B6N (Family)

Visual comparison of the Nakajima B6N bombers

Description

The Nakajima B6N designated as Tenzan is a faster, longer-range carrier-based attack bomber to replace the Nakajima B5N used by the Imperial Japanese Navy in World War II.

Nicknames being:

• ▅ - Tenzan (天山, Heavenly Mountain)
• ▃ - Jill

Vehicles

Rank II

• B6N1 Model 11 - Tenzan Model 11
• B6N2 Model 12 - Tenzan Model 12
• B6N2a Model 12Ko - Tenzan Model 12 Ko

History

Design

The B6N had a maximum range of around 1,700 km with a service ceiling of about 9,000 m. The plane itself had a total length of around 10.8 m and a total weight of 3,010 kg. The reliability of the B6N in the field was excellent, thanks to the engine power being much better than the B5N.

Development

From 1939, the navy requested a new torpedo bomber to replace the quickly ageing B5N.

The design team, led by Matsumura Kenichi, met the 1939 Navy specification to replace the B5N almost entirely by using a much more powerful engine and tweaked wing design.

Stowage restrictions on carriers ruled out significant improvements in the airframe, other than eliminating the forward sweep of the vertical tail surface on the B6N. Like the B5N, the B6N had no bomb bay, carrying its torpedo under the fuselage offset to the side (to clear the oil cooler).

The prototypes were ready in the spring of 1941, but it was found that the vertical tail surface had to be tilted slightly to compensate for propeller torque. The modified aircraft handled well, but the Nakajima NK7A Mamoru engine had serious teething problems as Nakajima was stubborn on using an engine of own design instead of complying with the navy's suggestion of using the Mitsubishi Kasei engine, and carrier acceptance trials at the end of 1942 showed the landing hook was too weak. Carrier trials were completed in early 1943, and the aircraft was finally accepted for production.

Even then, there were reports of rudders tearing loose during takeoff due to turbulence from the engine, requiring further redesign of the rudders.

But because of the complications of the engine hurt the economic side of the production and thus outweighed the benefits of its reliability and long-range. The full-scale production of the B6N could only be introduced by 1943. In the end, Nakajima grudgingly agreed to replace its own engine with that of Mitsubishi to allow full production.

Combat History

After the B6N1 was introduced in mid-1943, examples were immediately issued to the last remaining aircraft carrier groups, such as on the Japanese carrier Zuikaku. By late 1943, the B6N2 was in full service within naval and land-based units around the south pacific, even though it still didn't immediately replace all older B5Ns in service.

With the fewer remaining Japanese carriers, the B6N was used often from land-based units, with prime examples being its debut year seeing first combat at Bougainville in November 1943, operating from land bases around Rabaul. It was so common for B6Ns to be used as a regular bomber instead of a carrier-based bomber that Nakajima had to revise a 3rd model of the B6N, being the B6N3 to have a modified undercarriage to give it a better rough field capability. However, this variant didn't get produced as the war ended.

By 1944, B6N's operating from Japanese carriers engaged in the Battle of the Philippine Sea, but with the lack of experienced Japanese pilots, allied air power and air defence, little damage was sustained to enemy ships and results were averaged for the B6N.

By late 1944/1945, like most Japanese aircraft, the B6N was launched from land-based airfields to be used as Kamikaze as a last resort of the plane, as chances of coming back from a conventional attack were already as slim.

Variants

B6N1 mod. 11

Prototype stage of 2 planes fitted out with the Nakajima NK7A Mamori 11 engine. Production of the B6N1 went up to 133.

B6N2 mod. 12

Main production variant of the B6N featuring a Mitsubishi MK4T Kasei 25 engine. 1,131 Built as B6N2/B6N2a

B6N2a mod. 12A

Revised tail armament, 7.7 mm Navy Type 92 was replaced with a 13 mm Navy Type 2.

B6N3 mod.13

Performance improved by using the Mitsubishi MK4T-B Kasei 25b. Modified landing gear for land-based take-off and landing. 2 prototypes built.

Japan bombers
Navy
Carrier-based attack bomber
B5N	B5N2
B6N	B6N1 · B6N2 · B6N2a
B7A	B7A2 · B7A2 (Homare 23)
Carrier-based dive bomber
D3A	D3A1
D4Y	D4Y1 · D4Y2 · D4Y3 Ko
Shipboard Observation seaplane
F1M	F1M2
Land-based Attack bomber
G4M	G4M1
G5N	G5N1
G8N	G8N1
Flying boat
H6K	H6K4
H8K	H8K2 · H8K3
Land-based Bomber
P1Y	P1Y1
Army
Light	Ki-32
	Ki-48-II otsu
Heavy	Ki-21-Ia · Ki-21-I hei
	Ki-49-I · Ki-49-IIa · Ki-49-IIb · Ki-49-IIb/L
	Ki-67-I Ko · Ki-67-I otsu
Other countries	▅B-17E