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Mitsubishi K 37 / Ki-1

The Mitsubishi Ki-1, also known as Mitsubishi Army Type 93 Heavy Bomber, was a bomber for the Imperial Japanese Army in the 1930s.

The Ki-1 design was heavily based on the Junkers K 37 and a mock-up was ready in August 1932, with the first prototype being finished in March 1933.

Despite its antiquated appearance, the Ki-1 was used in Manchukuo and in North China during the early stages of the Second Sino-Japanese War, in areas where danger from enemy fighter aircraft was minimal.

The Mitsubishi Ki-1 was a low-wing, cantilever monoplane with fixed landing gear, twin fins and rudders, and was powered by two 701 hp (523 kW) Mitsubishi Ha2-II water-cooled V-12 engines, giving a maximum speed of 220 km/h (136.7 mph).

The pilot and co-pilot were seated in tandem under an enclosed canopy, while gunners sat in semi-enclosed nose and dorsal gun turrets, each armed with a single 7.7 mm (0.303 in) machine gun.

The usable bomb load was up to 1,500 kg (3,306.9 lb).

The Ki-1 shared a similar configuration with the Junkers S 36 first flown in 1927, militarized into the Junkers K37 by Junker’s Swedish subsidiary AB Flygindustri at Limhamn near Malmö.

It was able to reach altitudes not reachable for the fighters of 1927.

However, as soon as 1930 this advantage was lost due to British developments such as the Bristol Bulldog fighter, and Junkers was not successful in selling the design.

In 1931 however representatives of Mitsubishi from Japan visited the Limhamn facilities to study some of the military conversions of Junkers aircraft.

The sole K 37 prototype S-AABP (ex D-1252 – S 36-prototype), as well as all development papers were purchased in part by funds raised by donations in Japan.

The aircraft got the name Aikoku No.1 (patriotic gift).

The K37 prototype was brought to Japan and tested in combat during the Manchurian Incident of 1931, following which the Imperial Japanese Army Air Force authorized Mitsubishi to produce both heavy and light bomber variations.

The heavy bomber Ki-1 was much larger than the original Junkers K37 and first flew in August 1932.

A total of 118 aircraft were built in two versions between March 1933 and April 1936.



(Army Type 93-I Heavy Bomber)

Initial production variant, powered by two 701 hp (523 kW) Mitsubishi Ha2-II (Army Type 93-II 700 hp Water Cooled In-line) V-12 engines.


(Army Type 93-II Heavy Bomber)

Improved version with more powerful engines, strengthened airframe, powered by two 723 hp (539 kW) Mitsubishi Ha2-III (Army Type 93-III 700 hp Water Cooled In-line) V-12 engines.





14.8 m (48 ft 7 in)


26.5 m (86 ft 11 in)


4.92 m (16 ft 2 in)

Empty weight

4,880 kg (10,759 lb)

Gross weight

8,100 kg (17,857 lb)


2 × Mitsubishi Ha2-II,

V-12 water-cooled piston engines,

523 kW (701 hp) each


2-bladed wooden fixed-pitch propellers


Maximum speed

220 km/h (140 mph, 120 kn)

Service ceiling

5,000 m (16,000 ft)



3× 7.7 mm (0.303 in) machine guns


1,500 kg (3,300 lb) of bombs.



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