What happened
The pilot initiated contact with Flight Service Station (FSS) over Lewiston Regional Airport (LWS) to obtain a weather briefing for a route extending from Lewiston to Boise, Idaho. During this initial consultation, the FSS personnel advised that Visual Flight Rules (VFR) flight was not recommended for the intended route due to mountains being obscured by rain showers.
Approximately 30 minutes after the first contact, the pilot called FSS again to report that he had become lost in clouds while attempting to follow the planned route. Following this transmission, radio contact was lost at 23:05 Mountain Standard Time on April 26, 1986.
The wreckage was eventually located on rising terrain at an elevation of 4,500 feet. The aircraft was discovered by a U.S. Forest Service plane on July 31, 1987, situated approximately 33 miles northwest of Grangeville, Idaho.
Findings
The primary factor contributing to the accident was flight into instrument meteorological conditions without appropriate instrumentation or training. The pilot ignored safety advisories regarding obscured terrain and weather hazards, leading to spatial disorientation and loss of control in mountainous terrain.