Nakajima Ki-49 Donryu / HELEN

1939

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Nakajima Ki-49 Donryu / HELEN

The Nakajima Ki-49 Donryu (storm dragon) was designed early in 1938 to replace the JAAF's successful Mitsubishi Ki-21 heavy bomber which, in fact, was only just entering service with sentais based in China and Manchuria, Later code-named 'Helen', the Nakajima Ki-49 was a workmanlike design but was destined to be just not good enough for the conditions prevailing over the various fronts in 1942, when the initial production Ki-49-I (Army Type 100 Heavy Bomber Model 1) started operations with the 61st Hikosentai in China. Production was preceded by the flight of the first prototype in August 1939, powered by two 708kW Nakajima Ha-5 KAI radiais: the more powerful 932kW Ha-41 radial engines were installed in pre-production versions, and in the Ki-49-I bomber. In appearance the 'Helen' was deceptive in size, for it appeared to be a comparatively large aircraft because of its proportions: actually, its dimensions were similar to those of the Lockheed Hudson. However, a crew of seven or eight was crammed into the narrow fuselage. In the spring of 1942 the usual steps were taken to increase performance, protection and defensive firepower. The Nakajima Ki-49-IIa (Army Type 100 Heavy Bomber Model 2A), the first of the new series, was powered by two Nakajima Ha-109 radial engines with increased ratings. The aircraft was fast, well protected by 5mm armour plating and rubberized fuel cells, and heavily armed. The Ki-49-IIb was upgunned with 12.7mm Ho-103 machine guns. Both the Ki-49-IIa and Ki-49-IIb were in action with the 7th and 61st Sentais based in China in the summer of 1942, and made many attacks on Chungking and air bases of General C. L. Chennault's China Air Task Force. 'Helen' bombers equipped the 12th Sentai, based at Medan and Sabang (Sumatra) under the 3rd Air Army, and these attacked objectives in Burma and eastern India, joining Ki-21s on some occasions in raids on Calcutta. In 1943 the Ki-49s of the 7th and 61st Sentais, now operating from Timor, attacked Darwin to face strong reaction by the Supermarine Spitfire Mk.Vs of No.1 Fighter Wing. Units equipped with Ki-49s suffered most in New Guinea, where 4th Air Army came under constant attack on its airfields at Wewak, But and Dagua after August 1943, when the RAAF and the US 5th Air Force went onto the offensive. Six Ki-49-III bombers, powered by very potent 1805kW engines, were built as prototypes. Other variants produced in experimental form were the Ki-58 escort fighter, and the Ki-80 escort bomber. Total production amounted to 819 aircraft. After action in the Philippines in 1944, Ki-49s were used with increasing frequency on suicide missions.

Nakajima Ki-49 Donryu / HELEN

Specification 
 MODELKi-49-IIa
 CREW8
 ENGINE2 x Nakajima Ha-109, 1119kW
 WEIGHTS
  Take-off weight11400 kg25133 lb
  Empty weight6530 kg14396 lb
 DIMENSIONS
  Wingspan20.42 m67 ft 0 in
  Length16.5 m54 ft 2 in
  Height4.25 m14 ft 11 in
  Wing area69.05 m2743.25 sq ft
 PERFORMANCE
  Max. speed492 km/h306 mph
  Ceiling9300 m30500 ft
  Range w/max.fuel2950 km1833 miles
 ARMAMENT1 x 20mm cannon, 5 x 7.7mm machine-guns, 1000kg of bombs

3-View 
Nakajima Ki-49 Donryu / HELENA three-view drawing (752 x 961)

Comments
Barry, 17.06.2013 16:27

The Japanese called this a "heavy" bomber, by western standards it would be just about a medium bomber. The concept was for a fast heavily armed, armoured bomber which could reach targets without escort. Hopelessly under powered it failed in it's "raison d'etre" and fell easy prey to Allied fighters. So overall not a great success.

reply

thomas, e-mail, 19.06.2020 Barry

No unescorted bomber stood up to interceptors, from
any nation.

reply

Hiroyuki Takeuchi, e-mail, 23.03.2012 09:38

Undoubtedly, the aircraft outperformed the Ki21, but not to the extent that it improved the survivability of the bomber against full on attacks by enemy fighters. On the other hand, the Ki49 were harder to fly and engines were less reliable, causing more non-combat losses.

So as far as the bomber crews were concerned, they could expect longer lives on a Ki21 because there was less chance of accidents and if they were met by a formation of P-47s they were going to get shot down regardless of whether they were on a 21 or a 49.

reply

lucy, 21.06.2011 05:23

Did japan ever have a significant number of bombers carrying more than 1 ton.

reply

thomas, e-mail, 19.06.2020 lucy

Japanese designed philosophy was to maximize striking range so weight (space) was given to fuel capacity.

On shorter range missions or one way missions, less fuel, less crew and armament weight allowed most Japanese planes to carry more bomb load.
(roughly double to triple)
Few made it to target.

reply

Feyd, e-mail, 23.04.2009 16:44

Have heard mixed reviews about this one. Some sources say it was a mediocre aircraft surpassed in some ways by the Ki-21 it was designed to replace. Is this actually true? The performance specs seem to say otherwise. Light bomb load, though. Did japan ever have a significant number of bombers carrying more than 1 ton?

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