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Nakajima B6N Tenzan


At a time when the triumphs of the B5N were still almost three years in the future, the Japanese navy issued a specification for a replacement, recognizing that only limited overall design improvement of the B5N could be achieved in the B5N2. Accordingly design went ahead in 1939 of the Nakajima B6N and, despite the Navy's preference for the Mitsubishsi Kasei radial, a Nakajima Mamoru was selected for the prototype which flew on 14 March 1941, demonstrating several problems, notably the poor engine reliability. With the delay of 2 years, by 1943 the engine had improved to the point where serial production was allowed to start, but after only 133 B6N1s had been delivered the Navy ordered the switch to the 1,850 hp (1380 kW) Mitsubishi MK4T Kasei 25. The rest of the 1,268 B6N2s were Kasei powered.


Superficially the B6N Tenzan (Heavenly Mountain) resembled the earlier aircraft, but the much increased power and torque of the big engine and four-blade propeller was found to impose considerable directional stability problems, demanding that the vertical tail surfaces be offset to one side. Flight trials dragged on, and were further delayed by troubles during carrier acceptance tests. Then Nakajima was ordered to stop production of the Mamoru engine, so modifications had to be introduced to suit installation of the Kasei.

In due course B6N1 aircraft (of which only 133 were built) were embarked in the carriers Shokaku, Taiho, Hiyo, Junyo and Zuikaku, and took part in the Battle of the Philippine Sea of June 1943, many being lost when the three Shokaku, Taiho, and Hiyo were sunk.

In that month production started of the slightly improved B6N2 (of which 1,133 were produced before the end of the war), but the heavy losses among Japanese carriers resulted in the 'Jill' being largely deployed ashore, particularly after the Battle of Leyte Gulf. Thereafter many BSNs were consigned to the kamikaze role.




Engine: 1 x Mitsubishi MK4T "Kasei-25", 1850 hp
Wingspan: 14.9 m / 48 ft 11 in
Wing area: 37.2 sq.m / 400.42 sq ft
Length: 10.87 m / 35 ft 8 in
Height: 3.8 m / 12 ft 6 in
Empty weight: 3010 kg / 6636 lb
Max take-off weight: 5650 kg / 12456 lb
Max. speed: 480 km/h / 298 mph at 16,076 ft
Ceiling: 9040 m / 29650 ft
Service ceiling: 26,660 ft
Range w/max.fuel: 3045 km / 1892 miles
Armament: 1 x 13 mm, 2 x 7.9mm machine-guns
Bomb load: 1 x 1764 lb torpedo or 6 x 220 lb bombs
Crew: 3




Nakajima B6N Tenzan / JILL



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