Flight Maneuvers
During an aerial survey flight, the helicopter was maneuvering to position for another run along a contour line in mountainous terrain. The flight elevation along the contour was reported to be about 150 feet above ground level. The terrain was covered with deciduous and coniferous trees varying in height to about 50 feet.
Passenger Account
The surviving passenger, seated directly behind the pilot on the left side, reported that the helicopter was making a descending right turn when he suddenly felt a jolt. He saw the pilot's head jerk up as the helicopter pitched straight up, then fell backwards and collided with the terrain in an inverted and nose low attitude at the base of a dead tree located on an outcropping along a ridge. This tree was taller than any of the surrounding trees and the top was broken off. The snag was dark in coloration and void of branches. Plexiglas fragments and two rivets were found embedded in the section that broke off.
Impact Damage
Structural impact signatures noted that the helicopter came in contact with the tree on the right side lower fuselage section with rearward crushing damage through the anti-torque pedals and traveling aft to the cyclic control stick socket. Wood particles were embedded within the deformed fuselage structure and also to the forward section of the landing skids.
Post-Crash Inspection
The passenger reported that he did not detect any mechanical anomalies prior to the jolt, nor did the pilot indicate any problems over the headset prior to the collision. Post-crash inspection of the wreckage did not reveal evidence of a mechanical failure or malfunction.