Kawasaki Ki-61

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 Macchi C.202,
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 all-metal, semi-monocoque fuselage was basically oval in cross-section,
changing to a tapered, semi-triangular oval behind the cockpit canopy, with a
maximum depth of 1.35 m (4 ft 5 in). An unusual feature of the Ki-61 was that
the engine bearers were constructed as an integral part of the forward fuselage,
with the cowling side panels being fixed. For servicing or replacement, only the
top and bottom cowling panels could be removed. A tapered, rectangular
supercharger air intake was located on the port-side cowling. Behind the engine
bulkhead were the ammunition boxes feeding a pair of synchronized 12.7 mm (.50
in) Ho-103 machine guns which were set in a "staggered" configuration (the port
weapon slightly further forward than that to starboard) in a bay just above and
behind the engine. The breeches partly projected into the cockpit, above the
instrument panel. The Ho-103 was a light weapon for its caliber (around 23 kg/51
lb) and fired a light shell, but this was compensated for by its rapid rate of
fire. The ammunition capacity was limited, having only around 250 rounds for
each weapon. A self-sealing fuel tank with a capacity of 165 L (44 US gal) was
located behind the pilot's seat. The windshield was armored and there was a 13
mm (.51 in) armor plate behind the pilot. The radiator and oil cooler for the
liquid-cooled engine were in a ventral location below the fuselage and wing
trailing edge, covered by a rectangular section fairing with a large, adjustable
exit flap.

Compared to the Ki-61-I, the Ki-61-II had 10% greater wing area, used more
armour and was powered by the Kawasaki Ha-140 engine generating 1,120 kW (1,500
hp). After overcoming 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, the Ha-140 engine had severe reliability problems that
were never fully resolved, and around half of the first batch of engines
delivered were returned to the factory to be re-built. A US bombing raid on 19
January 1945 destroyed the engine factory in Akashi, Hyogo, and 275 Ki-61-II-KAI
airframes without engines were converted to use the Mitsubishi Ha-112-II radial
engine, resulting in the Ki-100. While the Ha-112 solved the problems
encountered with the Ha-140, the new engine still had a major weakness: a lack
of power at altitude, which diminished its ability to intercept high-flying B-29
Superfortresses relative to the Ki-61-II.

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 new Ki-61 Hien fighters entered service with a special training unit, the
23rd Chutai, and entered combat for the 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, the 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.

However, the increasing numerical strength of Allied bomber units, along with
inadequate anti-aircraft systems, imposed crippling losses on Japanese units.
Approximately 100 out of 130 Japanese aircraft based in the Wewak area were lost
during the attacks of August 17–21 1943. By the end of the campaign, nearly
2,000 Japanese aircraft had been lost in air attacks from up to 200 Allied
aircraft at a time, around half of which were Consolidated B-24 Liberators and
North American B-25 Mitchells armed with fragmentation bombs. After the Japanese
retreat, over 340 aircraft wrecks were later found at Hollandia.

Owing to the additional weight, the Ki-61's performance and agility suffered
when its armament was increased, but it still remained capable with a 580 km/h
(313 kn) maximum speed. The cannon armament was needed to counter the Allied
bombers, which proved to be difficult to shoot down with only 12.7 mm (.50 in)
machine guns. The empty and maximum weights for the Ki-61 prototype (2 × 12.7
mm/0.50 in + 2 × 7.7 mm/0.303 in) were 2,238 kg (4,934 lb) and 2,950 kg (6,504
lb), respectively; for the Ki-61-I basic (4 × 12.7 mm/.50 in) 3,130 kg (6,900
lb); and for the Ki-61-KAI (2 × 12.7 mm/0.50 in + 2 × 20 mm), 2,630 kg (5,798
lb) and 3,470 kg (6,750 lb).

A number of Ki-61s were also used in Tokkotai (kamikaze) missions launched
toward the end of the war. The Ki-61 was delivered to 15th Sentai (group/wing),
as well as some individual Chutaicho (Squadron Leaders) in other Sentai, and
even to operational training units in the JAAF. 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 Special Attack Unit

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 Chutai (squadrons) of the 244th: the 1st Chutai
"Soyokaze", 2nd Chutai "Toppu", and the 3rd Chutai known as "Mikazuki".

First Lieutenant Toru Shinomiya was selected to lead the Hagakure-Tai. On 3
December 1944, Shinomiya – along with Sergeant Masao Itagaki and Sergeant
Matsumi Nakano – intercepted a B-29 raid; Shinomaya rammed one B-29, but was
able to land his damaged Ki-61, which had lost most of the port outer wing, back
at base. After attacking another B-29 Itagaki had to parachute from his damaged
fighter, while Nakano rammed and damaged Long Distance of the 498th BG and
crash-landed his stripped-down Ki-61 in a field. Shinomaya's damaged Ki-61 was
later displayed inside Tokyo's Matsuya department store while Nakano's Ki-61 was
displayed outside, alongside of a life-size cut-away drawing of the forward
fuselage of a B-29. These three pilots were the first recipients of the Bukosho,
Japan's equivalent to the Victoria Cross or Medal of Honor, which had been
inaugurated on 7 December 1944 as an Imperial Edict by Emperor Hirohito (there
are 89 known recipients, most of whom fought and scored against B-29s). The
existence of the ramming unit had been kept confidential until then, but it was
officially disclosed in the combat results announcement and officially named
"Shinten Seiku Tai" ("Body Attack Detachment") by the Defense GHQ. On 27 January
1945, Itakagi survived another ramming attack on a B-29, again parachuting to
safety, and received a second Bukosho; he survived the war as only one of two
known double-Bukosho recipients. Sergeant Shigeru Kuroishikawa was another
distinguished member of the unit.

Despite their successful attacks, these pilots gained no reprieve, and were
obliged to continue these deadly and dangerous ramming tactics until they were
killed, or else wounded so badly that they could no longer fly. They were
regarded as doomed men and were celebrated among the ranks of those who were
going to certain death as Tokkotai (kamikaze) pilots.

Some other Ki-61 pilots also achieved renown, among them Major Teruhiko
Kobayashi of the 244th Sentai, who was credited by some with a dozen victories
mostly due to conventional attacks against B-29s.

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, 310 kn) at 5,000 m (16,000 ft)
Range: 580 km (360 mi, 310 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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