On December 7, 2017, a Eurocopter AS-3COB3, registration RA-07277, departed from the Hydrostroy landing pad in Bratsk for a planned business flight to the settlement of Chistyy. The pilot had submitted an IFR flight plan to the Novosibirsk Air Traffic Control Center the previous day, intending to fly through airspace classes C and G.
Prior to departure, the pilot refueled the aircraft and performed pre-flight maintenance. While the pilot did not request a weather briefing from AMSG Bratsk, regulations allowed the pilot to authorize the crew for flight at this specific landing pad due to the lack of an on-site medical professional.
At 12:37, the pilot and one passenger departed the Hydrostroy landing pad and established contact with Bratsk-Approach. By 12:42, the pilot had transferred control to Bratsk-Region area control, reporting an altitude of 350 meters based on the QNH pressure setting. The pilot's final communication with area control occurred at 12:44, during which the pilot requested to close the flight plan.
Following the loss of contact, the accident resulted in two fatalities. No mechanical failures of the helicopter's onboard systems or components were identified prior to the incident.