Incident Details
During cruise at flight level 200 in visual meteorological conditions, the pilot detected a smell of smoke, followed by visible smoke emanating from the windshield defrosters and beneath the instrument panel. The pilot notified Houston Center of the situation, then deactivated all electrical equipment. An uneventful descent and landing was subsequently performed at Lake Charles, Louisiana.
Investigation Findings
Post-incident examination revealed that one of the three resistors within the cigar lighter resistor assembly had overheated. This overheating caused the resistor to burn through the phenolic backing on which it was mounted. The resulting heat then damaged approximately 2 feet of black rubber vacuum tubing.
Related Service Information
Further research indicated that Piper had issued Service Bulletin (SB) #654 concerning this component. The service bulletin called for the removal of these resistor assemblies from all PA-31, PA-31-325, and PA-31-350 aircraft following a similar incident in June 1980. However, the service bulletin and the subsequent Airworthiness Directive (AD) 79/20/07 did not address the same type of resistors installed in PA-31P aircraft.