What happened
During operations near a refueling station, the flight instructor of N971SH attempted to land his helicopter in close proximity to another aircraft, N991RW, which had recently repositioned near the fuel pump. The intent was to clear access for other helicopters waiting to refuel. After the pilot of N971SH set the aircraft down and lowered the collective, he experienced a repeated thumping sensation in the flight controls. This prompted him to raise the collective and maneuver away from the other helicopter.
Simultaneously, the instructor operating N991RW reported that approximately one minute into his cooldown period after setting down, he felt a jerk in the controls.
The investigation
A subsequent inspection of both aircraft was conducted to assess the impact. The investigation revealed damage to the tops of both blades on N991RW. Additionally, at least one blade on the N971SH was found to have sustained damage.