On August 17, 2015, about 1100 eastern daylight time, a Cessna 172K, N84308, 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. The airplane was registered to and operated by Adventure Seaplanes LLC. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 personal flight from Perry-Foley Airport, Perry, Florida, to Winter Haven's Gilbert Airport, Winter Haven, Florida. The flight originated about 30 minutes earlier.

The pilot reported that after arrival at the airport, he checked the fuel tank sump drains and also the gascolator drain before fueling. Records indicate a total of 12.59 gallons of 100 low lead fuel were added which filled the airplane, and after fueling, the pilot reported waiting 15 minutes and then 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 the both position, he felt a vibration and noticed a lack of engine performance. He first established a suitable forced landing location and turned towards it, and while descending, he applied carburetor heat and left it applied, which did not restore engine power. He also reported moving the fuel selector to the left and right positions and activated the auxiliary fuel boost pump; none of the efforts restored engine power. He 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 also reported pumping the throttle control and reported each time he did so the engine would slowly gain 200 to 400 rpm, but would not achieve sustained power. He indicated he only had 1/2 power available during the descent.

The pilot further indicated that he began his approach to land in a hay field running parallel to a country road but noted a barb wire fence ahead. He proceeded to go-around and 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 which forced the nose landing gear to the ground causing it to break off; the airplane slowly nosed over.

Examination of the airplane at the accident site was performed by a Federal Aviation Administration (FAA) airworthiness inspector who reported that once the airplane was uprighted, a total of 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. Copies of the NTSB Record of Conversations with the FAA inspector are contained in the NTSB public docket.

Following recovery of the airplane, another FAA inspector performed an examination of the engine which included removal of all spark plugs; no discrepancies were reported. The crankshaft was manually rotated and there was no evidence of a stuck valve. In preparation of an engine run, a temporary fuel supply was plumbed directly into the carburetor, which was the same carburetor installed at the time of the accident. The engine was started and operated to 2,500 rpm and was reported to run stable. Safety concerns prevented full power application. A check of the magnetos was performed at 1,800 rpm and the right magneto drop was 150 rpm and the left magneto drop was 120 rpm. Following the engine run, a differential compression test of the cylinders was performed at 80 psi with the following results noted; #1 78; #2 69; #3 71; #4 56. Subsequent retesting revealed all cylinders were 78 psi or better.

Examination of the fuel supply system by a NTSB investigator verified the fuel supply system from each wing through the fuel selector to the engine compartment was confirmed for the both, left, and right fuel tank selector positions; no obstructions were noted. The investigator also verified that the crossover fuel vent line was free of obstructions. A copy of the NTSB Record of Conversation with the NTSB investigator is contained in the NTSB public docket.

According to records provided by the airport that last fueled the airplane, a total of 12.59 gallons of 100 low lead fuel were added. A review of the fuel facility inspection record for August indicates that on the day of fueling, the fuel facility was given a daily inspection which included a check of the storage tank sump with the results indicating slight solids and bright. The inspection also included a check of the filter sump, with the results reported to be clear and bright. The airport manager reported there have been no reported fuel related issues. Copy of the fuel invoice and inspection record and also the NTSB Record of Conversation with the airport manager are contained in the NTSB public docket.

According to the airplane Type Certificate Data Sheet, the maximum engine limit is 2,700 rpm.

A review of Meteorological Upper Air Data for the accident area about the time of the accident revealed at 5,198 feet mean sea level, or about the altitude of the accident flight, the temperature and dewpoint were 63 and 56 degrees, Fahrenheit, respectively, which was favorable for serious carburetor icing at glide power. A copy of the upper air data and excerpt from the FAA Special Airworthiness Information Bulletin (SAIB) pertaining to carburetor ice conditions are contained in the NTSB public docket.