In May 1935 the Imperial Japanese Army Air Force instituted a modernization plan and the Mitsubishi Ki-30 was a result of that program.
Koku Hombu ordered Mitsubishi and Kawasaki to make two prototypes of a light bomber by December 1936 that met these specifications:
- Speed: 248.5 mph / 400 kph at 9,845' / 3,000 m
- Climb to 9,845' / 3,000 m in 8 minutes
- Engine: One Mitsubishi Ha-6 or Nakajima Ha-5 radial engine or Kawasaki Ha-9-IIb water cooled
- Bomb Load: 992 lb / 450 kg
- Armament: 1 forward firing and 1 rear firing machine guns
- Crew: 2
- Weight: not to go over 7,275 lb / 3,200 kg
The Mitsubishi Ki-30 was designed under the direction of Colonel Komamura by Kawano, Ohki, and Mizuno.
The Mitsubishi Ki-30 was the first light bomber to have a two row radial engine, internal bomb bay, flaps, and a constant / variable speed propeller.
The Ki-30 was of all metal construction with fabric over the control surfaces.
Due to the mid wing design, the landing gear had to have long legs. The original design had retractable landing gear, but due to complexity and added weight it was decided to have fixed legs that included spats.