Incident Summary
While climbing through Flight Level 180, the crew of a commercial aircraft noticed an electrical arcing sound accompanied by a slight burning odor of electrical origin. Following emergency procedures, the issue temporarily resolved, and the climb continued. However, upon reaching Flight Level 330, a loud arcing sound recurred, and flames were observed emanating from the aft overhead panel in the flight deck. Flight attendants successfully extinguished the fire, and the aircraft returned to Denver, where it landed without further incident.
Examination Findings
Post-incident examination of the aircraft revealed a short circuit in a wire bundle located in the flight deck. The bundle was not shielded or anchored, unlike another major bundle in the same compartment. The short was attributed to chafing of the wire bundle against the flight deck entry door frame. Additionally, testing determined that the wire gauge used in part of this application was insufficient for the electrical load carried.