The aviation authorities have named the official reason for the icing of the S7 aircraft

The Federal Air Transport Agency has named the official reason for the icing of the S7 aircraft, which was flying from Magadan to Novosibirsk on December 2 and urgently landed in Irkutsk. The document is at the disposal of Izvestia.

So, according to the department, in preparation for the flight, in accordance with the decision of the crew, only the surfaces of the wing and the stabilizer of the aircraft were treated from icing. In this case, the snow from the side fuselage was not removed.

“Snow removal from the fuselage surface was not carried out, which, while the aircraft was parked for 2.5 hours in a heavy rainfall, led to the accumulation of a large amount of snow on the upper surface of the fuselage,” the Federal Air Transport Agency noted.

After turning on the heating of the windshields, the snow melted, and in taxiing conditions at low temperatures caused the appearance of a layer of frozen ice in the front part of the fuselage in front of the total pressure receivers (PPD).

“These ice build-ups led to a distortion of the air flow (violation of its laminarity) when entering the RPM after takeoff, which led to the failure of three control systems in the mode of minimum operation, the autopilot and autothrottle were turned off,” the department stressed.

Earlier that day, Izvestia wrote that the Federal Air Transport Agency recommended that airlines and airports prohibit flights in the presence of snow or icing on airplanes.

In addition, airlines and airports were encouraged to include in their programs for the protection of aircraft from ground icing a requirement to prohibit the commencement of an aircraft flight. It is noted that the flight cannot be performed if there are deposits on the surfaces of the aircraft in the form of any snow (not only wet).

On December 7, the general director of the Magadan airport, Dmitry Sivolobov, denied the likelihood that the S7 plane had been treated with a low-quality “anti-freeze”. He also added that not all aircraft are treated with de-icing fluid before departure.

Prior to that, on December 6, the Eastern Interregional Directorate of the Investigative Committee (IC) of the Russian Federation opened a criminal case on the provision of services that did not meet security requirements. Also on this day, it was reported that an analysis of the quality of anti-icing treatment is being carried out in Magadan.

According to Izvestia, the problems with the S7 control began after the plane was switched to the “direct” autopilot mode. The aircraft began to wobble violently, and its speed began to fluctuate. The system gave a “stall danger” signal, and also notified about icing of the first and second engines. As a result of the buildup, the plane lost 2.7 thousand meters of height.