On September 26, 2005, at 1246 Pacific daylight time, a Cessna A185F, N8548Q, collapsed the landing gear during a forced landing in an open field near Tracy, California. The pilot/owner operated the airplane under the provisions of 14 CFR Part 91 as a personal cross-country flight. The airplane sustained substantial damage. The certificated airline transport pilot (ATP) and three passengers were not injured. The flight departed Tracy Municipal Airport (TCY), Tracy, about 1240, and was destined for Corvallis, Oregon. Visual meteorological conditions prevailed for the flight and no flight plan had been filed. According to the pilot, he conducted a preflight inspection of the accident airplane that included the sumping of all four fuel tanks, as well as the low points for water contamination. No discrepancies were noted. He checked the weather prior to departure and noted no significant weather anomalies. The startup and taxi to runway 30 were uneventful. He indicated that he had to wait to for the oil temperature to rise before conducting the engine run-up; there were no discrepancies noted with the engine run-up, the takeoff roll or initial climb performance. About 300 feet above ground level (agl), the pilot reduced the throttle and rpm's (revolutions per minute) to 25 inches of manifold pressure (MAP) and 2,500 rpm. The pilot reported that at that point climb performance "seemed to lag, despite checks and adjustments to ensure 25/25." He reported that the climb performance was marginal and he decided to land in an open field. He noted a maximum altitude gain of 400 feet above agl. The pilot reported that he made a left 180-degree turn to remain over a cropless field, and at that point the engine started to misfire. The pilot indicated that the airplane was configured with all power levers full forward, mixture was rich, fuel selector was selected to BOTH; however, the power began to decay. With only partial engine power, he setup for the emergency landing at an airspeed of 75 knots and no flaps. While on downwind he noted farm equipment and telephone lines, and believed at his current rate of descent he would overrun the field and impact those items. He lowered the flaps to 20 degrees and started a left 90-degree turn for a more clear area. The pilot believed that the airplane was level when it contacted the ground; however, while out in the field he noted that the left wing tip impacted first. The airplane bounced once, and on the second touchdown the right main landing gear collapsed, the nose skidded to the left, and the right wing and strut contacted the ground opening the right door. After coming to a stop, the pilot checked that the passengers were OK, and noted a fuel leak from the right main wing tank. Upon securing the airplane, the pilot and passengers exited the airplane. The Federal Aviation Administration (FAA) accident coordinator inspected the engine and noted no obvious mechanical malfunctions. He performed an engine ground run, which was normal, and could not reproduce the loss of engine power.