On September 27, 2004, at 2343 mountain daylight time, an American Eurocopter AS-350 B3 helicopter, N497AE, operated by Southwest Air Ambulance, was substantially damaged when while hovering after lift off from the Las Cruces Memorial Hospital helipad (73E), Las Cruces, New Mexico, the helicopter's skid struck the helipad and the helicopter subsequently rolled over on its side. Night visual meteorological conditions prevailed at the time of the accident. The positioning flight was being operated under the provisions of Title 14 CFR Part 91 without a flight plan. The airline transport pilot sustained minor injuries. The flight was originating at the time of the accident and was en route to the Las Cruces International Airport. The pilot initially reported that just after lift off from the helipad, he experienced a loss of tail rotor capability. He reported the helicopter spun and impacted the ground coming to rest on its right side. In his written statement, the pilot said that prior to liftoff he checked for and had freedom of controls and no warning or caution lights. He said he had no lights on in the cockpit except "very dim instrument and nav-radio lights." The pilot said the moon was full, overhead, and bright, so he elected not to turn on his searchlight and landing and taxi lights for takeoff. The pilot said the helicopter came up light on the skids. He then began a vertical ascent. "The nose began to go left, so I applied right pedal - it seemed stuck/blocked. Within 1 to 2 seconds the aircraft began a right roll. I applied left pressure with the cyclic, but it too seemed extremely stiff and/or stuck." The pilot said he was aware the helicopter was rolling over. He said he felt and heard the main rotor blades hit the ground. The weather conditions at the time of the accident were reported as clear skies, 10 miles visibility, and winds of 170 degrees at 4 knots. The helicopter was examined at the accident scene. The helicopter was resting on its right side approximately 25 feet west of the helipad center. An examination of the helicopter showed substantial damage to the main rotor blades, tail rotor, tail boom, right side of the cabin, and the right skid. An examination of the helicopter's flight controls showed no anomalies. An examination of the helicopters remaining systems revealed no anomalies. The helipad was located in a former gravel pit with pale white-colored sandy soil surrounding and rising above the pad in all quadrants. Ground scars and paint transfers observed were consistent with the ground resonance spring on the right skid coming in contact with the pad. The ground scars' pattern indicated the helicopter was moving laterally and aft when the spring made first contact with the pad, subsequently initiating a dynamic rollover of the aircraft.