CHI90IA064

Factual narrative

AIRLINE GROUND PERSONNEL FOUND HEAT/FIRE DAMAGE IN THE AFT CARGO BAY IN THE VICINITY OF THE MID-SHIP DRAIN MAST. IT COULD NOT BE DETERMINED WHEN THE DAMAGE OCCURRED; THERE WAS NO RECORD OF A CREW REPORT OF FIRE/SMOKE DETECTION/WARNING. A FUNCTIONAL CHECK OF THE SYSTEMS INDICATED THAT THEY WERE CAPABLE OF NORMAL OPERATION. THERE WERE NO POPPED CIRCUIT BREAKERS. THE DRAIN MAST AND ASSOCIATED GROUND/AIR RELAY SWITCH WERE TESTED AT THE MANUFACTURER'S FACILITY, AND THERE WAS NO EVIDENCE OF FAILURE OF THOSE COMPONENTS. PREVIOUS SIMILAR OCCURRENCES HAVE BEEN ATTRIBUTED TO INADEQUATE HOUSEKEEPING. THE AREA AROUND THE DRAIN MAST IS A LOW POINT IN THE FUSELAGE, AND A NATURAL PLACE FOR TRASH/LITTER TO COLLECT. INJURY INDEX PRESUMED. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12