In picture: a So-4 Sokol fighter of the VK.12 no. 19, piloted by the popular ace Lt. Dominik Chkalov.

Sobol So-4 "Sokol"

The Sobol So-4 "Sokol" (lit. Falcon) is a single-engined single-seat monoplane fighter designed by Sobol Aviation Company for the Alyaskan Imperial Air Force (AVVS) in 1935. It was the first Alyaskan monoplane fighter, and was the most advanced of its time.

The first series Sokol is powered by the large 1100 hp Krupin F1-400/C air-cooled radial engine, giving the maximum speed of almost 460 km/h at 3.000 m altitude. It is armed with 3 × 13 mm AvP-29U machine guns with 300 ammunitions for the wing guns and 400 for the fuselage gun, giving a total of 1000 ammunition. The Krupin engine is extremely powerful for the size of the Sokol, giving it supreme acceleration. The Sokol is also moderately maneuverable with decent energy retention. It can also carry a payload up to a 100 kg bomb. The open cockpit of the Sokol disallows it most of the time to reach neither maximum speed nor altitude.

Variants
- So-4A (1935, this one)
Krupin F1-400/C radial engine
3 × AvP-29U machine guns
1 × BON-100 bombs
- So-4B (1936)
- So-4T (1937)
- So-4bis (1939)

Controls
AG2 : Flaps