The helicopter pilot reported that after landing to refuel, he reduced power to flight idle and initiated a 2-minute cool down prior to shutting off the engine. He further reported that one minute into the cool down, the fuel truck approached the helicopter from the rear and struck the main rotor blades.
The helicopter sustained substantial damage to the main rotor blades.
The pilot reported that there were no preaccident mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.