Country of origin:

Japan

Description:

Single-seat fighter and fighter bomber

Power Plant:

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

Specifications:

History:

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.