The Mitsubishi K3M 'Pine' was a single-engined crew trainer that also saw service as a light liaison aircraft during the Pacific War. Mitsubishi had first tried to sell a single-engined crew trainer in 1928-29, but this Herbert Smith designed biplane had not been a success.
It was followed by the Ka-2, a new design produced by Eng Hattori. His aircraft was a high-wing parasol monoplane, with a fabric covered metal fuselage and powered by a 340hp Hispano-Suiza V8 inline engine produced by Mitsubishi. The aircraft had an open cockpit for the pilot and a second for the gunner, and an enclosed cabin for an instructor and two pupils.
The first prototype, which was completed in May 1930, was somewhat disappointing, suffering from poor stability in the air and engine vibration. The second prototype was identical, but the third and four introduced dihedral on the wings, which improved the aircraft's stability in flight. The vibration problems remained, but these were solved on the K3M2 by replacing the V8 engine with a 340hp Hitachi Amakaze 11 radial engine. This version of the aircraft was accepted for production as the Navy Type 90 Crew Trainer Model 1.
The K3M was used as a crew trainer throughout the Second World War. It was also used as a light transport and liaison aircraft. Many of the 624 aircraft produced survived the war and were used in similar roles by a number of Asian countries.
The K3M1 was the designation given to the four prototypes of the K3M.
K3M2 Navy Type 90 Crew Trainer Model 1
The K3M2 was the first production version of the aircraft. It was powered by a 340hp Hitachi Amakaze 11 radial engine, but was otherwise similar to the last prototypes. The first 70 K3M2s were built by Mitsubishi, but the last 247 aircraft were produced by Aichi.
The final production version was the K3M3, which was built by K.K. Watanabe Tekkosho. This version used the 580hp Nakajima Kotobuki 2 KAI 2 radial engine, and had larger tail surfaces that had first been used on the civil MS-1, itself a conversion of the second Ki-7 prototype. A total of 301 K3M3s were built between 1939 and 1941.
This designation was given to a small number of aircraft that were modified to carry either five passengers or a light cargo in the enclosed cabin.
The designation Ki-7 was given to two prototypes produced for the Japanese Army. No production aircraft followed.