What happened
The incident occurred while the aircraft was approximately one and a half miles from its destination. A fire ignited on the left side of the floorboard, positioned against the firewall. The pilot immediately turned off the electrical system and, prior to landing, shut off the fuel selector. After the aircraft landed, the occupants exited the plane. The aircraft continued to burn until fire department personnel arrived and applied dry chemical extinguishers.
The investigation
Investigators examined the wreckage and identified a fuel line with areas of thinning. This line was routed from the firewall to the fuel shutoff valve on the left side of the cabin, an area exposed to high heat during the fire. A possible ignition source was identified as 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 this power supply unit revealed an area of intensive heat around the relay assembly.
Findings
An engineering report concluded that the wall thinning of the aluminum alloy 3003 fuel line resulted from loss of material at the inner surface. The proximity of the fuel line to the radio power supply suggests a potential contact point for ignition. The loss of material in the fuel line likely allowed fuel to escape or ignite, contributing to the fire.
Safety message
This incident highlights the importance of proper routing and protection of fuel lines near electrical components to prevent chafing and potential ignition sources.