On July 31, 2008, about 1120 Pacific daylight time, a Cessna TU206E, N1499M, descended from its departure climb and impacted terrain 7 miles north-northeast of French Valley Airport, Murrieta, California. The private pilot operated the airplane under the provisions of 14 Code of Federal Regulations Part 91. The pilot was not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan had been filed. The local flight departed French Valley Airport at 1115. The pilot reported that shortly after takeoff the airplane was climbing to 3,500 feet mean sea level when he felt a shift in the airplane's attitude. He tried to correct it with rudder input, then with manual trim, but neither actions corrected the out-of-trim condition. He looked to see if something was jamming the rudder pedals but could find nothing. At this point the airplane was in a slight descent and a shallow left turn. Exerting a great amount of effort he was able to get some response with the ailerons. He was making a large left descending orbit when the engine lost power; at that point he identified a field where he could land. Attempts to restart the engine were not successful. The pilot lowered 40 degrees of flaps and made an off field landing that sheared off the nose gear. First responders reported that fuel was leaking from both wings when they arrived on scene. A Federal Aviation Administration (FAA) inspector responded to the scene, and reported that he found no anomalies with the airplane's flight controls. During the recovery of the airplane, 60 to 80 gallons of fuel was removed from the fuel tanks. The airplane was equipped with an S-Tec 50 autopilot and a Garmin 530 (an all-in-one, GPS, navigation, and communications system). The pilot said that he did not have the autopilot engaged during the flight. The National Transportation Safety Board investigator-in-charge and a technical representative from Cessna examined the airplane on September 3, 2008, at the Chino Airport, Chino, California. The airplane's wings had been removed for transport from the accident location to the airport; aileron control cables had been disconnected at the turnbuckles near both wing roots. The aileron, elevator, and rudder control cables were traced from their respective control surface to the cockpit. When pulled on, all control cables moved smoothly and in the appropriate direction; cable runs were clear of any obstructions or evidence of binding. The S-Tec autopilot was energized; the aileron and elevator servos responded to the flight director. When the autopilot disconnect switch on the yoke was depressed, the elevator and aileron servos deenergized. There was no rudder servo. When the autopilot was energized investigators were able to physically override the autopilot using the control yoke. The engine remained mounted to the airframe and was examined in place. The top spark plugs were removed and examined. The electrodes all had similar gaps, exhibited no mechanical damage, and were light gray in color. The engine was rotated by hand and thumb compression was achieved on all 6 cylinders. The spark plugs were reinstalled. The propeller, which was bent around the nose cowling, was removed and replaced with a 2-bladed constant speed propeller. The dip stick indicated 10 quarts of oil in the engine. An external fuel tank was plumbed directly into the fuel boost pump. The engine was successfully started and ran for 2 minutes, achieving 2,000 rpm and 17 inches of manifold pressure. The magnetos were selected on one at a time, resulting in a 50-rpm drop for each one. The engine was shut down by pulling the mixture to the idle cutoff position.