On October 29, 1999, a Piper PA-22-150 (registration N2648P) was involved in an aviation accident near Newberry, SC. Investigators recorded the probable cause as: A faulty exhaust muffler caused the aircraft's firewall to overheat and smolder the aircraft's firewall insulation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A pilot reported smoke from the right defrost duct, followed by a cockpit fire near the rudder pedals. Investigation found a faulty muffler caused firewall overheating and insulation smoldering.
Incident Overview
After 30 minutes of flight, the pilot reported that smoke began entering the cockpit through the right side defrost duct. He elected to divert to the nearest airport, located 14 nautical miles north of his position. Approximately 3 miles from the airport, a fire started inside the cockpit near the right side rudder pedals. The pilot reduced power and began descending toward a field. The last thing he recalled was crossing power lines.
Investigation Findings
A detailed inspection of the muffler revealed two areas of burn-through damage. The aircraft's firewall had an area approximately 14 inches in diameter with indications of severe overheating. Investigators concluded that a faulty exhaust muffler caused the aircraft's firewall to overheat, which in turn led to smoldering of the firewall insulation. Maintenance records did not indicate that the exhaust muffler had ever been replaced.
Probable cause
A faulty exhaust muffler caused the aircraft's firewall to overheat and smolder the aircraft's firewall insulation.