Incident
Shortly after takeoff, the aircraft's cockpit and cabin filled with smoke. Both occupants—the pilot and a passenger—detected an odor of burning electrical wiring and observed flames at the firewall in the area of the rudder pedals. The pilot turned the aircraft 180 degrees and executed a landing on Runway 35. Upon landing, the two occupants immediately egressed from the aircraft.
Investigation Findings
Examination revealed that the left engine exhaust stack, part number 63726-O2, had become displaced. This component is designed to be inserted into the muffler assembly, part number 66704-00, and secured with a clamp assembly, part number 65442-03. The clamp assembly was present on the muffler, with the nut installed and the clamp flush with the outside diameter of the muffler extension. The locater pin extended through the muffler extension. The exhaust stack had its locator hold in place, and inspection did not indicate that the pin was worn or sheared, which would have allowed disengagement.
As a result of the displacement, hot exhaust gases were directed onto the firewall in the vicinity of the starter solenoid and brake reservoir. The fire caused damage to the aircraft from the firewall aft to the baggage/rear area. Additionally, fluid from the melted brake reservoir appeared to have contributed to the spread of the fire.
Damage
The aircraft sustained fire damage extending from the firewall through the baggage compartment and rear sections. The brake reservoir was melted, and its fluid release appeared to exacerbate the fire.