Thursday, July 18, 2013
Nakajima Ki-44 (Tojo)
The Nakajima Ki-44 Shōki (鍾馗, Zhong Kui) 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. The Allied reporting name was "Tojo"; the Japanese Army designation was "Army Type 2 Single-Seat Fighter" (二式単座戦闘機).
It was less maneuverable than its predecessor, the nimble Ki-43, and pilots disliked its poor visibility on the ground, its higher landing speed, and severe restrictions on maneuvering. Yet, it was obvious the Ki-44 was clearly superior overall as a combat aircraft compared to the Ki-43. As an interceptor it could match Allied types in climbs and dives, giving pilots more flexibility in combat and greater pilot confidence than the Ki-43. Moreover, the basic armament of four 12.7mm machine guns or two 12.7mm guns and two 20mm cannons,(plus a few aircraft which carried two Ho-301 40 mm cannons of limited performance) was far superior to the older Ki-43's two 12.7mm Mgs. These characteristics made the fighter despite performance restrictions at altitude, a useful B-29 Superfortress interceptor and one of the Japanese High Command priorities during the last year of war. However, like most of the Japanese aircraft flown in the last part of the war, the low availability of properly trained pilots made them easy targets for experienced, aggressive, and well trained Allied pilots flying superior aircraft.
Nakajima began development of the Ki-44 in 1940 as a pure interceptor with emphasis being placed on airspeed and rate of climb rather than maneuverability. The Japanese Army Air Force specification called for a maximum speed of 600 km/h (370 mph) at 4,000 m (13,130 ft), to be attained in five minutes. A set of Ki-43 like "butterfly" combat flaps was fitted for improved maneuverability. Armament consisted of a pair of 7.7 mm (.303 in) and a pair of 12.7 mm (.50 in) machine guns.
The engine selected for the new interceptor was Nakajima's Ha-41 (a development of the Nakajima Ha-5) 14-cylinder double-row radial, originally intended for bomber aircraft. Although the Ha-41 was not the ideal choice due to its large-diameter cross section, the design team was able to marry this engine to a much smaller fuselage with a narrow cross section. At 1,260mm in diameter, the Ha-41 was 126mm larger in diameter than the 1,144mm Nakajima Sakae (used in the Mitsubishi A6M "Zero" and Nakajima Ki-43 "Hayabusa"). However, the Sakae was only 27.8L in displacement and 1,000hp, while the Ha-41 was 37.5L and made 1,260hp (1,440 in the later Ha-109 version). In any case, since the Sakae wasn't powerful enough, the only alternative available was the Mitsubishi Kinsei, which was slightly smaller than the Ha-41 in diameter, five liters smaller in displacement, and was less powerful. Unfortunately, this was already in demand for many other aircraft, so the Ha-41 was chosen as the best powerplant. In order to achieve its design goals, the wing area was relatively small leading to a high wing loading and a comparatively high landing speed that could be daunting to the average Japanese pilot, who was more used to aircraft with a low wing loading like the Ki-44s predecessors, the Ki-43 and Ki-27.
The first Ki-44 prototype flew in August 1940 and the initial test flights were generally encouraging, with handling considered acceptable considering the high wing loading. Problems encountered included a high landing speed and poor forward visibility during taxiing due to the large radial engine.
A second pre-production batch of 40 aircraft were ordered, which featured four 12.7mm machine guns, a relocated air cooler and main gear doors.
The pre-production Ki-44 aircraft and two of the prototypes were turned over to the Army for service trials on 15 September 1941. The type commenced operations with one experimental unit, the 47th Chutai (Independent Air Company) ("Kawasemi Buntai", Kingfisher Unit) sent to Saigon, Indochina in December 1941 with nine aircraft under the command of Major Toshio Sakagawa.
The unit later became the 47th Sentai, when flying home defense in Japan. More aircraft were later sent to China, and others were used in defense of oil wells in Sumatra, Indonesia, the China-Burma-India theater of operations, Philippines, Japanese metropolitan defense (mainly concentrated around Japan's large industrial cities) and even kamikaze operations in the last stages of the war.
The Ki-44-2c version of the "Tojo" was armed with the relatively compact Ho-301 40mm heavy cannon firing caseless ammunition that was only useful at near point blank range due to very low muzzle velocity. It was used against B-29s by one special kamikaze unit (a company of four aircraft minimum) of the 47th Sentai, which specialized in bomber collision tactics, the Shinten unit ("Shinten Seiku Tai"(Sky Shadow) 47th Sentai (Air Regiment) based at Narimasu airfield), during the defense of Tokyo. It is presumed that at least part of the tactics of these aircraft were to get in very close to the B-29's and attempt a shoot down with the heavy cannon, but also to use the aircraft as a final weapon when the low ammunition supply of the H0-301 was expended. Although in concept it appeared easy, collision with a B-29 at altitude was very difficult to pull off although the tactic certainly created significant anxiety for B-29 squadrons when it occurred.
The Nakajima Ki-44 at one point equipped 12 sentais of the Japanese Army Air Force (the 9th, 22nd, 23rd, 29th, 47th, 59th, 64th, 70th, 85th, 87th, 104th and 246th Air Regiments (Sentai)) which saw action before their (partial) replacement with the far superior (except in maintenance and reliability) Ki-84 Hayates for the final battles of the war. The Manchukuo Air Force also received some examples of these aircraft during wartime.
After World War II, the Nationalist Chinese 18th Squadron of the 12th Fighter Group was equipped with Ki-44s formerly of the 9th Sentai, which had disbanded in Nanking, and of the 29th Sentai, which had disbanded at Formosa and they participated in the Chinese Civil War. The People's Liberation Army Air Force managed to get hold of aircraft formerly belonging to 22nd and 85th Sentai, who had disbanded in Chosen, the Japanese name for Korea during their imperial rule (1910–1945) over that country. These aircraft were flown by Japanese mercenary pilots, who used them until the last two Ki-44s finally retired in the early 1950s.