Accident Flight
Aircraft on a personal sightseeing flight in the Sierra Nevada Mountains collided with trees at the 8,300-foot level in a box canyon. The floor of the canyon rises steeply from the entrance, ascending approximately 3,000 feet over 3 miles. Surrounding ridge tops forming the box canyon exceed 11,000 feet mean sea level (msl). According to witness observations and National Weather Service data along the route, light wind conditions prevailed in and around the accident site, with no documented unusual meteorological phenomena.
Video Evidence
A passenger recorded videotapes of the accident flight and two previous flights. The earlier flight footage showed the aircraft flying extremely low in and out of mountain valleys, along the desert floor, and at wave-top level along a beach. The accident flight video depicted the aircraft low flying along the desert floor in a canyon, then buzzing a lake. The remainder of the tape showed the aircraft flying up the river valley leading to the accident site until it abruptly stopped at a damaged portion of the tape.
Pilot Report
The pilot reported flying up the river valley approximately 1,800 to 2,000 feet above the river (elevation 6,000 to 7,000 feet msl). He then turned right at a fork in the river that leads up to the accident site canyon. The pilot stated he was at 12,000 feet msl when he turned and was over the surrounding ridges. Nearing the accident site area, the aircraft suddenly rolled and yawed to the right due to very strong turbulence. The pilot said he had the impression that the aircraft was being pushed forward and down toward the ground by some strong force. The aircraft was descending, and the pilot reported managing to recover to level flight just before colliding with trees.