|Nakajima B5N2 "Kate" in flight|
|Role||Carrier-based torpedo bomber|
|Manufacturer||Nakajima Aircraft Company|
|Primary user||Imperial Japanese Navy|
Although the B5N was substantially faster and more capable than its Allied counterparts, the American Douglas TBD Devastator monoplane (the U.S. Navy's first all-metal, carrier-borne monoplane of any type with retracting gear), and the British Fairey Swordfish and Fairey Albacore torpedo biplanes, it was nearing obsolescence by 1941. Nevertheless, the B5N operated throughout the whole war, due to the delayed development of its successor, the B6N. In the early part of the Pacific War, flown by well-trained IJN aircrews and as part of well-coordinated attacks, the B5N achieved particular successes at the battles of Pearl Harbor, Coral Sea, Midway, and Santa Cruz Islands.
Design and development
The B5N was designed by a team led by Katsuji Nakamura in response to a 1935 specification by the Navy for a torpedo bomber to replace the Yokosuka B4Y. Internally designated Type K by Nakajima, it successfully competed with the Mitsubishi B5M for a production contract. The first prototype flew in January 1937 and was ordered into production soon afterwards with the full designation Type 97 Carrier Attack Bomber (kyū-nana-shiki kanjō kōgeki-ki or kankō for short  九七式艦上攻撃機).
The B5N soon saw combat, first in the Sino-Japanese War, where combat experience revealed several weaknesses in the original B5N1 production model. These were mainly concerned with the lack of protection that the design offered its crew and its fuel tanks. Keen to maintain the high performance of the type, the Navy was reluctant to add weight in the form of armor, and instead looked to obtaining a faster version of the aircraft in the hopes of outrunning enemy fighters. The B5N2 was given a much more powerful engine - Nakajima's own Sakae Model 11, 14-cylinder twin-row radial, as used in the initial models of the Mitsubishi A6M fighter — and various modifications were made to streamline it. Although its performance was only marginally better, and its weaknesses remained un-remedied, this version replaced the B5N1 in production and service from 1939.
It was this version that would be used by the Navy in the attack on Pearl Harbor. The B5N2 Kate carried Mitsuo Fuchida, the commander of the attack, with one from the carrier Hiryu credited with sinking the battleship Arizona. Five torpedo bombers were shot down in the first wave. Apart from this raid, the greatest successes of the B5N2 were the key roles it played in sinking the United States Navy aircraft carriers Lexington and Hornet, and the disabling of the Yorktown, which led to its sinking by the Japanese submarine I-168.
The B5N served as the basis for a follow-on design, the B6N, which eventually replaced it in front line service. The B5N continued to fly in secondary roles, such as training, target towing, and anti-submarine warfare. Some of the aircraft used for this latter purpose were equipped with early radars and magnetic anomaly detectors. B5Ns were also used as bombers during the unsuccessful defence of the Philippines in October 1944, suffering severe losses. Later in the war, they were also used for kamikaze attacks.
- Type K:Prototype.
- B5N1:First production model.
- B5N1-K:Many B5N1s were converted into advanced training aircraft.
- B5N2:Improved version.
None of the 1,150 production B5Ns survived World War II intact. Only two partially-recovered B5Ns are known to exist, neither of them airworthy.
Replicas of the B5N2s were made using stretched fuselages from U.S. North American T-6 Texan trainers, and Aichi D3A dive bombers were created using BT-13 Valiant training aircraft, which were modified to represent Japanese aircraft for the movie Tora! Tora! Tora!, and have been used in a number of movies and airshows since to depict the aircraft.
Specifications (Nakajima B5N2)
Data from Japanese Aircraft of the Pacific War 
- Crew: 3
- Length: 10.3 m (33 ft 10 in)
- Wingspan: 15.518 m (50 ft 11 in)
- Wing area: 37.7 m2 (406 sq ft)
- Airfoil: root: NN-5 mod (16%) ; tip: NN-5 mod (8%)
- Empty weight: 2,279 kg (5,024 lb)
- Gross weight: 3,800 kg (8,378 lb)
- Max takeoff weight: 4,100 kg (9,039 lb)
- Powerplant: 1 × Nakajima Sakae 11 14-cylinder air-cooled radial piston engine, 750 kW (1,000 hp) for take-off
- 720 kW (970 hp) at 3,000 m (9,843 ft)
- Propellers: 3-bladed constant-speed metal propeller
- Maximum speed: 378 km/h (235 mph, 204 kn) at 3,600 m (11,811 ft)
- Cruise speed: 259 km/h (161 mph, 140 kn) at 3,000 m (9,843 ft)
- Range: 978 km (608 mi, 528 nmi)
- Ferry range: 1,991 km (1,237 mi, 1,075 nmi)
- Service ceiling: 8,260 m (27,100 ft)
- Rate of climb: 6.5 m/s (1,280 ft/min)
- Time to altitude: 3,000 m (9,843 ft) in 7 minutes 40 seconds
- Wing loading: 100.8 kg/m2 (20.6 lb/sq ft)
- Power/mass: 0.196 kW/kg (0.119 hp/lb)
- Guns: 1 × 7.7 mm Type 92 machine gun 'Ru' (Lewis) in rear dorsal position, fed by hand loaded drum magazines of 97 rounds. A number of B5N1s were equipped with 2 × 7.7 Type 97 machine guns in the wings.
- Bombs: 1 × 800 kg (1,760 lb) type 91 torpedo or 1 × 800kg (1,760lb) bomb or 2 × 250 kg (550 lb) bombs or 6 × 60 kg (132 lb) bombs
Aircraft of comparable role, configuration and era
- Angelucci, Enzo (1988). Combat aircraft of World War II. p. 18. ISBN 0-517-64179-8.
- Parshall and Tully 2007, p. 80.
- Francillon 1970, pp. 412–413.
- "Nakajima B5N2 'Kate' Unveiled at Pacific Aviation Museum Pearl Harbor". Warbirds News. Warbirds News. 21 April 2016. Retrieved 29 April 2016.
- Francillon 1970, p. 416.
- Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
- Wieliczko, Leszek (in Polish). Nakajima B5N (Kate). „Lotnictwo” No. 5/2018(199), p. 87.
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