Primary finding
Probable cause
The pilot’s decision to fly at low level over mountainous terrain and his inability to recover when the helicopter encountered a downdraft that resulted in a collision with terrain.
Investigator assessment
Analysis narrative
The pilot of the helicopter was flying over mountainous terrain, about 500 ft agl, with moderate wind and turbulence conditions. After he slowed the helicopter to 60-70 knots it suddenly and uncontrollably descended at a rapid rate in a severe downdraft. The pilot maneuvered toward lower terrain to accelerate but was unable to arrest the descent before the helicopter collided with the ground tail first. The helicopter fuselage was substantially damaged. The pilot reported that there were no preaccident malfunctions or failures with the helicopter that would have precluded normal operation.