On July 27, 1999, approximately 0730 mountain daylight time, an American AA-1, N5989L, was substantially damaged when it collided with terrain near Centennial, Wyoming. The private pilot and his passenger received minor injuries. Visual meteorological conditions prevailed for the personal cross-country flight being conducted under Title 14 CFR Part 91, and no flight plan had been filed. The flight originated at Rawlins, Wyoming, at 0630. In his accident report, the pilot said he was en route to North Platte, Nebraska, and his final destination was Biddeford Maine. After departing Rawlins and flying for approximately one hour, he entered the Medicine Bow Mountains at 9,500 feet msl (mean sea level) and was "unable to negotiate the rising terrain." He saw a clearing and decided to make a forced landing. Unexpected downdrafts caused him to land hard and short of his intended point of touchdown. In a telephone conversation with the pilot after he had returned home, he explained that the airplane could not outclimb the rising terrain. He tried turning left and started losing altitude. When he tried to turn right, he lost airspeed. After the accident, he was able to contact the pilot of an overflying United Airlines flight, who in turn relayed the information to search and rescue officials. The pilot and his passenger were rescued later that morning and airlifted to a Laramie hospital. The reported temperature and altimeter setting at Laramie, Wyoming, located 31 miles east of the accident site and situated at an elevation 7,278 feet msl, was 24 degrees C. (75.2 degrees F.) and 30.33 inches of mercury, respectively. The computed pressure and density altitudes at Laramie were 6,868 feet msl and 9,421 feet msl, respectively. According to the AA-1 Pilot Operating Handbook, the normal and utility category service ceiling is 11,000 and 13,150 feet msl, respectively. The Handbook also indicates that under standard atmospheric conditions, the maximum rate of climb at 8,500 feet msl is 240 feet per minute. The accident took place in the Medicine Bow Mountains at a location of 41 degrees, 25.15 minutes north latitude, and 106 degrees, 10.80 minutes west longitude.