Safety board warns of airplane fire risk Last Updated Thu

November 15, 2002 - Watchdog Says Heater Ribbon Caused Air Canada Fire

TORONTO, Canada - A fire in the cargo hold of an Air Canada jet in May was sparked by failed heater ribbon, used to prevent water lines from freezing, Canada's transportation safety watchdog said on Thursday.

The fire broke out on the Boeing 767-300 airliner, which had 177 passengers and eight crew aboard, as the flight from Vancouver was on its final approach to Toronto's Pearson International Airport.

The crew activated fire extinguishers in the hold, which put out the fire, and the aircraft landed safely. But smoke poured out of the cargo hold when it was opened and closer examination revealed substantial damage on and under the cargo bay floor, investigators said.

In a report released on Thursday, the Transportation Safety Board said an Electrofilm brand heater ribbon, used to prevent the jet's potable water drain and supply line from freezing, "failed and exhibited signs of overheating and arcing." It recommended the federal Transportation Department take action to eliminate the risk of similar heater ribbon insulation failures. It also wants to remove the risk of contaminated insulation and debris propagating fires.

In the Air Canada incident, the heater ribbon, spiral-wrapped around the water line, burned through both its protective tape and foam thermal insulation, the board said. That ignited the Mylar covering of a thermal acoustic insulation blanket. Fed by debris such as lint and discarded cardboard cargo tickets, the fire spread through the floor of the aft cargo compartment, according to the board report.

"The fire became self-propagating, burning its way forward, inboard and outboard, spreading approximately 46 centimeters (18 inches) up the right side wall of the aircraft before it was extinguished by halon from the fire extinguishing system," the board added. "Heat from the fire was intense enough to burn holes through the aluminum web of a floor beam and significantly distort the top cap (chord) of the beam structure." Board investigators found burned heater ribbons, tape and foam insulation behind another wall of the jet's aft cargo area.

They also found burned heater ribbon in a similar cargo area of another Air Canada Boeing 767-300. A subsequent inspection by the Montreal-based airline of its fleet of 55 Boeing 767-200s and 767-300s produced "numerous occurrences of overheated/burned heater ribbons," the board said. "Thirty of the aircraft were found to have defective heater ribbons...resulting in 66 ribbons being either removed or de-activated," the board said.

As a result of the Air Canada fire, Boeing issued an alert on May 28 asking operators to inspect heater ribbons and remove debris near the water line. In early June, the U.S. Federal Aviation Administration issued an airworthiness directive on the problem.

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