Primary finding
Probable cause
Ground personnel's movement of cargo in windy conditions, which allowed a previously secured cargo sack to blow into the main rotor blades.
Investigator assessment
Analysis narrative
The pilot landed the helicopter at an off-airport site in windy conditions. While he was performing the engine cool-down portion of the checklist, a worker at the site picked up a storage container that was weighing down an empty cargo sack. When the weight was removed, the sack was picked up by the wind, and it contacted the helicopter's main rotor system, resulting in substantial damage to the main rotor blades.
Source record
Factual narrative
The pilot landed the helicopter at an off-airport site in windy conditions. While he was performing the engine cool-down portion of the checklist, a worker at the site picked up a storage container that was weighing down an empty cargo sack. When the weight was removed, the sack was picked up by the wind, and it contacted the helicopter's main rotor system, resulting in substantial damage to the main rotor blades.