What happened
Prior to the departure of a scheduled passenger flight, a flight attendant detected an electrical odor in the rear section of the aircraft. The first officer was notified and consulted a mechanic; however, no issues were identified, and the flight proceeded as planned.
During the flight, a flight attendant reported the return of the electrical odor in the same area. Following an investigation by the captain, the odor appeared to diminish after the temperature in the rear cabin was lowered. Shortly after this adjustment, smoke and fire became visible in the floor and side wall area.
The captain declared an emergency and diverted the aircraft to an alternate airport. The fire was extinguished during the approach, and the aircraft completed an uneventful landing with no injuries reported.
The investigation
Post-flight examination of the burned area identified that a cable for the audio-entertainment system had experienced a short circuit. This electrical failure resulted in minor damage to the airplane. Investigators determined that the cable had not been properly installed. Furthermore, it was noted that the Supplemental Type Certificate (STC) lacked specific instructions for routing the cable, providing only the requirement that it be placed under a seat rail cover.