Mitsubishi Ki-15 'Babs'

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The Mitsubishi Ki-15 'Babs' was the main reconnaissance aircraft in use with the Imperial Japanese Army at the start of the Sino-Japanese War in 1937, and was still in front line service during the Japanese conquests at the start of 1942.

The Ki-15 was developed in response to a specification issued in 1935 that called for an aircraft with a top speed of 280mph at 9,845ft, an operating altitude of 6,560-13,125ft and the ability to spent one hour operated over targets that were 250 miles from its base.

Mitsubishi responded with a low-wing monoplane with a cantilevered wing. The wing had a flat central section while the outer panels sloped upwards. The aircraft had a fixed undercarriage with the wheels contained within streamlined spats. The prototype and first production version were powered by the Nakajima Ha-8 nine-cylinder radial engine. This engine had quite a wide diameter, and needed a large cowling, and would be the main flaw in the Ki-15-I, badly reducing forward visibility.

The prototype Ki-15 made its maiden flight in May 1936. Its performance greatly exceeded expectations, most notably in its endurance. With a range of 1,491 miles at its cruising speed of 199mph the Ki-15 could spend six and a half hours loitering over a target 250 miles from its base. Despite the poor forward visibility, and unexpectedly long take-off and landing distances, the Ki-15 was ordered into production.

The first production aircraft was delivered in May 1937, and were given the designation Army Type 97 Command Reconnaissance Plane. The Ki-15-I was followed by the Ki-15-II, which entered production in September 1939, and by two prototypes of the Ki-15-III, the fastest version of the aircraft. A total of 439 Ki-15s were built for the Japanese Imperial Army.

The Ki-15-I was the main Army reconnaissance aircraft at the start of the Second Sino-Japanese War in 1937. The Chinese air force was operating a mixed bag of older aircraft, most of which could not hope to catch the speedy Ki-15 (the only exception was the Soviet Polikarpov I-16). As a result the Japanese aircraft were able to range freely over Chinese territory, given their armies a great advantage. This success attracted the attention of the Japanese Navy, which ordered the type into production as the C5M.

The Ki-15-II was still in front line service when Japan entered the Second World War. It was used against the Allies during the first year of the fighting, but its lack of protective armour and self-sealing fuel tanks meant that it became very vulnerable as the Allies built up their aerial strength. At the end of 1942 the Ki-15 was withdrawn from front line service, and was instead used as an advanced trainer and communications aircraft. Towards the end of the war surviving aircraft were used in kamikaze attacks.

The Ki-15 first came to the attention of the outside world in 1937 The Asahi Shimbun, a leading newspaper, was granted permission to buy a civil version of the aircraft, and to use it to try and set a record time for a flight between Japan and Britain, timed to mark the coronation of George VI. The second prototype, with the type name Karigane I (Wild Goose I) was completed in March 1937, and delivered to the newspaper, which named it Kamikaze (Divine Wind), (a name that had not yet gained its association with suicide attacks). This aircraft flew from Tachikawa to London in 94 hours, 17 minutes and 46 seconds, covering the 9,542 miles in just over 51 hours in the air at an average speed of 101.2mph. After this success a small number of Ki-15-Is and Ki-15-IIs entered civil service.

Ki-15-I

Engine: Nakajima Ha-8 (Army Type 94) nine-cylinder air-cooled radial
Power: 640hp at take-off, 900hp at 11,810ft
Crew: 2 (pilot and radio-operator/ observer/ gunner)
Wing span: 39ft 7/16 in
Length: 27ft 10 1/4 in
Height: 10ft 11 1/2 in
Empty Weight: 3,084lb
Loaded Weight: 4,482lb
Maximum Weight: 5,071lb
Max Speed: 298mph at 13,125ft
Cruising Speed: 199mph
Service Ceiling: 37,400ft
Climb to 16,405ft in 8 min 27 sec
Range: 1,491 miles
Armament: One flexibly mounted rear-firing 7.7mm Type 89 machine-gun

Ki-15-II

Work on the Ki-15-II began in 1938, and saw the Nakajima engine of the Ki-15-I replaced by a more powerful Mitsubishi Ha-24 fourteen-cylinder radial engine. This had a smaller diameter than the earlier engine, and allowed the installation of a smaller cowling, flush with the forward fuselage. This greatly improved forward visibility. The new engine also increased the speed, climb rate and service ceiling of the Ki-15.

The prototype Ki-15-II made its maiden flight in June 1938, but the type wasn't placed into production until September 1939, as the Army Type 97 Command Reconnaissance Plane Model 2.

Engine: Mitsubishi Ha-25-I (Army Type 99 Model 1) 14-cylinder air-cooled radial
Power: 850hp at take-off, 900hp at 11,810ft
Crew: 2 (pilot and radio-operator/ observer/ gunner)
Wing span: 39ft 4 7/16 in
Length: 28ft 6 17/32 in
Height: 10ft 11 1/2 in
Empty Weight: 3,510lb
Loaded Weight: 4,826lb
Maximum Weight: 5,470lb
Max Speed: 317mph at 14,205ft
Climb to 16,405ft in 6 min 49 sec
Armament: One flexibly mounted rear-firing 7.7mm Type 89 machine-gun

Ki-15-III

The Ki-15-III was the final version of the aircraft to be developed, and was also the fastest. It was designed in 1939, and was powered by the much more powerful Mitsubishi Ha-102 radial engine. This gave it a top speed of 329mph. This was similar to the speed of the new Mitsubishi Ki-46, but the new aircraft was expected to out-perform the Ki-15-III in every other way, and so work on the Ki-15-III came to an end. 

Engine: Mitsubishi Ha-102 14-cylinder air-cooled radial
Power: 1,080hp at take-off, 1,055hp at 9,185ft and 950hp at 19,030ft
Crew: 2 (pilot and radio-operator/ observer/ gunner)
Max Speed: 329mph

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How to cite this article: Rickard, J (12 February 2010), Mitsubishi Ki-15 'Babs', http://www.historyofwar.org/articles/weapons_mitsubishi_ki-15.html

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