|A Nakajima Ki-49 Donryu bomber of the Army Heavy Bomber School in Hamamatsu|
|Manufacturer||Nakajima Aircraft Company|
|First flight||August 1939|
|Primary user||IJA Air Force|
The Nakajima Ki-49 Donryu (中島 キ-49 呑龍) "Storm Dragon"  was a twin-engine Japanese bomber aircraft of World War II. Despite its official designation as Army Type 100 Heavy Bomber, the requirements of the Ki-49 – to operate unescorted, with heavy defensive armament and armor – restricted it to a small bomb load, initially 1,000 kg (2,200 lb).
A mid-wing, cantilever monoplane of all-metal construction, the Ki-49 was one of the first Japanese aircraft fitted with a retractable tailwheel. During World War II, it was known to the Allies by the reporting name "Helen".
The Ki-49 was designed to replace the Mitsubishi Ki-21 ("Sally"), which entered service with the Imperial Japanese Army Air Force in 1938. Learning from service trials of the Ki-21, the Army realized that however advanced it may have been at the time of its introduction, its new Mitsubishi bomber would in due course be unable to operate without fighter escorts. As a result, the Japanese Army stipulated that its replacement should have the speed and defensive weaponry to enable it to operate independently.
The prototype first flew in August 1939 and the development programme continued through three prototypes and seven pre-production aircraft. This first prototype was powered by a pair of 708 kW (950 hp) Nakajima Ha-5 KA-I radial engines, but the next two had the 932 kW (1,250 hp) Nakajima Ha-41 engines that were intended for the production version. Seven more prototypes were built, and these completed the test programme for the aircraft. Eventually in March 1941, the Donryu went into production as the Army Type 100 Heavy Bomber Model 1.
Going operational from autumn 1941, the Ki-49 first saw service in China. After the outbreak of the Pacific War it was also active in the New Guinea area and in raids on Australia. Like the prototype, these early versions were armed with five 7.7 mm (0.303 in) machine guns and one 20 mm cannon. Combat experience in China and New Guinea showed the Donryu to be underpowered, with bomb capacity and speed suffering as a result. Thus, in the spring of 1942 an up-engined version was produced, fitted with more powerful Ha-109 engines, and this became the production Army Type 100 Heavy Bomber Model 2 or Ki-49-IIa. The Model 2 also introduced improved armor and self-sealing fuel tanks and was followed by the Ki-49-IIb in which 12.7mm (0.5 in) Ho-103 machine guns replaced three of the 7.7 mm (0.303 in) Type 89 machine guns.
In spite of these improvements however, losses continued to mount as the quantity and quality of fighter opposition rose. An attempt was made to stop the rot in early 1943 by further up-engining the type. This petered out, however, owing to development difficulties with the 1,805 kW (2,420 hp) Nakajima Ha-117 engines and the Ki-49-III never entered production with only six prototypes ever being built.
In the face of its increasing vulnerability to opposing fighter aircraft while performing its intended role, the Ki-49 was used in other roles towards the end of the Pacific War, including ASW patrol, troop transport and, ultimately, as kamikaze.
- Prototypes and pre-series models with a 708 kW (950 hp) Nakajima Ha-5 KAI or the 1,250 hp Ha-4. The pre-series with little modifications from the prototype.
- Army Type 100 Heavy Bomber Model 1, first production version.
- Two prototypes fitted with two Nakajima Ha-109 radial piston engines.
- Army Type 100 Heavy Bomber Model 2A - Production version with Ha-109 engines and armament as Model 1.
- Version of Model 2 with 12.7 mm Ho-103 machine gunes replacing rifle calibre weapons.
- Six prototypes fitted with two 1,805 kW (2,420 hp) Nakajima Ha-117 engines.
- Escort fighter with Ha-109 engines, 5 x 20 mm cannon, 3 x 12.7 mm (0.5 in) machine guns. 3 prototypes built.
- Specialised pathfinder aircraft - 2 prototypes; employed as engine test-beds.
- Total production: all versions 819 examples (including 50 built by Tachikawa)
- Imperial Japanese Army Air Force
- No. 61 Hikō Sentai IJAAF
- No. 62 Hikō Sentai IJAAF
- No. 74 Hikō Sentai IJAAF
- No. 95 Hikō Sentai IJAAF
- No. 110 Hikō Sentai IJAAF
- No. 11 Hikōshidan IJAAF
- Hamamatsu Army Heavy Bomber School
- 3 captured aircraft were used between 1946 and 1949 in Indochina
- Indonesian Air Force - Ex-Japanese Aircraft were operated by Indonesian guerilla forces after the war.
- Royal Thai Air Force - Utilized 1 Nakajima Ki-49 as a transport post war, during 1945-46
- Crew: 8
- Length: 16.5 m (54 ft 1.5 in)
- Wingspan: 20.42 m (67 ft 0 in)
- Height: 4.25 m (13 ft 11.25 in)
- Wing area: 69.05 m² (743.27 ft²)
- Empty weight: 6,530 kg (14,396 lb)
- Loaded weight: 10,680 kg (23,545 lb)
- Max. takeoff weight: 11,400 kg (25,133 lb)
- Powerplant: 2 × Nakajima Ha-109 14-cylinder radial engine, 1,119 kW (1,500 hp) each
- Maximum speed: 492 km/h (266 kn, 306 mph)
- Cruise speed: 350 km/h (189 kn, 217 mph)
- Range: 2,950 km (1,594 nmi, 1,833 mi)
- Service ceiling: 9,300 m (30,510 ft)
- Wing loading: 3.6 kg/m² (7.8 lb/ft²)
- Guns: 1× 20 mm Ho-1 cannon in the rear cockpit and 5 × 7.7 mm (0.303 in) Type 89 machine guns (one nose, two waist, one ventral, and one tail).
- Bombs: 1,000 kg (2,205 lb) bombload
Aircraft of comparable role, configuration and era
- Fokker T.V
- Heinkel He 111
- Ilyushin Il-4
- Junkers Ju 188
- Martin B-26 Marauder
- Mitsubishi G4M
- Mitsubishi Ki-67
- North American B-25 Mitchell
- Vickers Wellington
- Francillon, 1970, p.223
- Francillon 1979, p. 223.
- Francillon 1979, p. 225.
- Francillon 1979, p. 226.
- Francillon 1979, p. 227.
- Francillon 1979, pp. 227–228.
- Francillon 1979, p. 229.
- Japanese Aircraft in Foreign Service WWII and Post WWII retrieved 24 August 2010
- Mondey 1996, p. 228.
- Francillon 1979, pp. 228–229.
- Bueschel, Richard M. (2004). Nakajima Ki-49 Donryu in Japanese Army Air Force Service. Atglen, PA: Schiffer Publishing Ltd. ISBN 0-7643-0344-9.
- Francillon, Ph.D., René J. (1979). Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd. pp. 223–229). ISBN 0-370-30251-6.
- Mondey, David (1996). Axis Aircraft of World War II. London: Chancellor Press. ISBN 0-7537-1460-4.
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