The Kawasaki Ki-61 Hien

Allied codename 'Tony'

Japan
Japan

Sorry, No ID pictures yet

Very unlike it's other contemporary Japanese brothers, the Hien (or Swallow) had an inverted-Vee engine. In fact, it was a license built German Daimler-Benz DB 601A. This, and other features made the Allied pilots think it was maybe a license built Messerschmitt Bf 109, or an Italian aircraft. This resulted in the Allied codename 'Tony'.
A number of reasons resulted in the development of the radical different fighter in the Japanese arsenal. Kawasaki failed to receive contracts for their models with other types of liquid cooled engines, so work started on a license built version of a proven type. Also German engineers worked with the Kawasaki company to design and build fighters that would win a production contract. Furhtermore Kawasaki learned some facts of the airial warfare in the North European Theatre during 1939 - 1940. This resulted in self sealing fuel tanks and armor protection for the pilot.
Work on the Ki-61 Hien was designed in paallel with the Ki-60, a cannon-armed interceptor whose emphasis was more on speed and climb-rate than on agility and range. The Ki-61 was to be the multi-role stable-mate of the Ki-60, with an emphasis on agility and long range.

Versions:

Further pictures:

Kawasaki Ki-61-I-Otsu, note the Messerschmitt bf 109's engine resemblance
Kawasaki Ki-61-I-Otsu, note the Messerschmitt bf 109's engine resemblance

Kawasaki Ki-61-I-Otsu in full flight
Kawasaki Ki-61-I-Otsu in full flight

 

Technical data on the Kawasaki Ki-61-I-Otsu Hien
Powerplant 1 × Kawasaki Ha-40 (Army Type 2) inverted-Vee, rated at 1175 hp (875.95 kW) Role during war
Length 28 ft 8.5 inch Height 12 ft 1.75 inch
Empty weight 4872 lb Operational weight 7165 lb max
Wing Span 39 ft 4.25 inch Wing Aspect ratio 7.2
Wing Area 215.28 sq ft Service ceiling 37730 ft
Maximum speed 368 mph at 15945 ft Cruising speed 249 mph at 13125 ft
Initial climb rate Climb to 16,405 ft in 5 min 31 sec Range 373 miles typical,
684 miles max
Fuel capacity internal 121 Imp gal (145 US gal) Fuel capacity external Up to 88 Imp gal (106 US gal) in 2 × 44 Imp gal (53 US gal) drop tanks
Machine guns
  • 2 × 0.50 inch fixed forward-firing in the upper nose
  • 2 × 0.50 inch fixed forward-firing in the wing leading edge, 200 rounds each
Cannons -
Bomb load - Torpedoes/rockets -
Crew 1 Naval or ground based Ground
First flight (prototype) December 1941 Operational Service Februari 1943 - 1945
Manufacturer Kawasaki Kokuki kogyo K.K. Number produced 3.078 total, 1.380 Ki-61-I's
Metric system
Length 8.75 m Height 3.7 m
Empty weight 2210 kg Operational weight 3250 kg max
Wing Span 12 m Wing Aspect ratio 7.2
Wing Area 20 m² Service ceiling 11500 m
Maximum speed 592 km/h at 4860 m Cruising speed 401 km/h at 4000 m
Initial climb rate Climb to 5.000 m in 5 min 31 sec Range 600 km typical,
1101 km max
Fuel capacity internal 550 liters Fuel capacity external Up to 400 liters in 2 × 200 liters drop tanks
Machine guns
  • 2 × 12,7 mm fixed forward-firing in the upper nose
  • 2 × 12,7 mm fixed forward-firing in the wing leading edge, 200 rounds each
Cannons -
Bomb load - Torpedoes/rockets -

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

Different versions of the Kawasaki Ki-61  Hien
Kawasaki Ki-61-I-Ko One of the two initial models to enter service, produced in parrallel with the Kawasaki Ki-61-I-Otsu. This version was armed with 2 × 0.50 inch (12,7 mm) Ho-103 (Type 1) guns in the upper nose, and 2 × 0.303 inch (7,7 mm) in the wing leading edges.
Number built: unknown out of a total of 1.380 Ki-61-I's
Kawasaki Ki-61-I-Otsu Twin brother of the Kawasaki Ki-61-I-Ko, except it's armament (see details above).
Number built: unknown out of a total of 1.380 Ki-61-I's
Kawasaki Ki-61-I-KAI-Hei Hien Initially it was planned that the Ki-61 would carry a pair of Japanese 20 mm cannons in the nose, but delivery of these weapons meant a reversion to the pair of 0.50 inch (12,7 mm) guns. Later aircraft were refitted with 2 × 20 mm MG 151/20 cannons in the wing. The Kawasaki Ki-61-I-KAI-Hei Hien would not only carry 2 × 20 mm Ho-5 cannons in the fuselage, 120 rounds each, but also had a simplified and stronger construction, and changes to increase it's maintainability. Other differences are as follows: powered by 1 × Kawasaki Ha-40 radial, rated at 1,180 hp (880 kW), a lengthened fuselage with a detacheable tail, and strengthened wings with 2 hardpoints rated at 551 lb (250 kg). Other details are: ;ength of 29 ft 4 inch (8,94 m), empty weight of 5,798 lb (2.630 kg), normal take-off weight of 7,650 lb (3.470 kg), max level speed of 360 mph (590 km/h) at 13,980 ft (4.260 m), max range of 1,119 miles (1.800 km), Climb to 16,405 ft (5.000 m) in 7 min 0 sec, and a service ceiling of 32,810 ft (10.000 m)
Number built: 1.274
Kawasaki Ki-61-II-KAI-Ko Hien The Ki-61-I series aircraft had excellent performance in the low and medium altitudes, but this declined rapidly in the higher altitudes. To overcome this problem the Kawasaki team modified it. The resulting prototypes were powered by 1 × Kawasaki Ha-140 inverted-Vee, rated at 1,500 hp (1.118 kW). This was a Japanese improvement on the original German designed Ha-40. The wing was also increased in area, to 236.81 sq ft (22,00 m²).
Initial trials were disappointing, because the new engine showed regular crankshaft problems, and the wing was suspected to be too weak. It was then decided that the 9th prototype would have the standard wings of the Ki-61-I series, resulting in the designation Ki-61-II-KAI. The rudder was also enlarged, and the fuselage length increased to 30 ft 0.625 inch (9,16 m). These changes were sufficient to solve the structural and handling problems. The empty weight was 6,261 lb (2.840 kg), normal take-off weight was 8,333 lb (3.780 kg), max take-off weight was 8,433 lb (3.825 kg), max level speed was 379 mph (610 km/h) at 19,685 ft (6.000 m), max range of 994 miles (1.600 km) with drop tanks, typical range was 684 miles (1.100 km) with internal fuel, climb to 16,405 ft (5.000 m) in 6 min 0 sec, and service ceiling of 36,090 ft (11.000 m). It was produced in parallel with it's twin brother, the Ki-61-II-KAI-Otsu Hien, and differed only in it's armament: 2 × 20 mm cannons and 2 × 0.50 inch (12,7 mm) guns for this version. 274 airframes were produced, but due to the fact that the engine factory of Kawasaki was totally destroyed, only 99 of both versions were produced.
Number built: unknown out of a total of 99 Ki-61-II-KAI's
Kawasaki Ki-61-II-KAI-Otsu Hien This version was produced in parallel with it's twin brother, the Ki-61-II-KAI-Ko Hien, and differed only in it's armament: 4 × 20 mm cannons for this version. 274 airframes were produced, but due to the fact that the engine factory of Kawasaki was totally destroyed, only 99 of both versions were produced.
Number built: unknown out of a total of 99 Ki-61-II-KAI's
Army Type 3 Fighter Model I-Ko Official Imperial Japanese Army Air Force designation for the Kawasaki Ki-61-I-Ko
Redesignated aircraft
Army Type 3 Fighter Model I-Otsu Official Imperial Japanese Army Air Force designation for the Kawasaki Ki-61-I-Otsu
Redesignated aircraft
Army Type 3 Fighter Model I-Hei Official Imperial Japanese Army Air Force designation for the Kawasaki Ki-61-I-KAI-Hei
Redesignated aircraft
Army Type 3 Fighter Model II-Ko Official Imperial Japanese Army Air Force designation for the Kawasaki Ki-61-II-KAI-Ko
Redesignated aircraft
Army Type 3 Fighter Model II-Otsu Official Imperial Japanese Army Air Force designation for the Kawasaki Ki-61-II-KAI-Otsu
Redesignated aircraft
Kawasaki Ki-61-Ia Hien Western designation of the Ki-61-I-Ko
Redesignated aircraft
Kawasaki Ki-61-Ib Hien Western designation of the Ki-61-I-Otsu
Redesignated aircraft
Kawasaki Ki-61-I KAIc Hien Western designation of the Ki-61-II-KAI-Ko Hien
Redesignated aircraft
Kawasaki Ki-61-II KAIa Hien Western designation of the Ki-61-II-KAI-Ko Hien
Redesignated aircraft
Kawasaki Ki-61-II KAIb Hien Western designation of the Ki-61-II-KAI-Otsu Hien
Redesignated aircraft

Remarks:

The Hien was extensively used in the South-West Pacific, the Philippines, Okinawa, and Japan, in the last theatre as a home defense fighter. It was as good as any Allied fighter, but no other operational facts are known to me at this time.

Strengths:

Weaknesses:

 

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© by Frans Bonné, 2000
Last revision: 12/11/00