On August 17, 2014, about 1430 eastern daylight time, a Cessna R182, N292LC, was substantially damaged when it caught fire while returning to Republic Airport (FRG), Farmingdale, New York. The private pilot and the passenger were not injured. Visual meteorological conditions prevailed, and the flight was operating on an instrument flight rules flight plan between FRG and Dutchess County Airport (POU), Poughkeepsie, New York. The personal flight was conducted under the provisions of 14 Code of Federal Regulations Part 91. According to the pilot, the airplane took off about 1415, and was cleared to 5,000 feet mean sea level (msl). Shortly after leveling off, the pilot noted a fuel pressure drop and a fuel flow rate increase. The pilot requested a priority return to FRG and kept the airplane at 5,000 msl feet until he believed that he could land at the airport in the event of an engine failure, then descended it to 3,000 feet msl for a visual approach to runway 32. When the airplane was on a high right downwind leg of the traffic pattern, smoke appeared in the cockpit along with an "acrid, insulation smell." The pilot then declared an emergency and requested that fire rescue equipment be standing by. As the airplane descended through 1,400 feet msl, and with the engine still running "normally," flames were observed entering the cockpit in the vicinity of the rudder pedals. The pilot subsequently lowered the flaps and completed the landing to runway 32. He then turned the airplane onto a taxiway and stopped it where he and the passenger disembarked, and firefighters extinguished the fire. According to a responding Federal Aviation Administration (FAA) inspector, the AN911-2D nipple fitting that connected the fuel line Tee (AN917-2D) to the carburetor was fractured and had separated, which allowed fuel to be pumped into the engine compartment. The inspector subsequently suggested through FAA channels that an Airworthiness Directive (AD) be issued to change the AN911-2D aluminum nipple fitting to an MS fitting made of steel. He also noted that the nipple fitting was likely original to the airframe, which had about 4,010 hours of operation. In response, the FAA Aircraft Certification Office (ACO) stated that they reviewed National Transportation Safety Board accident/incident and Monitor Safety Analyze Data databases for the last 15 years for other like occurrences and/or failures and found no additional reports to support the issuance of an AD. The response further noted that the AN911-2D nipple fitting was an industry standard part which was used in numerous fuel, hydraulic and pneumatic systems, throughout the aerospace industry, including in the fuel systems of many other Cessna airplanes. Cessna indicated that they had not received any other reports wherein an AN9l1-2D nipple cracked and caused a fuel leak, and that it was "very likely the nipple was cracked for a time prior to complete separation. Evidence of this crack should have been detectable during ground inspection prior to complete failure of the nipple in the form of fuel staining and/or a strong fuel odor…" Both Cessna and the FAA ACO did not agree to the proposed fitting material change to steel. The pilot reported that the airplane had been operated for 150 hours since its most recent annual inspection, which was performed on February 15, 2014.