On July 31, 2005 about 1615 Pacific daylight time, a Cessna A150M, N8166V, collided with mountainous terrain during an en route climb from the Trinity Center Airport, Trinity Center, California. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot, the sole occupant, sustained minor injuries; the airplane was destroyed in the impact sequence and post crash fire. The personal cross-country flight departed Trinity Center about 1550, with a planned destination of Weed Airport, Weed, California. Visual meteorological conditions prevailed, and a flight plan had not been filed. In a written statement, the pilot reported that after flying into Trinity Center earlier in the morning, he spent the day engaged in physical exercise including biking and hiking. The pilot opted to takeoff from runway 14, making a left downwind departure. He noted the temperature to be about 90 degrees Fahrenheit when he departed from the 2,390-foot mean sea level (msl) airport. In an effort to divert from cumulus clouds ahead, the pilot maneuvered the airplane in a north-easterly direction toward a pass in the mountainous terrain ahead. He additionally performed a 360-degree climbing turn. The pilot further stated that about 20 minutes into the flight, he realized that deceptively level-looking terrain below was in actuality the relatively steep walls of a narrowing canyon. He noted the air becoming more turbulent and an increase in downdraft conditions. He attempted to maneuver the airplane out of the canyon, but was too late; he made a forced landing on a logging road at an elevation of about 6,000 feet msl. Prior to touchdown, the left wing impacted a tree and the airplane subsequently landed hard on the road. After coming to rest, the pilot noticed that the airplane was becoming engulfed in flames and his clothes started to catch on fire. He egressed the airplane and extinguished the flames on his clothes. Only sustaining minor injuries to his left knee, the pilot began a 3-hour task of dousing the airplane's fire with water he found in a nearby waterhole. After being satisfied that the fire would not spread to the nearby trees, he hiked out of the mountains. The pilot reported no pre-impact mechanical malfunctions or failures with the airplane. In addition, the pilot stated that he believed the cause of the accident to be his failure to acknowledge cumulative warning signals in a timely manner. He stated that contributing factors to the accident were his fatigue from physical exercise and lack of food, as well as air turbulence associated with cumulous activity and high density altitude. At 1556 a Meteorological Aviation Routine surface weather report (METAR) was issued at the airport located in Mount Shasta, California, located about 26 miles northeast of Trinity Center. It reported a temperature of 30 degrees Celsius and an altimeter setting of 30.05 InHg. Based upon the atmospheric conditions provided by the METAR, a Safety Board computer program calculated the density altitude at the 3,537-foot airport to be 6,028 feet. Using the standard lapse rate of 3-degrees Celsius per 1,000 feet of altitude, the density altitude computed to be about 8,600 feet at the accident site.