Nakadžima B5N Kankó [Kate]

Nakajima B5N Kankō - přehled verzí

Nakajima B5N1 - version overview


中島 B5N - 九七式艦上攻撃機 - kyū-nana-shiki kanjō kōgeki-ki - Type 97 deck attack aircraft


Japanese name: 艦攻 Kankō (unofficial designation)


Allied code name: Kate



DesignationAircraft design - description
Nakajima B5N1 10-Shi In 1936, a prototype was produced with a nine-cylinder Nakajima Hikari 2 engine with 800 hp.
Nakajima B5N1 11 mass production from 1938 to 1939; Nakajima Hikari 3 engines with 840 hp
Nakajima B5N1-K several bombers were modified for continued training
Nakajima B5N2 12 final version, production from 1939, Nakajima NK1B Sakae 11 engine with 1,000 hp



A total of 1,149 aircraft of this type were produced.


The production of prototypes took place in factories:
中島飛行機株式会社 - Nakajima Hikōki Kabushiki Kaisha, Ota , 669 prototype aircraft, B5N1 and B5N2
愛知航空機株式会社 - Aichi Kōkūki Kabushiki Kaisha, Nagoya , 200 aircraft B5N2 and
第十一海軍航空廠 - Dai-Jūichi Kaigun Kōkū-shō, Hiro , 280 B5N2 aircraft



Sources used:
Tadeusz Januszewski and Kryzysztof Zalewski, Japońskie samoloty marynarski 1912-1945 díl 2, Lampart, 2000, ISBN 83-86776-00-05
http://www.combinedfleet.com/ijna/b5n.htm
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Nakajima B5N - type history


10-Shi specifications
Based on the need for new aircraft types, the Japanese Naval Air Command (大日本帝國海軍航空隊 - Dai-Nippon Teikoku Kaigun Kōkū-tai) developed its technical specifications for the 10-Shi in 1935. Through them, it informed the aircraft manufacturers of the requirements it had for new aircraft of these categories:
1. the B-category B-deck torpedo bomber (B5M1 and B5N1)
The 2nd C-category C-category C airborne reconnaissance aircraft (the specifications have been handed over to the Nakajima Hikoki K.K. factory and two prototypes C3N1 are being built)
3rd floatplane observation aircraft of F category (F1A1, F1K1 and F1M)


The competition for the deck torpedo bomber was entered by 三菱重工業 - Mitsubishi Jūkōgyō Kabushiki Kaisha (hereafter Mitsubishi), its aircraft B5M1 was conceived more conservatively than a competing project B5N1 10-Shi by 中島飛行機株式会社 - Nakajima Hikōki Kabushiki Kaisha (hereafter Nakajima). The latter began work on two new projects for the naval aviation in 1936, firstly a deck reconnaissance aircraft, this was given the designation project "S", the naval aviation adopted it under the abbreviated designation C3N1 and then it was project "K", which was a deck torpedo bomber project.


Project "K" was worked on by a design team led by Katsuji Nakamura. The specifications for this aircraft called for the main characteristics of the future aircraft. The new bomber was to be single-plane, a crew of three was required, the wingspan was not to exceed 16 m, and the wings had to fold so that the width of the folded machine was no more than 7.5 m. The aircraft had to be able to carry a Type 94 torpedo or 800 kg bombs (at least two 200 kg bombs were required), the maximum speed had to be at least 333 km/h at an altitude of 2,000 m, the flight endurance 4 hours with bombs suspended and up to 7 hours without suspended armament at economic speed. Furthermore, the aircraft was required to be capable of night operations. The engine could be either Nakajima Hikari 2 or Mitsubishi Kinsei, the propeller had to be adjustable.


The proposed prototype "K" was a sleek looking all-metal downwind glider that had hydraulically retracted landing gear, the monoplane wings also folded hydraulically and were equipped with Fowler type flaps. The powerplant chosen was an in-house produced Hikari 2 radial engine with a maximum output of 800 hp.


Prototypes
The first prototype was completed and flew on 18 January 1937, and was designated by the Naval Air Service upon adoption as the 10-Shi deck attack bomber, or B5N1 10-Shi for short. Acceptance of the aircraft by the Naval Air Forces was slightly delayed by the collapse of a landing gear leg, this accident occurred on 25 January 1937 during taxiing. During the tests the prototype was evaluated quite well, it was reproached with hydraulic wing folding, which did not work reliably, and reservations were made about the Fowler type flaps, the Navy was cautious and accepted many technical innovations with suspicion, so it also demanded the abolition of hydraulic wing folding. [On the other hand, by the end of the war the Japanese were literally fighting with hydraulics and their reliability and tightness.
The second prototype was modified as required and already had manual folding of the wing tips and the flaps were simple. The next major change was to the engine, a Nakajima type Hikari 3 with a maximum output of 840 hp was used. Significant weight savings came from the interestingly designed wing fuel tanks, the top of which formed the wing area. The tests lasted three months and were carried out at the Oppama naval base.


B5N1 model 11 - trials and combat deployment
The Kaigun Kōkū Hombu thoroughly and rigorously compared the prototypes of the two factories, Mitsubishi B5M1 with its fixed chassis represented a simpler and more robust design, and Nakajima with its B5N1 type again presented a more modern and above all more powerful solution. After much hesitation, the Navy was more inclined to the B5N1 prototype, which had higher performance, but it was able to make clever use of the existence of the Mitsubishi prototypes, using them in the role of "pressure aircraft", the Nakajima factory design team had to speed up production as much as possible, troubleshoot quickly and urgently, and respond flexibly to all the needs and wishes of the Navy. Eventually, a committee of naval officers was appointed, and they also favored the higher performance potential of the B5N1 prototypes, and the aircraft was accepted into service as a Type 97-1 deck torpedo bomber. Series production began on 5 April 1938.
A competing bomber was eventually produced in the same quantity as the B5N1, i.e. 125 units. This was mainly due to the ongoing war conflict in China, the Mitsubishi B5M1 was adopted as the Type 97-2 deck bomber and operated mainly from ground bases due to its more robust fixed landing gear. Of course, Nakajima B5N1 Model 11 aircraft were also deployed to fight on this battlefield. Following an agreement between Kaigun Koku Humbu and the Chinese Expeditionary Corps command, they were first deployed at the Chinese city of Changchou, the bombers then wiping out the city's defenses and greatly assisting the Japanese troops in their further advance on the Tri-Cities. The B5N1 bombers then took part in a number of more operations in which they were accompanied by Mitsubishi A5M2a fighters and later also Mitsubishi A5M4 fighters. The Chinese Air Force was far from an equal opponent, however, and so losses were very small, despite the fact that many operations were conducted entirely without fighter escort.
Nakajima rectified minor defects during production, which became apparent during combat operations. Unfortunately, the major deficiencies were not yet apparent here; they were the usual design flaws of Japanese aircraft of the time:
(a.) weak defensive armament - one machine gun was rather symbolic in the event of an encounter with a fighter
b.) insufficient or completely missing armour protection for the crew and important parts of the aircraft
c.) the complete lack of self-locking tanks.

Had the new Japanese bombers come into conflict with European machines, the Kaigun Kōkū Hombu would have discovered these deficiencies much earlier. On the other hand, however, American intelligence did not pay attention to this type and settled for Japanese images of obsolete biplane deck bombers Yokosuka B4Y1, while the Japanese, on the other hand, based on the experience gained in China, perfected the training of aircrews to a truly excellent level. Bomber crews achieved a high percentage of hits, both in bomb and torpedo attacks, and Japanese torpedoes were at least one class higher in all parameters than American torpedoes. These facts soon brought the Americans a very bitter surprise.


I must still recall the fate of the second project at Nakajima, marked with the letter "S", two prototypes were produced and tested with unequivocal success on the Chinese battlefield, but its further production was cancelled because the Kaigun Kōkū Hombu came to a decision, that it would be fully replaced by a torpedo bomber; later it turned out that the decision was not entirely justified, bombers were scarce and specialized reconnaissance aircraft were needed, the navy had to solve the shortage by buying modified army aircraft Mitsubishi Ki-15 Babs.
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B5N2 - vznik legendy a ústup ze slávy
Na základě získaných bojových zkušeností v roce 1939 vzniká verze B5N2 Model 12, již na základě označení je jasné, že hlavní změnou byl nový výkonnější motor - dvouhvězdicový čtrnáctiválec Nakajima NK1B Sakae 11. Vývoj nového motoru započal zároveň s projektem B5N1, konstruktéři již od začátku uvažovali o tomto motoru. První vzlet prototypu KM-3 se konal v listopadu 1938 a bylo zjištěno, že tato verze dosahuje jednoznačně vyšších výkonů, což bylo způsobeno jednak vyšším výkonem motoru, ale také malým čelním odporem. Díky tomu, že nový motor měl válce uspořádány do dvojité (dvouřadé) hvězdice, měl proti motoru Hikari 3 o 36% menší čelní průřez. Zástavba byla jednoduchá, jen bylo nutno posunout protipožární přepážku o sto milimetrů vzad. Jedinou nevýhodou bylo zkrácení doletu, ten byl zkrácen o sedmdesát kilometrů což bylo přijatelné.
Výroba nové verze, označené jako typ 97-3, se rychle rozeběhla a do výroby se zapojily také továrny 愛知航空機株式会社 - Aichi Kōkūki Kabushiki Kaisha v Nagoji a letecký námořní arzenál 第十一海軍航空廠発動機部 – Dai Jūichi Kaigun Kōkūshō Hatsudōkibu v Hiru. Staré torpédové dvouplošníky B4Y1 byly již jen ve výcvikových základnách a od prvoliniových jednotek začaly být stahovány starší B5N1 Model 11, v době útoku na Pearl Harbor byla ve službě pouze nová verze.


Podle mého názoru lze těžko rozhodnout, zda byl, nebo nebyl tento letoun nadprůměrný, jisté však je, že osádky těchto letounů byl skvěle vycvičeny a připraveny, snad proto byl téměř každý torpédový útok osudový pro americké a spojenecké lodě. Americký protějšek Douglas TBD-1 Devastator nebyl příliš hodnotným soupeřem a navíc svou úlohu sehrála i kvalita torpéd a ta americká byla velmi nekvalitní. Letoun B5N2 během prvních měsíců války získal pověst dokonalého stroje, zasazoval Spojencům těžké rány, v této první fázi války byl při všech významných operacích. Skutečnou slávu si získal při přepadení Pearl Harboru, tomuto útoku však předcházela dlouhá a náročná příprava. Následovaly akce proti Filipínám, ostrovu Wake, přístavu Rabaulu, bombardovány byly základny Madang, Kavieng, Lae a Salamaua. Dobývaly Jávu a Sumatru a konečně 81 letounů Kate zaútočilo osmisetkilovými pumami na australský Port Darwin. Další akce pokračovaly ale alarmujícím se stal fakt, že již během těchto prvních měsíců války (do května 1942) bylo ztraceno na 200 letadel, přitom na úplném začátku bojů byly ještě ztráty minimální. Bitva o Midway, kde Japonci ztratili jádro nejzkušenějších osádek letadel, byla zároveň zlomem v úspěšnosti tohoto typu. Po Midway se ztráty již jen zvyšují a úspěchy jsou stále méně časté.


Torpédové letouny obecně byly pomalé, samotný útok byl riskantní, neboť pilot musel držet bombardér v nízkém, pomalém a poměrně dlouhém letu, zaměřit nepřátelskou loď, odhodit torpédo a přeletět napadenou loď, vším tím musely projít i pomalu zastarávající bombardéry Kate (Kate byl spojenecký kód přidělený tomuto typu). Americké námořní letectvo sílilo a zlepšovalo se nejen kvantitou ale i kvalitativně, proletět stíhací obranou Hellcatů a mít na vlastní obranu pouze jediný kulomet Type 92 ráže 7,7 mm a pod trupem těžké torpédo... V bitvě o Filipíny (1944) již musely být staženy z oblasti bojů, tak velké byly ztráty.


Takto stažené stroje našly ještě své uplatnění v protiponorkovém hlídkování, pro tento účel nesly detektory magnetických anomálií Jikitanchiki, nebo protilodní radar H-6, jehož montáž se projevila řadou antén na bocích trupu a na křídlech. Japonská námořní doprava velmi trpěla neustálými nájezdy amerických ponorek a tak byla tato činnost nanejvýš záslužná.


Několik málo desítek letadel bylo upraveno na cvičný letoun označený B5N1-K, tyto letouny potom sloužily v leteckých školách. Smutný konec v podobě role sebevražedného letounu potkal i tento typ, skončilo tak několik desítek letadel.


Smutným osudem tohoto letounu bylo, že nástupce Nakajima B6N Tenzan se zpozdil, přišel pozdě a navíc v nedostatečném počtu, Kate potom musel nadále operačně létat a to v době, kdy měl být již stažen z bojových operací.


Tento typ byl posledním palubním bombardérem, který operoval v 2. světové válce. Stalo se tak dne 18. srpna 1945, tehdy čtyři bombardéry B5N2 zaútočily na sovětskou minonosku a následně ji potopily. Stalo se tak po 15. srpnu, od toho dne měly být ukončeny všechny bojové akce. Pro zachování objektivity musím říci, že Rusové 17. srpna 1945 v oblasti Kamčatky bombardovali japonské území a zmíněný útok byl tak japonskou odpovědí.
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Použité zdroje:
René J. Francillon Ph.D., Japanese Aircraft of the Pacific War, Naval Institute Press, Annapolis. Maryland, Reprinted, 1990, ISBN: 0-87021-313-X
Tadeusz Januszewski a Kryzysztof Zalewski, Japońskie samoloty marynarski 1912-1945, díl 2., Lampart, rok 2000, ISBN 83-86776-00-05
Famous Aircraft Of World, No. 32, Nakajima Typ 97 Carrier Attack Bomber, Bunrin-Do, Tokyo 1997.
Václav Němeček, Vojenská letadla 3., Naše vojsko, Praha rok 1992, 3. doplněné vydání; ISBN 80-206-0117-1
Jaroslav Schmid, Stíhací a bombardovací letadla Japonska, díl 2., Nakladatelství Fraus Plzeň, rok 2000; ISBN 80-7238077-x
Zbyněk Válka, Jednomotorová bombardovací a torpédová letadla 1939 - 1945, Nakladatelství Jan Piszkiewicz, rok 2003, ISBN 80-86768-01-5
M. F. Hawkins, Nakajima B5N "Kate", Aircraft Profile No.141, Profile Publications, rok 1969
L+K 14/1992, str 55, Letadla 39-45
http://www.airwar.ru/enc/bww2/b5n.html
www.xs4all.nl
http://www.go2war2.nl/artikel/524
http://www.cofe.ru/avia/N/N-3.htm
archiv autora
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