Accident Summary
An aircraft conducting a localizer DME approach to an airport collided with mountainous terrain approximately 16 minutes after the pilot was cleared for the approach. The accident occurred at an elevation of about 2,000 feet, while the airport elevation was 776 feet. The aircraft was on a heading of approximately 220° at about 8.5 DME on a bearing of 051° from the airport. According to the LOC/DME runway 23 approach plate, the minimum altitude between the outer marker (6.6 DME) and 10 DME was 3,000 feet.
Circumstances
All three occupants were killed. An autopsy revealed multiple extreme impact injuries. The pilot's carboxy hemoglobin level was measured at 20%. Products of combustion were found on the fresh air side of the cabin heater and heat exchanger, but the source of the combustion products was not determined.
Post-Crash Fire
A post-crash fire consumed most of the wreckage. The cabin heater was not located within the fire area.
Probable Cause
The official probable cause for the in-flight collision with terrain was the pilot in command not following IFR procedure and not maintaining proper altitude. Contributing factors included high terrain, weather conditions (clouds and fog), a leak in the air conditioning/heating/pressurization system, and physical impairment due to carbon monoxide.