B5N / B6N

The B5N or Type 97 was Japan's primary carrier based attack plane when the war began.

Concieved in 1936, the prototype of teh 'Kate' first flew in Jan. 1937. It was intended for both torpedo and level bombing, in the latter role the bombardier viewing the target through the opening of small folding doors under the fuselage. The early B5N1 aircraft flew bombing missions over China, most of them converted to B5N1-K trainers. The definitive B5N2, which first flew in Dec. 1939, equipped carrier squadrons from 1939-1940.

A total of 1,149 of both variants were build.

The low-wing monoplane had a clean configuration with a fully retractable undercarriage. The large wings folded upward for carrier stowage, arranged so that the wing tips overlapped the fuselage. The plane had a long, "greenhouse"-style cockpit. The radial engine had a variable-pitch propeller. The plane lacked armor protection for the crew and self sealing fuel tanks, hence it was highly vulnerable to allied fighters.

The B6N Tenzan (Heavenly Mountain) aircraft (Allied code name Jill) was delivered to the front line units early B6N1) and late 1943 (B6N2). It was was employed in large numbers as a torpedo aircraft and then as a kamikaze.

The 'Jill' replaced the aging B5N 'Kate' in the naval torpedo and reconnaissance roles, being generally similar but with a much more powerful engine.

Production totaled 133 of the B6N1 and 1,133 of the B6N2 variants. A B6N3, with a more powerful engine, was developed but not produced.

With a conventional carrier aircraft design, the 'Jill' was a low-wing, single-engine aircraft. It had a long, fully glazed cockpit. The lack of armor or leak-proof fuel tanks made the 'Jill' as vulnerable to allied fighters as was the 'Kate'.

TECHNICAL DATA

Description: Single-engined three-seat carrier-borne torpedo-bomber. All-metal construction with fabric-covered control surfaces.

Accommodation: Crew of three comprising pilot, observer/navigator/bomb-aimer and radio operator/gunner, in enclosed cockpit.

Powerplant:

One Nakajima Hikari 2 nine-cylinder air-cooled radial rated at 700 hp for take-off, and 800 hp at 3,500 m, driving a three-blade variable-pitch propeller (first prototype).

One Nakajima Hikari 3 nine-cylinder air-cooled radial rated at 770 hp for take-off, and 840 hp at 3,000 m, driving a three-blade constant-speed metal propeller (B5N1).

One Nakajima NK1B Sakae 11 fourteen-cylinder air-cooled radial rated at 1,000 hp for take-off, and 970 hp at 3,000 m, driving a three-blade constant-speed metal propeller (B5N2).

Armament:

One flexible rear-firing 7.7 mm Type 92 machine-gun.

Bomb-load: 800 kg of bombs or one 800 kg torpedo.

	B5N1	B5N2
Dimensions:
Span	15.52 m	15.52 m
Length	10.30 m	10.30 m
Height	3.70 m	3.70 m
Wing area	37.7 m2	37.7 m2
Weights:
Empty	2,106 kg	2,279 kg
Loaded	3,700 kg	3,800 kg
Maximum	4,015 kg	4,100 kg
Wing loading	98.1 kg/m2	100.8 kg/m2
Power loading	4.8 kg/hp	3.8 kg/hp
Performance:
Maximum speed	199 kt at 2,000 m	204 kt at 3,600 m
Cruising speed	138 kt at 2,000 m	140 kt at 3,000 m
Climb to	3,000 m	3,000 m
in	7 min 50 sec	7 min 40 sec
Service ceiling	7,400 m	8,260 m
Normal range	590 naut miles	528 naut miles
Maximum range	1,220 naut miles	1,075 naut miles

Production: A total of 1,149 B5Ns were built as follows:

Nakajima Hikoki K.K., at Koizumi:

669 B5N1, B5N1-K and B5N2 (1936-41)

Aichi Tokei Denki K.K., at Nagoya:

200 B5N2 (1942-43)

Dai-Juichi Kaigun Kokusho, at Hiro:

280 B5N2 (1942-43)

TECHNICAL DATA

Description: Single-engined three-seat carrier-borne torpedo-bomber. All-metal construction with fabric-covered control surfaces.

Accommodation: Crew of three comprising pilot, observer/navigator/bomb-aimer and radio-operator/gunner in enclosed cockpit.

Powerplant:

One Nakajima NK7A Mamoru 11 fourteen-cylinder air-cooled radial, rated at 1,800 hp for take-off, 1,750 hp at 1,400 m and 1,600 hp at 4,900 m, driving a four-blade constant-speed metal propeller (14-Shi prototypes and B6N1 Model 11).

One Mitsubishi MK4T Kasei 25 fourteen-cylinder air-cooled radial, rated at 1,850 hp for take-off, 1,680 hp at 2,100 m and 1,540 hp at 5,500 m, driving a four-blade constant-speed metal propeller (B6N2).

One 1,850 hp Mitsubishi MK4T-C Kasei 25c fourteen-cylinder air-cooled radial, driving a four-blade constant-speed metal propeller (B6N3).

Armament:

One flexible rear-firing 7.7 mm Type 97 machine-gun (14-Shi prototypes).

One flexible rear-firing 7.7 mm Type 97 machine-gun and one flexible 7.7 mm Type 97 machine-gun firing through a ventral tunnel (B6N1 and B6N2 Model 12).

One flexible rear-firing 13mm Type 2 machine-gun and one flexible 7.7 mm Type 97 machine-gun firing through a ventral tunnel (B6N2a Model 12a and B6N3).

Bomb-load: 800 kg of bombs, or one torpedo.

	B6N1	B6N2
Dimensions:
Span	14.89 m	14.89 m
Length	10.37 m	10.87 m
Height	3.70 m	3.80 m
Wing area	37.2m2	37.2m2
Weights:
Empty	3,223 kg	3,010 kg
Loaded	5,200 kg	5,200 kg
Maximum	5,650 kg	5,650 kg
Wing loading	139.8 kg/m2	139.8 kg/m2
Power loading	2.9 kg/hp	2.8 kg/hp
Performance:
Maximum speed	251 kt at 4,800 m	260 kt at 4,900 m
Cruising speed	180 kt at 4,000 m	180 kt at 4,000 m
Climb to	5,000 m	5,000 m
in	11min 1 sec	10 min 24 sec
Service ceiling	8,650 m	9,040 m
Normal range	790 naut miles	943 naut miles
Maximum range	1,861 naut miles	1,644 naut miles

Production: A total of 1,268 B6Ns were built by Nakajima Hikoki K.K. as follows:

2 14-Shi prototypes (1941-42)

133 B6N1 production aircraft (Feb 1943-July 1943)

1,133 B6N2 production aircraft (June 1943-Aug 1945)

(2) B6N3 prototypes (modified from B6N2 airframes)

Of the 1,266 production B6N1s and B6N2s built, 296 were built in the Koizumi plant and 970 in the Handa plant.