armed with 4x ShKAS in the roots of the upper main-plane, synchronised to fire through the propeller.. IS-2 – The second airframe with improvements and M-88 engine in a long-chord NACA cowling, armed with 2x BS and 2x ShKAS. IS-3 – Projected version, no information available. IS-4 – Final design version with AM-120 or AM-37 engine, refined aerodynamics and tricycle undercarriage. Specifications (IS-1) See also References Bibliography Green, William and Gordon Swanborough. "Ingenious and Innovative, but...! The 'Folding Fighters' of the 'Forties". Air Enthusiast Quarterly, No. 2, n.d., pp. 186–190. Gunston, Bill. "Encyclopaedia of Russian Aircraft 1875-1995". London:Osprey. 1995. http://issuu.com/jeanlulu/docs/-aviation--soviet-x-planes--yefim-gordon---bill-gu External links Aviation.ru Youtube.com 1940s Soviet fighter aircraft IS Variable-geometry-wing aircraft Single-engined tractor aircraft Aircraft first flown in 1940