What happened
During a flight from Chelyabinsk to Moscow, the crew began their approach toward Moscow-Domodedovo under deteriorating weather conditions. As the aircraft descended to 3,600 meters, it encountered a passing cold front characterized by heavy rainfall and icing. This environmental change led to the obstruction of the pitot tubes, which resulted in erroneous instrument readings, including an airspeed indicator reading zero.
Believing the aircraft was approaching a stall, the pilot initiated an emergency descent at a rate of 100 meters per second and a speed of 813 km/h. During this maneuver, the aircraft experienced positive acceleration of 3.2 g, which caused significant structural damage to the airframe. Despite the severe turbulence and damage, the crew successfully diverted to Moscow-Sheremetyevo Airport and performed an emergency landing. While all 185 occupants evacuated without injury, the aircraft was subsequently determined to be a total loss due to irreparable damage to the fuselage.
Findings
Investigations revealed that the primary cause of the instrument failure was the failure to activate the pitot heating system. This oversight occurred because the crew did not properly prepare the aircraft's lights or complete the required pre-takeoff checklist while at Chelyabinsk Airport.