Incident Overview
On September 25, 2013, at approximately 1830 central daylight time, a Weatherly 620 airplane, registration N4623M, was destroyed following an in-flight fire and subsequent forced landing near Ulysses, Kansas. The commercial pilot, who was the sole occupant, was not injured. The flight was conducted under 14 Code of Federal Regulations Part 91 as a ferry flight, with visual meteorological conditions prevailing. No flight plan was filed. The flight had originated from Ulysses Airport (ULS) at about 1820, with Eads Municipal Airport in Eads, Colorado, as the intended destination.
Pilot's Account
The pilot reported that about 10 minutes after departure, while in cruise flight at 200 feet above ground level, he detected smoke in the cockpit. Within 10 seconds, the cockpit filled with dense smoke, significantly reducing visibility. He indicated that the odor did not resemble that of an electrical fire. The pilot turned the master switch to the OFF position, after which the engine lost power. He then turned the master switch back on and activated the fuel boost pump in an attempt to restart the engine, but the engine did not restart. He executed a forced landing in a corn field. After exiting the airplane, the fire consumed most of the aircraft, leaving only the radial engine, empennage, and right wing relatively intact.
Maintenance History
According to the airplane's owner, the aircraft had not been flown for approximately two to three years. Maintenance records showed that the airplane had undergone an annual inspection on April 20, 2012, at which time the total airframe time was 2,099.1 hours. After that inspection, the airplane was flown to another maintenance facility to have GPS database updates installed; during that flight, an oil leak was discovered. The engine was subsequently removed and replaced with an overhauled unit. A ground run of about one hour was conducted to check for leaks, and none were found. The total airframe time after the engine replacement was 2,101.6 hours. The maintenance facility manager reported that the area behind the engine firewall was not accessed during the engine replacement.
Wreckage Examination
Examination of the wreckage revealed that the radial engine and components forward of the firewall exhibited minimal fire damage. The area of most intense fire damage was located between the chemical hopper and aft of the engine firewall, encompassing the fuel boost pump, fuel strainer, and fuel lines. A section of the fuel line connecting the right fuel tank to the fuel pump showed cracks and areas of incipient melting. A metallurgical examination by the National Transportation Safety Board's Materials Laboratory determined that these fuel line anomalies were the result of the post-impact fire, not pre-existing cracks. The extensive fire damage to the airplane's fuel and electrical systems precluded further examination.
Summary
The accident resulted in the destruction of the aircraft, with no injuries to the pilot. The fire originated in the area behind the engine firewall, but the exact ignition source could not be determined due to fire damage.