Kawasaki Ki-61

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Ki-61 Hien

Type	Fighter
Manufacturer	Kawasaki Heavy Industries
Designed by	Takeo Doi Shin Owada
Maiden flight	December 1941
Retired	1945
Primary user	Imperial Japanese Army Air Force
Number built	3,159
Variants	Kawasaki Ki-100

The Kawasaki Ki-61 Hien (飛燕, "flying swallow") was a World War II fighter aircraft used by the Imperial Japanese Army Air Force. The allied code name was "Tony", by the United States Department of War. The Japanese Army designation was "Type 3 Fighter" (三式戦闘機). It was the only mass-produced Japanese fighter of the war to use a liquid-cooled V engine.

1 History
2 Ki-61 Special Attack Unit
3 Variants
4 Specifications (Ki-61-I-KAIc)
5 References
6 External links
7 Related content

[edit] History

The Ki-61 Hien was designed in parallel with the Kawasaki Ki-60 interceptor by Takeo Doi and Shin Owada. Created around the Kawasaki V12 engine with denomination Ha-40 engine, a license-built version of the German Daimler-Benz DB 601A, Ki-61 improved on the Ki-60 design by incorporating a revised wing and various streamlining and weight-saving measures. The aircraft first flew in December 1941. Although test pilots were enthusiastic about self-sealing fuel tanks, upgraded armament, and good dive performance, the wing loading of 146.3 kg/m² (30 lb/ft²) was considered excessive by Japanese standards (92.6 kg/m² (19 lb/ft²) in Ki-43-Ia was considered borderline). To address these concerns, Kawasaki staged a fly-off between the Ki-61 prototype and Ki-43-II, Ki-44-I, Bf 109E-3, and captured P-40E Warhawk. Ki-61 proved the fastest of all the aircraft and was inferior only to Ki-43 in maneuverability ^[1].

Ki-61 entered combat for first time in the Spring of 1943 during the New Guinea campaign. The aircraft was utilized in South and Southwest Pacific, Philippines, Southeast Asia, Okinawa, China, Manchuria and Japanese Metropolitan defense against American B-29 Superfortresses. Some were also used in Kamikaze missions toward the end of the war. Initially, due to its unusual appearance for a Japanese fighter, the Allies believed it to be of Italian design or a license-built Bf 109. The Italian-like appearance led to its codename of "Tony". The Ki-61 was delivered to fifteen Sentai (squadrons), State Major Chutais and other operational training units in the IJAAF. The aircraft was largely trouble-free in service except for the liquid-cooled engine which tended to overheat when idling on the ground and suffered from oil circulation and bearing problems.

Ki-61-II was a high altitude interceptor with 10% larger wing area, more armor, and a more powerful engine. After initial fuselage and wing stability problems, the new interceptor reverted to the original wing and was put into service as the Ki-61-II KAI. However, engine reliability problems with the improved version of the Ha-40 engine named Ha-140 were never resolved. After a US bombing raid on 1945-01-19 destroyed the engine factory in Akashi, Hyogo, the 275 Ki-61-II KAI airframes without engines were converted to use the Mitsubishi Ha-112-II radial engine, resulting in the Ki-100.

[edit] Ki-61 Special Attack Unit

The tactic of using aircraft to ram B-29s was nothing new in November of 1944. The first recorded Ki-61 ramming strike occurred in late August, when enlisted pilot Shigeo Nobe of the 4th Sentai intentionally sliced into a B-29 on a mission from bases in China to the steel factories at Yahata, Fukuoka Prefecture in Kyushu. Other attacks of this kind followed when individual pilots decided it was the only way to bring success.

But then on November 7, 1944, the officer commanding the 10th Hiko Shidan made ramming a matter of policy by asking the men of the units under his command to form ramming attack flights specifically to oppose the B-29s at high altitude. They were to use aircraft stripped of their armament and protective systems in order to attain the required altitudes. The weapon would be controlled collision.

The units assigned to the 10th included the 244th Hiko Sentai. Following orders, then, Captain Takashi Fujita, commanding the 244th at the time, took the necessary steps to begin organizing a ramming flight nicknamed "Hagakure-Tai" Special Attack Unit and conformed by nexts sections: 2nd Chutai under name "Toppu", 1st Chutai was called "Soyokaze" and the 3rd Chutai was known as "Mikazuki".

Selected to lead this daring attack unit was 1st Lt. Toru Shinomiya, who would eventually lose his life as a Tokkotai pilot in the battle for Okinawa, but not before he became famous by scoring a victory using the ramming attack and living to tell the tale. Shinomiya attacked a B-29 on December 3, 1944, and brought himself and his damaged plane home.

Another 244th man, Masao Itagaki, performed a similar feat on the same occasion, but had to parachute from his damaged fighter. A third pilot, Officer Nakano, of the Hagakure-Tai of the 244th got another B-29 and crash landed his stripped-down Ki-61 in a field. On behalf of the 244th Sentai, Sergeant Shigeru Kuroishikawa was another distinguished member in the unit.

The existence of the ramming unit had been kept confidential until then, but it was officially disclosed in the combat-result announcement and officially named "Shinten Seiku Tai" (Heart of Heaven Intercept Unit) by the Defense GHQ.

But these pilots gained no reprieve for their successes in this dangerous work. They remained members of the deadly ramming unit, and would until they were wounded so badly that they could no longer fly or were killed. They were doomed men, and, therefore, they should be counted among the ranks of those who were going to certain death as Tokkotai pilots.

[edit] Variants

Ki-61-Ia: The first production variant, 2x 7.7 mm (0.303 in) and 2x 12.7 mm (0.50 in) machine guns, some fitted with a pair of German 20 mm MG 151 cannon instead of wing machine guns
Ki-61-Ib: Armed with 4x 12.7 mm machine guns, some fitted with a pair of German 20 mm MG 151 cannon instead of wing machine guns
Ki-61-I-KAIc: Reinforced wings to permit carrying bombs or external fuel tanks, 190 mm (7.5 in) fuselage stretch, fixed tail wheel, revised rear fuselage, 2x 20 mm cannon in the nose.
Ki-61-I-KAId: Interceptor variant with 2x 12.7 mm fuselage machine guns and 2x 30 mm wing cannon
Ki-61-II: Prototype with 10% larger wing area, Ha-140 engine with 1,120 kW (1,500 hp) for takeoff; first flight December 1943, 8 built.
Ki-61-II-KAI: Pre-production version with the original wing, 220 mm (8.7 in) fuselage stretch, enlarged rudder, and Ha-140 engine, 30 built.
Ki-61-II-KAIa: 2x 12.7 mm machine guns in the wings, 2x 20 mm cannon in the fuselage.
Ki-61-II-KAIb: 4x 20 mm cannon.

A total of 3,159 Ki-61 were built.^[2]

[edit] Specifications (Ki-61-I-KAIc)

Data from The Great Book of Fighters^[3]

General characteristics

Crew: One
Length: 8.94 m (29 ft 4 in)
Wingspan: 12.00 m (39 ft 4 in)
Height: 3.70 m (12 ft 2 in)
Wing area: 20.00 m² (215.28 ft²)
Airfoil: NACA 2R 16 wing root, NACA 24009 tip

Internal fuel capacity: 550 L (145.2 US gal)
External fuel capacity: 2x 200 L (53.8 US gal) drop tanks

Empty weight: 2,630 kg (5,800 lb)
Loaded weight: 3,470 kg (7,650 lb)
Powerplant: 1× Kawasaki Ha-40 liquid-cooled inverted V-12, 875 kW (1,175 hp)

Performance

Maximum speed: 580 km/h (360 mph) at 5,000 m (16,405 ft)
Range: 580 km (360 mi)
Service ceiling: 11,600 m (38,100 ft)
Rate of climb: 15.2 m/s (2,983 ft/min)
Wing loading: 173.5 kg/m² (35.5 lb/ft²)
Power/mass: 0.25 kW/kg (0.15 hp/lb)

Time to altitude: 7.0 min to 5,000 m (16,405 ft)

Armament

2x 20 mm Ho-5 cannon, 120 rounds/gun
2x 12.7 mm (0.50 in) Ho-103 machine guns, 200 rounds/gun
2x 250 kg (550 lb) bombs

[edit] References

^ Francillon RJ (1966). Aircraft profile 118: Kawasaki Ki-61 Hien. Profile publications. ASIN B0007KB5AW.
^ The Kawasaki Ki-61 Hien ("Tony") & Ki-100 (2003). Retrieved on February 20, 2007.
^ Green, W; Swanborough, G (2001). The great book of fighters. MBI Publishing. ISBN 0-7603-1194-3.