What happened
A noninstrument-rated commercial pilot departed under Visual Flight Rules (VFR) conditions at twilight. During the en route phase of flight, the pilot encountered marginal VFR conditions. Radar data indicated that the aircraft performed a gradual left turn toward rising terrain as it entered an area characterized by poor weather.
Following this turn, the aircraft flew into rising wooded terrain at an elevation of approximately 1,600 feet near the top of a mountainous ridge. Witnesses located in a sparsely inhabited rural area about 3 miles from the accident site reported that the aircraft flew low over their location during "pitch black" light conditions and that Instrument Meteorological Conditions (IMC) were prevailing. While torrential rains had recently ended at the witnesses' location, such rains continued in the area where the aircraft impacted the terrain.
The investigation
The investigation found no evidence of a preaccident mechanical malfunction of the aircraft. However, another pilot who had recently operated the same aircraft noted that the heading indicator would precess 30 degrees within a 10-minute period. Additionally, the pilot's flight instructor confirmed that while the pilot was working toward an instrument rating, he was not yet qualified to fly by reference to instruments.