The last design authorised from OKB-3 was to provide comparision against Mil and Yak single-rotor submissions to VVS requirement for a three-seat all-weather communications helicopter. Dynamic parts were as previous Bratukhin except for hydraulic rotor-hub dampers and faired masts with oil-cooler inlets. Wing of lifting section are set at zero incidence. The fuselage had improved form, with round instead of polyhedral top and bottom. The tail was basically as the B-5. The pilot was in B-5 type nose, main cabin for two seats, with space at rear for freight ot two stretchers (in lieu of passengers) loaded through enlarged door. Improved differential rotor controls with reduced friction were fitted. The B-11 was equipped for blind flight.
Two prototypes were completed in April 1948, flying in June and September. Progress was made with measured performance, sustained (47 min) single-engine flight, autorotative landings and in eradication of various faults stemming mainly from vibration was achieved. One problem was lack of wing lift resulting from incidence setting, causing the rotors to stall at high forward speeds. A further snag was hydraulic leaks difficult to rectify. On 13 Decemeber 1948 first machine shed a blade from the right rotor, killing Ponomaryov and I.G.Nilus.
After several modification, including installation of new engines (same series), it was presented on an Aviation Parade.
The favored scheme of twin-rotor helicopter became "The Flying Banana" (due to less drag), and the transversal scheme was not used again until the Mil Mi-12.
Engine: 2 x AI-26GRF, 575hp
Rotor diameter: 10.0m
Take-off weight: 4150kg
Empty weight: 3398kg
Max speed: 155km/h
Service ceiling: 2550m