Incident Description
Following an uneventful landing, while taxiing to the parking position, the cabin crew alerted the flight crew to an electrical-smelling smoke enveloping the cabin area. Concurrently, the flight crew heard circuit breakers popping and cabin chimes sounding. In response, the flight crew halted the aircraft and determined that an immediate evacuation was necessary. They instructed the cabin crew to deploy the emergency slides and evacuate all passengers. All slides were deployed successfully, and the evacuation was completed without any injuries.
Investigation Findings
Subsequent inspection by maintenance personnel revealed minor damage to the aircraft caused by a chaffed wire bundle located in the mid-cargo pit ceiling at station 750. The wire bundle had arced, generating smoke that entered the cabin. The affected area was identified as part of a Boeing-designed and retrofitted over-wing heater wiring installation. Engineers from both the aircraft operator and manufacturer determined that the arcing likely occurred because the left and right over-wing heater blanket wiring contacted the edge of the 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. They further established that vibration arising from normal aircraft operations allowed the bracket to gradually cut through the wire insulation, eventually making contact with the conductor and causing arcing.
Corrective Actions
Following the incident, the operator inspected its entire fleet of similarly configured aircraft and identified one additional wire bundle discrepancy. The aircraft manufacturer also discovered one other operator with a comparable wiring setup. In response, a service bulletin was issued, outlining the problem and providing instructions for adjusting the wire bundles to prevent future occurrences.