Designed 1934, this used Bratukhin’s rotor with alternate large articulated blades and small rigid blades but sealed up to absorb power of large US water-cooled V-12 engine. Latter mounted in nose of steel-tube fuselage covered in fabric for streamlining, with tandem cockpits at rear behind main rotor pylons. Engine arranged facing to rear with reduction gear driving second reduction gearbox at foot of rotor shaft. Auxiliary drive from rear wheelcase to three-blade cooling fan drawing air through main radiator on nose. Rotor torque reacted by two 2250mm three-blade propellers near tips of small fixed wing. Complete aeroplane flght controls – ailerons, elevators, rudder – in addition to improved cyclic/collective controls on main rotor. Intention was to test as helicopter and later arrange for drive to main rotor to be disconnected and aircraft flown as autogyro, with all power used for forward populsion via propellers, with aeroplane flight control.
11-EA was completed summer 1936 and completed tethered testing on a platform, using front cockpit as observer and rear as pilot, though dual controls provided. Considerable difficulties with distribution of power, main blade construction and maintenance of steady height whilst varying pull power of propellers. Late 1937 wave of arrests removed Chyeremukhin, Izakson and many other helicopter engineers and virtually halted further work through fear of accusation of sabotage.
After much calculation Bratukhin dared 1938 to begin alterations and in spring 1938 aircraft emerged as 11-EA PV (Propulsivnyi Variant).
Bill Gunston "The Osprey's Encyclopedia of Russian Aircraft", 2000
Experiments with 5-ÅÀ rotor allowed I.P.Bratukhin to build substantially bigger and heavier aircraft. The engine was housed in the front end of fuselage, together with cooling fan and radiator. Main rotor was same as on the 5-ÅÀ, but control rotors were placed on the wing (actually 11-EA had an appearance of a monoplane with helicopter rotor and two tractor propellers on the wing).
Controls included both for helicopter and airplane 'components' of the apparatus.
Flown on the rope only, due to over-complicated control system. One built.
Technical data for 11-EA
Crew: 2, engine: 1 x "Conqueror" pistone engine, rated at 630hp, rotor diameter: 15.4m and 9.2m, length: 8.5m, height: 3.5m, wingspan: 10.6m, wing area: 11.3sq.m, take-off weight: 2600kg, ceiling: 40m