Kawasaki Ki-60

Kawasaki Ki-60

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Kawasaki Ki-60

The Kawasaki Ki-60 was a single-engine heavy interceptor powered by the German DB 601A inline engine that reached the prototype stage during 1941 but that was rejected in favour of the lighter Kawasaki Ki-61 Hien.

In 1938 Kawasaki gained the right to build and develop their own version of the Daimler Benz DB 601A, one of the best inline aircraft engines of the period. In April 1940 a Kawasaki team visited Daimler-Benz in Stuttgart, and returned to Japan with the blue-prints for the DB 601 and a number of completed engines. Work then began on Kawasaki's own version of the engine. The result was the Ha-40, with an improved take-off power of 1,175hp and a slight reduction in weight. The first Ha-40 was completed in July 1941 and it passed its ground tests by November, entering production as the 1,100hp Army Type 2 Engine. Kawasaki had a long record of co-operation with German engineers, and their design team had been led by Dr Richard Vogt for ten years, ending in 1933. He had used his influence to help Kawasaki in the negotiations with Daimler Benz, and the Kawasaki design team, headed by Takeo Doi, was still influenced by him. This may have explained why Kawasaki continued to work with inline engines at a time when most Japanese aircraft manufacturers moved onto radial engines.

While work on the new engine was going on the Air Headquarters of the Imperial Japanese Army was watching the progress of the air war over Europe, where the Spitfire, Hurricane and Bf 109 dominated the fighting. All three aircraft were high-performance aircraft with inline engines, some armour, and heavy armament, very different to the lightly armed, un-armoured, radial powered and slower but manoeuvrable fighters in Japanese service. In February 1940 the Japanese Army initiated the design of three aircraft - the Kawasaki Ki-61 light fighter, the Nakajima Ki-62 and the Kawasaki Ki-60 heavy interceptor, each to be powered by the Ha-40.

Previous Japanese fighter designs had focused on manoeuvrability rather than speed. This required a relatively low wing loading (weight divided by size of wing). The Ki-60 had a wing loading of 35.4lb/ square foot, nearly twice as high as on the Ki-43-Ia, which many Japanese pilots considered to be too heavily loaded. Generally the smaller the wing the higher the wing loading, the high the speed of the aircraft but the worse its manoeuvrability and the longer it's landing and take-off distances. On the Ki-60 speed, climb-rate and armament were seen as key, and the first aircraft were to be designed by two 20mm cannon and two 12.7mm machine guns. The pilot and fuel tanks received armour protection.

The first of the three prototypes, Ki-6001, made its maiden flight in March 1941. It had small wings, and was armed with two 20mm cannon and two 12.7mm machine guns. Speed was disappointing, at 342mph, down from the predicted speed of 373mph, and Japanese army pilots didn't like the high wing loading and resulting loss of manoeuvrability.

The second prototype, Ki-6002, had larger wings and a refined engine cowling. Its top speed increased to 348mph and manoeuvrability increased, but not by enough to impress the army pilots.

The third and final prototype, Ki-6003, retained the larger wings and had another new cowling. Weight was saved by replacing the 20mm cannon with two more machine guns, and speed increased to 354mph.

The Ki-60 was technically a success, but it didn't match the expectations of the Japanese pilots. In the skies over Europe high speed fighters were proving to be superior to slower but more manoeuvrable aircraft as long as suitable tactics were used. The faster aircraft were well suited to 'hit and run' tactics rather than to the more familiar dog-fighting techniques. Both the Japanese army and navy preferred the lighter, more manoeuvrable aircraft, and the early days of the Pacific war appeared to have proved their point, as the Mitsubishi Zero in particular gained a fearsome reputation. These early successes would turn out to have been misleading, having been gained against comparatively small numbers of second-string (at best) Allied aircraft. The lighter Japanese fighters would soon be outclassed by heavier, faster but less manoeuvrable Allied aircraft which had more in common with the Ki-60.

By the end of 1941 work on the Ki-60 had ended, and the Ki-61 was given high priority. The Ki-61 was not actually much lighter than the Ki-60. It was a rather more elegant design, with a 5ft wider wing span and 2ft longer fuselage than the Ki-60, and its wing loading was reduced at first, but soon increased against, and reached 30lb/ sq ft on the Ki-61-Ib, lower than on the Ki-60, but still higher than on earlier Japanese fighter aircraft.

Dimensions for second prototype
Engine: Daimler-Benz DB 601A twelve cylinder inverted-vee inline engine
Power: 1,150hp at take off, 1,100hp at 13,125ft
Crew: 1
Wing span: 34ft 5in
Length: 26ft 9.5in
Height: 12ft 1 2/3in
Empty Weight: 4,740lb
Loaded Weight: 6,603lb
Wing loading: 34.8lb/ sq ft
Max Speed: 348mph at 14,765ft
Cruising Speed:
Service Ceiling: 32,810ft
Armament: Two 12.7mm Ho-103 machine guns and two 20mm Mauser MG 151 cannon in first and second aircraft, cannon replaced with two 12.7mm Ho-103 machine gun in third

Messerschmitt Bf 109 Imposter – Kawasaki Ki-61 “Tony” in Photos

The Kawasaki Ki-61 Hien was a Japanese fighter aircraft, built by Shin Owada and Takeo Doi, used by the Imperial Japanese Army Air Force (JAAF) during World War II.

It was designated an “Army type 3” fighter. Over 3,000 Ki-61s were produced during the war.

In 1939, The Japanese Imperial Navy Air Service tendered a request for two fighters to be built around the specifications of the Daimler-Benz DB 601Aa. These two fighters became the Ki-60 and Ki-61.

Wartime photo of a captured Ki-61 being tested by the USAAF

The premier prototypes were used in the Doolittle raid on 18 April 1942, as well as in many other combat missions.

Ki-61 “Hien”

The Ki-60 was designed to be a specialized interceptor with high wing loading, while the Ki-61 was projected to be more of a general purpose fighter, used in offensives and operated at low to medium altitudes. They were both single-seat, single-engine fighters.

The Ki-60 was made of all-metal alloys, with a tensile, stressed hybrid skin.

Kawasaki Ki-61 being used by the Chinese Nationalist Air Force.

The Ki-60 was prioritized and the first prototype flew in April 1941, while work began on the Ki-61 in December 1940. Some changes were made to the Ki-61 design to correct the flaws discovered in the the Ki-60. The Ki-60’s fuselage, which was oval in cross-section, became semi-triangular in the Ki-61.

The engine bearers were integrated into the forward fuselage, with fixed side panels covering them. Its fuel tank was self-sealing, with a capacity of nearly 44 gallons, and was located behind the pilot’s seat.

A Japanese Kawasaki Ki-61 Hien (Allied code name “Tony”).

The ammunition boxes were located behind the engine bulkhead and fed a pair of 12.7mm Ho-103 machine guns that operated in unison. The windshield was armored, and there was a .5″ thick armor plate at the rear of the cockpit.

A Japanese Kawasaki Ki-61 “Tony” pictured at Kengun Airfield, Kumamoto Prefecture, Kyūshū Island (Japan).

During testing, two Ki-61s were flown against a Ki-43-I, a Curtiss P-40E War Hawk, and a Messerschmitt Bf 109E-7. The Ki-61 proved to be the fastest, although it was less maneuverable than the Ki-43-I.

A Japanese Kawasaki Ki-61 Hien (Allied code name “Tony”) of 149th Shimbu Unit at Ashiya airfield in Fukuoka, Japan.

At first sighting, the Allies did not realize the Ki-61 was a Japanese aircraft because it looked different from the usual Japanese fighters. During the Doolittle raid, it was first misidentified as a Bf-109 by U.S. Army Air Forces Capt. C. Ross Greening.

Aircrew with a Kawasaki Ki-61 Hien at an unidentified airfield. This aircaft was probably assigned to the of the 244th Squadron. Note the (at least) 12 “kill” markings below the cockpit.

The codename “Tony” was adopted after it was also misidentified as an Italian aircraft.

The first service of the Ki-61 was with the 23rd Chutai, which was a special training unit.

An ex-23rd Sentai, 2nd Chutai Ki-61 photographed at Inba airbase by USAAF personnel in 1946.

Ki-61s first saw combat in early 1943 in the New Guinea campaign. The 68th Sentai was the first air wing to be fully equipped with Ki-61s. The second was the 78th Sentai at Rabaul.

Both units were deployed to stations with adverse weather conditions and thick foliage, which hindered the efficiency of the Ki-61s and forced the JAAF to instead continue using the almost obsolete Ki-43 aircraft.

Derelict Ki-61s in 1945 after the surrender.

USAAF pilots found that they could no longer go into a dive to escape when pursued by a Ki-61, as they did before with other Japanese fighters.

The Japanese made use of the Ki-61 as an interceptor during U.S. bombing raids, even against Boeing B-29 Superfortresses, but it was observed that the Ki-61s’ performance declined under increased armament.

Kawasaki Ki-61 (Hien) in Kakamigahara Aerospace Science Museum.Photo 名古屋太郎 CC BY-SA 4.0

Ki-61s were also used in kamikaze missions launched toward the end of the war. In 1945, the Ki-61s were finally retired, with 12 variants and over 3,000 units produced.

Ki-61s in Luzon 1945

Ki-61 under attack in Wewak New Guinea 9144

Ki-61 Tail in Cape Gloucester 1943

Ki-61 in 1942

Ki-61 Hien in Beijing – 1945

Kawasaki Ki-61 Hien

Early Variant of Ki-61 – 1942

Captured Kawasakie Ki-61 with F4U Corsair in background – Okinawa 1945

Assembly line for Ki-61 in Japan

A captured Japanese Kawasaki Ki-61 Hien fighter (Allied code name “Tony”) at Clark Field, Luzon (Philippines), in 1945.

A Japanese Kawasaki Ki-61 Hien

A Kawasaki Ki-61 Hien (Ki-61-I Hei) of the 244th squadron (Fighter Regiment), Imperial Japanese Army Air Force. �” was the plane assigned to captain Kobayashi Teruhiko.

Front veiw of an Imperial Japanese Army Air Force Kawasaki Ki-61 Hien (Allied code name “Tony”) with a camouflage paint scheme at an unidentified airfield.

Kawasaki Ki-61 (Hien) in Kakamigahara Aerospace Science Museum. Photo 名古屋太郎 CC BY-SA 4.0

Specifications (Ki-60 2nd prototype)

Data fromWarplanes of the Second World War, Volume Three: Fighters [10] WW2 Aircraft Fact Files: Japanese Army Fighters, Part 1 [7] Japanese Aircraft of the Pacific War [11]

General characteristics

  • Crew: 1
  • Length: 8.47   m (27   ft 9   in)
  • Wingspan: 10.5   m (34   ft 5   in)
  • Height: 3.7   m (12   ft 2   in)
  • Wing area: 16.2   m 2 (174   sq   ft) (1st prototype 15.9   m 2 (171   sq   ft))
  • Empty weight: 2,150   kg (4,740   lb)
  • Gross weight: 2,750   kg (6,063   lb) (1st prototype 2,890   kg (6,370   lb))
  • Powerplant: 1 × Daimler-Benz DB 601A V-12 inverted liquid-cooled piston engine, 875   kW (1,173   hp) for take=off
  • Propellers: 3-bladed Constant-speed propeller
  • Maximum speed: 560   km/h (350   mph, 300   kn) at 4,500   m (14,800   ft)
  • Service ceiling: 10,000   m (33,000   ft)
  • Time to altitude: 1st prototype:5,000   m (16,000   ft) in 8 minutes 2nd and 3rd prototypes 5,000   m (16,000   ft) in 6 minutes [12]
  • Wing loading: 169.8   kg/m 2 (34.8   lb/sq   ft)
  • Power/mass: 0.310 kW/kg (0.189 hp/lb)
  • Guns:
  • 2 x 20   mm (0.787   in) Mauser MG 151 cannon or 2 x 12.7   mm (0.50   in) Ho-103 machine guns (3rd prototype) in the wings
  • 2 x 12.7   mm (0.50   in) Ho-103 synchronized machine guns in the fuselage


* The Hien entered combat in the spring of 1943 in the New Guinea war zone, covering 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. 5th Air Force Commander General George Kenney 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 demonstrated only a few teething problems in field use, such as a tendency towards engine overheating during ground running under tropical conditions. However, despite the heavier armament, it still didn't have the punch to easily knock rugged and well-armed Allied bombers out of the sky.

The Kawasaki designers had foreseen this problem. The Japanese Ho-5 20-millimeter cannon wasn't available at the time, but the Japanese obtained 800 Mauser MG 151/20 20-millimeter cannon from Germany in August 1943, and modified 388 Ki-61-I airframes on the production line to carry the German weapons in place of the two 12.7-millimeter wing guns. The cannon had to be mounted on their sides to fit into a wing, with an underwing blister for the breech, and some reinforcements were added to the wing to absorb the heavier recoil.

Once the Ho-5 cannon finally became available, Kawasaki designers then reversed the arrangement of the guns, putting the 20-millimeter cannon in the nose and the 12.7-millimeter guns in the wings. While they were making these modifications, they also made a few changes to streamline manufacturing and simplify field maintenance.

This new variant was designated the "Ki-61-I KAIc" (where "KAI" was for "kaizo", or "modified"). It was 19 centimeters (7.5 inches) longer than its predecessors, and also featured a detachable rear section a fixed tailwheel instead of the earlier retractable tailwheel stronger wings and stores pylons outboard of the main landing gear, allowing it to carry two 250-kilogram (550-pound) bombs.

The Ki-61-I KAIc went into production in January 1944 and ultimately replaced production of all earlier models in August 1944. A few "Ki-61-I KAId" bomber interceptors were also built in late 1944. These aircraft featured two 12.7-millimeter guns in the fuselage and a 30-millimeter Ho-105 cannon in each wing. Total production of the Ki-61-I KAIc/d was 1,274 aircraft.

Design and history

The Ki-60 was designed by Takeo Doi and his deputy Shin Owada of Kawasaki Aircraft Industries ( 川崎航空機工業株式会社 , Kawasaki Kōkūki Kōgyō K.K. ? ) in response to a 1939 Imperial Japanese Army Aviation Bureau requirement for a heavily armed specialised interceptor fighter to be powered by the liquid-cooled Daimler-Benz DB 601 inverted V12 engine, which had been selected for license production by Kawasaki as the Ha-40. The emphasis in the requirements was for a high speed and a good rate of climb, along with a cannon armament. This was a complete change from the usual IJAAF penchant for lightly armed, highly manoeuvrable fighters with lightweight structures, epitomised by the Nakajima Ki-27 and the later Nakajima Ki-43. A requirement was issued at the same time for a lighter, less heavily armed, general-purpose fighter which was to be designed almost in parallel with the Ki-60 this became the Ki-61. Priority was to be given to the Ki-60, design of which started in February 1940. [1] [2]

The first prototype of the Ki-60 emerged in March 1941 [3] as a compact, all metal, stressed skin monoplane with a relatively deep fuselage (1.46 metres or 4 feet 9 inches) and tapered wings with rounded tips built around a system of 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 3 metres (9 ft 10 in). The pilot's seat was mounted high over the rear spar, giving the fuselage a distinctive "humped" profile the hood featured a framed, rear sliding canopy and an elongated rear transparent section. The main coolant radiator was housed in a long ventral bath under the wing centre-section and central fuselage, while the oil cooler was mounted under the engine with a long air intake. The prototype was powered by an imported DB 601A as production of the Ha-40 had not yet started. A total fuel capacity of 410 l (90.2 Imp gallons)) was carried. [4] [5]

The armament carried was two synchronized, fuselage mounted 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. One German made Mauser MG 151/20 20 mm cannon was housed in a weapons bay in each wing. With a normal loaded weight of 2,890 kilograms (6,370 lb) and a gross wing area of 15.9 square feet (1.48 m 2 ) the wing loading was 181.76 kg/m² (37.23 lb/ft²), which was extremely high by Japanese standards (the standard IJAAF fighter, the Ki-27, had a wing loading of 70 kg/m² (14.33 lb/ft²)). [6]

From the start of flight testing it became apparent that the design was seriously flawed in several key areas. The take-off run was unacceptably long, while in flight the aircraft displayed some lateral instability, excessively heavy controls and poor control response. The spinning characteristics were described as "dangerous" and the stalling speed was extremely high. Although a top speed of 600 kilometres per hour (370 mph) had been projected the Ki-60 was only able to achieve 548 kilometres per hour (341 mph). [7]

As a result, the second and third prototypes, which were still being built, were hurriedly modified in an attempt to mitigate some of the more undesirable traits. Approximately 100 kilograms (220 lb) were removed, primarily by replacing the MG 151 cannon with Ho-103 machine guns. This reduced the normal loaded weight to 2,750 kilograms (6,060 lb). Coupled with a slight increase in wing area to 16.20 square feet (1.505 m 2 ), this resulted in a slightly lower wing loading of 169.7 kg/m² (34.76 lb/ft²). Detail changes were made to airframe sealing and to the contours of the air intakes and radiator bath. Flight tests were still disappointing, with both of the modified prototypes displaying most of the shortcomings of the first. A top speed of only 560 kilometres per hour (350 mph) was reached, with a climb rate still well below specifications. By this time the Nakajima Ki-44, which had also been designed as a dedicated interceptor, was beginning to show some promise and the Koku Hombu selected this in fulfilment of its requirements. From early 1941 the full attention of Takeo Doi and Shin Owada was focused on the Ki-61 the Ki-60 became important in that the Ki-61 design was able to be improved using the lessons learned from the poor characteristics of the Ki-60. [8] Plans for production were cancelled in late 1941 after three airplanes had been built. [9]

Kawasaki Ki-60 - History

One 877 kw (1,175 hp) Kawasaki Ha-40 (Army Type 2) twelve-cylinder inverted-VEE liquid-cooled engine



In February 1940 Kawasaki Kokuki Kogyo KK was asked to design a fighter around the licence-built Daimler-Benz DB 601A twelve-cylinder VEE engine, and to this end the Ki.60 evolved, the prototype flying in March 1941. Initial trials were not particularly successful, and the aircraft was re-designed as the Ki.61 Hien (Swallow).

At one stage it was thought the Ki.61 was a licence-built variant of the Messerschmitt Bf 109 when first encountered in Papua New Guinea in April 1943, but in fact the prototype flew six months before the arrival in Japan of an example of the Bf 109. The Daimler-Benz DB-601A engine was modified by Kawasaki’s Akashi plant to comply with Japanese production techniques and the aircraft was placed in production as the Ki.61. The first of 12 prototypes made its first flight in December 1941. They were tested against an imported Messerschmitt Bf 109E and a captured Curtiss P-40E.

The first production model was the Ki.61-I Hien Type 3 Fighter Model 1, production commencing at the Kagamigahara plant, 34 fighters being delivered in 1942. Production increased to 100 aircraft per month in November 1943, and reached a peak of 254 aircraft per month in July 1944.

The Hien was introduced to combat in Papua New Guinea in April 1943 and was soon encountered over Rabaul in New Britain and the Admiralty Islands. It was also operated over the Chinese mainland and later The Philippines. In April 1943 27 Hiens of the 68th Sentai were loaded aboard the aircraft carriers ‘Kaguga Maru’ and ‘Taiyo’ and were delivered to Truk, a Japanese facility north of Rabaul. There they received some testing before entering service, one being lost at this time.

On 27 April the surviving 26 Hiens left Truk for Rabaul in two groups of 13, having been fitted with long-range fuel tanks, each group being escorted by a Mitsubishi Ki.46 Dinah. The first group arrived safely at Vunakanau but the second group ran into bad weather and, of the 13, two returned to Truk, two went missing, one reached Kavieng, and eight ditched offshore in Nuguria Lagoon in rough seas 300 km (186 miles) from their destination, only one of the pilots surviving. Of the 16 survivors of both groups, one was lost on 3 May on a test flight.

On 16 June 1943 the 78th Sentai left Akeno in Japan to fly to Rabaul via Formosa, The Philippines, Celebes and Madang, 45 aircraft leaving but only 33 of these reaching Rabaul after the 9,000 km (5,592 miles) journey. First patrols with the type commenced on 17 May 1943 but soon the unreliability of the Ha-40 engine came to the fore, when a number were lost due to engine failures.

On 3 July 1943 a group of Ki.61 Hiens of the 68th Sentai took up residence at Lae, later moving to Madang and Wewak, PNG. On 4 July 1943 two Hiens joined a number of Ki.43s in operations over the Solomon Islands. First successful combat with the type was in July 1943 when a Consolidated B-24 Liberator was shot down over Madang.

Initial armament was two 7.7 mm (0.303 in) machine guns in the fuselage and two 12.7 mm (0.50 in) machine guns in the wings, but this was supplanted by a pair of imported German-built 20 mm Mauser MG 151 cannon. However, only 400 aircraft received the latter cannon as Germany could not spare many from its over-worked production lines. It was replaced by the Japanese built Ho-5 cannon but this was in short supply and a lot of aircraft were fitted with four 12.7 mm (0.50 in) machine guns. The type was fitted with armour protection for the pilot, and self-sealing fuel tanks. First model to receive the Ho-5 cannon was the Ki.61c (Model 1c), which was followed by the Ki.61-1d, which had 30 mm cannon in lieu of the 20 mm units.

Next variant was the Ki.61-II (Model 2) which had an up-rated Ha-140 engine providing 1,119 kw (1,500 hp). Some design changes took place. However, problems delayed its introduction into service and eventually the Ki.61-IIa (Type 3 Fighter Model 2A) fitted with two 12.7 mm (0.50 in) machine guns and two 20 mm cannon entered service. But the new engine was unreliable and eventually production of the liquid-cooled variant was stopped in favour of the Ki.100 series, which was the same basic aircraft with a radial engine.

The Ki.61 established an ascendancy over early variants of the Curtiss P-40 Kittyhawk and the Bell P-39 Aircobra, but had problems dealing with the Lockheed P-38 Lightning. However, by 1944, when the North American P-51 Mustang and Grumman F-6F Hellcat entered combat, its career quickly declined. Also, by this time American bombing raids on Japanese factories were having an effect on production and the availability of spares, and in the field serviceability rates were becoming very low.

A few Ki.61s were captured during the war and restored for testing, one undergoing testing at Eagle Farm, QLD, by the ATAIU (Allied Technical Air Intelligence Unit) in 1944, this being a Ki.61-IIIb which received the serial XJ003 and was flown by Royal Australian Air Force (RAAF) and United States Army Air Force (USAAF) personnel. Others were tested in the United States.

Production totalled 3,159 aircraft, comprising 12 prototypes, 2,734 Ki.61-I and Ki.61-1 KAI, eight Ki.61-II and 405 K.61-II KAI. The type saw considerable service in the Pacific Theatre of operations, particularly with the 68th Sentai operating from Rabaul. The type is known to have been used to escort Japanese bombers on raids on northern Australia and at least one example was shot down on Australian soil in 1943 near Darwin, NT.

Only a few complete examples are known to have survived. One (serial 195) has been placed on display in New Ireland two in the United States and two in Japan. Serial 640, recovered from a crash site in New Guinea in 1984, was placed in storage dismantled at the National Museum in Port Moresby, NG, awaiting restoration. Eventually restoration commenced at Precision Aerospace, Wangaratta, VIC. However, later the Ki.61 wrecks were moved to Albion Park, NSW, where further work commenced at the Historical Aircraft Restoration Society (HARS) facility.

Other wrecks are known to have existed in Papua New Guinea and other islands in the Pacific but, due to the effects of corrosion since World War II, will probably never be recovered. The forward fuselage of one (Serial 299) recovered from Papua New Guinea was placed on display at a museum in South Australia, later being delivered to Wangaratta for restoration and in late 2000 another Hien was recovered to Sydney, NSW for restoration.

Further wrecks have been recovered, the Precision Aerospace team commencing work to rebuild four examples of the Ki.61, three to airworthiness, one for an American in Virginia to join his collection, one to remain in Australia, and one to be placed in a museum in Port Moresby. Another one has been undergoing restoration at Ardmore in New Zealand.

World War Photos

Experimental Japanese fighter Kawasaki Ki-60 Three prototypes of Ki-60, 1941 Kawasaki Ki-60, 1941 Mechanics using a hand crank to start the engine of Ki-60

The Kawasaki Ki-60 was a Japanese World War 2 fighter aircraft that used a license-built DB 601 liquid-cooled engine. The majority of Japanese aircraft at that time used air-cooled radial engines. A total of three Ki-60s were built in 1941. Although the aircraft’s performance was improved somewhat, test pilots still had a negative reaction to the model and it was abandoned in favour of the Ki-61.

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Kawasaki Ki-61 Hien (Swallow)

With its liquid-cooled engine, long tapered nose and wings of high aspect ratio, the Ki-61 was unique among Nipponese fighter aircraft of World War II and it marked the first attempt by the JAAF to incorporate in a fighter design the armour protection and self-sealing fuel tank which had been shown to be indispensable by early war reports received from Europe. The Hien (Swallow) was so un-Japanese in its appearance that it was initially reported as being a licence-built version of either the Messerschmitt Bf 109 or of an unspecified Italian aircraft, the latter report earning for it the Allied code-name ‘Tony’.

During the twenties and thirties, initially under the guidance of Dr Richard Vogt, the German engineer who later became the chief designer of Blohm und Voss, Kawasaki Kokuki KK were the leading exponents in Japan of liquid-cooled engines and held manufacturing rights for the German BMW VI, a V-12 engine, which powered most of their aircraft during the period. Following the Army’s selection of the Nakajima Ki-27 over their own Ki-28, Kawasaki decided to negotiate with Daimler-Benz for a licence for the new series of twelve-cylinder inverted-vee engines which the German company had developed. Negotiations were successfully concluded in April 1940 when a Japanese technical team brought back from Stuttgart the blueprints for the DB 601A as well as a number assembled engines to serve as production patterns. Adaptation to Japanese production techniques began immediately at Kawasaki’s Akashi plant and the first Japanese-built DB 601A, designated Ha-40, was completed in July 1941. Four months later the Ha-40 had successfully passed all ground tests and production started under the designation Army Type 2 (Kawasaki Ha-40) liquid-cooled engine, rated at 1,175 hp for take-off and 1,100 hp at 4,200 m (13,780 ft).

While negotiating with Daimler-Benz, Kawasaki had approached the Army with initial design studies for various fighter aircraft making use of this engine. As reports from the air war in Europe were showing the apparent superiority of aircraft powered by liquid-cooled engines, the Koku Hombu instructed Kawasaki to proceed with two aircraft of this type: the Ki-60, a heavy interceptor fighter, and the Ki-61, a lighter all-purpose fighter, priority being given to the heavier aircraft. In December 1940, however, the emphasis shifted to the Ki-61 for which Takeo Doi and Shin Owada were responsible. The Ki-61 was a low-wing monoplane of all-metal construction with a wide-track inward-retracting main undercarriage and a retractable tailwheel. It was characterised by a large ventral radiator bath under the fuselage just beneath the wing leading edge. The pilot sat in an enclosed cockpit with a backward-sliding canopy. The aircraft, powered by a Kawasaki Ha-40, showed in its design the strong influence left by Dr Vogt on his Japanese pupils. To provide good manoeuvrability and to obtain long endurance a wing of high aspect-ratio and large area was selected by Takeo Doi, considerable attention being given to weight and drag reduction. An armament of two 12.7 mm (0.5 in) Type 1 (Ho-103) machine-guns mounted in the upper fuselage decking and either two 7.7 mm (0.303 in) Type 89 or two 12.7 mm (0.5 in) Type 1 (Ho-103) wing-mounted machine-guns was selected, this armament representing a one hundred per cent increase over that carried by the Ki-43-I then just entering service.

One year after receiving authorisation from the Koku Hombu to proceed with the design, the first aircraft was completed at the Kagamigahara plant where flight tests began in December 1941. Prior to this event, Kawasaki had been authorised to prepare for production and to purchase the necessary tooling and material. Fortunately the wisdom of this decision was vindicated when the prototype met the most sanguine hopes of its designers and the Army staff. Eleven additional prototypes and pre-production machines were built in the early part of 1942, and following handling and performance tests during which a maximum speed of 591 km/h (367 mph) at 6,000 m (19,685 ft) was reached, Service trials began. The wing loading of 146 kg/sq m (29.9 lb/sq ft), high by Japanese standards of the time, was criticized by military pilots, but the majority of those who flew the aircraft were impressed by its high diving speed, and its armour protection, self-sealing fuel tanks and armament were also commented upon favourably.

The thirteenth Ki-61, the first machine to be built with production tooling, was completed in August 1942 and differed from the prototypes only in minor equipment details, the deletion of a small window on each side of the fuselage ahead of the windshield providing the only recognition feature. During competitive trials against prototypes of the Nakajima Ki-43-II and the Ki-44-I, an imported Messerschmitt Bf 109E and a captured Curtiss P-40E, the Ki-61 was judged to have the best overall performance and to be an effective weapon against enemy aircraft.

Consequently, late in 1942, the fighter was accepted for Service use under the designation Army Type 3 Fighter Model 1A when armed with two fuselage-mounted 12.7 mm (0.5 in) Type 1 machine-guns and two wing-mounted 7.7 mm (0.303 in) Type 89 machine-guns and Model 1B when the wing guns were the 12.7 mm (0.5 in) Type 1. Initial deliveries of the aircraft were made in February 1943 to the 23rd Dokuritsu Dai Shijugo Chutai at Ota, which acted as a pilot conversion and training unit. Combat operations began two months later when the 68th and 78th Sentais were deployed to Wewak on the north coast of New Guinea. Immediately these units proved that the Ki-61s, then named Hien, were better suited to combat the US and Australian aircraft than the Ki-43s, which they supplemented in this theatre, due to their heavier armament, good protection and high diving speed – a performance required to overcome the enemy fighters which favoured hit and run attacks from higher altitude against the nimbler Nipponese fighter aircraft. The idiosyncrasies of the liquid-cooled Ha-40 which powered the Hien caused the aircraft to be difficult to handle on the ground because of the prevailing hot and damp weather but in the air the Ki-61-I was an outstanding aircraft liked by its pilots and respected by its foes.

At an early stage in the design of the Ki-61 replacement of the fuselage-mounted machine-guns by a pair of 20 mm (0.79 in) cannon had been contemplated. However, as cannon of domestic design were not yet available, 388 Ki-61-Ias and -Ibs were modified on the assembly line to carry one 20 mm (0.79 in) Mauser MG151 in each wing. As space in the wing was limited, the cannon had to be mounted on its side, a small underwing fairing covering the breech, while some local strengthening was required because of the increased recoil force. One other aircraft was modified to test the surface evaporation cooling system which Takeo Doi proposed to use on the Ki-64. This experimental Hien had its large ventral radiator replaced by a smaller retractable unit, for use on the ground, mounted further forward, while in flight cooling was provided by steam evaporation through wing condensers with a total area of 14 sq m (150.694 sq ft). Tests began in October 1942 and thirty-five flights – during which a maximum speed of 630 km/h (391 mph) was attained – were made until the end of 1943 when the purpose of the tests was sufficiently achieved.

Operations in New Guinea, New Ireland and New Britain had shown that ease of maintenance had to be improved and Takeo Doi decided to simplify the Hien’s structure in the next version of the aircraft. With the availability of the indigenous 20 mm (0.79 in) Ho-5 cannon the Ki-61-I-KAIc was produced with a pair of these replacing the two fuselage-mounted 12.7 mm (0.5 in) Type 1 machine-guns. Stronger wings, allowing an increase in diving speed and featuring provision for fixed pylons for external stores outboard of the wheel wells, were mated to a slightly longer fuselage with detachable rear section. On this version the retractable tailwheel was replaced by a fixed unit while minor control modifications were incorporated. production of the Ki-61-I-KAIc began in January 1944, and the type had completely supplanted the earlier versions on the Kagamigahara assembly line in August of the same year. Following the introduction of this version the Hien’s production, which so far had been somewhat slow, quickly gained tempo and the monthly rate reached a peak of 254 aircraft in July 1944. Including a few Ki-61-I-KAIds, which were armed with a pair of 30 mm (1.18 in) Ho-105 cannon in the wings and two fuselage-mounted 12.7 mm (0.5 in) Type 1 machine-guns, a total of 2,654 Ki-61-Is and Ki-61-I-KAIs – of which the former type accounted for over half of the total – were built until January 1945 when production was terminated. Many of the Ki-61-Is and Ki-61-I-KAIs saw operation in the New Guinea/Rabaul area with the two previously mentioned Sentais, but they were mostly active in the Philippines campaign of 1944-45 (17th, 18th and 19th Sentais) and over Formosa (Taiwan) and Okinawa (19th, 37th, 59th and 105th Sentais, and 23rd Dokuritsu Dai Shijugo Chutai). Finally the type played an important role in the defence of the Japanese homeland where the Hien-equipped 18th, 23rd, 28th and 244th Sentais were assigned to the Tokyo Defence Area, the 59th Sentai to the Western Defence Area and the 55th and 56th Sentais to the Central Defence Area. Over Japan the Hiens were engaged against the B-29s, US Navy carrier aircraft and, later, against Iwo Jima based P-51 Mustangs. Against the high-flying B-29s the Ki-61-I lacked the necessary altitude performance, but the type was not really outclassed until the arrival of the superb Mustang.

Soon after commencing production of the Ha-40 at the Akashi plant, the Kawasaki engineering team began developing a more powerful version of this engine, the Ha-140. Primary emphasis was placed on altitude rating, and Takeo Doi, urged by the Army Staff to develop an advanced version of the Hien, decided to mount the Ha-140 rated at 1,500 hp for take-off and 1,250 hp at 5,700 m (18,700 ft) in a specially redesigned version of the Ki-61. Completed in December 1943, the first prototype Ki-61-II had a wing area increased by 10 per cent to 22 sq m (236.806 sq ft) and a redesigned aft canopy providing improved pilot visibility. However, flight trials were disappointing as the Ha-140 had more than its fair share of teething troubles, the crankshaft proving particularly weak. Even the airframe was not without its problems, and the enlarged wings, which had been designed to enhance the aircraft’s manoeuvrability and performance at high altitude, suffered from several failures. The handling characteristics, too left much to be desired. Consequently, only eight of the eleven Ki-61-IIs built were tested and the ninth airframe was modified as the Ki-61-II-KAI before completion in April 1944. The fuselage length was increased from 8.94 m (29 ft 4 in) to 9.16 m (30 ft 0 5/8 in), the rudder area was enlarged to offset the increased wetted area and the larger wings were replaced by standard Ki-61-I-KAI wings. The airframe problems were thus eradicated and, when the engine performed smoothly, Ki-61-II KAI was an outstanding interceptor with a maximum speed of 610 km/h (379 mph) at 6,000 m (19,685 ft) and a climb rate of 5,000 m (16,405 ft) in six minutes. Still confident that the persistent engine teething troubles would be eradicated, the Ministry of Munitions, acting on behalf of the Army, instructed Kawasaki to proceed with the mass production of the aircraft under the designation Army Type 3 Fighter Model 2.

Starting in September 1944 the Ki-61-II-KAI was built in two versions, the Model 2A with an armament of two fuselage-mounted 20 mm (0.79 in) Ho-5 cannon and two wing-mounted 12.7 mm (0.5 in) Type 1 machine-guns and the Model 2B with an armament of four 20 mm (0.79 in) Ho-5 cannon, two in the fuselage and two in the wings. The Ki-61-II-KAI never supplanted the Ki-61-I-KAI in operational units as its engine was still suffering from chronic weaknesses, and the comparatively few Hiens of this model saw only limited operational service in Japan. When the engine was operating smoothly the Ki-61-II-KAI was an effective interceptor and was the only Japanese fighter able to maintain combat formation at the operating altitude of the B-29s. However, the lack of skilled workers was by then being badly felt and seldom did the Ha-140 give its full rated power. Finally, production of the Army Type 3 Fighter Model 2 was dealt a crippling blow when, on 19 January, 1945, the US Army Air Force destroyed the Akashi engine plant. Only 374 Ki-61-II-KAI airframes were built in slightly less than a year but some thirty were destroyed on the ground prior to delivery to Service units and 275 were left without engines until the successful adoption of the Mitsubishi Ha-112-II fourteen-cylinder radial engine which gave birth to the Ki-100. Prior to this conversion it had been proposed to incorporate various modifications in a new version, the Ki-61-III, but only one aerodynamic prototype was built, this aircraft being characterised by having a cut-down rear fuselage and the fitting of an all-round vision canopy to a modified Ki-61-II-KAI.

Among the Japanese aces who flew the Ki-61 was Major Shogo Takeutchi. He flew with the 68th Sentai over New Guinea and claimed 16 enemy aircraft destroyed before being killed in a crash-landing on 21 December, 1943.

Plagued by engine troubles and production difficulties, the Hien never saw as extensive a Service use as the more numerous Nakajima fighters, but during the mid-war years it was the only Japanese aircraft which could successfully engage the fast Allied fighters by combining some of the Nipponese machines’ traditional manoeuvrability with a strong and well protected structure.

Units Allocated

17th, 18th, 19th, 23rd, 26th, 28th, 37th, 55th, 56th, 59th, 65th, 68th, 78th, 105th and 244th Sentais. 23rd and 28th Dokuritsu Dai Shijugo Chutais. 8th Kyo-iku Hikotai. 5th,11th, 16th and 18th Lensei Hikotais. Akeno Fighter Training School.

Technical Data

Manufacturer: Kawasaki Kokuki Kogyo KK (Kawasaki Aircraft Engineering Co Ltd).

Type: Single-engined interceptor fighter and fighter bomber.

Crew (1): Pilot in enclosed cockpit.

Powerplant: (Ki-61- prototypes) One 1,100 hp Kawasaki Ha-40 twelve-cylinder inverted-vee liquid-cooled engine, driving a three-blade constant-speed metal propeller (Ki-61-Ia, -Ib and KAIc and KAId)) One 1,100 hp Army Type 2 (Kawasaki Ha-40) twelve-cylinder liquid-cooled engine, driving a three-blade constant-speed metal propeller (Ki-61-II and II-KAI) One Kawasaki Ha-140 twelve-cylinder liquid-cooled engine, driving a three-blade constant-speed metal propeller.

Armament: Two (Ki-61-Ia) fuselage-mounted 12.7 mm (0.5 in) Type 1 machine-guns and two wing-mounted 7.7 mm (0.303 in) Type 89 machine-guns two (Ki-61-Ib) fuselage-mounted 12.7 mm (0.5 in) Type 1 machine-guns and two wing-mounted 12.7 mm (0.5 in) Type 1 machine-guns two (modified Ki-61-Ia and -Ib) fuselage -mounted 12.7 mm (0.5 in) Type 1 machine-guns and two wing-mounted 20 mm (0.79 in) Mauser MG 151/20 cannon two (Ki-61-I-KAIc, Ki-61-II and -II-KAIa) fuselage-mounted 20 mm (0.79 in) Ho-5 cannon and two wing-mounted 12.7 mm (0.5 in) Type 1 machine-guns two (Ki-61-I-KAId) fuselage-mounted 12.7 mm (0.5 in) Type 1 machine-guns and two wing-mounted 30 mm (1.18 in) Ho-105 cannon two (Ki-61-II-KAIb) fuselage-mounted 20 mm (0.79 in) Ho-5 cannon and two wing-mounted 20 mm (0.79 in) Ho-5 cannon.

External stores: Two 200 litre (44 Imp gal) drop tanks, or (Ki-61-I KAI and -II KAI) two 250 kg (551 lb) bombs.

Dimensions: Span (Ki-61-Ib, -I-KAIc and -II-KAIa) 12 m (39 ft 4 7/16 in) length (Ki-61-Ib) 8.75 m (28 ft 8 1/2 in), (Ki-61-I-KAIc) 8.94 m (29 ft 4 in), (Ki-61-II-KAIa) 9.16 m (30 ft 0 5/8 in) height (Ki-61-Ib, -I-KAIc and -II-KAIa) 3.7 m (12 ft 1 11/16 in) wing area (Ki-61-Ib, -I-KAIc and -II-KAIa) 20 sq m (215.278 sq ft).

Weights: Empty (Ki-61-Ib) 2,210 kg (4,872 lb), (Ki-61-I-KAIc) 2,630 kg (5,798 lb), (Ki-61-II-KAIa) 2,840 kg (6,261 lb) loaded (Ki-61-Ib) 2,950 kg (6,504 lb), (Ki-61-I-KAIc) 3,470 kg (7,650 lb), (Ki-61-II-KAIa) 3,780 kg (8,333 lb) maximum (Ki-61-Ib) 3,250 kg (7,165 lb), (Ki-61-II-KAIa)3,825 kg (8,433 lb) wing loading (Ki-61-Ib) 147.5 kg/sq m (30.2 lb/sq ft), (Ki-61-I-KAIc) 173.5 kg/sq m (35.1 lb/sq ft), (Ki-61-II-KAIa) 189 kg/sq m (38.8 lb/sq ft) power loading (Ki-61-Ib) 2.51 kg/hp (5.53 lb/hp), (Ki-61-I-KAIc) 2.94 kg/hp (6.48 lb/hp), (Ki-61-II-KAIa) 2.52 kg/hp (5.56 lb/hp).

Performance: Maximum speed (Ki-61-Ib) 592 km/h (368 mph) at 4,860 m (15,945 ft), (Ki-61-I-KAIc) 590 km/h (366 mph) at 4,260 m (13,980 ft), (Ki-61-II-KAIa) 610 km/h (379 mph) at 6,000 m (19,685 ft) cruising speed (Ki-61-Ib) 400 km/h (249 mph) at 4,000 m (13,125 ft) climb to 5,000 m (16,405 ft) in (Ki-61-Ib) 5 min 31 sec, (Ki-61-I-KAIc) 7 min, (Ki-61-II-KAIa) 6 min service ceiling (Ki-61-Ib) 11,600 m (37,730 ft), (Ki-61-I-KAIc) 10,000 m (32,810 ft, (Ki-61-II-KAIa) 11,000 m ( 36,090 ft) range – normal (Ki-61-Ib) 600 km (373 miles), (Ki-61-II-KAIa) 1,100 km (684 miles), – maximum (Ki-61-1b) 1,100 km (684 miles), (Ki-61-I-KAIc) 1,800 km (1,120 miles), (Ki-61-II-KAIa) 1,600 km (995 miles).

Production: A total of 3,078 Ki-61s were built by Kawasaki Kokukai Kogyo KK in their Kagamigahara plant as follows:

12 Ki-61 prototypes – 1941-42

1,380 Ki-61-I production aircraft – August 1942-July 1944

1,274 Ki-61-I-KAI production aircraft – January 1944-January 1945

8 Ki-61-II prototypes – August 1943-January 1944

30 Ki-61-II-KAI prototypes and pre-production aircraft – April-September 1944

374* Ki-61-II-KAI production aircraft – September 1944-August 1945.

Kawasaki Motorcycle History

The striking Kawasaki H1 (aka Mach III) a 500cc three-cylinder two-stroke is released. Although its handling leaves something to be desired, the motor is very powerful for the day. It’s one of the quickest production bikes in the quarter-mile. The Mach III establishes Kawasaki’s reputation in the U.S. (In particular, it establishes a reputation for powerful and somewhat antisocial motorcycles!) A wonderful H1R production racer is also released – a 500cc racing bike.

Over the next few years, larger and smaller versions of the H1, including the S1 (250cc) S2 (350cc) and H2 (750cc) will be released. They’re successful in the marketplace, and the H2R 750cc production racer is also successful on the race track, but Kawasaki knows that the days of the two-stroke streetbike are coming to an end.

The company plans to release a four-stroke, but is shocked by the arrival of the Honda 750-Four. Kawasaki goes back to the drawing board.

Kawasaki’s big-bore KZ1300 is released. Honda and Benelli have already released six-cylinder bikes by this time, but Kawasaki’s specification includes water cooling and shaft drive. To underline the efficiency of the cooling system, its launch is held in Death Valley. Despite its substantial weight, journalists are impressed.

Over the next few years, the KZ1300 will get digital fuel injection and a full-dress touring version will be sold as the ‘Voyager.’ This model is marketed as “a car without doors”!

Kawasaki releases the GPz550. It’s air-cooled and has only two valves per cylinder, but its performance threatens the 750cc machines of rival manufacturers. This is the bike that launches the 600 class.

Kawasaki Ki-61 Hien / Ki-100 Book Review

In World War II Imperial Japanese Army Air Force service, nothing resembled Kawasaki's sleek Ki-61 Hein.

That's because it remains the only Japanese fighter with a liquid-cooled engine to see widespread production and combat.

Now it's the subject of superbly informative, beautifully illustrated study from Kagero – available in North America from Casemate.

Author Leszek A. Wiliczko's monograph really remains the story of three aircraft – the Ki-61, Ki-100 and Ki-60. And contents commence with illuminating design and development notes on all.

All other IJAAF fighters previously sported radial powerplant – and meager armament. Kawasaki's Hein, by contrast, principally employed the Ha-40 engine – an extrapolation of Daimler-Benz's legendary DB 601. Design variants also packed potent combinations of heavier 12.7mm machine guns and 20mm canon.

Operational history follows. There you learn that the Ki-61's unofficial combat debut surprisingly occurred during April 1942's Doolittle raid. That's when four Heins with ineffective practice ammunition attacked Capt Charles Ross Greening's B-25B. Greening's top-turret gunner reportedly scored hits on at least two of the unidentified enemy interceptors with inline engines.

Kawasaki's design soon began appearing in Asian and Pacific war zones. Its silhouette proved so singular, that Allied intelligence initially deemed it a version of Fascist Italy's Macchi C.202. And that's how the Ki-61 acquired its code name "Tony".

The unreliable Ha-40 liquid-cooled powerplant, however, proved difficult-to-maintain in typically hot, humid, dusty combat conditions. Spares were scarce, too. And deliveries of the inline engine further failed to match Kawasaki's airframe production pace.

So in a case of "convergent evolution" mirroring Lavochkin's La-5 development, Kawasaki replaced the inline propulsion with a compact radial. Thus emerged the Ki-100 Goshikisen – the IJAAF's last operational fighter to enter World War II service.

Wiliczko charts the story of Kawasaki's fighters through Imperial defeats in, for instance, New Guinea, Burma, the Philippines and Japanese Home Islands. And coverage concludes with notes on captured examples, appendices and selected bibliography.

Kagero expertly and authoritatively illumines its colorful subject. Extended captions, tables and annotations augment the account. And photos, color profiles and scale drawings – to 1:72, 1:48 and 1:32 – visually season the study. Modelers will really love this one.

Watch the video: FMS. DIAMOND HOBBY KAWASAKI Ki-61 995mm TONY Full Flight Reveiw By: RCINFORMER


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