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Sh-Tandem
Light Attack Aircraft
UPM MAI

Sh-Tandem is an experienced two-seater light attack aircraft of the original tandem scheme of Pyotr Dmitrievich Grushin, the future creator of the S-300 missile system. When choosing a scheme, it was meant that it would allow, in the presence of an inevitable mass separation along the length of the aircraft, to obtain fairly good characteristics of the longitudinal stability of the aircraft.

The admissibility of using more rear alignments allowed Grushin to place a machine-gun mount directly in the tail section of the aircraft, which, in combination with the two-fin tail, provided large firing angles. The tandem scheme made it possible to reduce the diameter of the circle into which the contour of the aircraft fit in the plan, which contributed to the lesser attackability of the attack aircraft. At the same time, the distribution of payload and armor was simplified.

Small wingspan hindered the use of wood as the main structural material to a lesser extent. The main, front wing, was low-lying and the landing gear struts and wheels were retracted into it. The crutch wheel is non-retractable. The hind wing, which had an upper location, with an area equal to 45% of the main wing, also served as a horizontal tail. Ailerons were on both wings, and on the rear wing they simultaneously served as elevators. The vertical tail was made in the form of washers attached to the ends of the horizontal tail.

Initially, the aircraft was planned to be equipped with an air-cooled M-88 engine. But since it was not ready, the M-87 was put on the Sh-Tandem, and then the M-87A.



Sh-Tandem
Crew 2
Dimensions
Wing span, m 11.00
Wing area, m² 30.40
Length, m 8.50
Powerplant
1 × PE M-87, power, h.p. 1 × 930
Weight, kg:
Empty
Loaded weight 2,560
Performance
Maximum speed at the ground, km / h 406
Maximum speed at altitude, km / h 488
Ceiling, m
Armament
5 × 7.62 mm ShKAS machine gun, bombs on the suspension, kg 200

The fuselage, center section and main wing were manufactured by a team of MAI training and production workshops of 18 people in just 45 days. By January 8, 1939, the aircraft in a single-seat version and without weapons passed preliminary flight tests with the M-87 engine. A fairly high maximum flight speed was reached, which was quite consistent with the TTT for the aircraft. At the ground, it was 406 km / h, at an altitude of 4250 m - 488 km / h. According to the test results of P.D. Grushin was recommended to move the navigator's cabin a few more back on a two-seater version and equip it with an MV-5 rifle mount.

In September-October 1939, a two-seater version of the Sh-Tandem with the M-87A engine (rated power at an altitude of 4700 m - 950 hp) and with a variable pitch propeller VISH-3 underwent joint (factory and state) tests ... The test report was approved on October 10th. The navigator's cockpit was shifted back, and a shielded MV-3 ​​turret was installed. The armament of the attack aircraft was standard for light attack aircraft of that time: 4 wing-mounted ShKAS machine guns with 2400 rounds of ammunition, one ShKAS machine gun on a turret (700 rounds of ammunition) and 200 kg of bombs. During the tests, 51 flights were performed with a total flight time of 18 hours 38 minutes. With a flight weight of 2800 kg, the attack aircraft had a maximum speed at the ground of 361 km / h, and at an altitude of 5600 m - 444 km / h. Landing speed without flaps is 140-145 km / h. Takeoff run - 400 m, run - 480 m. The flights were carried out with a CAP of 34-44% of the MAR. It was noted that the aircraft is very easy to operate.

The plane did not pass the state tests due to the discrepancy between the flight data of the TTT, insufficient directional stability ("when the speed increases, the plane scours"), a cramped navigator's cabin, an unsuccessful landing gear, and insufficient strength of the front wing. The takeoff of the plane was difficult. Longitudinal stability reserves were insufficient. The plane reacted sluggishly to the rudders. It was believed that the excess of the rear wing over the front was not a very good decision. The armament was also undelivered. Since the MV-3 ​​turret "ate" 34 km / h of flight speed, it was proposed to make the rear gun mount conical, allowing the machine gun to move in a plane passing through the longitudinal axis of the mount and rotate this plane around the axis by 360 °. At the same time, it was noted that the Sh-Tandem combat scheme is of interest. It was proposed to transfer the plane to TsAGI, bring it and again submit it for testing.

A backup for the Sh-Tandem aircraft was built. On the second copy, the rear wing was lowered down. When the degree of readiness of the understudy was 65-70%, all work was stopped. The unusual layout and rather weak armament did their job. In May 1939, the NKAP decided to stop all work on the Sh-Tandem.

Photo Description

Drawing Sh-Tandem

Bibliography

  • The history of designs of planes in USSR 1938-1950 /Vadim Shavrov/
  • Red Army stormtroopers / Vladimir Perov, Oleg Rastrenin /
  • Transformer engineer Grushin / Andrey Averin /