It's Grusihin's Sh-Tandem (also known as Sh-MAI, MAI-3 and MAI-Tandem). It was build on december 5, 1937 as experimental light attack aircraft in Moscow Aviation University. The flght program was conducted by famous Russian test pilot a polish origin Stefanovsky.
It was wooden and armor-plated, built by a group of 18 students in 45 days.
In 1937 it was powered by M-87 and in 1939 by M-87A engine
Sorry for bad syntax - just translated this from a Russian site:
On January 8th, 1939К the plane with one pilot was certified for initial flight testing program with M-87 engine, where it reached the speed of 406 kph. at ground level and 488 kph at 4280 m height.
Afte rthe flight test Grushin was advised to put the navigator's cockpit further back.
At September and october of 1939 it was equiped with 950hp M-87A engine and VISh-3 propeller
and was taken to factory and state flight tests. The test results were published on October 10th.
The armanent was standrd for the light attack aircraft of the age – 4 wing-mounted ShKAS machine guns, 1 turret ShKAS machine gun and 200kilos of bombs.
Flight tests included 51 flight with a total flight time of 18 hrs 38 mins. With a TOW of 2800 kilos the olane was able to reach 361 kph at ground level and 444 kph at 5600 m. The landing speed without air brakes was 140-145 kph. Take-off run was 400 m and the landing run 480 m.
The pilot said that the aircraft was very easy to maintain.
The plane failed state test program for weak performance, poor rudder stability, small navigator’s cockpit, weak landing gear and weak front wing.
The take off was difficult due to elevator instability and weak rudder response. It was considered that the larger size of the rear wing wasn’t a successful solution.
The armament was far fro pefect too – the MV-3 turret was so heavy that the plane lost 34 kph of speed with it. The solution was to replace it with a Fokker G1- like construction,
At the same time the averall scheme was seen as a success. It was planned to move the plane to Central Aerohydrodynamics Institute for an upgrade and successive testing,
Another Tandem-Sh was built with a lower rear wing.
The main feature of the plane was retractable tricycle gear.
The second plane was equipped with 800 hp M-63 engine
