On October 6, 2012, about 1714 Pacific daylight time, a Cessna 180H, N2780X, sustained substantial damage during a forced landing near the St. Maries Municipal Airport (S72) St. Maries, Idaho. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The private pilot was uninjured and the passenger sustained minor injuries. Visual meteorological conditions prevailed and no flight plan was filed for the personal flight which originated from Lewiston-Nez Perce County Airport (LWS) Lewiston, Idaho at about 1600 with a planned destination of S72.
The pilot reported that during descent to S72, the engine started making popping sounds and then lost total power. The pilot reported that he does not recall the position of the fuel selector, or if he moved it prior to attempting an engine restart. Despite the pilot attempts, the engine would not restart and he initiated a forced landing on a dirt road about 15 miles southwest of S72. During the landing roll, the left wing struck a tree and the airplane came to rest inverted. The pilot stated that following the accident, he turned off the fuel selector to off and turned off all of the electrical switches.
Examination of the airplane by a Federal Aviation Administration (FAA) inspector was conducted at the accident site. The inspector observed fuel in both tanks and in the fuel inlet line to the carburetor. The airplane was recovered to a local storage facility. According to an airframe and powerplant airplane mechanic who examined the recovered engine under the supervision of a FAA inspector, no pre-accident mechanical malfunctions or failures were observed on the engine or engine systems. Fuel was present in the carburetor, the accelerator pump operated normally and no blockages were observed. The fuel was clear of contamination.
The spark plugs were removed and were slightly worn but not fouled. The cylinder combustion chambers were examined using a lighted borescope and the piston heads, combustion chambers, intake and exhaust valves had normal operating signatures. The rocker covers were removed and were unremarkable. The crankshaft could be rotated by hand and rotational continuity was established throughout the engine and cylinder valve train. All engine accessories remained attached to the engine via their respective mounts. The magnetos would produce spark at all the respective leads when to engine crankshaft was rotated.
Weather conditions recorded at S72, located about 15 miles northeast from the accident site, at 1715, wind from 060 degrees at 4 knots, visibility 10 statute miles, clear sky, temperature 61 degrees Fahrenheit, dew point 18 degrees Fahrenheit, and an altimeter setting of 30.23 inches of mercury. According to the FAA Special Airworthiness Information Bulletin, entitled Carburetor Icing Prevention, weather conditions were not conducive to the formation of carburetor icing.