On July 5, 1998, at 1400 hours Pacific daylight time, a Piper PA-28-140, N592SP, experienced a loss of engine power after takeoff from runway 15 at Ranchaero airport, Chico, California. The airplane, operated under 14 CFR Part 91, subsequently struck a tree and was destroyed in a postimpact fire. The private pilot/owner sustained minor injuries and the passenger incurred serious injuries and succumbed to those injuries approximately 16 days later. Visual meteorological conditions existed for the personal flight and no flight plan was filed. The pilot stated that the airplane had been refueled with 50 gallons of fuel the day before the accident at Woodland airport prior to departing for Ranchaero. He stated that the flight took approximately 1 hour, and after arrival they went to a family residence where they spent the night. The next day the pilot and family members went to the airport to have a picnic and to give airplane rides around Chico. The pilot stated that at the departure end of the runway is an orchard. After takeoff for the first flight of the day, he noted a decrease in engine rpm, and the airplane did not have sufficient power to maintain altitude. The pilot stated that as the airplane started to lose altitude it started to impact the tops of the trees. After impacting the trees, the pilot noted flames coming from the right side of the cowling. In an interview with a Deputy from the Butte County Sheriff's Office, the pilot stated that he had selected the left tank for takeoff as he had already ran the right tank "very low." The Deputy stated that the right wing and cockpit were destroyed by the fire. He further reported that the left wing was also destroyed, and he could smell and see fuel leaking from the left wing fuel tank. The airplane and engine were inspected at Plain Parts, Pleasant Grove, California, on August 28, 1998. Control continuity was established from the cockpit to the tail, and aileron continuity was established at the wing roots. The right side cables had been cut by retrieval personnel. The fuel selector was inspected and the right tank was selected. A fuel sample was inspected at Plain Parts. The sample was blue in color and smelled like aviation fuel. The engine inspection revealed no discrepancies with the engine. Crankshaft rotation produced thumb compression in each cylinder in proper firing order, and valve train continuity was established. The spark plugs were examined, and according to the Champion Spark Plugs Check-A-Plug chart AV-27, exhibited coloration consistent with normal operation. The magnetos were found securely clamped to the engine; however, the internal timing could not be established due to the postimpact fire. The impulse coupler drives were found intact and properly installed in both magnetos. The fuel pump and carburetor were destroyed by the postimpact fire. Ground witnesses that were interviewed did not see the accident airplane's ground roll, takeoff, or initial climb. Witnesses did state that they heard a popping sound, but could not verify whether they heard that noise before or after the airplane struck the trees. According to the Pilot's Operating Handbook for a like make and model airplane, the fuel burn at cruise power is about 8 gallons per hour. The fuel capacity of the airplane is 50 gallons, 25 gallons per wing fuel tank.