Kawasaki Ki-61 - AbsoluteAstronomy.com

The Kawasaki Ki-61 Hien (飛燕, roughly "flying swallow") was a Japanese World War II fighter aircraft

Fighter aircraft

A fighter aircraft is a military aircraft designed primarily for air-to-air combat with other aircraft, as opposed to a bomber, which is designed primarily to attack ground targets...

used by the Imperial Japanese Army Air Force. The first encounter reports claimed Ki-61s were Messerschmitt Bf 109

Messerschmitt Bf 109

The Messerschmitt Bf 109, often called Me 109, was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid 1930s...

s: further reports claimed that the new aircraft was an Italian design, which led to the Allied reporting name

World War II Allied names for Japanese aircraft

The World War II Allied names for Japanese aircraft were reporting names, often described as codenames, given by Allied personnel to Imperial Japanese aircraft during the Pacific campaign of World War II. The names were used by Allied personnel to identify Japanese aircraft for reporting and...

of "Tony", assigned by the United States War Department

United States Department of War

The United States Department of War, also called the War Department , was the United States Cabinet department originally responsible for the operation and maintenance of the United States Army...

. The Japanese Army designation was "Army Type 3 Fighter" (三式戦闘機). It was the only mass-produced Japanese fighter of the war to use a liquid-cooled inline

Inline

inline may relate to:* Inline citation or reference* Inline engine * Computers** Inline expansion** Inline function** Inline assembler** inline tag * Internet Posting Style** Inline replying...

V engine

A V engine, or Vee engine is a common configuration for an internal combustion engine. The cylinders and pistons are aligned, in two separate planes or 'banks', so that they appear to be in a "V" when viewed along the axis of the crankshaft...

. Over 2.500 Ki-61s were produced, first seeing action around New Guinea in 1943, and continuing to fly combat missions throughout the war.

Design and development

The Ki-61 was designed by Takeo Doi

Takeo Doi (aircraft designer)

was a Japanese aircraft designer.He designed many World War II fighter aircraft used by the Imperial Japanese Army Air Force. His most important work was the , aka Kawasaki Ki-61 or "Tony"....

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 601

Daimler-Benz DB 601

|-See also:-Bibliography:* Mankau, Heinz and Peter Petrick. Messerschmitt Bf 110, Me 210, Me 410. Raumfahrt, Germany: Aviatic Verlag, 2001. ISBN 3-92550-562-8.* Neil Gregor Daimler-Benz in the Third Reich. Yale University Press, 1998-External links:...

Aa. Production aircraft would use a Kawasaki licensed DB 601, known as the Ha-40

Kawasaki Ha-40

|-See also:-Bibliography:* Monogram Closeup 13. ISBN 0-914144-13-8.* Francillon, R. J., Japanese Aircraft of the Pacific War, Putnam, London, 1970 SBN 370 00033 1-External links:* * *...

, which was to be manufactured at its Akashi

Akashi, Hyogo

is a city located in southern Hyōgo Prefecture, Japan, on the Seto Inland Sea west of Kobe.As of April 1, 2011, the city has an estimated population of 290,776, with 117,392 households, and a population density of 5,907.68 persons per km²...

plant. The Ki-60

Kawasaki Ki-60

-See also:-References:NotesBibliography* Bueschel, Richard M. Kawasaki Ki.61/Ki.100 Hien in Japanese Army Air Force Service, Aircam Aviation Series No.21. Canterbury, Kent, UK: Osprey Publications Ltd, 1971. ISBN 0-85045-026-8....

was to be a heavily armed specialised interceptor

Interceptor aircraft

An interceptor aircraft is a type of fighter aircraft designed specifically to prevent missions of enemy aircraft, particularly bombers and reconnaissance aircraft. Interceptors generally rely on high speed and powerful armament in order to complete their mission as quickly as possible and set up...

, with a high wing loading

Wing loading

In aerodynamics, wing loading is the loaded weight of the aircraft divided by the area of the wing. The faster an aircraft flies, the more lift is produced by each unit area of wing, so a smaller wing can carry the same weight in level flight, operating at a higher wing loading. Correspondingly,...

; 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 alloy

Alloy

An alloy is a mixture or metallic solid solution composed of two or more elements. Complete solid solution alloys give single solid phase microstructure, while partial solutions give two or more phases that may or may not be homogeneous in distribution, depending on thermal history...

s with semi-monocoque fuselage

Fuselage

The fuselage is an aircraft's main body section that holds crew and passengers or cargo. In single-engine aircraft it will usually contain an engine, although in some amphibious aircraft the single engine is mounted on a pylon attached to the fuselage which in turn is used as a floating hull...

s and three-spar

Spar (aviation)

In a fixed-wing aircraft, the spar is often the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries flight loads and the weight of the wings whilst on the ground...

wings, with alloy-framed, fabric-covered aileron

Aileron

Ailerons are hinged flight control surfaces attached to the trailing edge of the wing of a fixed-wing aircraft. The ailerons are used to control the aircraft in roll, which results in a change in heading due to the tilting of the lift vector...

s, elevator

Elevator (aircraft)

Elevators are flight control surfaces, usually at the rear of an aircraft, which control the aircraft's orientation by changing the pitch of the aircraft, and so also the angle of attack of the wing. In simplified terms, they make the aircraft nose-up or nose-down...

s and rudder

Rudder

A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

s. 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

Cockpit

A cockpit or flight deck is the area, usually near the front of an aircraft, from which a pilot controls the aircraft. Most modern cockpits are enclosed, except on some small aircraft, and cockpits on large airliners are also physically separated from the cabin...

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

Cowling

A cowling is the covering of a vehicle's engine, most often found on automobiles and aircraft.A cowling may be used:* for drag reduction* for engine cooling by directing airflow* as an air intake for jet engines* for decorative purposes...

side panels being fixed. For servicing or replacement, only the top and bottom cowling panels could be removed. A tapered, rectangular supercharger

Supercharger

A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...

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 gun

Ho-103 machine gun

The 12.7mm Type 1 was a Japanese aircraft machine gun widely used during World War II and also known as the Ho-103. The Ho-103 was actually a fixed gun and the Ho-104 a flexible gun...

s 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

Self-sealing fuel tank

In aviation, self-sealing fuel tank is a fuel tank technology in wide use since World War II that prevents fuel tanks primarily on aircraft from leaking fuel and igniting after being damaged by enemy fire....

with a capacity of 165 L (44 US gal) was located behind the pilot's seat. The windshield was armoured and there was a 13 mm (.51 in) armour plate

Vehicle armour

Military vehicles are commonly armoured to withstand the impact of shrapnel, bullets, missiles, or shells, protecting the personnel inside from enemy fire. Such vehicles include tanks, aircraft, and ships....

behind the pilot. The radiator

Radiator

Radiators are heat exchangers used to transfer thermal energy from one medium to another for the purpose of cooling and heating. The majority of radiators are constructed to function in automobiles, buildings, and electronics...

and oil

Motor oil

Motor oil or engine oil is an oil used for lubrication of various internal combustion engines. The main function is to lubricate moving parts; it also cleans, inhibits corrosion, improves sealing, and cools the engine by carrying heat away from moving parts.Motor oils are derived from...

cooler for the liquid-cooled engine were in a ventral location below the fuselage and wing trailing edge

Trailing edge

The trailing edge of an aerodynamic surface such as a wing is its rear edge, where the airflow separated by the leading edge rejoins. Essential control surfaces are attached here to redirect the air flow and exert a controlling force by changing its momentum...

, covered by a rectangular section fairing with a large, adjustable exit flap.

The evenly tapered wings had an aspect ratio

Aspect ratio

The aspect ratio of a shape is the ratio of its longer dimension to its shorter dimension. It may be applied to two characteristic dimensions of a three-dimensional shape, such as the ratio of the longest and shortest axis, or for symmetrical objects that are described by just two measurements,...

of 7.2 with a gross area of 20 m² (215.28 ft²) and featured three spars; a Warren truss main spar and two auxiliary spars. The rear spar carried the split flap

Flap (aircraft)

Flaps are normally hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed an aircraft can be safely flown at and to increase the angle of descent for landing without increasing air speed. They shorten takeoff and landing distances as well as...

s and long, narrow-chord

Chord (aircraft)

In aeronautics, chord refers to the imaginary straight line joining the trailing edge and the center of curvature of the leading edge of the cross-section of an airfoil...

ailerons, while the front spar incorporated the undercarriage

Undercarriage

The undercarriage or landing gear in aviation, is the structure that supports an aircraft on the ground and allows it to taxi, takeoff and land...

pivot points. The undercarriage track was relatively wide at 4 m (13 ft 1.5 in). Each wing had a partially self-sealing 190 L (50 US gal) fuel tank behind the main spar, just outboard of the fuselage. A single weapon (initially a 7.7 mm/0.303 in Type 89 machine gun

Type 89 machine gun

Type 89 refers to two families of unrelated Imperial Japanese Army aircraft machine guns. The first family is the recoil-operated Vickers gun. The Type 89 FIXED gun was a license-built Vickers E class gun chambered for the Type 89 cartridge . It was used in synchronized applications in fighter...

) was able to be carried in a weapons bay located behind the main spar.

The first prototype

Prototype

A prototype is an early sample or model built to test a concept or process or to act as a thing to be replicated or learned from.The word prototype derives from the Greek πρωτότυπον , "primitive form", neutral of πρωτότυπος , "original, primitive", from πρῶτος , "first" and τύπος ,...

of the San-shiki-Sentohki ichi gata ("Type 3 Fighter, Model 1", the official IJAAF designation) first flew in December 1941 at Kagamigahara Airfield

Gifu Air Field

is a military aerodrome of the Japan Air Self-Defense Force . It is located in Kakamigahara City, east of Gifu in the Gifu Prefecture, Japan.- Units :* Air Defense Command** Central Air Defense Force*** 4th Air Defence Missile Group**** 13th Fire Unit...

. Although test pilots were enthusiastic about its self-sealing fuel tanks, upgraded armament, and good dive performance, the wing loading of 146.3 kg/m² (30 lb/ft²) at an all-up weight of 2,950 kg (6,500 lb) was viewed with scepticism by many of the senior officers of the Koku Hombu, who still believed in the light, highly manoeuvrable, lightly armed fighter epitomised by the then new Ki-43-I-Hei

Nakajima Ki-43

The Nakajima Ki-43 Hayabusa was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in World War II...

which had a wing loading of 92.6 kg/m² (19 lb/ft²) (and even that was considered borderline compared to the earlier Ki-27).

To address these concerns, Kawasaki staged a fly-off between two Ki-61 prototypes and the Ki-43-I

Nakajima Ki-43

The Nakajima Ki-43 Hayabusa was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in World War II...

, a pre-production Ki-44-I

Nakajima Ki-44

The Nakajima Ki-44 Shōki was a single-engine fighter aircraft used by the Imperial Japanese Army Air Force in World War II. The type first flew in August 1940 and entered service in 1942...

, a LaGG-3 (flown to Manchuria by a defector), a Bf 109E-3

Messerschmitt Bf 109

The Messerschmitt Bf 109, often called Me 109, was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid 1930s...

, and a captured P-40E Warhawk

Curtiss P-40

The Curtiss P-40 Warhawk was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. The P-40 design was a modification of the previous Curtiss P-36 Hawk which reduced development time and enabled a rapid entry into production and operational...

. The Ki-61 proved the fastest of all the aircraft and was inferior only to the Ki-43 in manoeuvrability.

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 engine

Radial engine

The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders point outward from a central crankshaft like the spokes on a wheel...

s being developed (and already nearing the mass-production stage) to power the next generation of combat aircraft such as the Messerschmitt Bf 109 G

Messerschmitt Bf 109

The Messerschmitt Bf 109, often called Me 109, was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid 1930s...

, or the Republic P-47. Moreover the inline

Inline

inline may relate to:* Inline citation or reference* Inline engine * Computers** Inline expansion** Inline function** Inline assembler** inline tag * Internet Posting Style** Inline replying...

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 to be a "stretch" 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.

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 which 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, Hyōgo

Akashi, Hyogo

, and 275 Ki-61-II-KAI airframes without engines were converted to use the Mitsubishi Ha-112

Mitsubishi Kinsei

|-See also:-Bibliography:* Matsuoka Hisamitsu, Nakanishi Masayoshi. The History of Mitsubishi Aero Engines 1915-1945. Miki Press, Japan, 2005. ISBN 4-89522-461-9...

-II radial engine, resulting in the Ki-100

Kawasaki Ki-100

The Kawasaki Ki-100 was a fighter aircraft used by the Imperial Japanese Army in World War II. The Japanese Army designation was "Type 5 Fighter"...

. 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-29s relative to the Ki-61-II.

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

Operational history

The Ki-61 looked so different compared with 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

Messerschmitt Bf 109

The Messerschmitt Bf 109, often called Me 109, was a German World War II fighter aircraft designed by Willy Messerschmitt and Robert Lusser during the early to mid 1930s...

. 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

Doolittle Raid

The Doolittle Raid, on 18 April 1942, was the first air raid by the United States to strike the Japanese Home Islands during World War II. By demonstrating that Japan itself was vulnerable to American air attack, it provided a vital morale boost and opportunity for U.S. retaliation after the...

. 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

New Guinea

New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...

campaign. The first Sentai (Air Group/Wing) fully equipped with the Hien was the 68th in Wewak

Wewak

Wewak is the capital of the East Sepik province of Papua New Guinea. It is located on the northern coast of the island of New Guinea. It is the largest town between Madang and Jayapura. It is the see city of the Roman Catholic Diocese of Wewak....

, New Guinea, followed by the 78th Sentai stationed at Rabaul

Rabaul

Rabaul is a township in East New Britain province, Papua New Guinea. The town was the provincial capital and most important settlement in the province until it was destroyed in 1994 by falling ash of a volcanic eruption. During the eruption, ash was sent thousands of metres into the air and the...

. 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

Imperial Japanese Army Air Service

The , was the land-based aviation force of the Imperial Japanese Army. As with the IJA itself, the IJAAF was developed along the lines of Imperial German Army Aviation so its primary mission was to provide tactical close air support for ground troops while maintaining a limited air interdiction...

(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

Chuuk

Chuuk — formerly Truk, Ruk, Hogoleu, Torres, Ugulat, and Lugulus — is an island group in the south western part of the Pacific Ocean. It comprises one of the four states of the Federated States of Micronesia , along with Kosrae, Pohnpei, and Yap. Chuuk is the most populous of the FSM's...

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

George Kenney

George Churchill Kenney was a United States Army Air Forces general during World War II. He was commander of the Allied air forces in the Southwest Pacific Area from August 1942 until 1945.-Early life:...

[Allied air forces commander in the Southwest Pacific

South West Pacific theatre of World War II

The South West Pacific Theatre, technically the South West Pacific Area, between 1942 and 1945, was one of two designated area commands and war theatres enumerated by the Combined Chiefs of Staff of World War II in the Pacific region....

] found his P-40s completely outclassed, and begged for more P-38s 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

Bombing of Wewak

The Bombing of Wewak was a series of air raids by the USAAF Fifth Air Force, on 17–21 August 1943, against the major air base of the Imperial Japanese Army Air Force on the mainland of New Guinea, at Wewak...

. 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 B-24

B-24 Liberator

The Consolidated B-24 Liberator was an American heavy bomber, designed by Consolidated Aircraft of San Diego, California. It was known within the company as the Model 32, and a small number of early models were sold under the name LB-30, for Land Bomber...

s and B-25

B-25 Mitchell

The North American B-25 Mitchell was an American twin-engined medium bomber manufactured by North American Aviation. It was used by many Allied air forces, in every theater of World War II, as well as many other air forces after the war ended, and saw service across four decades.The B-25 was named...

s armed with fragmentation bombs. After the Japanese retreat, over 340 aircraft wrecks were later found at Hollandia

Jayapura

Jayapura City is the capital of Papua province, Indonesia, on the island of New Guinea. It is situated on Yos Sudarso Bay . Its approximate population in 2002 was 200,000....

.

The Ki-61 was also utilised in Southeast Asia

South-East Asian theatre of World War II

The South-East Asian Theatre of World War II was the name given to the campaigns of the Pacific War in Burma , Ceylon, India, Thailand, Indochina, Malaya and Singapore. Conflict in the theatre began when the Empire of Japan invaded Thailand and Malaya from bases located in Indochina on December 8,...

, Okinawa, China

Second Sino-Japanese War

The Second Sino-Japanese War was a military conflict fought primarily between the Republic of China and the Empire of Japan. From 1937 to 1941, China fought Japan with some economic help from Germany , the Soviet Union and the United States...

and as an interceptor during US bombing raids over Japanese home islands, including against Boeing B-29 Superfortresses. The Ki-61 was notable for many reasons: initially identified as of either German or Italian origin, these aircraft were capable of matching Allied aircraft such as the P-40 in speed, and as evaluation had already showed, were superior in almost every respect. However, the armament of the early Hien was lighter, but still sufficient for most purposes. Some authors claim that the Lockheed P-38 Lightning was measurably superior. The Ki-61 carried a great deal of fuel, but due to having self-sealing fuel tanks, it did not have the reputation for being "easily flammable", as were many other Japanese aircraft.

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/50 in + 2 × 7.7 mm/.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/.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

The were suicide attacks by military aviators from the Empire of Japan against Allied naval vessels in the closing stages of the Pacific campaign of World War II, designed to destroy as many warships as possible....

(kamikaze) missions launched toward the end of the war. The Ki-61 was delivered to 15th Sentai

Sentai

in Japanese language is a word for a military unit and may be literally translated as "squadron", "task force", "group" or "wing". The terms "regiment" and "flotilla", while sometimes used as translations of Sentai, are also used to refer to larger formations....

(group/wing), as well as some individual Chutaicho (junior operational commanders) 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

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

Yawata, Kyoto

is a city located in Kyoto, Japan.As of May 31, 2011, the city has an estimated population of 74,150, with 31,120 households and the density of 3,042.68 persons per km². The total area is 24.37 km²....

. Sergeant

Sergeant

Sergeant is a rank used in some form by most militaries, police forces, and other uniformed organizations around the world. Its origins are the Latin serviens, "one who serves", through the French term Sergent....

Shigeo Nobe of the 4th Sentai intentionally flew his Kawasaki Ki-45

Kawasaki Ki-45

The Kawasaki Ki-45 Toryu was a two-seat, twin-engine fighter used by the Imperial Japanese Army in World War II. The army gave it the designation "Type 2 Two-Seat Fighter"; the Allied reporting name was "Nick"....

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

Ramming

In warfare, ramming is a technique that was used in air, sea and land combat. The term originated from battering ram, a siege weapon used to bring down fortifications by hitting it with the force of the ram's momentum...

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

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

Hagakure

Hagakure , or is a practical and spiritual guide for a warrior, drawn from a collection of commentaries by the samurai Yamamoto Tsunetomo, former retainer to Nabeshima Mitsushige, the third ruler of what is now the Saga prefecture in Japan...

-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".

First Lieutenant

First Lieutenant

First lieutenant is a military rank and, in some forces, an appointment.The rank of lieutenant has different meanings in different military formations , but the majority of cases it is common for it to be sub-divided into a senior and junior rank...

Toru Shinomiya was selected to lead the Hagakure

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

Victoria Cross

The Victoria Cross is the highest military decoration awarded for valour "in the face of the enemy" to members of the armed forces of various Commonwealth countries, and previous British Empire territories....

or Medal of Honor

Medal of Honor

The Medal of Honor is the highest military decoration awarded by the United States government. It is bestowed by the President, in the name of Congress, upon members of the United States Armed Forces who distinguish themselves through "conspicuous gallantry and intrepidity at the risk of his or her...

, which had been inaugurated on 7 December 1944 as an Imperial Edict by Emperor

Emperor

An emperor is a monarch, usually the sovereign ruler of an empire or another type of imperial realm. Empress, the female equivalent, may indicate an emperor's wife or a woman who rules in her own right...

Hirohito

, posthumously in Japan officially called Emperor Shōwa or , was the 124th Emperor of Japan according to the traditional order, reigning from December 25, 1926, until his death in 1989. Although better known outside of Japan by his personal name Hirohito, in Japan he is now referred to...

(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.

However, these pilots gained no reprieve and despite their successes they were obligated 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 became well-renowned, among whom was Major

Major

Major is a rank of commissioned officer, with corresponding ranks existing in almost every military in the world.When used unhyphenated, in conjunction with no other indicator of rank, the term refers to the rank just senior to that of an Army captain and just below the rank of lieutenant colonel. ...

Teruhiko Kobayshi of the 244th Sentai, who was credited by some with a dozen victories mostly due to conventional attacks against B-29s.

Ki-61 units

The Hiko Sentai, usually referred to as Sentai, was the basic operational unit of the Imperial Japanese Army Air Force, composed of three or more Chutai (companies or squadrons). A Sentai had 27 to 49 aircraft, with each Chutai having 16 aircraft and pilots plus a maintenance and repair unit. Several sentai had other units under their operational control, most notably the Hagakure-Tai ("Special Attack Units") of the 244th Sentai. By 1944, with the depredations of Allied attacks on supply lines and airfields, as well as the loss of pilots and aircraft through combat attrition and accidents, few sentai were able to operate at full strength.

Units operating the Ki-61 "Hien", data from
Sentai	Established	Aircraft type(s)	Area of operations	Disbanded	Notes
17th	10 February 1944 at Kagamigahara Kakamigahara, Gifu is a city located in the Gifu Prefecture of central Japan. It was founded on 1 April 1963 by the merger of Naka, Sohara, Unuma, and Inaba. Kakamigahara covers a total area of... , Gifu Prefecture Gifu Prefecture is a prefecture located in the Chūbu region of central Japan. Its capital is the city of Gifu.Located in the center of Japan, it has long played an important part as the crossroads of Japan, connecting the east to the west through such routes as the Nakasendō...	Ki-61, Ki-100 Kawasaki Ki-100 The Kawasaki Ki-100 was a fighter aircraft used by the Imperial Japanese Army in World War II. The Japanese Army designation was "Type 5 Fighter"...	Philippines Philippines The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam... , Formosa Formosa Formosa or Ilha Formosa is a Portuguese historical name for Taiwan , literally meaning, "Beautiful Island". The term may also refer to:-Places:* Formosa Strait, another name for the Taiwan Strait... , Japan	End of war	One of Kawasaki's main factories was located at Kagamigahara which, in 1944 was not yet a city.
18th	10 February 1944 at Chōfu Chofu, Tokyo is a city located in the western end of Tokyo Metropolis, Japan. As of 2010, the city has an estimated population of 224,878 and a population density of 10,440 persons per km². The total area was 21.53 km². Tokyo Stadium in Chōfu hosts soccer games for two J. League teams: F.C... from the 244th Sentai	Ki-61, Ki-100 Kawasaki Ki-100 The Kawasaki Ki-100 was a fighter aircraft used by the Imperial Japanese Army in World War II. The Japanese Army designation was "Type 5 Fighter"...	Philippines, Japan	End of War	Lt Mitsuo Oyake won Bukosho for shooting down three B-29s (one by ramming) 7 April 1944 and damaging three others.
19th	10 February 1944 at Akeno Fighter School	Ki-61	Indonesia Indonesia Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an... , Philippines, Formosa, Okinawa	End of War (Formosa)
23rd	11 October 1944 at Inba Inba, Chiba was a village located in Inba District, Chiba, Japan.Inba Village was created on March 10, 1955 through the merger of Rokugo and Munakata Villages. The development of Chiba New Town greatly accelerated the development of the village, which became a bedroom community for Chiba... , Chiba Prefecture Chiba Prefecture is a prefecture of Japan located in the Kantō region and the Greater Tokyo Area. Its capital is Chiba City.- History :Chiba Prefecture was established on June 15, 1873 with the merger of Kisarazu Prefecture and Inba Prefecture...	Ki-43 Nakajima Ki-43 The Nakajima Ki-43 Hayabusa was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in World War II... , Ki-44 Nakajima Ki-44 The Nakajima Ki-44 Shōki was a single-engine fighter aircraft used by the Imperial Japanese Army Air Force in World War II. The type first flew in August 1940 and entered service in 1942... , Ki-61	Iwo Jima Iwo Jima Iwo Jima, officially , is an island of the Japanese Volcano Islands chain, which lie south of the Ogasawara Islands and together with them form the Ogasawara Archipelago. The island is located south of mainland Tokyo and administered as part of Ogasawara, one of eight villages of Tokyo... , Formosa, Japan	End of war (Inba)
26th	Late 1944	Ki-51, Ki-43 Nakajima Ki-43 The Nakajima Ki-43 Hayabusa was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in World War II... , Ki-61	Formosa Formosa Formosa or Ilha Formosa is a Portuguese historical name for Taiwan , literally meaning, "Beautiful Island". The term may also refer to:-Places:* Formosa Strait, another name for the Taiwan Strait...	End of war (Formosa)
28th	June 1939 in Manchuria Manchuria Manchuria is a historical name given to a large geographic region in northeast Asia. Depending on the definition of its extent, Manchuria usually falls entirely within the People's Republic of China, or is sometimes divided between China and Russia. The region is commonly referred to as Northeast...	Ki-46 Mitsubishi Ki-46 The Mitsubishi Ki-46 was a twin-engine reconnaissance aircraft used by the Imperial Japanese Army in World War II. Its Army Shiki designation was Type 100 Command Reconnaissance Aircraft ; the Allied nickname was "Dinah".... , Ki-61, Ki-102 Kawasaki Ki-102 -See also:-References:NotesBibliography* Francillon, Ph.D., René J. Japanese Aircraft of the Pacific War. London: Putnam and Company Ltd., 1979. ISBN 0-370-30251-6....	Manchuria, Japan	July 1945
31st	July 1938 in China	Ki-10 Kawasaki Ki-10 \|-See also:-External links:* *... , Ki-43, Ki-61	Manchuria, Philippines	30 May 1945 at Singapore Singapore Singapore , officially the Republic of Singapore, is a Southeast Asian city-state off the southern tip of the Malay Peninsula, north of the equator. An island country made up of 63 islands, it is separated from Malaysia by the Straits of Johor to its north and from Indonesia's Riau Islands by the...
33rd	Late 1943	Ki-10, Ki-27 Nakajima Ki-27 The was the main fighter aircraft used by the Imperial Japanese Army Air Force up until 1940. Its Allied nickname was "Nate", although it was called "Abdul" in the "China Burma India" theater by many post war sources; Allied Intelligence had reserved that name for the nonexistent Mitsubishi Navy... , Ki-43 Nakajima Ki-43 The Nakajima Ki-43 Hayabusa was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in World War II... , Ki-61	New Guinea, Manchuria (Manchoukuo), East Indies	End of war, Medan Medan - Demography :The city is Indonesia's fourth most populous after Jakarta, Surabaya, and Bandung, and Indonesia's largest city outside of Java island. Much of the population lies outside its city limits, especially in Deli Serdang.... , Dutch East Indies
53rd	23 March 1944 at Tokorozawa, Saitama Saitama Prefecture is a prefecture of Japan located in the Kantō region of the island of Honshu. The capital is the city of Saitama.This prefecture is part of the Greater Tokyo Area, and most of Saitama's cities can be described as suburbs of Tokyo, to which a large amount of residents commute each day.- History...	Ki-61, Ki-45	Japan, Eastern Defence Sector		flew Ki-61 for a short time in Home Island Defence
55th	30 May 1944 at Taishō Taisho-ku, Osaka is one of 24 wards of Osaka, Japan. As of October 1, 2006, the ward has an estimated population of 72,742 and the total area is 9.43 km². - Transport :... , Osaka Prefecture Osaka Prefecture is a prefecture located in the Kansai region on Honshū, the main island of Japan. The capital is the city of Osaka. It is the center of Osaka-Kobe-Kyoto area.- History :...	Ki-61	Philippines, Japan	End of war at Sana Sana -Geography:* Sana'a, the capital of Yemen* Sana, Haute-Garonne, France, a commune in the Haute-Garonne département* Sana, Bhutan, a town in Bhutan* Sana, Greece, a village in the northern part of the prefecture of Chalkidiki... , Nara Prefecture Nara Prefecture is a prefecture in the Kansai region on Honshū Island, Japan. The capital is the city of Nara.-History:The present-day Nara Prefecture was created in 1887, making it independent of Osaka Prefecture....
56th	August 1944 at Taishō Taisho-ku, Osaka is one of 24 wards of Osaka, Japan. As of October 1, 2006, the ward has an estimated population of 72,742 and the total area is 9.43 km². - Transport :... Osaka Prefecture Osaka Prefecture is a prefecture located in the Kansai region on Honshū, the main island of Japan. The capital is the city of Osaka. It is the center of Osaka-Kobe-Kyoto area.- History :...	Ki-61	Japan	End of war at Itami, Hyōgo Prefecture Hyogo Prefecture is a prefecture of Japan located in the Kansai region on Honshū island. The capital is Kobe.The prefecture's name was previously alternately spelled as Hiogo.- History :...	Unit claimed 11 B-29s for 30 pilots lost. Warrant Officer Tadao Sumi (five B-29s plus one P-51 Mustang destroyed, four B-29s damaged) Bukosho recipient.
59th	1 July 1938 at Kagamigahara Kakamigahara, Gifu is a city located in the Gifu Prefecture of central Japan. It was founded on 1 April 1963 by the merger of Naka, Sohara, Unuma, and Inaba. Kakamigahara covers a total area of... , Gifu Prefecture Gifu Prefecture is a prefecture located in the Chūbu region of central Japan. Its capital is the city of Gifu.Located in the center of Japan, it has long played an important part as the crossroads of Japan, connecting the east to the west through such routes as the Nakasendō...	Ki-27 Nakajima Ki-27 The was the main fighter aircraft used by the Imperial Japanese Army Air Force up until 1940. Its Allied nickname was "Nate", although it was called "Abdul" in the "China Burma India" theater by many post war sources; Allied Intelligence had reserved that name for the nonexistent Mitsubishi Navy... , Ki-43, Ki-61, Ki-100	China, Manchuria (Nomonhan Nomonhan Nomonhan is a small village near the border between Mongolia and Inner Mongolia, China south of the Chinese city of Manzhouli.In the summer of 1939 it was the location of the Nomonhan Incident, as it is termed in Japan, or the Battle of Khalkhin Gol as it is known in Soviet and Mongolian People's... ), Indochina Indochina The Indochinese peninsula, is a region in Southeast Asia. It lies roughly southwest of China, and east of India. The name has its origins in the French, Indochine, as a combination of the names of "China" and "India", and was adopted when French colonizers in Vietnam began expanding their territory... , East Indies East Indies East Indies is a term used by Europeans from the 16th century onwards to identify what is now known as Indian subcontinent or South Asia, Southeastern Asia, and the islands of Oceania, including the Malay Archipelago and the Philippines... , New Guinea New Guinea New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago... , Okinawa, Japan	End of War at Ashiya Ashiya, Fukuoka is a town located in Onga District, Fukuoka, Japan.As of 2003, the town has an estimated population of 16,125 and a density of 1,412.00 persons per km². The total area is 11.42 km².... , Fukuoka Prefecture Fukuoka Prefecture is a prefecture of Japan located on Kyūshū Island. The capital is the city of Fukuoka.- History :Fukuoka Prefecture includes the former provinces of Chikugo, Chikuzen, and Buzen....	1st Lieutenant Naoyuki Ogata Bukosho recipient. Warrant Officer Kazuo Shimizu flew with unit from February 1942 right through to August 1945; 18 victories, including nine bombers.
65th		Ki-32, Ki-51, Ki-43, Ki-61, Ki-45	Philippines, Formosa, Okinawa, Japan	End of war, Metabaru, Saga Saga Sagas, are stories in Old Norse about ancient Scandinavian and Germanic history, etc.Saga may also refer to:BusinessSaga DAB radio, a British radio stationSaga Airlines, a Turkish airline*Saga Falabella, a department store chain in Peru...	Unit used Ki-61 from the summer of 1944
68th	March 1942 at Harbin Harbin Harbin ; Manchu language: , Harbin; Russian: Харби́н Kharbin ), is the capital and largest city of Heilongjiang Province in Northeast China, lying on the southern bank of the Songhua River... , Manchuria	Ki-27, Ki-61	Rabaul Rabaul Rabaul is a township in East New Britain province, Papua New Guinea. The town was the provincial capital and most important settlement in the province until it was destroyed in 1994 by falling ash of a volcanic eruption. During the eruption, ash was sent thousands of metres into the air and the... (New Britain New Britain New Britain, or Niu Briten, is the largest island in the Bismarck Archipelago of Papua New Guinea. It is separated from the island of New Guinea by the Dampier and Vitiaz Straits and from New Ireland by St. George's Channel... ), New Guinea, Halmahera Halmahera Halmahera is the largest island in the Maluku Islands. It is part of the North Maluku province of Indonesia.Halmahera has a land area of 17,780 km² and a population in 1995 of 162,728...	25 July 1944	First unit to convert to the Ki-61. Unit was destroyed by Allied air forces in New Guinea. Most surviving ground and aircrew were used as infantry, with few survivors. A Ki-61-1-Otsu, manufacturer's No. 640 is one of the best preserved aircraft wrecks in New Guinea. Captain Shogo Takeuchi transferred from 64th Sentai, April 1942. KIA 15 December 1943 30+ victories. Sgt. Susumu Kaijinami officially credited with eight victories plus 16 unofficially.
78th	31 March 1942 in China	Ki-27, Ki-61	Manchuria, Rabaul, New Guinea	25 July 1944	Second unit to convert to the Ki-61. Unit was destroyed by Allied air forces in New Guinea. Most surviving ground and aircrew were used as infantry, with few survivors.
105th	August 1944, Taichung Taichung -Demographics:Taichung’s population was an estimated 1,040,725 in August 2006. There are slightly more females in the city than males.24.32% of residents are children, while 16.63% are young people, 52.68% are middle-age, and 6.73% are elderly.... , Formosa	Ki-61	Okinawa, Formosa	End of war (Formosa)
244th	April 1942, reorganised from 144th Sentai	Ki-27, Ki-61, Ki-100	Okinawa, Formosa	End of war (Yokaichi, Shiga Prefecture Shiga Prefecture is a prefecture of Japan, which forms part of the Kansai region on Honshu Island. The capital is the city of Ōtsu.- History :Shiga was known as Ōmi Province or Gōshū before the prefectural system was established... )	Nine Bukosho recipients. Major Teruhiko Kobayashi JAAF's youngest Sentai commander. Also had an air-to-air B-29 ramming unit. Sentai claimed 73 B-29s shot down plus 92 damaged. Most famous of the Home Defence Sentais. Captain Nagao Shirai considered the ranking ace of 244 Sentai and possibly leading B-29 "killer" of JAAF (11 B-29s plus two F6Fs F6F Hellcat The Grumman F6F Hellcat was a carrier-based fighter aircraft developed to replace the earlier F4F Wildcat in United States Navy service. Although the F6F resembled the Wildcat, it was a completely new design powered by a 2,000 hp Pratt & Whitney R-2800. Some tagged it as the "Wildcat's big... destroyed, six other aircraft damaged using Ki-61 and Ki-100. Captain Chuichi Ichikawa nine B-29s plus one F6F destroyed, six B-29s damaged. Major Teruhiko Kobayashi, three B-29s plus two F6Fs destroyed.
Training Units
23rd Dokuritsu Dai Shijugo (Independent Chutai)	Chōfu Chofu, Tokyo is a city located in the western end of Tokyo Metropolis, Japan. As of 2010, the city has an estimated population of 224,878 and a population density of 10,440 persons per km². The total area was 21.53 km². Tokyo Stadium in Chōfu hosts soccer games for two J. League teams: F.C... , 1941	Ki-61	Japan	Became basis of 23rd Sentai	Evaluation and conversion unit for Ki-61.
Akeno Fighter School	Akeno Akeno Station is a Kintetsu train station in Ise, Mie, Japan.-Adjacent stations:-External links:... , Mie Prefecture Mie Prefecture is a prefecture of Japan which is part of the Kansai regions on Honshū island. The capital is the city of Tsu.- History :Until the Meiji Restoration, Mie prefecture was known as Ise Province and Iga Province.... , 1935	Ki-10, Ki-27, Ki-43, Ki-44, Ki-45 Kawasaki Ki-45 The Kawasaki Ki-45 Toryu was a two-seat, twin-engine fighter used by the Imperial Japanese Army in World War II. The army gave it the designation "Type 2 Two-Seat Fighter"; the Allied reporting name was "Nick".... , Ki-61, Ki-84, Ki-100	Japan	End of war	Main flight training school for Army fighter pilots. Many of the instructors participated in missions in defence of Japan 1944-1945. Akeno Airbase still in operational use.
37th Kyoiku Hikotai (Flight Training Company)	Matsuyama airfield, Formosa, 1943	Ki-43, Ki-44, Ki-45 Kawasaki Ki-45 The Kawasaki Ki-45 Toryu was a two-seat, twin-engine fighter used by the Imperial Japanese Army in World War II. The army gave it the designation "Type 2 Two-Seat Fighter"; the Allied reporting name was "Nick".... , Ki-61, Ki-84	Formosa	End of war	Flight training school for Army fighter pilots. Many of the instructors participated in missions in defence of Japan 1944-1945

Variants

Note: Ko, Otsu, Hei and Tei are the Japanese equivalents to a, b, c, d. Kai ('modified' or 'improved') was also used for some models of the Ki-61.
Ki-61

12 original prototypes.

Ki-61-I-Ko

The first production version. This version had a fully retractable tailwheel and two 7.7 mm (0.303 in) Type 89 machine gun

Type 89 machine gun

s in the wings and two synchronized 12.7 mm (0.50 in) Ho-103 machine gun

Ho-103 machine gun

The 12.7mm Type 1 was a Japanese aircraft machine gun widely used during World War II and also known as the Ho-103. The Ho-103 was actually a fixed gun and the Ho-104 a flexible gun...

s in the fuselage forward decking. The wings had racks outboard of the wheelwells, which were capable of carrying one 151 L (40 gal) drop tank or a light bomb. Weights: 2,238-2,950 kg (wing loading 147 kg/m2).

Ki-61-I-Otsu

The second production fighter variant. As it was found the armament was too light against allied aircraft and the tailwheel retraction mechanism was unreliable, the aircraft was modified accordingly. Two 12.7 mm (.50 in) Ho-103 machine guns replaced the wing 7.7 mm (.303 in) machine guns, with modifications to the upper-wing bulges, and the tailwheel doors were removed and the tailwheel locked in the "down" position (although the mechanism was still intact). Max takeoff weight 3,130 kg.

Ki-61-I-Hei

800 German-made 20 mm Mauser MG 151/20

MG 151 cannon

The MG 151 was a 15 mm autocannon produced by Waffenfabrik Mauser starting in 1940. It was in 1941 developed into the 20 mm MG 151/20 cannon which was widely used on many types of German Luftwaffe fighters, fighter bombers, night fighters, ground attack and even bombers as part of or as...

cannons and ammunition supplies were imported to Japan by submarine. The Hei was built in conjunction with the Otsu variant on the Kawasaki production lines but some "conversion kits" were directly sent to New Guinea. In this variant, the wing machine guns were replaced by Mauser cannons. The fuselage was longer (engine bulkhead forwarded of 19 cm, added a small fuel tank). Trial fittings found that these could be placed into the existing wing if the gun was laid on its side and a fairing was provided on the underside of the wing for clearance of the breech mechanism. 388 Ki-61s were so modified; the first of these was completed in September 1943 or January 1944. The last was completed in July 1944. Max takeoff weight 3,470 kg, max speed 580 km/h at 5,000 m, time to that height was seven minutes.

Ki-61-I-Tei

This machine featured two 12.7 mm (.50 in) Ho-103s in the modified (stronger) wings, provisions of external storage using fixed underwing pylons, and a non-retractable tail wheel. The forward fuselage was elongated by 190 mm (7.5 in) just after the exhaust line and forward of the windscreen to make room for the installation of Japanese 20 mm Ho-5 cannon

Ho-5 cannon

The Ho-5 was a Japanese aircraft autocannon used during World War II. Developed from the Ho-103 machine gun, it was a version of the American Model 1921 Browning aircraft machine gun. It replaced the Ho-1 and Ho-3 in general service. The Ho-5 was belt-fed using typical Browning-style steel...

in the fuselage decking (the same as with Hei version). The continued supply of MG 151's via submarine was not able to be guaranteed and the Ho-5 was ready. Several internal changes were also made. These included the simplification of several systems for increased dependability and ease of maintenance. The rear section of the fuselage was also made to be easily removable to further facilitate the ease of repair work. There is now some doubt as to whether the Tei ("d") designation was used.

Ki-61-I-KAId

Interceptor variant with 2 × 12.7 mm (.50 in) fuselage machine guns and 2 × 30 mm (1.18 in) wing cannon.

Ki-61-I- w.c.e.s.

An experimental aircraft with a wing cooling evaporation system, modelled on that used by the Heinkel He 100

Heinkel He 100

The Heinkel He 100 was a German pre-World War II fighter aircraft design from Heinkel. Although it proved to be one of the fastest fighter aircraft in the world at the time of its development, the design was not ordered into series production. Approximately 19 prototypes and pre-production machines...

. It was the fastest Ki-61 built, achieving 630 km/h (395 mph), and the last with a retractable tail wheel.

Ki-61-II

Prototype with 10% greater wing area and a slightly different airfoil. An Ha-140 engine with 1,120 kW (1,500 hp) for takeoff was fitted; the cowling panels were redesigned and the supercharger air intake was longer. A redesigned windscreen incorporating an extra panel was mounted further forward. The transparency to the rear of the sliding canopy was redesigned to increase rearward visibility. The prototype was first flown in December 1943; flight trials showed that the new wing was unsatisfactory and only eight Ki-61-IIs were built. The Ki-61-II was one of only very few Japanese aircraft able to reach the operational altitude of the B-29s raiding Japan with decent firepower. Subsequently, the majority of B-29s lost to Japanese fighters were shot down by the Ki-61-II. Due to the unreliability of the Ha-140 and the destruction of the Akashi

Akashi, Hyogo

plant by a B-29 bombing attack, the bulk of the Ki-61-II-KAIs built were airframes only, which were later converted to Ki-100-Is

Kawasaki Ki-100

The Kawasaki Ki-100 was a fighter aircraft used by the Imperial Japanese Army in World War II. The Japanese Army designation was "Type 5 Fighter"...

. ;Ki-61-II-KAI

Pre-production version which reverted back to the Ki-61-I-Tei wing, a 220 mm (8.7 in) fuselage stretch, enlarged rudder, and Ha-140 engine; 30 built.

Ki-61-II-KAIa

Armed with 2 x 12.7 mm (.50 in) machine guns in the wings and 2 x 20 mm cannon in the fuselage.

Ki-61-II-KAIb

Armed with 4 x 20 mm cannon.

Ki-61-III

One prototype only. This version had a cut-down rear fuselage and a canopy design which was later used by the Ki-100-II

Kawasaki Ki-100

The Kawasaki Ki-100 was a fighter aircraft used by the Imperial Japanese Army in World War II. The Japanese Army designation was "Type 5 Fighter"...

A total of 3,159 Ki-61 were built.

Operators

Chinese Nationalist Air Force

Operated some captured aircraft

People's Liberation Army Air Force
People's Liberation Army Air Force
The People's Liberation Army Air Force is the aviation branch of the People's Liberation Army, the military of the People's Republic of China...

Also operated some captured aircraft

Indonesia

In 1945, Indonesian People's Security Force (IPSF) (Indonesian pro-independence guerrillas) captured a small number of aircraft at numerous Japanese air bases, including Bugis Air Base in Malang (repatriated 18 September 1945). Most aircraft were destroyed in military conflicts between the Netherlands and the newly proclaimed-Republic of Indonesia during the Indonesian National Revolution of 1945–1949.

Imperial Japanese Army Air Force

Specifications (Ki-61-I-KAIc)

External links

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.