In 1932 a 7-Shi requirement was issued and Aichi, Mitsubishi, and Nakajima made prototypes. However, none of these were satisfactory to the Imperial Japanese Navy.
A 9-Shi requirement was issued and the Navy Type 96 Carrier Attack Bomber (B4Y1) was developed and produced but it was to be just an intermediary before a more modern plane was designed.
The Nakajima B5N was designed to a 10-Shi requirement issued in 1935. These were:
- Span of 52 ' / 52' 5.90625" / 16 m that could be folded to 24' / 24' 7.28125" / 7.5 m
- Armament of one 1,764 lb / 800 kg torpedo or bomb load and one 7.7 mm machine gun
- Speed of 207 mph at 6,560' / 2,000 m
- Endurance of 4 hours at 155 mph
The design team was headed by Katsuji Nakamura.
The wings were foldable for storage on a carrier. They also had Fowler flaps.
Unusual for a plane, much less a carrier plane, at the time, the B5N had an inward retracting landing gear.
The fuselage was all metal stressed skin.
The engine drove a variable pitch propeller.
1941 Torpedo Bomber Comparison