On April 26, 1997, approximately 1555 mountain daylight time, a Piper PA-28-140, N6121J, experienced a gear collapse during an emergency landing while attempting to climb over rising terrain after taking off from Rawlins Municipal Airport, Rawlins, Wyoming. The private pilot and his passenger were not injured, but the aircraft sustained substantial damage. The FAR Part 91 personal pleasure flight, which was departing for Rangely, Colorado, was being operated in visual meteorological conditions at the time of the accident. The pilot had filed a VFR flight plan prior to departure, and the ELT, which was activated by the impact, was turned off at the scene. According to the pilot, who was operating near maximum allowable gross weight, there was no problem with the aircraft's engine, but he was unable to outclimb the rising terrain after encountering downdrafts after takeoff . When it became apparent that the aircraft would not clear the terrain, the pilot elected to make an emergency landing on the rough/uneven ground. During the initial touchdown, both main gear were torn from the wings. The aircraft came to rest about one mile from the departure end of the runway, at an altitude 150 to 200 feet higher than that of the runway surface. Based upon a field elevation of 6,820 feet MSL, and an outside air temperature of 11 degrees centigrade (52 degrees Fahrenheit) , the density altitude was determined to be approximately 7,400 feet. According to the graph in the Operator's Handbook, the rate of climb should have been about 250 feet per minute. According to the pilot, he checked the weight and balance prior to takeoff, but he did not calculate the expected rate of climb under the conditions.