Accident Details
On October 6, 2012, at about 1714 Pacific daylight time, a Cessna 180H, registration 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 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) at about 1600 with a planned destination of S72.
During descent to S72, the pilot reported that the engine began making popping sounds and then lost total power. The pilot stated he did not recall the position of the fuel selector or whether he moved it prior to attempting an engine restart. Despite attempts, the engine would not restart, and the pilot initiated a forced landing on a dirt road approximately 15 miles southwest of S72. During the landing roll, the left wing struck a tree, and the airplane came to rest inverted. Following the accident, the pilot turned the fuel selector to off and turned off all electrical switches.
Post-Accident Examination
A Federal Aviation Administration (FAA) inspector examined the airplane at the accident site and observed fuel in both tanks and in the fuel inlet line to the carburetor. The airplane was recovered to a local storage facility, where an airframe and powerplant mechanic, under FAA supervision, examined the recovered engine. 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 found. The fuel was clear of contamination.
Spark plugs were removed and found to be slightly worn but not fouled. Cylinder combustion chambers were examined using a lighted borescope, revealing normal operating signatures on piston heads, combustion chambers, and intake and exhaust valves. 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 produced spark at all respective leads when the crankshaft was rotated.
Weather Conditions
Weather conditions recorded at S72 at 1715 reported wind from 060 degrees at 4 knots, visibility 10 statute miles, clear sky, temperature 61°F, dew point 18°F, and an altimeter setting of 30.23 inches of mercury. According to the FAA Special Airworthiness Information Bulletin on carburetor icing prevention, weather conditions were not conducive to the formation of carburetor icing.