What happened
The flight was operating under an instrument flight rules (IFR) flight plan and had received clearance from air traffic control for an instrument landing system (ILS) approach. Prior to the accident, the aircraft owner and a flight instructor—who had performed the pilot's instrument training and aircraft checkout—had specifically instructed the pilot not to operate the unspecified aircraft in IFR conditions.
The aircraft maintained an altitude of 13,000 feet for 32 minutes before beginning its approach. Notably, the airplane was not equipped with cabin pressurization or supplemental oxygen. During the approach, the pilot failed to maintain the specified ground track. The aircraft subsequently impacted mountainous terrain approximately 13-1/2 nautical miles north-northeast of the airport. This impact occurred in heavy snow conditions and at a location roughly 15-1/2 nautical miles beyond the point where the approach procedure required a turn onto the localizer.
At the time of the accident, the airport was not equipped with an approach control radar or a control tower, and the aircraft was not in radar contact with air traffic control. A witness near the site, a hunter, observed the airplane flying at a low altitude through heavy snowfall. The witness reported hearing a loud metallic 'clank' approximately 20 to 30 seconds after the aircraft moved out of his line of sight. The time recorded by the witness's watch aligned with the estimated time of the accident.
Findings
The investigation determined that the pilot failed to follow the specified ground track for the approach, leading to the impact with terrain.