Nakajima B5N (Kate) History

The Nakajima B5N series of torpedo bombers originating from Japan were considered the best of their type anywhere in the world by the time of the American entry into the conflict during late-1941. The aircraft saw development against an Imperial Japanese Navy (IJN) requirement in 1935 and a first-flight followed in January of 1937. It was in operational service at the outbreak of World War 2 (1939-1945) and was one of the more crucial and effective aircraft deployed by the Japanese Navy in its various attacks - including the assault on Pearl Harbor, Hawaii in December of 1941. The B5N was produced across 1,149 examples and saw service through most of the global conflict.

The aircraft's general arrangement was conventional for the period and fitted the single air-cooled radial engine in the nose. The wing mainplanes were low-mounted along the fuselage sides and fitted slight ahead of midships. The tail used a single vertical plane with two low-mounted horizontal planes. The crew of three - pilot, bombardier-navigator, and rear machine gunner - were seated in line under a long-running "greenhouse-style" canopy. The main legs of the undercarriage were retractable and the tail wheel stayed exposed during flight.

The B5N was powered by a single in-house Nakajima radial piston engine - B5N1 models were given "Hikari" radials while B5N2s carried "Sakae 11" radials of 1,000. The B5N2 managed a maximum speed of 235 miles-per-hour, ranged out to 1,240 miles, and could reach a service ceiling of 27,100 feet.

Armament consisted of a single 7.7mm Type 92 machine gun set on a trainable mounting at the rear gunner's position. Some B5N1 models were equipped with 2 x 7.7mm Type 97 machine guns in the wings for a broader frontal "punch". For offensive work, the aircraft was cleared to carry a single Type 91 torpedo of 1,760lb or, in its place, 2 x 550lb bombs along with 6 x 295lb bombs for conventional bombing sorties.

The initial B5N form became the "Type K" prototype of 1937 and this was followed in 1938 by combat-quality B5N1 production models. The B5N1-K designation was used to signify B5N1s converted for the training role. The improved B5N2 - with more powerful Sakae engines and smaller cowlings - appeared in 1939 and marked the final production form.

Initial combat actions placed the B5N over China and these were used both as carrier-based attackers and land-based warplanes. The aircraft was quick to earn the respect of the world with its striking ability and accuracy and made up a portion of the Japanese attack force used at Pearl Harbor on December 7th, 1941. At least 144 B5N2 aircraft took part in the assault. The aircraft would find future successes at Coral Sea, Midway, and over the Santa Cruz Islands in the campaigns that followed - destroying many Allied vessels across the Pacific Theater and credited with the sinking of the important American aircraft carriers USS Hornet, USS Lexington, and the USS Yorktown.

Once Allied pilots became combat-tested and handed much improved fighters, the B5N's inherent deficiencies shown through - they were weakly-armed defensively, poorly protected overall, and suffered from weight issues when carrying their potent war loads. This meant that those unlocky enough to find themselves in the crosshairs of Allied gunners could very easily fall prey. As such, losses began to mount and the last major engagements involving B5N aircraft were recorded over the Philippine Islands during 1944. The series was being phased out towards the end of the war but active aircraft - due to their still-excellent operational ranges - were used in non-direct-combat roles such as anti-ship, reconnaissance, and maritime patrol sorties. Some were featured as Kamikaze attackers leading up to the war's final months.

The Nakajma B6N "Jill" (detailed elsewhere on this site) became the B5N's direct successor and appeared in August of 1943. It was produced to the tune of 1,268 examples and managed its own wartime combat record.

Nakajima B5N (Kate) Specification


Retired, Out-of-Service


[ 1,149 Units ]:
Nakajima - Imperial Japan


- Ground Attack

- Navy / Maritime

- Training



33.79 ft (10.3 m)


50.92 ft (15.52 m)


12.14 ft (3.7 m)


Empty Weight:

5,024 lb (2,279 kg)


9,039 lb (4,100 kg)

(Diff: +4,015lb)


1 x Nakajima NK1B Sakae 11 radial piston engine developing 1,000 horsepower.


Maximum Speed:

235 mph (378 kph; 204 kts)

Service Ceiling:

27,100 feet (8,260 m; 5.13 miles)

Maximum Range:

1,237 miles (1,990 km; 1,075 nm)


1,230 ft/min (375 m/min)



1 x 7.7mm Type 92 machine gun in trainable position at rear cockpit.

2 x 7.7mm Type 97 machine guns in wings (some B5N1 models).


1 x 1,760 lb torpedo OR 2 x 550lb bombs with 6 x 295lb bombs.


B5N - Base Model Series Designation

Type K - Prototype Designation

B5N1 - Initial Production Model

B5N1-K - B5N1 aircraft converted for the training role.

B5N2 - Improved B5N1 with Sakae 11 radial engine and revised engine cowling.

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