What happened
On 13 May 2002, Air Canada Flight 116, a Boeing 767–300 (registration C–GHML), was performing a scheduled flight from Vancouver to Toronto/Lester B. Pearson International Airport. While on final approach, approximately 10 miles from the destination, the flight crew received an alert indicating a fire in the aft cargo bay. The crew immediately followed emergency protocols, activated the cargo bay fire extinguishers, and declared an emergency.
Although the fire warning light extinguished roughly 50 seconds after the extinguishers were deployed, the aircraft landed on runway 06L and stopped to allow airport emergency services to inspect the plane. While external infrared scans by firefighters showed no active flames, the crew reported a smell of smoke and a haze inside the cabin. Upon opening the cargo compartment doors, firefighters encountered significant smoke and fumes. A subsequent inspection in a hangar revealed substantial soot and fire damage on the cargo bay floor.
The investigation
The investigation focused on the source of the ignition and the materials that allowed the fire to spread. Investigators identified a B110 heater ribbon, attached to a water supply line, as the ignition source. The failure occurred near a recent repair to the water line. The investigation found that the repair created uneven heat distribution, causing localized overheating of the heater ribbon. This heat caused the electrical insulation to degrade, eventually leading to arcing between the heating elements.
Furthermore, the investigation examined the presence of combustible materials in the cargo area. It was determined that the fire was able to propagate due to the presence of flammable debris, including paper, candy wrappers, and Styrofoam, which had accumulated in the bilge area. Additionally, the investigation found that the PET covering on the insulation blankets was contaminated and flammable, contributing to the fire's spread.
Findings
- The primary cause of the fire was the failure of a B110 heater ribbon at the site of a recent water line repair, which created an electrical arc.
- The presence of flammable materials, specifically contaminated PET insulation blankets and accumulated debris like paper and plastic, allowed the fire to grow and spread.
- The fire had breached the cargo compartment liner and entered an unprotected area of the aircraft.
- The heater ribbon remained powered throughout the event, as there was no mechanism for the crew to deactivate it from the flight deck.