Incident Description
The flight instructor of N971SH reported that after the flight instructor of N991RW had repositioned his helicopter close to the refueling station, he attempted to set his helicopter down in close proximity to N991RW. This was intended to allow another group of helicopters closer access to the refueling station. After setting down and lowering the collective, the instructor of N971SH felt a "repeated thump" in the controls, prompting him to raise the collective and move away from N991RW.
The flight instructor of N991RW reported that after setting down and about one minute into the cool down period, he felt a "jerk" in the controls.
Damage
A subsequent inspection of both aircraft revealed damage to both of the tops of the blades of N991RW and to at least one of the blades of N971SH.
No injuries were reported in the incident.