Kawasaki Ki-61 "Hien"

https://en.wikipedia.org/wiki/Kawasaki_Ki-61

The Kawasaki Ki-61 Hien (??, "flying swallow") is a Japanese World War II
fighter aircraft used by the Imperial Japanese Army Air Service. The Japanese
Army designation was "Army Type 3 Fighter". Allied pilots initially believed
Ki-61s were Messerschmitt Bf 109s and later an Italian aircraft, which led to
the Allied reporting name of "Tony", assigned by the United States War
Department. It was the only mass-produced Japanese fighter of the war to use a
liquid-cooled inline V engine. Over 3,000 Ki-61s were produced. Initial
prototypes saw action over Yokohama during the Doolittle Raid on 18 April 1942,
and continued to fly combat missions throughout the war.

The Ki-61 was designed by Takeo Doi and his deputy Shin Owada in response to a
late 1939 tender by the Koku Hombu for two fighters, each to be built around the
Daimler-Benz DB 601Aa. Production aircraft would use a Kawasaki licensed DB 601,
known as the Ha-40, which was to be manufactured at its Akashi plant. The Ki-60
was to be a heavily armed specialised interceptor, with a high wing loading; the
Ki-61 was to be a more lightly loaded and armed general-purpose fighter,
intended to be used mainly in an offensive, air superiority role at low to
medium altitudes.

Both single-seat, single-engine fighters used the same basic construction, being
of all-metal alloys with semi-monocoque fuselages and three-spar wings, with
alloy-framed, fabric-covered ailerons, elevators and rudders. Priority was given
to the Ki-60, which first flew in April 1941, while design work on the Ki-61 did
not begin until December 1940. Although the Ki-61 was broadly similar to the
Ki-60, it featured several refinements exploiting lessons learned from the
disappointing flight characteristics of the earlier design.

The Ki-61 was the last of the fighters powered by the DB-601 or its foreign
derivatives, and it was soon overshadowed by fighters with more powerful
engines. By the time it first flew in December 1941, one year after the Macchi
C.202's first flight and three years after the first Bf 109E, the engine was
already underpowered compared to the new 1,120 kW (1,500 hp) inline or 1,491 kW
(2,000 hp) radial engines being developed (and already nearing the
mass-production stage) to power the next generation of combat aircraft such as
the Republic P-47 Thunderbolt. Moreover, the inline Ha-40 engine proved to be an
unreliable powerplant.

The DB-601 engine required precise and sophisticated manufacturing; the Ha-40
was lighter by roughly 30 kg (70 lb) and required even higher manufacturing
standards. Reaching these standards proved difficult for Japanese manufacturers,
an issue further complicated by the variable quality of materials, fuel, and the
lubricants needed to run a sensitive, high-performance engine. The Japanese
equivalent of the more powerful DB-605 engine was the Ha-140, which was fitted
onto the Type 3 to produce the Ki-61-II high-altitude interceptor.

During testing, the Hien proved capable, but several shortcomings were
subsequently revealed in operational service, namely the armor protection that
was insufficient against larger guns and a sub-standard engine that eventually
led to a new engine being considered.


Role
Fighter aircraft

Manufacturer
Kawasaki Kokuki Kogyo K.K.

Designer
Takeo Doi

First flight
December 1941

Introduction
1942

Retired
1945

Primary users
Imperial Japanese Army Air Service
Chinese Nationalist Air Force
People's Liberation Army Air Force

Number built
3,078

Developed into
Kawasaki Ki-100

The Ki-61 looked so different than the usual radial-engined Japanese fighters
that the Allies at first believed it to be of German or Italian origin, possibly
a license-built Messerschmitt Bf 109. The first Ki-61 seen by Allied aircrew had
been misidentified as a Bf 109 by USAAF Capt. C. Ross Greening during the
Doolittle Raid. In early reports, when it was thought to have been a German
fighter, the Ki-61 had been code-named "Mike". The final, and better known code
name adopted was "Tony", because the Ki-61 looked like an Italian aircraft.

The new Ki-61 Hien fighters entered service with a special training unit, the
23rd Chutai, and entered combat for first time in early 1943, during the New
Guinea campaign. The first Sentai (Air Group/Wing) fully equipped with the Hien
was the 68th in Wewak, New Guinea, followed by the 78th Sentai stationed at
Rabaul. Both units were sent into a difficult theatre where jungles and adverse
weather conditions, coupled with a lack of spares, quickly undermined the
efficiency of both men and machines. Because the Ki-61 was so new, and had been
rushed into service, it inevitably suffered from teething problems. Almost all
of the modern Japanese aircraft engines, especially the Ki-61's liquid-cooled
engines, suffered a disastrous series of failures and ongoing problems, which
resulted in the obsolescent Ki-43 still forming the bulk of the JAAF's fighter
capability.

Initially, this campaign went successfully for the Japanese Army Air Force
(JAAF), but when the Allies re-organized and enhanced the combat capabilities of
their air forces, they gained the upper hand against the JAAF. High non-combat
losses were also experienced by the Japanese during this campaign. For example,
while in transit between Truk and Rabaul, the 78th lost 18 of its 30 Ki-61s.

Even with these problems, there was some concern in Allied aviation circles
regarding the Hien:
The new Japanese fighter caused some pain and consternation among Allied pilots,
particularly when they found out the hard way that they could no longer go into
a dive and escape as they had from lighter Japanese fighters. ...General George
Kenney [Allied air forces commander in the Southwest Pacific] found his Curtiss
P-40s completely outclassed, and begged for more Lockheed P-38 Lightnings to
counter the threat of the new enemy fighter.

The tactic of using aircraft to ram American Boeing B-29 Superfortresses was
first recorded in late August 1944, when B-29s from Chinese airfields attempted
to bomb the steel factories at Yawata. Sergeant Shigeo Nobe of the 4th Sentai
intentionally flew his Kawasaki Ki-45 into a B-29; debris from the explosion
severely damaged another B-29, which also went down. Other attacks of this
nature followed, as a result of which individual pilots determined it was a
practicable way of destroying B-29s.

On 7 November 1944, the officer commanding the 10th Hiko Shidan (Air division)
made ramming attacks a matter of policy by forming ramming attack flights
specifically to oppose the B-29s at high altitude. The aircraft were stripped of
their fuselage armament and protective systems in order to attain the required
altitudes. Although the term "kamikaze" is often used to refer to the pilots
undertaking these attacks, the word was not used by the Japanese military.

The units assigned to the 10th Hiko Shidan included the 244th Hiko Sentai
(Fighter group), then commanded by Captain Takashi Fujita, who organised a
ramming flight called "Hagakure-Tai" ("Special Attack Unit"), which was composed
out of volunteers from the three Chuatai (squadrons) of the 244th: the 1st
Chutai "Soyokaze", 2nd Chutai "Toppu", and the 3rd Chutai known as "Mikazuki".

Specifications (Ki-61-I-KAIc)

General characteristics
Crew: 1
Length: 8.94 m (29 ft 4 in)
Wingspan: 12 m (39 ft 4 in)
Height: 3.7 m (12 ft 2 in)
Wing area: 20 m2 (220 sq ft)
Airfoil: NACA 2R 16 wing root, NACA 24009 tip
Empty weight: 2,630 kg (5,798 lb)
Gross weight: 3,470 kg (7,650 lb)
Fuel capacity:

Internal 550 l (150 US gal; 120 imp gal)

External 2x 200 l (53 US gal; 44 imp gal)
Powerplant: 1 × Kawasaki Ha40 inverted liquid-cooled V-12 piston engine, 864 kW
(1,159 hp)
Propellers: 3-bladed variable pitch propeller

Performance
Maximum speed: 580 km/h (360 mph; 313 kn) at 5,000 m (16,000 ft)
Range: 580 km (360 mi; 313 nmi)
Service ceiling: 11,600 m (38,100 ft)
Rate of climb: 15.2 m/s (2,990 ft/min)
Time to altitude: 7.0 min to 5,000 m (16,000 ft)
Wing loading: 173.5 kg/m2 (35.5 lb/sq ft)
Power/mass: 0.25 kW/kg (0.15 hp/lb)

Armament

Guns:
2× 20 mm (0.79 in) Ho-5 cannon, 120 rounds per gun each
2× 12.7 mm (0.50 in) Ho-103 machine guns, 250 rpg each

Bombs: 2× 250 kg (550 lb) bombs




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