Accident Sequence
According to the pilot's written statement, after departing from runway 25, the aircraft turned southwest toward a ridge line at an altitude of approximately 7,900 feet MSL. Near the ridge, the aircraft encountered a sudden downdraft, and the pilot could not arrest the descent before colliding with trees.
Witness Observations
One eyewitness reported that the aircraft never exceeded about 300 feet AGL at any time after takeoff. The witness observed the aircraft in a nose-high attitude begin a right turn, after which it descended below the tops of some trees and out of view. Two other witnesses reported hearing the sounds of a loud and strong engine until the sounds of tree impacts were heard.
Airport and Terrain Information
The airport is situated in a mountain valley at an elevation of 6,750 feet. Mountain ridges and peaks rise an average of 2,000 feet above the valley floor on all sides of the airport. The airport is located at the east end of the valley, which also contains a large lake. A dam is at the west end of the valley, positioned within a V-shaped notch in the surrounding mountains. West of the dam, the terrain drops off rapidly toward the greater Los Angeles basin. The density altitude at the time of the accident was calculated to be about 9,400 feet.
Additional Reports
Other pilots who departed from the airport reported that turbulence existed over the valley near the surrounding ridges.