The Nakajima B4N Experimental 9-Shi Carrier Attack Aircraft was an unsuccessful Nakajima entry in a 1934 carrier bomber contest. This followed on from a 7-Shi Carrier Attack Aircraft contest of 1932 which had failed to produce a workable aircraft. Nakajima, Mitsubishi and Kusho all entered designs for the new contest. The Navy wanted a standard biplane, and Nakajima produced an aircraft with a welded steel tube fuselage, wooden wing structures and a fabric covering. The wings could be folded backwards.
Nakajima and Mitsubishi (the Mitsubishi B4M) produced their aircraft on time, with Nakajima building two prototypes of the B4N in 1936. Kusho delayed their design for long enough to adopt the more successful features of their rivals. This gave their design an edge, and in November 1936 it was adopted as the Type 96 Carrier Attack Aircraft.
Nakajima weren't entirely losers from this process. Production of the new Kusho B4Y was split between them, Mitsubishi and the Hiro Naval Arsenal, so they did gain some work from the project. The new aircraft had a very short service career and none were left in front line service by December 1941.
Engine: Nakajima Hikari 1 nine-cylinder air-cooled radial engine
Armament: Two 7.7mm machine guns, one fixed forward firing and one flexibly mounted
Bomb load: One 1,763lb torpedo, one 1,102lb, two 551lb bombs or six 66lb bombs