The intention being to combine the short field length and climb capabilities of the biplane with the speed of the monoplane fighter.
The fuselage forward of the cockpit, wing spar booms and the combined lower inner wing and undercarriage assemblies were built up from welded 30KhGSA steel tubing, whilst the rest of the airframe was constructed from D16 duralumin throughout except for fabric covering on the control surfaces.
The pneumatically actuated inwards retracting undercarriage was housed inside the inner lower-wing which folded at approx ½ span to lie in recesses in the sides of the fuselage.
Control of the undercarriage retraction and wing folding was accomplished with a single three position lever in the cockpit.
A second machine was built fitted with a more powerful engine but flight tests were interrupted by the German invasion in 1941.