The Nakajima B5N (, Allied reporting name "Kate") was the standard carrier-based torpedo bomber of the Imperial Japanese Navy (IJN) for much of World War II. It also served as a high level bomber.

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, when 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 (九七式艦上攻撃機) (kyū-nana-shiki kanjō kōgeki-ki or kankō for short).

Combat experience during the Second Sino-Japanese War 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 unremedied, this version replaced the B5N1 in production and service from 1939.

Equipment

The navigator/bombardier/observer position was equipped with a Type 90 bombsight, which was a long vertical tube located in the front-left of the seat. There was also a Type 3 reflector compass for precise navigation that was mounted on the top of the cockpit frame. The radio-operator/gunner position was equipped with one of the standard-issue radio sets for navy three-seater aircraft (Type 96 Mk3 earlier and Type 2 Mk3 later) that was mounted in front of the radio-operator/gunner's seat and behind the navigator/bombardier/observer's seat.

The radio-operator/gunner also operated one flexible 7.7 mm (.303 in) Type 92 machine gun at the rear end of the cockpit. One Type 91 torpedo could be mounted on the racks that were fixed eccentrically to the right at the bottom of the fuselage. Alternatively, racks could be replaced to carry either one 800 kg bomb (e.g., Type 99 No 80 armor-piercing bomb) or two 250 kg bombs (e.g., Type 98 No 25 land bomb) or six 60 kg bombs (e.g., Type 2 No 6 land bomb). Replacing the racks and exchanging between the torpedo and bombs was not a trivial process and could take more than two hours to complete.

Initially, most of the B5N bombers were painted in silver, which was the color used throughout the early stages of the Second Sino-Japanese War. The color eventually changed to dark green before the start of the Pacific War.

Operational history

The B5N was primarily employed as a carrier-based aircraft and occasionally as a land-based bomber. It carried a crew of three: pilot, navigator/bombardier/observer, and radio-operator/gunner. Like with other IJN multi-seat aircraft, an individual bomber was commanded by the senior ranking crew member aboard, which could be the observer rather than the pilot.

The initial model B5N1 first saw action in the Second Sino-Japanese War in 1938. The updated B5N2 played a major role in the Attack on Pearl Harbor. One of the B5N2s carried Mitsuo Fuchida, the commander of the attack, with one high-level bomber from the carrier  credited with sinking the American battleship . The B5N2 torpedo bombers also sank the battleships , ,  and . 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 carrier  at the Battle of the Coral Sea and the aircraft carrier  at the Battle of the Santa Cruz Islands, and the disabling of the aircraft carrier  at the Battle of Midway, later sunk by the .

B5N2 torpedo bombers normally performed a coordinated attack on enemy carriers with Aichi D3A dive bombers. Ideally, dive bombers would help to suppress the ship's anti-aircraft fire, which improved the chances of success for the slow-flying torpedo bombers. During the Battle of the Eastern Solomons, the IJN tried to minimize losses to torpedo bombers and initially sent only the dive bombers to attack and cripple US carriers for the subsequent torpedo strike, this proved unsuccessful, as the torpedo bombers did not launch until the battle was over.

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 defense of the Philippines in October 1944, suffering severe losses. Later in the war, they were used for kamikaze attacks.

Variants
Type K: Prototype.
B5N1: First production model.
B5N1-K: Many B5N1s were converted into advanced training aircraft.
B5N2: Improved version.

Operators

 Imperial Japanese Navy

Surviving aircraft

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. Canadian Car and Foundry "Harvard" - a variant of the North American T-6 Texan trainers, 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.

One recovered B5N2 is at the Wings Museum in Balcombe, West Sussex, UK. This large portion was recovered from the Kuril Islands by a British private collector in 2003.

A B5N was unveiled at the Pacific Aviation Museum in Honolulu, Hawaii on 18 April 2016.

Specifications (Nakajima B5N2)

See also

References

Notes

Bibliography
 Angelucci, Enzo and Paolo Matricardi. World Aircraft: World War II, Volume II (Sampson Low Guides). Maidenhead, UK: Sampson Low, 1978. .
 
 
 Francillon, René J. Japanese Bombers of World War Two, Volume One. Windsor, Berkshire, UK: Hylton Lacy Publishers Ltd., 1969. .
 
 
 .

External links

 https://www.pearlharboraviationmuseum.org/pearl-harbor-blog/nakajima-b5n2/ 
 Nakajima B5N, Joao Paulo Julião Matsuura
 Pictorial of B5N in multiplayer air-combat simulation of Battle of Coral Sea.

Low-wing aircraft
Carrier-based aircraft
B05N, Nakajima
B5N, Nakajima
B05N
Attack on Pearl Harbor
Single-engined tractor aircraft
Aircraft first flown in 1937
Retractable conventional landing gear
나카지마 97식 함상공격기는 보통 "97식 함공"이라 불린 일본 해군 항공대의 함상공격기로 1935년에 개발되어 항공모함에서 운용한 공격기이며, 진주만 공격 당시 주력 기종이었다. B5N이라는 제식명을 가졌으며, 케이트(Kate)는 미국이 붙인 식별 기호였다. 명칭은 공격기로 되어 있으나, 폭격기로 분류한다. 97식 함공은 동급인 영국의 소드피쉬 어뢰공격기나 미국의 TBD 디베스테이터보다 빠른 속도를 가졌으며 전체적인 성능이 우위였다. 97식 함상공격기는 전쟁 전 기간 동안 사용되었으나, 전쟁 중에 주적인 미국의 함재기들의 성능이 발전하고 방어력에 문제를 드러내면서 전쟁 후반에는 일본 본토에서 해안 정찰이나 대잠수함전을 수행하며 보냈고, 일부는 가미카제 자살특공대용으로 전용되어 사라져갔다.

개발 
97식 함공은 요코스카 B4Y를 대체하려는 일본 제국 해군의 요구를 나카지마 회사가 받아들여 가즈치 나카무라(Katsuji Nakamura)를 책임팀장으로 한 설계팀이 개발했다. 1935년, 일본 제국 해군은 B4Y 어뢰공격기의 성능에 불만을 가지고, 고성능 단엽기 개발을 요구했다. 이미 함재기 중에 단엽 전투기를 운용해본 결과, 충분히 가능하다는 결론을 내렸기 때문이었다 나카지마 사는 이에 따라 항공모함 운용을 전제로 양 주익을 거의 완전히 접을 수 있도록 한 저익 단엽기를 설계했다. 또, 항공모함 격납고에서 갑판으로 올리고 내리는 엘리베이터에 맞게 길게 동체를 설계했다. 개발 초기에는 K형(Type K)라는 이름이 붙여졌으며 미츠비시에서 개발한 B5M과 경쟁 기종이 되었다.

최초의 시제품은 1937년 1월에 등장했다. 시제품은 일본 해군이 요구했던 370km/h보다 그 이상의 속도를 발휘하여 소비자들을 만족시켰다. 속도 외에 전반적인 비행 성능도 양호했으나 일본 해군은 신기술을 많이 쓴 것을 걱정했고, 나카지마 사는 일본 해군의 의견에 따라 양산형에서는 항공모함에서 간단하게 수리/정비가 가능하도록 개수했다. 특히 주익의 경우, 시제품에서는 유압식이었으나, 일본 유압 기술의 문제점때문에 양산형에서는 유압 방식을 폐지하고 수동으로 접고 펴도록 바꾸었다.

이후 이 항공기는 나카지마 B6N의 기본 모체가 되었고, 전쟁 중후반에는 훈련용, 훈련용 목표물 예인용, 또는 대잠수함전에 이용되었다. 1,150대가 생산되었으나 현재 당시 사용된 기체로 남아있는 것은 없고, 2003년에 영국인 개인 수집가가 복원한 기체가 있다.

운용 
양산형은 항공모함에 배치되기 시작했고, 1938년에는 중일 전쟁에 투입되었다. 실전 운용 결과 초기형(1형)은 몇 가지 약점을 드러냈다. 주로 방어력 부족 문제가 있었는데, 승무원 구역 및 연료 탱크에 관심이 집중되었다.

특징 

승무원 3명은, 조종사/폭격수/관측수로 구성되어 있으며, 루이스 경기관총(루식 기관총)은 후방석 관측수가 담당하고, 폭격수는 중앙에 앉았다. 주로 항공모함에서 운용했으나, 육상 기지에서 운용하기도 했다. 중일 전쟁 중에는 상대할 중국 해군이 거의 없었기 때문에 주로 800 kg 폭탄을 장착하고 지상 목표물 공격 임무에 투입되었으며, 태평양 전선에서는 폭탄과 어뢰를 모두 운용했다.

제원 
 승무원: 3명
 길이: 10.30 m (33' 10")
 날개 너비: 15.52 m (50' 11")
 높이: 3.70 m (12' 2")
 날개 면적: 37.7 m² (406 ft²)
 비무장 상태 중량: 2,279 kg (5,024 lb)
 무장 만재 상태 중량: 3,800 kg (8,380 lb)
 최대 이륙 중량 : 4,100 kg (9,040 lb)
 동력: 1× 나카지마 사카에 11형 엔진, 750 kW (1,000 hp)
 최대 속도 : 367 km/h (229 mph)
 항속 거리 : 1,935 km (1,202 mi)
 비행 고도 : 8,260 m (27,100 ft)
 초당 상승 속도: 6.5 m/s (1,283 ft/min)
 익면하중: 101 kg/m² (21 lb/ft²)
 무장 : 후방석 7.7mm 92식 루식 기관총(루이스 경기관총). 97발들이 탄창 사용
 폭탄 : 91식 항공어뢰 1발 (800 kg) 또는 250 kg 폭탄 3발 또는 60 kg 폭탄 6발.

파생형 

 Type K : 시험 생산형
 B5N1 : 초도 양산형
 B5N1-K : 성능 향상형
 B5N2 : 많은 B5N1이 훈련용 항공기로 개조되었다.

영화 속 97식 함공 
영화 《진주만》이나 《도라 도라 도라》 등에 나온 97식 함공은 BT-13 밸리언트를 그럴듯하게 외관을 97식 함공으로 개조한 것이다.

각주 

제2차 세계 대전의 일본 폭격기
1937년 첫 비행한 항공기
진주만 공격
저익기