On July 7, 1999, at 2000 hours Pacific daylight time, an experimental Smith Avid Stol Hauler, N790GS, experienced a loss of engine power while descending toward the South Lake Tahoe, California, airport. The airplane, constructed owned and operated by the pilot under 14 CFR Part 91, was destroyed in the subsequent forced landing attempt. The commercial pilot was not injured. Visual meteorological conditions existed for the local area personal flight and no flight plan was filed. The flight originated at the accident airport at 1900 the day of the accident. On the accident flight the pilot had taken the airplane out to watch the sunset. He had flown approximately 1 hour before turning back toward the airport when the engine experienced a loss of power. The pilot was unsuccessful in attempts to restart the engine and made a forced landing in an open field. He stated that his airspeed was low during the turn from base to final approach and a high rate of descent developed, which culminated in a hard touchdown on the right main landing gear. The left main landing gear then collapsed, and the airplane came to rest on its belly. The pilot stated that at no time during the flight were there any indications from the instruments that "something was wrong." The pilot reported the airplane had been flown 3 hours since 1996. A review of the airplane logbook revealed that an engine break-in was conducted in June 1994 with no discrepancies noted. The pilot indicated that a mixture of fuel to oil at 50:1 was used for the break-in per the manufacturer's suggestion. In November 1995, and June 1996, the airplane was involved in two separate ground loop incidents, both of which damaged a wing and required rebuilding the airplane. In January 1997, the airplane was destroyed when heavy snow accumulation collapsed the hangar roof and it was subsequently rebuilt. Review of the logbook revealed that the airplane had not received a Condition Inspection since the Special Airworthiness Certificate and Operating Limitations were issued on September 14, 1995. The pilot indicated that the fuel tanks hold a total of 14 gallons, with a fuel consumption rate of 3.5 gallons per hour. According to the engine manufacturer, after the engine has sat in storage for 12 months, it should go through an inspection. A Federal Aviation Administration (FAA) inspector examined the airplane on-scene. He noted that there are right and left fuel shutoff valves located on the bulkhead behind the pilot's head. The right valve is located to the right of the pilot's head, and the left valve to the left of the pilot's head. Both fuel shutoff valves are equipped with a handle used to turn the fuel shutoff valves on or off. He stated that the left handle was attached to the bulkhead; however, he was unable to locate the right handle. The inspector interviewed the pilot, who stated that the right handle for the fuel shutoff valve was present prior to the accident. The fuel lines from the wings feed into a header tank that is located underneath the instrument panel. From the header tank the fuel, aided by an electric boost pump, is then fed to the engine. The pilot reported that the electric fuel pump was not on when the accident occurred. The FAA inspector reported that the airplane is equipped with an electronic ignition system. During the FAA's on-scene inspection, the battery was reconnected and the master switch was turned on. The inspector reported that the panel lights illuminated when turned on, and the fuel pump activated when the fuel pump switch was placed in the ON position. He found one tank full of fuel and the other tank was approximately 1/2 full, and identified the fuel as auto fuel. The inspector stated that there was no damage to the propeller, and that when he hand cranked the propeller it was not restricted. The airplane was inspected on the owner's property on July 14, 1999, by FAA inspectors and a certified Airframe and Powerplant mechanic. The engine, carburetors, and fuel tank had been removed from the airframe prior to their arrival. The engine mount was broken, preventing an engine run-up. Both carburetors were disassembled and were free of gum and tarnish build-up. One of the carburetors was found with the needle and seat valve stuck in the fuel shutoff position; however, this was attributed to the carburetor lying on its side prior to the inspection. According to the mechanic, removal of the cylinder head revealed normal combustion deposits on the pistons, which were unscorred and free to move in the cylinders. It was noted that the engine is inverted in this particular airplane design, making the spark plugs more susceptible to oil fouling. The spark plugs were found oil soaked, but tested normal with a spark plug tester. A load test was performed on the battery. The 11.8-volt battery was tested with a 300-amp charge. When the 300-amp load was applied, the battery returned to its original charge of 11.8 volts. No further discrepancies were noted with the engine.