Mountainous Terrain Impact During IFR Approach in Heavy Snow (N3729T)

Flight Operations and Aircraft Configuration The aircraft was operating under an instrument flight rules (IFR) flight plan and had received clearance from air traffic control (ATC) for an instrument landing system (ILS) approach. The airplane was flown at an altitude of 13,000 feet for 32 minutes prior to commencing the approach. The aircraft was not equipped with supplemental oxygen or cabin pressurization. The aircraft owner and the flight instructor, who had completed the pilot's instrument training and checkout in the accident aircraft, stated that they had instructed the pilot not to fly the aircraft in IFR conditions.