Event Details
The aircraft was on a test flight following the completion of an annual inspection. According to the pilot, shortly after takeoff, he detected the smell of an electrical fire and then felt heat on his legs. He remained in the traffic pattern and landed the airplane. After exiting the aircraft, a fire broke out in the cockpit area. Bystanders used water to help extinguish the fire.
Postaccident Examination
A postaccident examination of the airplane revealed evidence of electrical arcing on the firewall. The arcing originated from a cable that passed through the firewall. This electrical cable was routed from the battery relay, located aft of the aft seat, to the starter relay, which was positioned on the upper right section of the firewall.
Maintenance Background
The mechanic who performed the annual inspection used the manufacturer's checklist. Reportedly, no work had been performed on the instrument panel during this inspection.
Conclusion
The source does not provide a stated probable cause for the incident.