What happened
Following a normal landing, the aircraft was taxiing toward the parking area when the cabin crew alerted the flight crew to smoke with an electrical odor engulfing the cabin. During this period, the flight crew heard circuit breakers tripping and cabin chimes sounding. The crew determined that an immediate evacuation was necessary and brought the airplane to a stop. The order was issued to deploy emergency slides and evacuate all passengers. All emergency slides were successfully deployed, and there were no injuries incurred during the evacuation.
The investigation
Maintenance personnel identified minor damage to the aircraft caused by a chafed wire bundle located in the mid-cargo pit ceiling at station 750. This specific area was part of a Boeing-designed and retrofitted over-wing heater wiring installation. Engineers from both the operator and the manufacturer determined that arcing occurred because the left and right over-wing heater blanket wiring made contact with the edge of a wire bundle bracket. This bracket was attached to the second inboard lighting hole at station 750 on the left side of the mid-cargo pit ceiling.
Findings
The investigation concluded that vibration from normal airplane operations allowed the bracket to cut through the wire insulation, leading to contact with the wire conductor and subsequent arcing. Following the event, the operator inspected its entire fleet of affected aircraft and discovered one additional wire bundle discrepancy. The manufacturer also identified another operator utilizing a similar configuration. A service bulletin was subsequently issued to provide instructions for adjusting wire bundles to prevent future occurrences.