Accident
A private pilot and a pilot-rated passenger were returning to an airport in night visual meteorological conditions with a cloud ceiling about 1,500 ft above ground level. Radar data showed that the airplane overflew the airport, completed a 360° descending right turn, and overflew the airport again before entering an approximate 180° left climbing turn toward and over an unlighted area within a densely wooded national forest. The airplane continued the left turn and entered a descent, impacting a river about 1 mile from the airport.
Investigation
All major components of the airplane were recovered from the river except the outboard section of the left wing and the left aileron. An examination of the airframe and engine revealed no mechanical malfunctions or failures that would have precluded normal operation. Because each of the two pilots on board would have been capable of safely landing the airplane, it is unlikely that an acute event from either occupant's heart disease contributed to the accident. The night conditions, which included overcast clouds obscuring a nearly full moon, and the pilots' maneuvering for landing over an area devoid of cultural lighting provided conditions conducive to the development of spatial disorientation. It is likely that the pilots experienced a "black hole" illusion while maneuvering to align with the runway for landing, which resulted in an uncontrolled descent and impact with water.
Probable Cause
The official probable cause is the pilots' spatial disorientation while maneuvering for landing in night conditions over unlighted terrain, which resulted in an uncontrolled descent and impact with water.