Russians was the country with most ideas in airplanes, with multiple designers and other. This brands first type single seat polymorphic fighter was designed and produced in the USSR from 1938, ready to fly in 1940.
Expected top speed was expected of 720km/h! Unfortunately, as often happens, the engine didn't materialize, therefore designers installed mass-built AM-37 engine. New aircraft carried also more powerful armament.
The IS-4 was apparently flown sometime late 1940 or early 1941, but the flight records were lost in the German invasion.
As the press of the German invasion forced the Soviet aircraft industry to concentrate upon conventional designs which could be produced in greater numbers in a short period, and the fact that apparently the IS-4 had some rather unusual handling characteristics, further work was halted.
Its also easy to see some recembles with the Polikarpov, where also Nikitin was involved in design earlier......A lot of pretty ok ideas came, and was produced as prototypes,eg......if they just had motors that had function!
here is a S-2 where the hydraulic system for underwing is shown.
Im building the IS-4B in approx 900mm wingspan.
Typical me, when i build something, its totally unusual plane......(for most) . Problem here is to make a way to "retract" the lower wing into the upper wing. Hopefully i find something to use.