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Grušin Sh-tandem Грушин Ш-Тандем In parallel with work on the creation of a designed to install an armoured battle aircraft, continues in the mid-30's. years in the USSR work on the development of fast attack aircraft as specially designed, as developed on the basis of the already existing reconnaissance aircraft.
In 1935, launched a P. D. Grušin (П. Д. Грушин) the work on the project aircraft with the tandemovým wing, as guided by the consideration, that this arrangement could be a good basis for a battle aircraft with a rear turret. The only specimen of the machine Sh-tandem (Šturmovik-tandem, a further designation of the machine: Š-MAI, MAI-3, MAI-tandem - Ш-МАИ, МАИ-3, МАИ-Тандем) was built in the school workshops of the institute. From 5. December 1937procházel in the single-variant thorough tests, carried out by the pilot of a P. M. Stefanovským (П. М. Стефановский). The test lasted up to the r. 1939
The small margin of the wings facilitated the use of wood as the main construction material and at the same time the tandem scheme of reducing the diameter of the circle, into which you can place a floor plan of the aircraft. This led to the idea of a smaller vulnerability of the machines. A big advantage was considered to be also small demands on strategic materials and also a certain somewhat lesser technological intensity. The fuselage of the aircraft, the middle part of the wing and the main wing was constructed in the school production workshops MAI 18 people for 45 days.
The original air-cooled engine M-88. But because it was available, was used by the first motor M-87 and then the M-87A.
The main front of the wing was dolnoplošné, to him, zatahovaly the landing gear. Záďové wheel was fixed. The rear wing, hornoplošného arrangement, a surface area equal to 45% of the surface area of the wing of the front, to fulfil also the role of the horizontal tail. Ailerons were on both wings, while the one on the rear wing at the same time to serve as a stabilizer. The vertical tail surfaces were carried out in the form of circular surfaces, fixed to the ends of the horizontal tail. The first flights showed a directional instability, therefore, it was decided to supplement the rear wing of the directional surfaces. The total was tested five versions of the vertical tail. Finally, as the best have shown a simple circular area, formed by a fixed kýlovkou and směrovkami. As soon as there was the addition of directional surfaces with the we went with helms to the rear wing removed, the lack of directional stability, the airplane flew well. Double rudder on the tail surfaces pointing under the rear wing so as not to restrict the firing field of a shooter in the back of the tower (250° palebný sector).
Airframe type monocoque was built mostly of wood, with the coating delta-drevesiny (phenolic resins saturated with a heat moulded plywood).
To 8. January 1939 plane (in the single-variant and without arms) has undergone preliminary flight tests with the engine M-87. Was achieved by the relatively high maximum speed of the flight. By the land of 406 km/h, in the amount of 4250 m - 488 km/h . On the basis of the results of the tests it was recommended to P. D. Grušinovi překonstruovat the machine on the two-seat variant - the cabin of the navigator to place the rewind almost to the tail and equip it with electrically powered turret of the MV-5 with a 7.62 mm machine gun ŠKAS. In the period September-October 1939, went through at the same time the factory and state tests the two-seat variant of the Sh-tandem. Now the engine was equipped with M-87A (rated power of 4700 m - 950 k.with.) and propellers with a variable course of VIŠ-3. The tests were concluded 10. October.
The cabin of the navigator was shifted to the rear and has been fitted with opancéřovanou turret MV-3. Armament was the standard for light attack aircraft of the time: the 4 wing guns ŠKAS with a supply of ammunition 2400 rounds of ammunition, one machine gun ŠKAS in the turret (fighting inventory 700 charge) and 200 kg of bombs (according to the bosorka usually manifests herself of the springs in the overload up to 600 kg). During the tests, was conducted by 51 of the take-off, with a total airtime of 18 hours and 38 minutes. During the take-off of mass 2800 kg should combat the aircraft maximum speed for the country's 361 km/h, and the rate of 5600 m - 444 km/h Landing speed - 140-145 km/h take-off Distance available - 400 m runway - 480 m.
The factory tests confirmed that the aircraft is fairly nice and solid flying, state tests, however, the plane did not go for the mismatch of predicted and measured values. The plane was unable to get rid of their problems with directional stability at higher speeds, the movements of the control responded with a delay. Mattered and tight cabin gunner-navigator, not very suitable chassis, and the lack of strength of the main wing. The trouble caused and] the tower that the aircraft "to follow a" of about 34 km/h on the speed. This problem wanted the constructor to solve its recast into the form of zaskleného kónusu on the rear fuselage, similar to what had such as the Dutch Fokker G.1. This implementation, moreover, offered the possibility of free movement of the weapon 360 degrees in the longitudinal axis of the aircraft.
Yet all the concept of the tandem bitevníku continue drawing interest. It has been planned to moved the aircraft into the CAGI and perform a blasting test. Grušin began to build even one prototype, "doppelganger", the planned and the single variant with the engine M-63, he was working on the version with the nose landing gear, but the aircraft ultimately was not successful. Numerous complaints were related to the relatively weak armor of the engine and cabin crew. Experience from the Spanish battlefield had shown that the main losses of soviet naval aircraft R-5 and R-Z have been caused by the very fire of the earth. And whereas in this time of successfully passing the tests fighters P. About. The sukhoi's ones - BB-1 (ББ-1), the future of the SU-2 (Су-2), and With the. Iljušina - CKB-55 (ЦКБ-55), the future of Il-2, was in may 1939 decided to further work on the type Sh-tandem to stop. At that time, it was the second piece finished approximately 65 - 70 %.
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URL : https://www.valka.cz/Grusin-S-Tandem-t141716#459176
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