Nakadžima J1N Gekkó [Irving]

Nakajima J1N Gekko
Nakajima J1N Gekko - přehled verzí

Nakajima J1N - version overview


島 島 J1N
Japanese name: 月光 - Gekkō - Moonlight


Allied reporting name: "Irving"



Designation Aircraft design - description
Nakajima J1N1 - prototyp dle 13-Shi specifications built two prototypes with slots on the leading edges of the wings and flaps on the trailing edges, the Navy did not accept them as fighter
Nakajima J1N1-C 7 prototypes modified for reconnaissance, the engines already had the same sense of rotation and remote-controlled shooting ranges were launched.
Nakajima J1N1-C KAI modification from 1943 emergency assembly of 2-4 Type 99-1 cannons into the fuselage for shooting up and down under the aircraft, modification proved successful, other aircraft already factory production
Nakajima J1N1-R 12 aircraft in the reconnaissance version, a three-member crew, on the tropics was installed turret with a cannon Type 99 Model 1 caliber 20 mm, the tower caused a significant decline in performance.
Nakajima J1N1-S seriově manufactured night fighter, several machines were equipped with low-power radars Type 3 Mk 6 Model 4.
Nakajima J1N1-Sa 11A the latest version of the night fighter, the typical hump behind the cabin has disappeared, 2-3 cannons Type 99-2 model 3 for shooting obliquely upwards, again several machines were equipped
radar FD-1 or FD-2.



Made a total of 479 aircraft, including 9 prototypes.
Production took place at: 中 島 飛行 機 株式会社 - Nakajima Hikōki Kabushiki Kaisha, Koizumi, Ota


Sources used:
Tadeusz Januszewski and Kryzysztof Zalewski, Japońskie samoloty marynarski 1912-1945 part 2, Lampart, year 2000, ISBN 83-86776-00-05
Famous Airplanes Of The World, Nakajima Navy Night Fighter „Gekko“ No. 57, 1996/3, Bunrin Do Co., Ltd., Printed in Japan, ISBN 4-89319-054-7.
http://www.combinedfleet.com/ijna/j1n.htm

Nakadžima J1N Gekkó [Irving] - Nakadžima J1N1-S 11 Gekkó, foto z nočních nasazení proti B-29 jednotky 302. Kókútai.

Nakadžima J1N1-S 11 Gekkó, foto z nočních nasazení proti B-29 jednotky 302. Kókútai.
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Nakajima J1N Gekko


History:


In the early summer of 1938, the 大日本帝国海軍航空本部 - Dai-Nippon Teikoku Kaigun Kōkū Hombu (Command of the Imperial Japanese Naval Air Force) formulated its technical specifications marked 13-Shi[13-Shi]), these specifications, or more accurately one part of them, detailed the requirement for a three-seat long-range fighter bomber, to its two largest aerospace suppliers, 三菱重工業 - Mitsubishi Jūkōgyō Kabushiki Kaisha (hereafter Mitsubishi) and 中島飛行機株式会社 - Nakajima Hikōki Kabushiki Kaisha (hereafter Nakajima). Both of these companies were invited to submit their designs for this category of aircraft. The Kaigun Kōkū Hombu subsequently amended these requirements (October 1938) and newly requested a heavy multi-seat fighter, intended primarily to escort its own bombers, its other task being rapid reconnaissance. The Japanese naval air force felt the need for long-range fighters, deploying its G3M bombers in China at the time, but the fighter escorts could not escort the bombers over the target area, and it was over the target area that the Chinese fighters severely decimated them. Japanese losses in these raids soon exceeded a tolerable level. The Imperial Naval Air Force, however, had no suitable fighter aircraft with sufficient range in its armament. The armament of the fighter units consisted of the excellent A5M deck fighters, these had all the pros, only the range of all their versions corresponded to a deck fighter and not an escort aircraft. The last version to enter service, designated as A5M4, could carry additional fuel tanks, but even so the range was not sufficient. The attempt to purchase an escort aircraft abroad was also unsuccessful. Japanese naval pilots were disappointed with the flight characteristics of the S-type fighter, also designated as A8V1, which was an American two-seat Seversky 2PA-B3. The aircraft fell far short of the expectations placed on it and was rejected by the pilots.

It was clear to the naval officers responsible for the requirements for the new armament that only a twin-engined fighter with a large mass could meet such demanding requirements, but almost contradictory to this mass was the requirement for high manoeuvrability and handling, and these manoeuvrability qualities were required to the same level as those possessed by single-engined fighters. I will add that the Naval Air Forces were late this time, their rival, the Army Air Forces, commissioned the development and construction of a similar aircraft from 川崎航空工機業株式会社 - Kawasaki Kōkūki Kōgyō Kabushiki Kaisha in the early spring of 1937, Kawasaki's Ki-38 project was born, and after refinements in December of that year, work began on the later successful heavy fighter Kawasaki Ki-45 Toryu, in allied-code, named Nick.


The technical specifications of the 13-Shi thus required several rather demanding conditions to be met, only the required top speed was 519 km/h, plus a long range of 3,700 km, a decent climb rate, and the new aircraft was to ascend to an altitude of 4,000 m in a maximum of six minutes. In the specifications the requirement for armament was precisely formulated, even the type of engines was precisely specified.


Mitsubishi soon withdrew from the competition because of the complexity of the requirements and did not even start the design work. However, to remain unbiased, I must admit, that the company's designers and engineers were working on two major tasks at this time - the great airborne fighter A6M1 and then the improved version A6M2 and on the heavy bomber G4M1 Betty, both of which they managed to complete 100% of their missions, despite the forced unsuccessful diversion of a cruiser-type escort aircraft G6M1.


This left only the Nakajima design team in Koizumi to build the escort fighter, led by the young chief designer, engineer Katsuji Nakamura, who was the creator of the successful B5N Kate deck bomber. The design team under his direction designed an all-metal structure characterized by its subtle and graceful shapes. The new low-flying aircraft was completed in March 1941, designated as a "naval experimental three-seat escort fighter". Two powerful Nakajima Sakae NK1F 21 and 22 engines of 1,130 hp were chosen to power it. In an effort to provide the aircraft with good maneuverability, these engines, due to the reducers used, had opposite runs to each other, thus canceling out the reaction torque of the two propellers.


However, the results of the factory tests were rather poor, the aircraft suffered from aileron flutter, hydraulic failures (this was a constant problem with Japanese aircraft) and large forces had to be applied to the controls. The aircraft returned to the factory and was thoroughly modified there. The wing received automatic slots in the leading edges and flaps on the trailing edge. Handling was greatly improved, but the naval aviation representatives were not satisfied with the manoeuvrability. This was perhaps also due to the fact that they were comparing the twin-engine fighter with the Zero, an aircraft that had no rival in maneuverability. After several practice engagements, the Navy lost interest in the twin-engined aircraft as a fighter. This was probably helped by the defensive armament, which was also not accepted by the navy representatives. It consisted of two low machine gun turrets, each with a twin machine gun Type 97, these turrets were stepped into the rear dorsal fuselage and were remotely controlled by a gunner who sat in a communal oblong cockpit and sighted the guns with a reflex sight. The whole system was said to work well, but during trials it was the subject of constant criticism from the Navy, with accusations of complexity, weight and general unsuitability for rank-and-file service. Attacks from below were to be repelled by a second crew member using a movable machine gun firing through a firing slot in the floor of the machine. Fixed armament was accepted without reservation, carried initially by some reconnaissance machines, and consisted of a bow-mounted Type 99 and two 7.7 mm Type 97 machine guns. However, during sea trials the aircraft generally failed to meet the specification requirements (it met the requirement for take-off length and range) and so the Navy refused to include it as a escort fighter in its armament, the new Mitsubishi A6M2 Reisen (Zero) fighter had sufficient range even for long escort flights.


The Navy was therefore not interested in a fighter J1N1 and so it seemed to remain unused. Fortunately for the type, however, it needed to replace the aging Mitsubishi C5M (Babs) reconnaissance aircraft, and the unused J1N1, with its long range and decent speed, suited the requirements, so the 6th. July 1942, a contract was signed with Nakajima for the supply of simplified long-range reconnaissance aircraft designated J1N1-C Type 2 Model 11. The modified three-seat aircraft were delivered with a defensive armament of a single Type 97 machine gun, this weapon replaced the remotely operated gun turrets and the lower machine gun was dropped altogether. Fixed armament was soon dropped, the aircraft, according to Kaigun Kōkū Hombu's ideas, was to defend itself with its high speed. The engines had the same direction of rotation from the tenth aircraft delivered (tests showed that the flight characteristics did not change). The fuel system was fundamentally changed, the fuel supply was increased to 2,460 litres and was carried in ten wing tanks, originally the fighter had one unprotected tank in each wing. Now the tanks were self-locking, the supply could be increased by a further 620 litres of fuel carried in two auxiliary tanks suspended under the wings if required, later the capacity of the auxiliary tanks was increased to 660 litres. The spacious fuselage easily accommodated both K-8 fixed cameras and F-8 handheld cameras.


The reconnaissance aircraft first saw their first combat deployment over the Solomon Islands, and on this occasion were given the American code name Irving, which however belonged to the fighter aircraft. The J1N1-C reconnaissance aircraft were not very popular, nor were they numerous with the troops; Japanese pilots preferred the Yokusuka D4Y1-C reconnaissance aircraft.


As I mentioned earlier, the deciding officers of the Kaigun Kōkū Hombu had the idea that the reconnaissance aircraft's defense would be provided by its speed, and so the armament of the reconnaissance J1N1-C was reduced to a single rifle-caliber machine gun. Completely contrary to this doctrine, and also despite the protests of the designers, one aircraft was modified to install a large gun turret with a 20mm gun. This turret was originally designed for a four-engined bomber Nakajima G5N1, it was so large that it functioned more like an aerodynamic brake on the smaller twin-engined aircraft. The machine was tested from early October 1942 and the results were pronouncedly poor, and it is surprising that the Naval Air Command continued to require the use of the turret. Nakajima therefore designed a new smaller and more suitably shaped turret and a modified cabin for the purpose, and some twelve reconnaissance aircraft were built and tested in this way, designated J1N1-C (they are often referred to as J1N1-R, or, quite erroneously, as J1N1-F, but the letter F was reserved for designation of floatplane observation aircraft). A 20 mm Type 99 cannon was installed in the gun turret (a Type 3 machine gun of 13.2 mm calibre was probably also tested). The gun turret machines were only tested with combat units in mid-1943, and were reportedly considered for use as turret fighters, but eventually flew with training units. The turret was still a major source of aerodynamic drag.


Further development of the aircraft was due to the workshop modification of the reconnaissance aircraft. The modification was carried out in the 251 workshops. Kōkūtai (until the reorganization 31. 10. 1942, Tainan Kaigun Kōkūtai), this unit was commanded by 海軍中佐 - Kaigun Chūsa (frigate captain) Yasuna Kozono, who had already, as an executive officer, thought, how best to combat night raids by American four-engine bombers, which operated with relative impunity over the Japanese naval base Rabaul in the autumn of 1942. He was intrigued at the time by an attack by several C5M2 aircraft, which dropped phosphorus bombs on the bomber formation and managed to set several enemy bombers on fire. He realised that an attack by an aircraft with suitably placed guns could be carried out while flying above or below the target, depending on whether the bombers were more visible against the surface or the sky. The most suitable machine for night pursuit seemed to him to be the J1N1-C reconnaissance aircraft, which had sufficient performance and airframe strength (it was originally designed as a fighter) and the unit had several of these in its armament. After reorganizing this unit during its rest and replenishment in Japan, he became its commander and managed to convince the Naval Air Command. Convincing the bureaucratic and haughty officers of the Kaigun Kōkū Hombu was certainly no easy task, it took him from December 1942 to May 1943, when he finally got permission to modify two new J1N1-C reconnaissance aircraft for night interception. Kozonó's proposed modification consisted of the installation of four forward-slanting (two up and two down) Type 99-2 20 mm calibre cannons in the cockpit of the third crew member - the night fighter was a two-seater. One could say it was the equivalent of the German "Schräge Music". The guns were mounted at an angle of 30° from the longitudinal axis of the aircraft, each gun carrying a supply of one hundred rounds in a drum magazine. In addition to the installation of the guns, two sights had to be mounted - one for upward firing and one for downward firing, as well as glass in the nose and cabin floor to allow the pilot to see the target. The modification itself was quick - it took only a week on both machines. Both aircraft so modified passed their gunnery tests, and in a two-day test against a B-17E, a prey bomber on loan from the Army Air Corps, the results were a complete success. With nothing left but their combat deployment, the two night fighters were ready for the flyover to Rabaul, which they were to conduct accompanied by seven J1N1-C reconnaissance aircraft. During this overflight one night fighter was lost, this happened during an emergency landing at Tinian airfield. Only one night fighter was therefore added to Rabaul, but it proved its worth against the bombers immediately. Kaigun Chūsa Yasuna Kozono sent reports to his superiors describing the successes of the modified aircraft; several dozen reconnaissance aircraft were modified in this way in field conditions, these machines were designated J1N1-C KAI. The technical officers of the Kaigun Koku Hombu must have recognized the effectiveness of the angled guns, and the Nakajima company in Koizumi was ordered to start production of night fighters, the newly produced machines were designated J1N1-S, at the same time they were given the fighting name 月光 - Gekko (Moonlight). All of these aircraft carried four Type 99-2 Mark 3 guns.


The first night fighters J1N1-S left the production halls in August 1943, and production was ramped up as US bomber raids B-17 Flying Fortress escalated, B-24 Liberators and finally B-29 Superfortresses. The night-fighter version of the Gekko became the most widely used and was produced as a two-seater from the beginning. By the three-hundredth aircraft produced, the Gekko featured a hump behind the cockpit, the three-hundredth was lowered behind the cockpit, it was not a new version, just a modification of an existing version. Later, the little-used guns firing towards the underside of the aircraft were removed, and on the later version J1N1-Sa (also referred to as J1N3 23 somewhere) the gun line-up was strengthened to three, with the third gun, a Type 99-2 Mark 4, mounted on the left and slightly offset to the rear compared to the right pair of guns, and carrying a larger ammunition supply (150 rounds). Production ceased after 477 aircraft were delivered, this happened in November 1944.


Crews of Gekko night fighter aircraft initially had to rely on the pilot's and commander's good eyes to find enemy bombers. However, the absence of a radar did not mean that fairly substantial successes were not recorded. The Americans initially attributed the losses of their Flying Fortresses and Liberators to anti-aircraft fire and bombers colliding with each other in the air. Japanese crews had admirable success in visual searches for large bombers, but this success rate declined against twin-engine bombers North American B-25 Mitchell and Martin B-26 Marauder.


It is logical that Japanese engineers tried to improve the ability to search for enemy bombers by any means available. I will mention here the information that several Gekko's were said to carry a searchlight in the nose to illuminate the target in the final phase of the attack (personally, I think that by using it, the night fighter would give away its position and thus become a target for defensive fire, not to mention the unwanted glare to its own crew). On the contrary, the information about the installation of different types of radars is quite certain and proven. Firstly, a radar type completely unsuitable for night interception was installed, designated Type 3 Kú-6 (H-6), this was a radar designed to search for surface targets and so the few Gekko fighters were deployed for night attacks against ship targets. These machines can be identified by the Yagi antennas in the nose and sides of the aircraft. Greater hopes were placed on the 18-Shi Kú-2 radar (later designated FD-2), this radar operated with a wavelength of 60 cm and its design is revealed by the four small Yagi antennas in the nose of the aircraft. Tests of this radar were carried out at Atsugi with the participation of its designer Diaroku Yukoi and the now well-known "father of night fighters" Yasuno Kozono, the now fresh 海軍大佐 Kaigun Dais (naval captain) and commander of 302. Kōkūtai. Captain Kozono was satisfied with the results of the trials and recommended its introduction into the armament. The radar was able to detect a target at a distance of 400-3,000 m and guide the fighter to it with an accuracy of 200-300 m. Toshiba produced and delivered several dozen sets of the radar, and so in late 1944 and early 1945 the Gekkos equipped in this way reached the combat units, the 302s. Kōkūtai, 332. Kōkūtai and 210. Kōkūtai. For these fighters, the radar proved to be little help either, with the pilots spotting the enemy bomber before it was identified on the radar screen by the aircraft commander operating the radar. Aircrews often dismantled the radar to save 75 kilograms of weight. No enemy aircraft were shot down using the FD-2 radar.


Weaponry was experimented with on several aircraft, for example, the installation of a 30mm cannon Type 2 Model 1 was tried, but this weapon was more or less in the prototype stage. A few machines carried three Type 99-2 Mark 3 guns in the hump on the back, these guns were mounted symmetrically to the longitudinal axis of the aircraft, the lower guns were retained. Among the modifications, the installation of a 20 mm gun in the nose of the aircraft was done by the armourers of 321st Kōkūtai, and this modified night fighter was acquired by the Americans on Guam and their intelligence service entered this fact in the recognition plates of Japanese aircraft.


Gekko night fighters were deployed on many battlefields, and as the end of the war approached, raids on Japan became more frequent, and so Gekkos were withdrawn to units in charge of the defense of the Japanese islands, operating primarily from Atsugi Base.


As I wrote above, the Gekko attack against the four-engine Boeing B-17 Flying Fortress and Consolidated B-24 Liberator bombers was quite successful, the fighter crew locating the target due to its large size and also due to the exhausts of its four engines. The twin-engine North American B-26 Mitchell and Martin B-26 Marauder bombers were harder to locate, but on the other hand were not as durable. The Boeing B-29 Superfortress was the least vulnerable opponent; if the Bi-San operated at high or even medium altitude, the Gekko's sorties lost their effectiveness; later, the altitude of the sorties decreased and so the chances of a successful attack improved. However, the B-29 had the advantage of greater speed and endurance than the older Flying Fortresses and Liberators.


One more type of attack the Gekko was used for - suicide bombing. Perhaps all versions could suspend two bombs under the wings, each weighing 250 kg; with bombs so suspended, Gekkos were deployed as kamikazes, most likely manned only by the pilot. This inglorious end became the fate of many Japanese aircraft types.



Sources used:
René J. Francillon Ph.D., Japanese Aircraft of the Pacific War, Naval Institute Press, Annapolis Maryland, Reprinted 1990, ISBN-0-87021-313-X
William Green, War Planes of the Second World War - Fighters, Vol. Three, London Macdonald, seventh edition 1973, ISBN: 0-356-01447-9
Lampart, 2000, ISBN 83-86776-00-05
William Green and Gordon Swanborough, The Complete Book of Fighters, Salamander Books Ltd; New Ed edition, 2001, ISBN-10: 1840652691
Tadashi Nozawa, Encyclopedia of Japanese Aircraft 1900-1945, Volume 5, Nakajima Aircrafts. Shuppan-Kyodo Publishers, Tokyo, Japan, 1983
Krzysztof Zalewski, Nakajima J1N Gekko (Irving) Military Aviation 2/1998
Václav Němeček, Vojenská letadla 3 vol., second supplemented edition, Naše Vojsko, Prague 1992, ISBN 80-206-0117-1
http://www.airwar.ru/enc/fww2/j1n.html
http://en.wikipedia.org/wiki/Nakajima_J1N
en.wikipedia.org
http://cs.wikipedia.org/wiki/Jasuna_Kozono
http://www.gunsight.jp/b/english/data/jn-gun-e.htm
www.nasm.si.edu
www.csd.uwo.ca
http://avions.legendaires.free.fr/j1n.php
http://www.cofe.ru/avia/N/N-14.htm
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