Contract and Flight Plan
On 31 August 2018, Angara Airlines and the Siberian Research Institute of Geology, Geophysics and Mineral Resources (SNIIGGiMS) signed contract No. 239/18 for air transportation. On 2 September 2018, the crew of helicopter Mi-8MTV-1 RA-25502 was scheduled to fly from Ust-Kut airport to geographic coordinates 54°49′55.4″N 108°41′11.2″E and back, for commercial carriage of passengers and cargo (evacuation of a geological group). Departure was planned for 03:00 local time.
Pre-Flight Medical Check and Briefing
At 01:30 on 2 September 2018, the crew underwent a medical examination at the Ust-Kut airport medical station and were cleared for the flight, as recorded in the pre-flight medical log. Pre-flight preparation was conducted under the direction of the pilot-in-command (PIC). The crew obtained meteorological information on forecast and actual weather for the flight area from the Ust-Kut airport meteorological service. The PIC signed the pre-flight meteorological briefing form.
Fuel and Weight and Balance
According to the aircraft logbook, the helicopter was refueled with TS-1 fuel totaling 2,300 liters (1,835 kg). The total fuel on board before departure was 3,500 liters (2,795 kg). The fuel supplier, TZK Irkutsk, provided a quality certificate dated 28 August 2018. The fuel condition was confirmed by tests ordered by the Investigative Committee of the Russian Federation. The takeoff weight of the helicopter before departure from Ust-Kut was 10,600 kg, with a center of gravity at +75 mm, both within the limitations specified in the Mi-8MTV-1 flight manual (maximum takeoff weight 13,000 kg, forward CG limit +300 mm, aft CG limit -95 mm).
Decision to Depart
After completing the pre-flight inspection, the crew accepted the aircraft with no discrepancies, as noted in the logbook. At 02:46:15, the PIC made the decision to take off and requested clearance from air traffic control.