Aviation of World War II

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B4Y1 Jean
Shipborne Torpedo Bomber

B4Y Jean

B4Y1 Jean. Type 92 - Shipborne torpedo bomber. It was developed according to the 9 C specification, having won a competition with Mitsubishi and Nakajima, chief designer Sanae Kawasaki. The first flight of the prototype took place in late 1935, production began in November 1936, codenamed Jean.

Power plant. 9-cylinder radial air-cooled Nakajima Hikari-2 engine, maximum power 840 hp. with. with a two-bladed wooden propeller. (The prototype was powered by a liquid-cooled Hiro type 91-1 V-type 620 hp engine)

Armament. One 7.7 mm type 92 machine gun on a turret, up to 500 kg of bombs on an external sling, or one 800 kg torpedo.

Combat use. Until 1940, B4Y1, operating from the aircraft carriers "Hosho", "Akagi", "Kaga", "Soryu", "Ryuyo" and "Unyo" took part in hostilities against China. Due to their obsolete design, they did not correspond to the level of the fighter Mitsubishi A5M , which complicated the interaction of individual parts of carrier-based aircraft, so soon B4Y1 began to be transferred to land bases. By the end of 1941, only the oldest aircraft carrier, Hosho, had 8 B4Y1s on board, but she was soon rearmed with more modern torpedo bombers Nakajima B5N2. Subsequently, the remaining vehicles were used as training aircraft at the Suzuka airbase and in the second line from the training aircraft carriers "Hosho" and "Unyo" until 1943.

The aircraft were produced at the factories of Mitsubishi, Nakajima and the Imperial Navy's aviation arsenal in Hiro. A total of 205 aircraft were built.

Yokosuka B4Y1
Crew 3
Wing span, m 15
Wing area, m² 50.00
Length, m 10.15
Height, m 4.36
1×PE Nakajima Hikari-2
Power, hp. 840
Weight, kg:
Empty weight
Loaded weight 3,600
Maximum speed, km/h 278
Maximum rate of climb, m/min 215
Service ceiling, m 6,000
Service range, km 1,580

Photo Description
Drawing B4Y1

Drawing B4Y1

B4Y1 in flight

B4Y1 in flight


  • "Encyclopedia of military engineering " /Aerospace Publising/
  • "Japan Warplanes of World War II" /Oleg Doroshkevich/