Overview
An aircraft experienced a fire when it was about 1.5 miles from its destination. The fire originated on the left side of the floorboard against the firewall. The pilot responded by turning off the electrical system and, before landing, shutting off the fuel selector. After landing, the occupants egressed, and the aircraft continued to burn until fire department personnel arrived and applied dry chemicals.
Investigation Findings
During the investigation of the incident, a fuel line was found with areas of thinning. This line was routed from the firewall to the fuel shutoff valve on the left side of the cabin. The area had been exposed to high heat during the fire.
Possible Ignition Source
A possible source of ignition was a power supply for the radio, which was attached to the firewall under the instrument panel just above the fuel line. An internal examination of the power supply unit showed an area of intensive heat around the relay assembly.
Engineering Report
According to an engineering report, the wall thinning of the fuel line, which was made from aluminum alloy 3003, was a result of loss of material at the inner surface.