SAM-7 'Sigma', A.S.Moskalev

23k b/w drawing "History of aircraft construction in the USSR", Vol.2 p.105

Experimental all-metal 2-seat fighter, one of the most unusual designs in Soviet and World practice. Tailless low-wing monoplane with unswept tapered wing, carrying large endplates with rudders. Role of the elevator was assigned to full-span slotted flap, with their outer panels serving also as ailerons. Control system solution allowed the ailerons operate as both differential ailerons for roll control and as elevators for pitch control.

15k b/w drawing "History of aircraft construction in the USSR", Vol.2 p.105

Since the M-34 at the time had no reductor, wooden 4-blade propeller was installed. Major cooling system was of evaporative type, supplemented by retractable honeycomb radiator (behind the pilot's seat) for low speed operation (taxi, takeoff, landing).

12k b/w drawing "History of aircraft construction in the USSR", Vol.2 p.105

Rear part of fuselage was occupied by gunner in a glazed cockpit, operating twin ShKAS machineguns. Two other ShKAS (synchronized) were installed o n the engine.

Landing gear was retractable into the fuselage and leading edge of the wing. Tailskid - of a fixed type, almost completely hidden in the fuselage.

12k b/w drawing "History of aircraft construction in the USSR", Vol.2 p.105

SAM-7 had a center of gravity at 13...15% of a wing chord, but test flights proved its sufficient stability. Very clean layout in conjunction with all-smooth aluminum alloy skin could provide a high performance, but trials were restricted to high speed taxi and short straight-line hoops. Official version is that not all airdynamic issues were addressed and not all aircraft components had sufficient strength.

But it is also quite possible that canceling of SAM-7 (and other designs of the 'Sigma' line) was a resistance of aviation heavy-weight designers, profiting from production of conventional designs.