On September 20, 2012, about 1215 mountain daylight time, an experimental amateur-built Thompson model RV-6 airplane, N140RV, was substantially damaged while landing at Stevens Field Airport (PSO), Pagosa Springs, Colorado. The private pilot and passenger were not injured. The airplane was registered to and operated by the pilot, under the provisions of 14 Code of Federal Regulations Part 91, without a flight plan. Day visual meteorological conditions prevailed for the personal flight that originated from Las Vegas Municipal Airport (LVS), Las Vegas, New Mexico, about 1130.The pilot reported that before landing he obtained the current weather conditions from the airport’s automated weather broadcast, which indicated a calm wind condition and a density altitude of about 10,000 feet. He stated that since there was no appreciable wind, he chose to land on runway 1 (8,100 feet by 100 feet, asphalt) because of its slight upslope. He reported that he made an uneventful wheel-landing, with the wing flaps partially extended, and that he was able to maintain directional control until the tailwheel made contact with the runway. The pilot stated that the airplane immediately began to swerve left after the tailwheel contacted the runway. He reportedly overcorrected with an application of right rudder pedal input and the airplane swerved to the right. The pilot attempted to correct for the right swerve with a left rudder pedal input, but he overcorrected for a second time and the airplane swerved left. The pilot’s attempts to regain directional control were unsuccessful and the airplane departed off the left side of the runway. The right main landing gear collapsed and the right wing impacted terrain during the runway excursion. The right wing and firewall were damaged during the accident sequence. The pilot reported no preaccident mechanical malfunctions or failures with the airplane that would have precluded normal operation. He postulated that the airplane’s elevated true airspeed and ground speed, due to the high density altitude conditions, contributed to his inability to maintain directional control during landing roll. He further noted that he was unaccustomed with landing at high density altitudes and that the accident might have been prevented had he performed a full-stall (three-point) landing instead of a wheel-landing. At 1215, the airport’s automated surface observing system reported the following weather conditions: wind 220 degrees at 3 knots, visibility 10 miles, sky clear, temperature 22 degrees Celsius, dew point -11 degrees Celsius, and an altimeter setting of 30.34 inches of mercury. The airport elevation was listed as 7,664 feet mean sea level. The calculated density altitude was 10,081 feet.