On September 25, 2013, about 1830 central daylight time, a Weatherly 620 airplane, N4623M, was destroyed as a result of an in-flight fire and a forced landing near Ulysses, Kansas. The commercial pilot, the sole occupant, was not injured. The airplane was registered to and operated by a private individual under the provisions of the 14 Code of Federal Regulations Part 91 as a ferry flight. Visual meteorological conditions prevailed at the time of the accident, and no flight plan was filed. The flight originated from the Ulysses Airport (ULS) about 1820 with Eads Municipal Airport, Eads, Colorado, as the destination. The pilot reported that about 10 minutes after departing ULS he was in cruise flight at 200 feet above ground level, and he smelled smoke in the cockpit. Within 10 seconds, the smoke filled the cockpit and it was very dark. He stated that it did not smell like an electrical fire. He reported that he turned the master switch to the OFF position, and the engine subsequently stopped producing power. He turned on the master switch and the fuel boost pump to in an attempt to restart the engine, but without success. He executed a forced landing to a corn field. He exited the airplane, and the fire consumed most of the airplane excluding the radial engine, empennage, and right wing. According to the airplane's owner, the airplane had not been flown for about two to three years. The maintenance records indicated that the airplane had undergone an annual maintenance inspection on April 20, 2012. The airplane had a total of 2,099.1 hours at the time of the inspection. After the annual inspection was completed, the airplane was flown to another maintenance facility to get GPS database updates installed. During the flight, an oil leak was discovered. The engine was removed and an overhauled engine was installed. A ground run about one hour in length was conducted to check for leaks and none were found. The airplane had a total of 2,101.6 hours. The maintenance facility manager reported that the area behind the engine firewall was not accessed during the engine replacement. The examination of the wreckage revealed that the radial engine and the components located forward of the firewall exhibited minimal fire damage. However, the area that appeared to have the most intense fire damage was located between the chemical hopper and aft of the engine firewall, which included the fuel boost pump, fuel strainer, and fuel lines. A section of the fuel line that connected the right fuel tank to the fuel pump exhibited cracks and areas of incipient melting. A metallurgical examination of the fuel line by the National Transportation Safety Board's Materials Laboratory determined that it was the result of the post impact fire. No evidence of pre-existing cracks was observed. The examination of the airplane's fuel and electrical systems revealed extensive fire damage that precluded further examination.