What happened
On a flight from Cranbrook to Vancouver, British Columbia, an Air Canada Jazz De Havilland DHC-8-311, registration C-FRUZ, experienced an in-flight fire. While descending through 14,000 feet in instrument meteorological conditions, an electrical arc occurred within the left forward windshield heater terminal block, leading to a fire. The crew responded by cutting power to the windshield heater, which extinguished the flames after a few seconds, though the intense heat caused the inner pane of the windshield to shatter.
Despite the emergency, there were no injuries to the 33 passengers or 3 crew members on board. The aircraft landed safely at Vancouver at 195LT, with emergency services prepared on the runway. During the event, the captain encountered difficulty unlatching a fire extinguisher from its bulkhead mount, though the fire had subsided by the time the device was accessible.
The investigation
Investigators examined the windshield and the heat controller in a laboratory setting. They determined that the inner ply of the three-ply laminate had cracked due to the thermal shock from the arcing event, while the outer and middle plies remained intact. The investigation focused on the terminal block, finding that while the screw and ring terminal showed discoloration from heat, there was no evidence of improper threading or poor external contact.
Technical analysis suggested that the arcing originated from damage within the wire braiding leading to the L2 connection. This damage created a high-resistance path, eventually causing the wire to burn and creating a conductive carbon path. The investigators could not determine the original cause of the damage to the braid.
Additionally, the investigation noted that the cockpit voice recorder (CVR) was not secured following the event. Because the aircraft was not quarantined and power was applied to the CVR for over 30 minutes after arrival, valuable audio data from the immediate aftermath of the incident was overwritten.