What happened
On January 1, 2011, a scheduled passenger flight, 7K 348, was prepared for departure from Surgut to Moscow Domodedovo. The flight plan had been submitted to air traffic services on December 31, 2010. The aircraft, a Tupolev Tu-154B-2 with registration RA-85588, underwent operational technical maintenance at the Kogalymavia LLC aircraft workshop under the A1+OV service standard.
At the time of departure from Surgut, the aircraft was carrying a total of 134 people. This included 8 crew members and 10 members of a reserve crew who were scheduled for a different flight to Tyumen. The aircraft's payload was 1,137 kg, with 87 seats occupied. The taxi weight was recorded at 97,232 kg, and the takeoff weight was 96,732 kg.
The investigation
Technical records indicate that a pre-flight inspection was completed by the flight engineer in accordance with the flight manual requirements. The aircraft was fueled with 31,961 kg of TS-1 fuel, which included the addition of PVK-liquid to prevent ice crystal formation. Laboratory analysis of the fuel drained from the aircraft's system confirmed that the concentration of PVK-liquid "I-M" was 0.11%, which fell within the required operational parameters of 0.1% plus 0.05%.
Fuel levels were determined to be sufficient for the flight from Surgut to Moscow, including the necessary reserves for an alternate landing at Nizhny Novgorod.