What happened
During a scheduled Part 135 cargo flight operating under IFR flight rules, the pilot initially requested an ILS-DME approach for runway 10. Approximately two minutes after this initial request, the pilot modified the arrival procedure, requesting a VOR-B approach for runway 28 instead. Air Traffic Control cleared the aircraft for the approach to the non-towered airfield. Prior to arrival, the pilot contacted the airport's Unicom service to request that ground personnel be prepared with necessary fuel and oxygen supplies.
At the time of the incident, the aircraft was positioned 5.8 nautical miles from the approach end of runway 28 at an altitude of 7,900 feet. The established approach minimums for the VOR-B procedure required an altitude of 7,900 feet, a level the pilot was permitted to descend to at a distance of 8.7 nautical miles from the runway.
Findings
Data regarding the navigational aids showed the VOR was situated at a bearing of 285 degrees at a distance of 13.6 nautical miles from the site of the accident. The ILS-DME transmitter was located at 285 degrees at a distance of 5.6 nautical miles from the accident location. The aircraft's avionics configuration included a single DME display head and a selector switch for Nav 1 and Nav 2. The pilot's change in approach request occurred while the aircraft was already navigating the terminal area.