In-Flight Fire and Crash Following Electrical Problem Reported by Pilot (N6002N)

Accident Description

The pilot reported an in-flight electrical problem to air traffic control and requested a descent for an immediate landing at the next airport. The airplane was seen descending and emanating smoke from the cabin until it crashed about 12 miles from the airport.

Examination Findings

Examination of the airplane revealed evidence of an in-flight fire. The interior of the airplane's cabin had evidence of fire on the flight controls and heavy smoke accumulation. Portions of the airplane's windshield were no longer translucent due to sooting on the interior surfaces.

The source of fire was traced to a 100-amp inductive noise filter mounted directly to the airplane's firewall. There was evidence of an electrical insulation failure between an electrical terminal and the steel case of the filter. The filter was not marked as an FAA approved part and was not listed in the manufacturer's parts catalog.

Maintenance History

The airplane's electrical system had been altered with installation of a filter on the alternator output 3.5 years before the accident. There was no circuit protection or isolation mount for the 100-amp filter. The repair station that performed the work did not file an FAA Form 337. The airplane had a history of maintenance performed on the electrical system since the installation of the filter. The maintenance also included the completion of annual inspections and one repair station had replaced the 100-amp filter with another used filter.