Siberian Light Aviation Flight 42

Investigation

Crash investigators announced that they would be investigating four possibilities of the cause of the accident, including problems with the fuel, equipment malfunction, extreme weather, and pilot error, with a preliminary report expected around late August 2021. On July 19, investigators revealed that they had recovered the flight data recorder and that the data was being recovered. The aircraft was not equipped with a cockpit voice recorder.

In the days following the accident, a source close to the investigation told reporters that the main theory of the cause of the crash was that the aircraft entered a region of high humidity, which led to the air intakes of the engines becoming obstructed with ice. Still unknown was why the anti-icing systems aboard the aircraft failed to prevent the buildup and why the flight took off in the conditions in the first place. Another source indicated that there was a possibility that the pilots had failed to pay attention to the fuel levels in the aircraft, pointing to the severe damage to the aircraft and the fact that the fuel did not leak out and cause a fire or explosion in the crash. On July 16, 2021, the investigative authorities of the Investigative Committee of Russia opened a criminal case on the grounds of a crime under Art. 263 Criminal Code of Russia (violation of traffic safety rules and operation of air transport). However, if the investigation finds that the accident was caused by something outside the control of the pilots, the crew can count on awards for skill and courage in safely guiding the stricken aircraft to the ground.

On 28 July 2021, a source told reporters that the flight data showed that the aircraft had leveled off at 3100 m, which was lower than the assigned altitude. About a minute after leveling off, the engines failed, about three seconds apart. The automatic icing warning system did not indicate that the plane was suffering from icing, and the anti-ice system of the engines and airframe did not start. Investigators also revealed that they were looking into the work and rest schedule of the flight crews at the airline, after they discovered that the crew involved with the crash had performed ten flights totaling 12.5 hours in the previous 24 hours before the crash.

In September 2021, The Interstate Aviation Committee published a preliminary report on the accident. The report stated that the amount of oil, fuel, and hydraulic fluid that had been loaded on the aircraft were appropriate for the scheduled trip, but that the flight crew had been severely overworked in the days preceding the accident, including having flown nine other flights totaling nearly 14 hours in the previous 24 hours, and had not been given time to rest. The report stated that while in flight, the engines of the aircraft iced up and stalled, and were not able to be restarted before the crash. The committee resolved to release a final report on the accident at a future date.

In December 2021, investigators disclosed that they had narrowed their investigation to two possible causes of the crash. One possible explanation was that the anti-icing system had malfunctioned, causing the icing of the engines. The other possibility that they are investigating was whether the anti-icing system had been activated by the crew too late due to crew fatigue.

In July 2022, officials announced that they had concluded that the cause of the accident was determined to be that due to crew fatigue, the aircraft's anti-icing system had not been turned on at the appropriate time, which led to the accumulation of ice and engine failure. The pilot was criminally charged for a violation of aircraft safety rules.

In September 2023, the IAC published their final report on the accident, reiterating the findings of the preliminary report. The flight crew's stress and a faulty ice detection sensor were additional contributing factors. In December that year, the criminal case against captain Prytkov was closed due to the statute of limitations expiring.