A Stryzh Avia Antonov TR-301, chartered by a gold mining company, crashed in adverse weather conditions in Chukotka. All three occupants survived the crash but sustained various degrees of injuries. The TR-301 is an An-2, converted by Tekhnoregion into a monoplane by removing the lower wings. Conclusion: The aviation accident involving the TR-301 aircraft RA-84566 (collision with a mountainside) occurred in a mountainous area during daylight under meteorological conditions that did not permit Visual Flight Rules (VFR) operations, as a result of the pilot-in-command (PIC) losing visual contact with the ground. Contributing factors included: 1. The decision by the PIC to proceed with the flight despite forecasted meteorological conditions along the route and at the landing site that did not permit VFR operations (due to heavy precipitation). 2. The failure of the PIC to take measures to avoid a hazardous zone when signs of approaching dangerous meteorological phenomena became evident during the flight. 3. Conducting the flight in violation of the aircraft’s operational limitations under conditions unsuitable for VFR. 4. The PIC’s failure to make a timely decision to return to the departure airport or divert to an alternate airport when weather conditions deteriorated to levels below the minimums established for VFR operations.