On July 28, 2018, about 1045 eastern daylight time, a Cessna 172S airplane, N785SP, was destroyed following an inflight fire in the traffic pattern at Knox County Airport (4I3), Mount Vernon, Ohio. The student pilot sustained minor injuries. The airplane was registered to a private individual and operated by the pilot as a Title 14 Code of Federal Regulations Part 91 personal flight. Visual meteorological conditions prevailed, and no flight plan was filed for the cross-country flight that departed Newark-Heath Airport (VTA), Newark, Ohio, about 1025. The flight was destined for Zanesville Municipal Airport (ZZV), Zanesville, Ohio. According to the student, several minutes after takeoff, he maneuvered the airplane to enter the traffic pattern at 4I3, to accomplish touch-and-go landings. Initially, the student noticed his left foot was getting hot. Shortly thereafter, he noticed a fire near the rudder pedals. He pulled back the throttle and expedited his approach for landing. Subsequently, the fire continued to enlarge while he landed the airplane. After landing, he discharged the fire extinguisher and safely egressed from the airplane; a few seconds later the cockpit area was engulfed in flames. Postaccident examination of the airplane by Federal Aviation Administration (FAA) airworthiness inspectors revealed that there was evidence of a fuel-fed fire, which emanated from the rear, lower center portion of the engine. Substantial thermal damage was observed in the area where the mechanical fuel pump is mounted to the oil cooler. The bottom hose connection was observed to be separated from the oil cooler. Furthermore, the bottom portion of the fuel pump was observed missing. The fire started and eventually enlarged from an unknown source that could not be determined from the available evidence. According to the FAA inspector, the airplane had complied with all appropriate Airworthiness Directives (ADs). Furthermore, the airplane had no maintenance write ups for fuel leaks or odors in the previous 20 flight hours.