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Nakajima Ki-49 Donryu (Helen) - Imperial Japan, 1941

Detailing the development and operational history of the Nakajima Ki-49 Donryu (Helen) Medium Bomber Aircraft.

 Entry last updated on 5/10/2016; Authored by Staff Writer; Content ¬©

  Nakajima Ki-49 Donryu (Helen)  
Picture of Nakajima Ki-49 Donryu (Helen)

The Nakajima Ki-49 Donryu was destined to replace the ill-equipped Ki-21 though the Ki-49 itself was a general failure in design.

The Nakajima Ki-49 Donryu (meaning "storm dragon" and codenamed "Helen" by the Allies) heavy bomber was intended as a replacement for the out-classed Mitsubishi Ki-21 series of medium bomber. In reality, the newer Ki-49 design proved to be something of a disappointment to the Imperial Japanese Army Air Force as the type was a slow performer that - like most Japanese aircraft of the war - was ill-armed and under-armored. As a result, the type saw very limited production numbers (being limited to just over 800), appeared in a few variants and quickly was dismissed as a partner to the successful ki-21 instead of its direct replacement.

The Nakajima Ki-49 was drawn up by 1938 as a very utilitarian heavy bomber design. The term "heavy bomber" in this instance was carried quite loosely as the production Ki-49 could carry barely above 2,000 pounds of internal ordnance. The aircrafts design followed along the same lines of previous twin engine bomber attempts of Japanese ordnance that saw a slender fuselage with clean lines, a middle-mounted monoplane wing assembly, various gun positions adorning the design and a single vertical tail surface. Crew accommodations amounted to seven (or in some cases eight) personnel. Defensive armament (always an issue with Japanese bomber aircraft designs throughout the war) consisted of a nose-mounted 7.7mm machine gun, a 7.7mm machine gun in a tail gun position, 2 x 7.7mm machine guns in beam positions (1 gun per side), a 7.7mm machine gun in a ventral position and a 20mm cannon in a flexible dorsal mounting.

The first Ki-49 prototype went airborne in 1939 with Nakajima Ha-5 KAI radial engines of 950 horsepower each. Pre-production and the first production models would be mated with 2 x Nakajima Ha-41 radial engines of 1,250 horsepower each, increasing performance capabilities as a result. The Ki-49 would enter service in 1941 with mixed results, forcing the aircraft to undergo some much needed upgrades to armor and armament by 1942. The "improved" Ki-49 appeared in form as the Ki-49-IIa and was followed by another improved version in the Ki-49-IIb variant.

The Ki-49 was fielded extensively against China, Australia and the Burma region but the aircraft was generally outclassed by the latest crop of American and British fighters. As a result, the Ki-49 suffered heavy losses throughout the conflict and their reach was lessened by 1944. Afterwards, the Ki-49 - like most of the mid-sized Japanese aircraft of limited potential - could be seen focused on kamikaze attacks against Allied interests.

Nakajima Ki-49-IIa Donryu (Helen) Specifications

Service Year: 1941
Type: Medium Bomber Aircraft
National Origin: Imperial Japan
Manufacturer(s): Nakajima - Japan
Total Production: 819

Structural (Crew, Dimensions, Weights)

Operating Crew (Typical): 7
Overall Length: 54.13 feet (16.5 meters)
Overall Width: 66.99 feet (20.42 meters)
Overall Height: 13.94 feet (4.25 meters)

Weight (Empty): 14,396 lb (6,530 kg)
Weight (MTOW): 25,133 lb (11,400 kg)

Power / Performance (Engine Type, Top Speed)

Engine: 2 x Nakajima Ha-109 radial piston engines developing 1,450 horsepower each.

Maximum Speed: 266 knots (306 mph; 492 kph)
Maximum Range: 1,593 nautical miles (1,833 miles; 2,950 km)
Service Ceiling: 30,512 feet (9,300 meters; 5.78 miles)
Rate-of-Climb: 1,225 feet-per-minute (373 m/min)

Armament / Mission Payload

1 x 20mm Ho-1 cannon in dorsal turret (flexible mounting)
1 x 7.7mm Type 89 machine gun in nose position
1 x 7.7mm Type 89 machine gun in ventral position
1 x 7.7mm Type 89 machine gun in left beam position
1 x 7.7mm Type 89 machine gun in right beam position
1 x 7.7mm Type 89 machine gun in tail gun position

Up to 2,205 lb of internal stores.

Global Operators (Customers, Users)

Imperial Japan; Indonesia; Thailand

Model Variants

Ki-49-I - Initial Production Model Designation
Ki-49-IIa - "Improved" Ki-49-I Model; fitted with uprated 2 x Nakajima Ha-109 radial engines; improved armor and fuel protection; improved defensive armament.
Ki-49-IIb - At least three of the existing 7.7mm machine guns replaced by heavy caliber 12.7mm Ho-103 types for improved defensive armament.
Ki-49-III - Prototype Models fitted with 2,420 horsepower engines; 6 examples produced.
Ki-58 - Experimental Escort Fighter based on the Ki-49 platform.
Ki-80 - Experimental Escort Bomber based on the Ki-49 platform.
Army Type 100 Heavy Bomber Model 1 - Official Designation for the Ki-49-I production model.
Army Type 100 Heavy Bomber Model 2A - Official Designation for the Ki-49-IIa production model.
Army Type 100 Heavy Bomber Model 2B - Official Designation for the Ki-49-IIb production model.

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