Takeoff and Initial Events
The commercial pilot initiated a takeoff with a quartering tailwind. Following lift-off, the helicopter experienced a downdraft, causing the rotor RPM to begin deteriorating. In response, the pilot lowered the collective to compensate for the loss of rotor RPM.
Obstacle Avoidance
During the sequence, the pilot observed a fence ahead. The collective was increased to clear the obstacle. After clearing the fence, a run-on landing was attempted.
Collision and Outcome
During the run-on landing, the right front skid struck a small bush. Subsequently, the helicopter turned to the right and collided with a large rock covered with sand. The impact caused the helicopter to roll over onto its side.
Weather Information
Review of weather information revealed no record of turbulence, downdrafts, gusts, or windshear.