On March 18, 2008 approximately 1045 mountain daylight time, a Robinson R22 beta, N3055N, registered to Pacific Rim Aviation, Lafayette, Colorado, and operated by Premier Helicopters, Broomfield, Colorado, was substantially damaged when it impacted terrain following a loss of rotor rpm during a practice autorotation at Las Vegas Municipal Airport (LVS), Las Vegas, New Mexico. Visual meteorological conditions (VMC) prevailed at the time of the accident. The cross-country instructional flight was being conducted under the provisions of Title 14 Code of Federal Regulations (CFR) Part 91 without a flight plan. The commercial certificated flight instructor and student pilot on board the helicopter were not injured. The flight originated at Raton, New Mexico, at 0900, and was en route to Las Vegas, New Mexico. According to the instructor's accident report, they checked both the terminal forecast (TAF) and the Automated Weather Observation Station (AWOS) for LVS. Both reported the wind to be from 020 degrees, but the TAF reported wind velocity to be 10 knots, whereas AWOS reported it to be 15 knots with gusts to 20 knots. As the helicopter approached the airport, the student told the instructor he would like to practice a 180 degree autorotation. The maneuver was begun from 1,000 feet agl (above ground level), but due to poor rpm and speed control, the instructor assumed control of the helicopter and advised the student he would demonstrate the proper technique. The instructor said he kept the rpm "in the green" and kept the airspeed above 65 knots, but realized the helicopter was descending "at an unusually high rate of descent." As he rolled out to level, "it felt as if we had a huge downdraft that was pushing us towards the ground." The instructor added throttle and began to "pull all the power available." Lift was not sufficient to overcome the descent rate. Just prior to impact, the pilot applied slight aft cyclic control. The helicopter struck the ground, bounced, and continued to fly with some forward momentum. The instructor then landed the helicopter. Post-impact inspection revealed the skids were spread, the engine mounts were bent, and part of the pilot's window had popped out. The instructor said that at no time did the LOW ROTOR RPM horn sound.