On April 21, 2007, approximately 1000 central daylight time, a Robinson R22 Beta helicopter, N971SH collided with another Robinson R22 Beta helicopter, N991RW, while standing with engines operating at the Culberson County Airport, Van Horn, Texas. As a result of the collision, N991RW sustained substantial damage to one main rotor blade. Neither flight instructor or their students were injured. Both aircraft were operated by Silver State Helicopters, of North Las Vegas, Nevada. Visual meteorological conditions prevailed and a flight plan was not filed for the cross-country instructional flights, which were conducted in accordance with 14 CFR Part 91. Both aircraft had departed the El Paso International Airport, El Paso, Texas, about 0830 mountain daylight time. In a written statement, the flight instructor of N971SH reported that N991RW had already landed in close proximity to the fueling pump, and with two more groups of helicopters behind him he thought he could safely set down close enough to the fuel pump so the other helicopters could all refuel without having to move them around. The instructor stated that after N991RW had repositioned aft a few yards, "...I then started to taxi forward, intending to set down off of his right side. As I approached, I saw his helicopter start to get light on the skids and I stopped, backing up as he picked up off the ground adjusting his position a little, then setting down again." After the instructor of N971SH had confirmed that N991RW was down, he taxied closer to the helicopter at a slight angle off to his right and rear. The instructor of N971SH reported, "The slight tailwind that we had did not seem [to be] a factor and I was able to control the helicopter without any difficulty, so I intended to get us fairly close. I attempted to set us down close to N991RW with just my own judgment of the distance and no one to guide me. I got us to what I thought was a safe but close distance away from N991RW and proceeded to set the helicopter down." The instructor of N971SH stated that as he lowered the collective, "...I felt a quick repeated thump in the controls, and I immediately raised collective and moved us away from N991RW, and then set down again. Upon shutdown of both the helicopters we found damage to both of the tops of the blades of N991RW and to at least one of the blades of N971SH." In a written statement, the flight instructor of N991RW reported that he set the helicopter down close to the fuel station and was told by the instructor of N971SH to move back a little so that more aircraft would fit in a semicircle around the fuel station. The instructor stated, "...after I had set the helicopter down and was about one minute into the cool down period, I felt a jerk in the controls and looked to my right and saw the rotor disk of N971SH very close to me. After cool down we inspected for damage and noticed the dents in both rotors." **This narrative was modified on August 23, 2007.**