On October 03, 2024, about 1730 eastern daylight time, a North American Navion airplane, N9117R, was substantially damaged when it was involved in an accident at Rutherford County Airport / Marchman Field (FQD), Rutherfordton, North Carolina. The pilot and passenger sustained minor injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that he departed Concord-Padgett Regional Airport (JQF), Concord, North Carolina, and was destined for FQD. About 36 minutes into the flight and while on final approach to runway 19 at FQD, the pilot heard a loud “pop” and felt heat coming from behind the pilot and copilot’s seats. As the airplane approached the runway threshold, the cabin filled with smoke and fire was visible in the cabin. During the landing, the airplane’s nose landing gear collapsed and the airplane came to rest on the runway. The in-flight and postaccident fire consumed a majority of the airplane. A witness captured video of the airplane as it approached the runway that showed fluctuating flames along the lower fuselage. Postaccident examination showed that most of the fuel supply, vapor return, and vent lines were destroyed by fire. The fuel selector valve was observed in the auxiliary fuel tank position. The gascolator assembly was not located among the recovered wreckage. The main fuel tanks exhibited thermal expansion; the right tank displayed a breach along its inboard seam. The right fuel tank’s flexible vent hose remained attached, but its two hose clamps were unsecured. Hydraulic components in the engine area exhibited thermal damage, and a loose B-nut was observed on a high-pressure hydraulic hose attached to the controllable relief valve. Service publications indicated that the main fuel tank vent line extended into the atmosphere beneath the left side of the fuselage near the wing’s leading edge. A caution note in both the service and flight manuals advised against operating the airplane from the auxiliary fuel tank until the airplane has flown at least an hour or used a minimum of 10 gallons of fuel. The caution adds that use of auxiliary tank fuel, when the main tanks are full, will result in vapor return fuel flowing overboard through the vent lines, as this fluid normally flows into the main tanks. A preaccident photograph of the airplane showed the vent outlet located about 10 inches aft of, and generally aligned with, the left exhaust extension pipe. The pilot reported that he departed with the fuel selector on the auxiliary fuel tank and did not change positions during the flight.