Micubiši Ki 21 [Sally]

Mitsubishi Ki-21 - version overview

ū 式 重 爆 撃 機 - Kyūnana-shiki jūbakugekiki "- heavy bomber type 97"

Allied reporting name: Sally or Jane or Gwen



Made a total of 2,064 aircraft of this type (excluding Ki-57 aircraft).
The production of prototypes took place at the company:
Mitsubishi 重工業 株式会社 - Mitsubishi Jūkōgyō Kabushiki Kaisha, Nagoya [img_6 comment = Japan (JPN)] https://www.valka.cz/images/flags/jp.gif [/img_6]
and licensed construction at the company
Aj 島 飛行 機 株式会社 - Nakajima Hikōki Kabushiki Kaisha v Koizumi [img_6 comment = Japan (JPN)] https://www.valka.cz/images/flags/jpn.gif [/img_6]

Sources used:
René J. Francillion Ph.D., Japanese Aircraft of the Pacific War, 2nd edition, London, Putnam & Company Ltd., 1979, ISBN 0-370-30251-6.
René J. Francillion Ph.D., The Mitsubishi Ki-21 (Aircraft in Profile number 172), Leatherhead, Surrey, UK, Profile Publications Ltd., 1967.
Bill Gunston, The Illustrated Directory of Fighting Aircraft of World War II, Zenith Press, 1999, ISBN 0-86101-390-5.
Philip Jowett, The Japanese Army 1931-1945, Volume 2, Osprey, 2002, ISBN 1-84176-354-3.
Leszek A. Wieliczko, Nakajima Ki-19 and Mitsubishi Ki-21 - heavy bombers of the new generation, and the Air Force, no. 6, 2012, ISSN 1732-5323
https://www.ww2warbirds.net/ww2htmls/mitski21.html
author's archive

History:

Rikugun Koku Hombu (command of the imperial army air force) has drawn up in the spring of 1936, the technical specifications, in which it requested for its bombing Sentaie a new, modern bomber, which would allow to replace the japanese pilots not very popular Ji-shi-ki, or the Italian bombers Fiat B.R.20 and two types of already outdated japanese bombers Mitsubishi Ki-20 and the Mitsubishi Ki-1.

The requirements were sent to the three main suppliers of army letactva - companies 三菱重工業株式会社 - Mitsubishi Jūkōgyō Kabushiki Kaisha (hereinafter referred to as Mitsubishi), 中島飛行機株式会社 - Nakajima Hikōki Kabushiki Kaisha (hereinafter referred to as Nakajima) and 川崎航空工機業株式会社 - Kawasaki Kōkūki Kōgyō Kabushiki Kaisha (hereinafter called Kawasaki). The design teams of these companies immediately began to work on the projects. Nakajima submitted a project of a twin-engine airplane Ki-19 and after examination of the project of the military specialists was invited for the construction of the prototypes, the Mitsubishi with its project designated Ki-21 was similar, the project kontrukčního team company Kawasaki with the designation Ki-22 was, however, terminated without an order for the construction of prototypes.

If, we go back to the requirements, requested was an all-metal twin-engine monoplane with a payload of bombs 750 – 1 000 kg (under-range), a maximum speed of 400 km/h at a height of 3 000 m, to this height had the bomber to climb in a decent time of eight minutes. Endurance of the flight has been requested at least a five-hour defense of the armament should be composed of three rifle caliber machine guns. Engines should operate reliably even at low temperatures, because at that time it was envisaged with operations in north China and also in Siberia.

The company Mitsubishi has built two prototypes of the Ki-21, which differed in armament and equipment. Both were completed in December of 1936. The first had a classical dome with a machine gun on the back of the fuselage, the latter of which is already carried on the back of the hull characterized by a long glazed protrusion with a machine gun at the end. It was eventually the most reliable cognitive character of bombers Ki-21 for many years. The engines were Mitsubishi Ha-6 with the power of 825 hp.

Both of these prototypes have passed in the spring of 1937 at an air base in Tachikawě demanding comparative tests with competing prototypes Nakajima Ki-19. The first round went completely undecided - none of the prototypes significantly fall short of the competition. Technical office of the air force, however, came with a very interesting idea, requested the representatives of the two factories on the mutual replacement of the propulsion units.

Nakajima then mounted to your prototype competitive engines Mitsubishi Ha-6 and the Mitsubishi Ki-21 again received engines Nakajima Ha-5 KAI on the performance of 850 / 1 080 horsepower. Already during the first tests it was clear that the aircraft Ki-21 are now the clear winner of the contest, the flight characteristics were improved, and so it was only necessary to improve the stability of the flight for a better focus of the pum. When new porovnáváních trials was the Ki-21 significantly better and therefore was in November 1937 admitted to the weaponry as a "army bomber Type 97 Model 1A" and shall be drawn up and the order for mass production, that was launched in the spring of 1938 and took place in parallel in both air factories at Mitsubishi but also licensed in Nakajimy (for the latter, therefore, to be compensated for failure in the competition).

The first production aircraft Ki-21-Ia (Ko) (キ21-I甲) got into the armaments 60.Sentai and that has been recognized as operational already in late 1938. Immediately was sent to the chinese battlefield. Here are the new aircraft, exactly as expected, immediately assert. Armament was relatively weak, the three movable machine guns Type 89 caliber 7.7 mm (the bow, the upper and lower range), but on the other hand, the chinese air force was also a weak opponent and in addition a decent rate of Ki-21 enabled them to leave the battlefield, if a chinese fighter appeared. Eventually, however, the army air force on the basis of combat experience decided that the armament will have to be strengthened and then in October 1939 comes into its loadout version of Ki-21-Ib (Otsu) (キ21-I乙). She was carrying two more machine guns Type 89 one was designed for shooting from the side windows, and the second, remotely controlled, was in the end cone of the fuselage, controlled by the shooter was from the long roof of the greenhouse. This version has brought even more improvement of the passive safety - the fuel tanks were fitted with protective rubber covers. Visible went through an adjustment also the horizontal tail, has been substantially enlarged its area. Increased was also the bomb bay, but this adjustment was not visible from the outside of the aeroplane. The result of all these introduced changes, however uncomfortable increased weight of the aircraft.

The solution brought another version marked Ki-21-Ic (Hei) (キ21-I丙）, inter alia, was again strengthened the defensive armament - was completed with a second machine gun for shooting from the side windows, it was now possible to shoot at both sides at the same time. For increased range when průzkoumných missions was at this version possible to the bomb bay to hang additional fuel tank of 500 litre. Already last version přinela unpleasant growth of the weight, the established modifications has risen again, therefore the designers had to reconstruct the chassis, newly fitted larger wheels and their diameter necessitated the reconstruction of the engine nacelles.

If we evaluate the action of the Ki-21 over China, so there were clearly successful. Rikugun Koku Hombu, however, on the basis of the acquired combat experience and also on the basis of intelligence information, has informed, that in the event of conflict with the enemy, who had advanced in the air force, not the performances of the Ki-21 be sufficient, therefore, requested their further development, which would ensure an increase in performance.

In march 1940 began to test a new model of 2a in the system Kitai iznačená Ki-21-IIa (キ21-II甲）, the new version was driven by čtrnáctiválcovými engines Mitsubishi Ha-101 performance 1 340/ 1 500 horses. The new engines were kapotovány in greater motor nacelles, to them is then completely hid the undercarriage wheels, which previously stood out. Armament so far remained the same as in the previous version. Aircraft Ki-21 after December 1941, applied mainly in the support of the japanese procedure in Thailand, Burma and Malaya, much of the credit should in the conquest of Hong-Kong and Rangůnu. The allied air force, there was as yet little effective and also outdated, losses Ki-21 so they were still on the bearable level. However, as soon as in a greater number of appeared british Hurricanes and Spitfires or american Tomahawk and Warhawky, losses Ki-21 increased more than significantly. The last response of the designers was to eliminate the characteristic of the greenhouse, and in its place was installed a mechanical, pedal-operated turret with a machine gun Type 1 the caliber of 12.7 mm. Amplified was also protection for the pilot and tank, unfortunately, the Ki-21 and in this new version of Ki-21-IIb (キ21-II乙）, was past his prime and on the performance of bomber tasks already enough strained, or just for the price of a really large losses. Compensation in the form of a more modern bomber aircraftKi-49 Donryu was never available in sufficient quantities, but even so he was a bomber Ki-21 on some of the battlefields successfully deployed even in 1943 (e.g. Kolkata).

Many Sentaí replaced the Ki-21 in 1945, a modern and effective Mitsubishi Ki-67 Hiryu. Discarded bombers were then disarmed and used for military passenger and freight transport. With the consent of the army modified the aircraft enjoyed also the traffic company Dai Nippon Koku Kabushiki Kaisha, of course, there were flying without any armament and with civilian imatrikulačními numbers. The type designation was MC-21. At the time of the japanese surrender was the aircraft Ki-21 armed with only one heavy bomber Sentai.

Allied intelligence service assigned bombers Ki-21 three code names. The original code name was Jane, but because it was the name of the wife of general Macarthur and he felt prejudice was this label changed to Sally. When he appeared the model of the Ki-21-IIb with the towers, it was considered that this is a completely new type and so the aircraft got assigned to the third code name Gwen. Later apply a single label with Sally rozlišujícími digits..

sources:
Rene J. Francillion Ph.D., Japanese Aircraft of the Pacific War, Naval Institute Press, rok 1987, ISBN-10: 087021313X.
Robert C Mikesh and Shorzoe Abe, Japanese Aircraft 1910-1941, Putnam Aeronautical Books, 1990, ISBN: 1557505632
Vaclav Nemecek, Military aircraft 3., Our troops, Prague 1992, 3. supplemented edition, ISBN 80-206-0117-1
Jaroslav Schmidt, Fighter and bomber aircraft of Japan, part 2., Nakladatelství Fraus, Plzeň, 2000, ISBN 80-7238077-x
Rene J. Francillon, The Mitsubishi Ki-21, Aircraft in Profile No. 172, Profile Publications Ltd., Leatherhead, Surrey, UK, 1967
L+K 19/1976, Aircraft 39-45, Václav Němeček
www.xs4all.nl
www.aviastar.org
www.century-of-flight.net
http://www.airwar.ru/enc/bww2/ki21.html
www.airpages.ru
archives of the author.