Accident Summary
A helicopter pilot reported that while flying in a valley, he crested a ridge and descended into the next valley following the terrain downhill. The wind at the time felt calm. As he approached the far side of the valley, the pilot realized he needed to make a 360-degree climbing turn in order to clear the ridge.
Pilot Report
According to the pilot, after completing approximately 90 degrees of the turn, the helicopter was struck by a gust of wind from the rear. This caused a "significant decrease in apparent airspeed," and the helicopter began to settle toward the trees. The pilot then had to decide whether to attempt to complete the turn, risking a tree strike with ground speed, or attempt a touchdown with zero airspeed. He chose the latter.
Outcome
The helicopter settled into the trees and rolled over. No further details about injuries or damage were provided in the source.