In 1939 a requirement, 14-Shi, was given by the Imperial Japanese Navy and the Mitsubishi J2M Raiden was designed for it by Jiro Hirikoshi. Development started in October 1938, but was delayed a year while Mitsubishi concentrated on the A6M Zero.
The 14-Shi requirements were:
- Speed at 19,685' / 6,000 m: 373 mph / 600 kph
- Climb to 19,685' / 6,000 m: 5 1/2 minutes
- Landing speed: 81 mph / 130 kph
- Endurance: 45 minutes
- Armor behind pilot's seat
The J2M was to be a land based fighter for the Imperial Japanese Navy. It was to have more speed and climb than maneuverability as previous designs. Many felt it was the best of the land based Navy fighters produced by Japan during World War II.
There were issues with the early engines and they were replaced by the Mitsubishi MK4R-A Kasei 23a (1,800 HP) which had water injection to temporarily increase speeds when needed. However, the water injection has problems of its own.
To reduce the amount of drag an extension shaft was added to allow for a more tapered cowling.
Tail Wheel Problems
In 1943 there were two accidents with J2M2s that was caused by the mechanism that retracted the tail wheel had been installed incorrectly. The mechanism, in a dive, would block the controls.
To help the J2M fight the B-29 bombers at altitude two upward firing 20 mm guns were installed.