What happened
On April 5, 2015, an Robinson R-66 helicopter, registration RA-06382, was operating a flight plan between the settlements of Chistoye and Gorodki in the Tyulgansky district. The flight plan had been approved for operation within Class G airspace. The pilot had obtained meteorological information for the area via the internet prior to departure.
At approximately 06:00, the pilot departed for the mission. At 06:40, the aircraft landed on a snow-covered clearing in a forested area that had been packed down by a snowmobile. Following the landing, the pilot performed rocking motions with the aircraft to verify the stability of the surface. There were no passengers on board at the time of the incident. The flight and landing were completed without incident, leaving 210 liters of fuel remaining.
Approximately one hour after landing, the pilot decided to conduct an engine test. The engine was started and run at idle speed. About one minute after the engine was started, the helicopter's skids sank through the crust of the snow, causing the aircraft to slide backward and to the right into loose snow. During this movement, the main and tail rotor blades struck the snow surface, resulting in structural damage to the rotor system.
The investigation
Investigators reviewed the flight plan and the pilot's actions. The takeoff mass of the aircraft was recorded at 834kg, which was within the maximum takeoff weight limit of 1225kg specified in the R-66 flight manual. The center of gravity was measured at 2590mm, which was within the allowable range of 2310mm to 2605.5mm. The investigation noted that the pilot had used internet-based weather reports for the flight area.