Background
On August 17, 2015, about 1100 eastern daylight time, a Cessna 172K (registration N84308) operated by Adventure Seaplanes LLC nosed over during a forced landing in a field near Chiefland, Florida. The private pilot and two passengers were not injured, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan was filed for the personal flight, which was conducted under 14 CFR Part 91. The flight originated about 30 minutes earlier from Perry-Foley Airport, Perry, Florida, with a destination of Winter Haven's Gilbert Airport, Winter Haven, Florida.
Accident Sequence
The pilot reported that after arriving at the airport, he checked the fuel tank sump drains and the gascolator drain before fueling. Records indicate 12.59 gallons of 100 low lead fuel were added, which filled the airplane. After fueling, the pilot waited 15 minutes and again checked the fuel system; no contaminants were reported. He started the engine and performed an engine run-up before takeoff with no discrepancies reported. After takeoff, the flight climbed with the mixture control full rich to 5,000 feet and leveled off, where he leaned the fuel-to-air ratio; the engine was operating at 2,500 rpm. About 10 to 15 seconds later, with the fuel selector positioned to both, the pilot felt a vibration and noticed a lack of engine performance. He established a suitable forced landing location and turned toward it. During descent, he applied carburetor heat and left it applied, but it did not restore engine power. He also moved the fuel selector to the left and right positions and activated the auxiliary fuel boost pump; none of these efforts restored power. The pilot indicated he never had 100 percent power, and the engine acted as if it did not want to run on full or even 75 percent power. While descending, he pumped the throttle control, and each time the engine would slowly gain 200 to 400 rpm but would not achieve sustained power. He reported having only half power available during the descent.
The pilot began his approach to land in a hay field running parallel to a country road but noted a barb wire fence ahead. He executed a go-around, cleared the fence, then banked left and lined up with the rows of a watermelon field. He landed on the main landing gear and was attempting to stop when the empennage contacted the ground, forcing the nose landing gear to the ground and causing it to break off; the airplane slowly nosed over.
Post-accident Examination
A Federal Aviation Administration (FAA) airworthiness inspector examined the airplane at the accident site. After the airplane was uprighted, about 1 ounce of uncontaminated fuel was drained from the fuel strainer, and 6 ounces of uncontaminated blue fuel was drained from the carburetor bowl. The airplane was recovered for further examination. After recovery, another FAA inspector examined the engine. The spark plugs were removed with no discrepancies reported. The crankshaft was manually rotated, and there was no evidence of a stuck valve. A temporary fuel supply was plumbed directly into the carburetor (the same carburetor installed at the time of the accident), and the engine was started and operated to 2,500 rpm, running stable. Safety concerns prevented full power application. A magneto check at 1,800 rpm showed a right magneto drop of 150 rpm and a left magneto drop of 120 rpm. A differential compression test at 80 psi yielded results: #1: 78, #2: 69, #3: 71, #4: 56. Subsequent retesting showed all cylinders at 78 psi or better.
Fuel System Examination
A National Transportation Safety Board (NTSB) investigator verified the fuel supply system from each wing through the fuel selector to the engine compartment for the both, left, and right fuel tank selector positions; no obstructions were noted. The crossover fuel vent line was also free of obstructions.
Weather Information
According to the airport that last fueled the airplane, 12.59 gallons of 100 low lead fuel were added. The fuel facility inspection record for August indicated a daily inspection on the day of fueling, with results showing slight solids and bright for the storage tank sump, and clear and bright for the filter sump. The airport manager reported no fuel-related issues. Meteorological upper air data for the accident area near the time of the accident indicated that at 5,198 feet mean sea level (about the altitude of the accident flight), the temperature and dewpoint were 63°F and 56°F, respectively, which was favorable for serious carburetor icing at glide power.