History of Flight
On June 6, 2014, about 1315 mountain daylight time, a Cessna 150F, N3376B, was substantially damaged during an off-airport landing in a field near Ronan, Montana. Both the pilot and his passenger received minor injuries. The personal flight was conducted under Title 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and no flight plan was filed.
According to the pilot, the airplane was based at Polson Airport (8S1), Polson, Montana. The flight departed 8S1 with full fuel tanks, intending to travel to St. Ignatius Airport (52S) with an intermediate touch-and-go at Ronan Airport (7S0). After a straight-in approach to land to the south at 7S0, the pilot completed the landing routinely, then retracted flaps, shut off carburetor heat, and began a climbout. At about 300-400 feet agl, the engine began to slow down despite full throttle, full rich mixture, and no carburetor heat. The engine continued losing power; the pilot turned left to gauge the possibility of returning to the runway, but climb performance decreased substantially. The pilot decided to perform an emergency landing in a nearby field. He did not apply carburetor heat after the power decrease. When about 50 feet agl, the engine lost all performance. During the forced landing, the airplane bounced and struck a berm at about 35 knots, causing the airplane to nose over. It came to rest inverted; there was no fire.
Aircraft and Personnel
The 18-year-old pilot held a private pilot certificate with a single-engine land rating. He had 68 total flight hours, including 2 hours in the accident make and model. He passed his practical exam on March 19, 2014, and his most recent FAA third-class medical was issued June 20, 2013.
The Cessna 150F, manufactured in 1966, was equipped with a Continental Motors O-200 series engine. The most recent annual inspection was completed on February 5, 2014, at which time the airplane had 4,231 total hours, and the engine had 2,592 hours since major overhaul. The manufacturer's recommended overhaul interval was 1,800 hours or 12 years. Maintenance records showed no unusual entries.
Meteorological Conditions
The 1321 non-certified weather observation at Ronan reported wind from south-southeast at 2 knots, temperature 20°C, dew point 10°C, barometric pressure 29.97 inches of mercury, and relative humidity 53%.
Wreckage Examination
Post-accident inspection revealed that the propeller, engine, cowling, and nose gear were displaced aft. The fuselage was wrinkled aft of the main landing gear, and the vertical fin and rudder were deformed. The flaps were in the retracted position. The lower engine mounts were fractured. The fuel line was separated from the fuel strainer; no fuel system checks were conducted. The carburetor linkage and air box were deformed, preventing control movement; the carburetor heat control was in the off position, and throttle and mixture were at full throttle and full rich, respectively. Cold compression checks were normal for three cylinders; the No. 3 cylinder showed low pressure initially, but after staking valves, it became normal; the reason was not determined. Spark plugs showed varying wear and deposits; the No. 2 top spark plug appeared clean and consistent with a normal condition, but a non-firing plug could not be confirmed. The magneto switch tested satisfactory; magneto timing was 25 degrees BTDC (specified 24±1). Impact precluded functional magneto testing. Valve train components were intact. Carburetor heat system functionality could not be determined due to damage.
Additional Information
The airplane manufacturer's operating procedures specify carburetor heat verification before takeoff, and in-flight power reduction, full carburetor heat should be applied. The pilot reported normal engine start, taxi, and run-up, including proper carburetor heat and magneto checks. FAA Advisory Circular AC 20-113 discusses carburetor icing conditions; the ambient conditions at the time were near regions of serious icing possibility on icing envelope charts. Water contamination of fuel can cause power loss; the pilot reported draining sumps and strainer preflight with no water detected.