SEA01FA032 · Hughes 369HS

During an aerial survey flight, the aircraft was maneuvering to position for another run along a contour line in mountainous terrain. The flight elevation along the contour was reported about 150 feet above the ground level. The terrain was covered with deciduous and coniferous trees varying in height to about 50 feet. The surviving passenger reported that the helicopter was making a descending right turn when he suddenly felt a jolt. The passenger, seated directly behind the pilot on the left side, saw the pilots head jerk up, as the helicopter pitched straight up, then fall 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. This snag was also dark in coloration and void of branches. Plexiglas fragments and two rivets were found embedded in the section that broke off. 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. 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.

Verbatim NTSB analysis and probable cause from the NTSB dataset