The prototype Polikarpov I-16 took first time to the air 30. december 1933 under the designation TsKB-12. Right from the start it was demonstrating the ability to reach high speeds, and quit soon someone got the idea, that it could be turned into a courrier plane.
At that time Vozhd Stalin were getting increasely suspicious to almost anyone around him - in fact to la arge part of the russian population. After the Holodomor in 1933, when 3.5 - 5 millions ukrainians died of starvation, other groups in SSSR were soon to feel Stalins terror.
So there was a need for a fast plane to bring the orders of Stalin, the Politburo and OGPU (later NKVD) to all cornes of the Union of Soviet Socialist Republics. Orders that would send hords of people to distant prison camps, kill them or make them fall out of windows - sounds familiar?
The Polikarpov Design Bureau came up with Po-4, which were an slightly enlarged version of the I-16, with larger wings to hold more fuel and a longer fuselage with a two-seat, closed cockpitt. The first flight of the Po-4 was in april 1936, and a production run of 50 planes was almost immediately initiated.
My build will be based on the old (and awfull) Revell Poliparpov I-16 kit, of which I happens to have some in my stash.