Background
A contract between Barkol Airlines (OOO "Aviation Company 'Barkol'") and Novgorod Regional Oil Pipeline Directorate (OOO "Transneft-Baltika") dated June 9, 2018, stipulated aviation services. On November 7, 2018, the crew of Mi-8T helicopter RA-25600 was scheduled to fly from Veliky Novgorod to Bryansk for an aerial patrol of the main oil pipeline "BTS-2". However, the actual flight proceeded only to Andreapol, where a landing was made. Due to weather conditions not suitable for Visual Flight Rules (VFR), the commander decided to abort the mission and flew to Barkol's base at Pereslegino (Velikiye Luki).
Events of November 8, 2018
Around 05:00 on November 8, 2018, the crew arrived at Pereslegino to continue the work. Pereslegino does not have a medical worker authorized to conduct preflight medical examinations. Therefore, in accordance with paragraph 8.10.1 of Federal Aviation Regulations (FAP-128), the commander made the decision to clear the crew for the flight. The crew was subsequently cleared.
According to crew statements, the commander obtained meteorological information for the flight area via telephone and from dispatchers. Preflight preparation was conducted under the commander's supervision. During preparation, the helicopter was refueled with 683 kg (800 liters) of TS-1 fuel. The total fuel load before departure, as recorded in the logbook, was 3383 kg (4300 liters). The quality of the fuel was confirmed by tests ordered by the Investigative Committee of Russia.
The takeoff weight of the helicopter before departure from Pereslegino was 11159 kg, and the center of gravity was +130 mm. These values were within the operational limits specified in the Mi-8T flight manual (maximum takeoff weight 12000 kg, forward center of gravity limit +370 mm, aft limit -95 mm). After completing the preflight inspection, the flight proceeded.