Kawasaki Ki-61 Hien 飛燕

This aircraft was an incredible find back in the 1970’s and it’s so sad to see it in this state. Unfortunately because the PNG museum has been so neglected over the years it has been plundered by several private museum groups. The South Australian Museum even recently acquired at least two P-38 Lightnings from the museum with the aim of restoring them and returning at least one them back to the museum. Yeh right! Well all’s fair in love and war they say. When you see such a rare aircraft deteriorating in such away it’s hard to argue about what’s fair and what’s not.

Roy Worcester Historical Centre
Founder: Roy Worcester (deceased)

Founder Roy Worcester
Roy Worcester was an expatriate living in PNG who collected Wewak area aircraft wreckage. This private museum was started in the 1970's to hold Worcester's collection of aircraft wrecks from the Wewak area. His collection included several Ki-61 Tonys and Ki-43 Oscars that crashed or were abandoned in the area. Many were painted with 'property of R. O. Worcester, Wewak'. After his passing, the collection closed.

Fates of Artifacts
Some of his aircraft collection was donated to the PNG War Museum in Port Moresby, and others were sold off to private collectors and museums his collection included several Ki-43 and Ki-61 partial wrecks, the most intact being a Ki-61 Tony.

Ki-61 Tony Manufacture Number 379
Salvaged by Worcester in 1973, exported to USA 1980s exported to Fantasy of Flight Museum

Ki-43 Oscar
Recovered by Worcester in 1970s from Wewak area, PNG Museum illegally exported 2001


Kawasaki Ki-61 Tony Manufacture Number 640

JAAF  68th Sentai

Aircraft History
Built by Kawasaki in November 1943 (exact date unknown, no master data plate ever found) with 'Otsu' armament of 2 x 12.7mm fuselage; 2 x 12.7mm wings. It was natural silver finished, with dark green 'snake weave' camouflage sprayed on the upper surfaces and a white fin flash on the tail fin.

Wartime History
In December 1943 the first Ki-61s with the 'Otsu' armament arrived in New Guinea. Ferried from Japan to New Guinea via Okinawa - Taiwan - Clark Field - Davao - Manado - Sorong - Babo Airfield - Wewak. Assigned to the 68th Sentai, this aircraft was likely based at Boram Airfield in the Wewak area, or possibly Hollandia.

Mission History
Force landed gently in a grassy plain south of Aitape, with the landing gear retracted. It is unknown why this plane force landed, possibly out of fuel. No damage was present on the wreck. The only real damage to the landing was a broken engine reduction gear casting.

Because of its remote location, this wreck was rarely visited and was not vandalized or damaged. Undisturbed until the 1970's, tracer, armor piercing, and high explosive rounds were still belted in its machine guns.

When the book Pacific Aircraft Wrecks was published, it stated:
'caught near Wewak by an RAAF Kittyhawk and chased inland at low level until it ran out of fuel and force-landed near Nuka.' The book reported its location as Nuka (Nuku), but in fact the wreck was near Yiliwe. Also, there is no evidence of a combat with RAAF P-40. Author Charles Darby noted on the tail marking the was white [ figure of a fin-flash shaped like a solid 'V' pointed down toward L/E of horizontal stabilizer].'

Richard Dunn adds:
'My take on the RAAF Kittyhawk in combat near Wewak is that it did not happen. First, it didn't happen before Nov 43 because there were no RAAF Kittyhawk Squadrons within range of Wewak. The only fighters active over Wewak were P-38s from August 43 soon joined by P-47s and later by US P-40s. No P-39s and no RAAF Kittyhawks were involved in the late 43 to March 44 missions against Wewak. RAAF No. 78 Wing (75, 78 and 80 Squadrons) moved within theoretical range of Wewak in Jan 44 (Nadzab area) but its missions from there and later from New Britain simply did not include sweeps or escort missions to Wewak nor is there any record of air combat in these squadrons before Hollandia fell (Apr 44) and Wewak was totally isolated.'

Richard Leahy recalls visiting the wreck:
'I have a long standing friend named Kevin Trueman. He and myself walked into [this] Ki-61 Tony back in 1972 at a place called Yiliwe, south of Aitape. This is the correct location, rather than Nuku, the place usually stated where the wreck was located. When I visited the plane, most of it was still there, only the gun sight was missing, taken by someone. Also, of interest the aircraft had four 13mm [12.7mm] machine guns as its armament. The photos in Darby's book [Pacific Aircraft Wrecks] must have been taken sometime earlier, probably by Roy Worcester.'

Partial Recovery
Beginning in 1975, Roy Worcester begin recovering parts back to Roy Worcester Historical Centre in Wewak. The tail section of this wreck was removed, and attached to Ki-61 Tony 379. Later, the rest of the wreck was disassembled into three pieces by Justin Hoisington who hoped to export it. By the 1980s, all the guns and instruments were removed and there was no tail unit.

Bruce Hoy adds:
'The Worcester Tony [Ki-61 379] was bought by Justin Hoisington in Chino, California. Hoisington is reported to also been the individual who disassembled Ki-61 Tony 640, and was only able to retrieve the tail section. While in the United States in 1985, I saw in Hoisington's hangar, the Worcester Tony, and two tail units, one of which I am sure was off the Nuku Tony [Ki-61 640].'

RAAF Recovery & PNG Museum
The PNG Museum, under the direction of curator Bruce Hoy took control of the wreck. In 1984, with the help of a RAAF helicopter, the pieces were flown to Wewak and shipped to Port Moresby for display at the museum.

The RAAF recovered the fuselage first, which arrived at the PNG Museum on November 23, 1984, and was displayed in a dolly built by Bruce Hoy. The wings and engine were delivered later, and were stored separate from the fuselage. It was displayed at the museum for twenty years: 1984 - 2004.

On July 29, 2004 this aircraft was packed into a container bound for Australia by Robert Greinert / HARS. The airplane remained property of the PNG Museum, and was exported under the agreement that it would be restored to static condition, and returned to the PNG Museum, along with P-38F 42-12647. According to Greinert: 'as part of the Minister for Culture and Tourism's plan to undertake a restoration program for the museum.'

 Kawasaki Ki-61 Hien 飛燕

The Kawasaki Ki-61 Hien (飛燕, roughly 'flying swallow') was a Japanese World War II fighter aircraft used by the Imperial Japanese Army Air Force. The Allied code name assigned by the United States War Department was 'Tony'. 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 'V' engine.

Design and development
A factory fresh Ki-61-I-Ko being ferried to either the 68th or 78th Sentai in New Guinea; it has yet to receive the distinctive dark green 'palm leaf' pattern which was usually applied by front-line units in the Southern theatre, nor does it have the usual black anti-glare panel forward of the cockpit.

The Ki-61 which was designed by Takeo Doi and his deputy Shin Owada, was one of two parallel designs tendered for by Kawasaki to fulfill requirements framed by the Koku Hombu late in 1939 for two fighters. Each was to be built around the Daimler-Benz DB 601Aa, a derivative of which was to be manufactured as the Ha-40 by Kawasaki at its Akashi plant. The first design, known as the Kawasaki Ki-60, was for a heavily armed specialised interceptor, which would have a high wing-loading; the second, the Ki-61 was a more lightly loaded and armed general-purpose fighter 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 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. Design of the Ki-61 did not begin until December 1940. Although the Ki-61 was broadly similar to the Ki-60 it featured several refinements using 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, with a maximum depth of 1.35 m (4 feet 5 inches). 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 the top and bottom cowling panels only 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 12.7 mm caliber 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) 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 (36.2 Imp gallons) was located behind the pilot's seat. The windshield was armoured and there was a 13 mm armoured steel 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.

The evenly tapered wings had an aspect ratio 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 flaps and long, narrow chord ailerons, while the front spar incorporated the undercarriage pivot points. The undercarriage track was relatively wide at 4 m (13 ft 1.5 in). Each wing had partially self-sealing 190 l (42 gallon) 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) was able to be carried in a weapons bay located behind the main spar.

The first prototype of the San-shiki-Sentohki ichi gata (Type 3 Fighter, Model 1, the official IJAAF designation) first flew in December 1941. 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 (6,504 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 which had a wing loading of 92.6 kg/m² (19 lb/ft²) (even that was considered borderline).

To address these concerns, Kawasaki staged a fly-off between two Ki-61 prototypes and the Ki-43-I, a pre-production Ki-44-I, a LaGG-3 (flown to Manchuria by a defector), a Bf 109E-3, and a captured P-40E Warhawk. 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 DB-601-powered fighters and it was soon overshadowed by fighters with more powerful engines. By the time it first flew in December 1941 – only one year after the Macchi's first flight and three years after the Bf 109E – the DB-601 was already underpowered compared to the new 1,500 hp inline or 2,000 hp radial engines being developed (and already nearing the mass-production stage) to power the next generation of combat aircraft: the P-47, Fw 190 and Bf 109 G. Moreover, the inline Ha-40 engine proved to be an unreliable powerplant.

The DB-601 engine on which the Hien was based was designed with very critical tolerance limits, and in the Ha-40 Japanese technicians developed a lighter version (by roughly 30 kg) that required even higher tolerances. Reaching these levels proved to be a 'stretch' for Japan's aviation manufacturing capabilities, which was further complicated by the variable quality of the materials, fuel, and the lubricants needed to run this sensitive, high-performance engine smoothly. 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, more armor, and – with the Kawasaki Ha-140 engine – an increased power of 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 reliability problems of its own which were never fully resolved, and around half of the first batch of engines delivered were returned to the factory to be re-built. Shortly after, a US bombing raid on 19 January 1945 destroyed the engine factory in Akashi, Hyōgo, 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 weakness: the lack of power at altitude, which diminished its ability to intercept high-flying B-29s relative to the Ki-61-II.

Operational history
The new Ki-61 Hien fighters entered service with a special training unit, the 23rd Chutai, and entered combat for first time in spring 1943 during the New Guinea campaign. Initially, due to its unusual appearance for a Japanese fighter, the Allies believed it to be of German or Italian origin, possibly a license-built Bf 109; the Italian-like appearance led to its code name of 'Tony'.

The first Sentai (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; this was especially the case for new-design aircraft, which are particularly prone to teething problems, as the Ki-61s were. 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 aircraft losses were experienced in some incidents during this campaign. For example, while in transit between Truk and Rabaul, the 78th lost 18 of its 30 Ki-61s. Other units were involved and sometimes, even more unfortunate: only two of (possibly) 24 Nakajima Ki-49s reached Rabaul in June 1943. 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 forming the bulk of the JAAF's fighter capability. At the end of the campaign, nearly 2,000 Japanese aircraft had been lost in continuous air attacks from up to 200 Allied aircraft at one time (among them, around half were B-24s and B-25s armed with fragmentation bombs After the Japanese retreat, over 340 aircraft wrecks were later found at Hollandia.

Even with these problems, there was a general Allied concern regarding this new fighter:

The Hien entered combat in the spring of 1943 in the New Guinea war zone, covering [mainland] New Guinea, the Admiralty Islands, New Britain and New Ireland. 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 P-40 Warhawks completely outclassed, and begged for more P-38 Lightnings to counter the threat of the new enemy fighter.

The Ki-61 was also utilised in Southeast Asia, Okinawa, China and as an interceptor during US bombing raids over Japanese home islands, including against 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. Of the allied fighters encountered at the beginning of World War II, only the P-38 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.

Due 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 kt) maximum speed. The cannon armament was essentially needed to counter the Allied bombers, which proved to be difficult to shoot down with only 12.7 mm machine guns. The empty and maximum weights for the Ki-61 prototype (2 x 12.7 mm + 2 x 7.7 mm) were 2,238 kg (4,934 lb) and 2,950 kg (6,504 lb), respectively; for the Ki-61-I basic (4 x 12.7 mm) 3,130 kg (6,900 lb); and for the Ki-61-KAI (2 x 12.7 mm + 2 x 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 (groups/wings), 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
An ex-23rd Sentai, 2nd Chutai Ki-61 found and photographed at Inba airbase by USAAF personnel in 1946.

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

On 7 November 1944, the officer commanding the 10th Hiko Shidan made ramming 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 included the 244th Hiko Sentai, then commanded by Captain Takashi Fujita who organised a ramming flight named 'Hagakure-Tai' ('Special Attack Unit'), which was composed of three sections: the 1st Chutai 'Soyokaze', 2nd Chutai 'Toppu', and the 3rd Chutai known as 'Mikazuki'.

First Lt. Toru Shinomiya was selected to lead the attack unit, he would became famous by ramming an American B-29 and living to tell the tale. Shinomiya attacked the B-29 on 3 December 1944, and brought himself and his damaged aircraft home; Shinomaya's Ki-61, which had lost most of the port outer wing, was subsequently put on display in a major department store in Tokyo. He would eventually lose his life as a Tokkotai pilot in the battle for Okinawa. Another 244th pilot, Corporal Masao Itagaki, performed a similar feat on the same occasion, but had to parachute from his damaged fighter. A third pilot, Sergeant Nakano, of the Hagakure-Tai of the 244th rammed another B-29 and crash-landed his stripped-down Ki-61 in a field. 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.) 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 results announcement and officially named 'Shinten Seiku Tai' ('Heart of Heaven Intercept Unit') by the Defense GHQ.

But 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 Teruhiko Kobayshi who was credited by some with a dozen victories mostly due to conventional attacks against B-29s.

Ki-61 units
The Hikosentai, usually referred to as Sentai, was the basic operational unit of the IJAAF, 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 244 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.

Sentai Established Aircraft Type(s) Area of Operations Disbanded Notes Notable Pilots
17th 10 February 1944 at Kagamigahara, Gifu Prefecture[24] Ki-61, Ki-100 Philippines, Formosa, 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 from the 244th Sentai Ki-61, Ki-100 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, Philippines, Formosa, Okinawa End of War (Formosa)    
23rd 11 October 1944 at Inba, Chiba Prefecture Ki-43, Ki-44, Ki-61 Iwo Jima, Formosa, Japan End of War (Inba)    
26th Late 1944 Ki-51, Ki-43, Ki-61 Formosa End of War (Formosa)    
28th June 1939 in Manchuria Ki-46, Ki-61, Ki-102 Manchuria, Japan July 1945    
31st July 1938 in China Ki-10, Ki-43, Ki-61 Manchuria, Philippines 30 May 1945 at Singapore    
33rd Late 1943 Ki-10, Ki-27, Ki-43, Ki-61 New Guinea, Manchuria (Manchoukuo), East Indies End of War, Medan, Dutch East Indies    
53rd 23 March 1944 at Tokorozawa, Saitama 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, Osaka Prefecture Ki-61 Philippines, Japan End of War at Sana, Nara Prefecture    
56th August 1944 at Taishō Osaka Prefecture Ki-61 Japan End of War at Itami, Hyōgo Prefecture Unit claimed 11 B-29s for 30 pilots lost. Warrant Officer Tadao Sumi (five B-29s plus one P-51 destroyed, four B-29s damaged) Bukosho recipient.
59th 1 July 1938 at Kagamigahara, Gifu Prefecture Ki-27, Ki-43, Ki-61, Ki-100 China, Manchuria (Nomonhan), Indochina, East Indies, New Guinea, Okinawa, Japan End of War at Ashiya, Fukuoka Prefecture   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 Unit used Ki-61 from the summer of 1944  
68th March 1942 at Harbin, Manchuria Ki-27, Ki-61 Rabaul (New Britain), New Guinea, Halmahera 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.[25] 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, 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) 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 ranking ace of 244 Sentai and possibly leading B-29 "killer" of JAAF (11 B-29s plus two F6Fs 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, 1941 Ki-61 Japan Became basis of 23rd Sentai Evaluation and conversion unit for Ki-61.  
Akeno Fighter School Akeno, Mie Prefecture, 1935 Ki-10, Ki-27, Ki-43, Ki-44, Ki-45, 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[26] Ki-43, Ki-44, Ki-45, 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  

Source: Sakaida, Henry. Japanese Army Air Force Aces 1937-45. Bueschel, Richard M. Kawasaki Ki.61/Ki.100 Hien in Japanese Army Air Force Service.


Note: Ko, Otsu, Hei and Tei are the Japanese equivalents to a, b, c, d. Kai (modified) 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 tail wheel and two 2 x 7.7 mm (0.303 in) Type 89 machine guns in the wings and two synchronized 2 x 12.7 mm (0.50 in) Ho-103 machine guns in the fuselage forward decking. The wings had racks outboard of the wheelbays, which were capable of carrying one 40 gallon drop tank or a light bomb.
Ki-61-I-Otsu: The second production fighter variant. As it was found the armament was too light against allied aircraft and the tail wheel retraction mechanism was unreliable, the plane was modified accordingly. Two 12.7 mm Ho-103 heavy machine guns replaced the wing 7.7 mm machine guns, with modifications to the upper-wing bulges, and the tail wheel well doors were removed and the tailwheel locked in the 'down' position (although the mechanism was still intact).
Ki-61-I-Hei: 800 German made Mauser MG 151/20, 20 mm 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. 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; there is now some doubt as to whether the Hei ('d') designation was used.
Ki-61-I-Tei: This machine featured two 12.7mm 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 in the fuselage decking. 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.
Ki-61-I-KAId: Interceptor variant with 2 x 12.7 mm fuselage machine guns and 2 x 30 mm 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. It was the fastest Ki-61 built, achieving 630km/hr (395 m.p.h.), 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.
Note: Because of the unreliability of the Ha-140 and the destruction of the Akashi 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.
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 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.

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


China: Chinese Nationalist Air Force

Operated some captured aircraft

China: People's Liberation Army Air Force

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.

Japan: Imperial Japanese Army Air Force

Specifications (Ki-61-I-KAIc)

Data from The Great Book of Fighters

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 (121 Imp gal): * External fuel capacity: 2 x 200 l (44 Imp 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

*Bílý, Miroslav . Kawasaki Ki-61 a Ki.100 (Profily letadel II. Svetové války no.4) (in Czech with English and German captions). Praha, Czech Republic: Modelpres, 1992. ISBN 80-901328-0-4.
*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.
*Crosby, Francis. Fighter Aircraft. London: Lorenz Books, 2002. ISBN 0-7548-0990-0.
*Francillon, Réne J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1970 (2nd edition 1979). ISBN 0-370-30251-6.
*Francillon, Réne J. The Kawasaki Ki-61 Hien (Aircraft in profile number 118). Leatherhead, Surrey, UK: Profile Publications, 1966. ASIN B0007KB5AW.
*Gibertini, Giorgio. 'Rondini Giapponesi' (in Italian).Aerei Nella Storia N.8, August 1998. Parma, Italy: West-ward edizioni.
*Gallagher, James P. 'Meatballs and Dead Birds; A Photo Gallery Of Destroyed Japanese Aircraft In World War II'. Stackpole Books, 2004. ISBN 0-8117-3161-8:
* Green, William. 'An Oriental Swallow.' Air International Vol. 9, no. 2, August 1975.
*Green, William. Warplanes of the Second World War, Volume Three: Fighters. London: Macdonald & Co. (Publishers) Ltd., 1961 (seventh impression 1973). ISBN 0-356-01447-9.
*Green, William and Swanborough, Gordon. WW2 Aircraft Fact Files: Japanese Army Fighters, Part 1. London: Macdonald and Jane's, 1976. ISBN 0-356-08224-5.
*Gunston, Bill. World Encyclopedia of Aircraft Manufacturers: From the Pioneers to the Present Day. Annapolis, Maryland: Naval Institute Press, 1993. ISBN 1-55750-939-5.
*Hata, Ikuhiko, Izawa, Yasuho and Shores, Christopher. Japanese Army Air Force Fighter Units and Their Aces, 1931-1945. London: Grub Street Publishing, 2002. ISBN 1-902304-89-2.
*Janowicz, Krzysztof. 68 Sentai (in Polish). Lublin, Poland: Kagero, 2003. ISBN 83-89088-01-0.
*Januszewski, Tadeusz and Jarski, Adam. Kawasaki Ki-61 Hien, Monografie Lotnicze 5 (in Polish). Gdańsk, Poland: AJ-Press, 1992. ISSN 0867-7867.
*Mondey, David. The Hamlyn Concise Guide to Axis Aircraft of World War II. London: Bounty Books, 2006. ISBN 0-753714-60-4.
*Sakaida, Henry. Japanese Army Air Force Aces 1937-45. Botley, Oxford, UK: Osprey Publishing, 1997. ISBN 1-85532-529-2.
*Sakurai, Takashi. Rikugun Hiko Dai 244 Sentai Shi (History of the Army 244 Group) (in Japanese). Tokyo, Japan: Soubunsha, 1995. ISBN unknown.
*Sakurai, Takashi. Hien Fighter Group: A Pictorial History of the 244th Sentai, Tokyo's Defenders (in Japanese/English). Tokyo, Japan: Dai Nippon Kaga, 2004. ISBN unknown.
*Takaki, Koji and Sakaida, Henry. B-29 Hunters of the JAAF. Botley, Oxford, UK: Osprey Publishing, 2001. ISBN 1-84176-161-3:
* Tanimura, Masami; Tanaka, Kozo; Kishida, Yuji; Oda, Makoto; Nakano, Yoshiharu and Kawasaki, Saburo. Kawasaki Ki-61 (Tony). Blaine, WA: Paul Gaudette, Publisher, 1967.
*Vaccari, Pier Francesco. 'Guerra Aerea in Nuova Guinea' (in Italian). Rivista Italiana Difesa, N.8, 2000.

Web Reference: http://en.wikipedia.org/wiki/Kawasaki_Ki-61


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This webpage was updated 27th January 2020