Oscar'
Army Type 1 Fighter Model 1B Hayabusa Official Imperial Japanese Army Air Force designation for the Ki-43-Ib Hayabusa 'Oscar'
Army Type 1 Fighter Model 1C Hayabusa Official Imperial Japanese Army Air Force designation for the Ki-43-Ic Hayabusa 'Oscar'
Army Type 1 Fighter Model 2A Hayabusa Official Imperial Japanese Army Air Force designation for the Ki-43-IIa Hayabusa 'Oscar'
Army Type 1 Fighter Model 2B Hayabusa Official Imperial Japanese Army Air Force designation for the Ki-43-IIb Hayabusa 'Oscar'
Army Type 1 Fighter Model 3A Hayabusa Official Imperial Japanese Army Air Force designation for the Ki-43-IIIa Hayabusa 'Oscar'
Nakajima Ki-43 Allied codenames During the opening stages of the pacific War identification of Japanes aircraft was difficult. The Japanese designation system, coupled with the tight security around the capabilities and type of the Japanese hampered things even more. Therefor since Allied identification was started by using names for types, some aircraft received a different name in different theatres. The Ki-43 was known as Jim in the CBI (China, Burma and India) theatre. It was believed it was a version of the Ki-27 with retractable undercarriage, and such was a derivative of the Nate. In the Southwest Pacific theatre it became known as the Oscar, and after it was established that Jim and Oscar were the same the name Oscar was chosen.

Operational remarks:

The Hayabusa made it's combat début over Burma and Malay during the first weeks of the Pacific War. There it established due to it's good performance and maneuverability quiet a reputation and became the most feared fighter of the Imperial Japanese Army Air Force, in spite of it's lack of armor protection for the pilots and non-self-sealing fuel tanks.
Numerically the Hayabusa was the most important fighter of the Imperial Japanese Army Air Force, and served on any front of the Japanese Army. When the war drew to an end the Ki-43 was mostly phased out of front-line service, the remainder being used for taiatara (like kamikaze) suicide attacks.
Other users of the Ki-43 are the Thai air force during the War. After the War the Indonesian People's Security Force's pilots also used the Ki-43 when they fought for their independance against the Dutch forces. Even the French used the Ki-43 for a short period when fighting against Communist in Indo-China.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 9/23/01