Incident Overview
An Air Canada DC-9-32, carrying 5 crew members and 72 passengers, was being pushed back from Gate 1 at Vancouver International Airport for a flight to Calgary, Alberta. The captain initiated the starting sequence for the No. 2 (right) engine during pushback, which proceeded normally. When the captain started the No. 1 (left) engine, it did not start, and he identified a wet start, discontinuing the start and beginning the Wet Start and Unsatisfactory Start procedures.
Fire Reports and Evacuation
While completing engine shutdown procedures, the pilots were informed by ground personnel and the crew of a passing aircraft that black smoke and flames were visible near the left engine. There were no cockpit indications of fire. Based on these reports, the captain activated the No. 1 engine fire extinguisher bottle and informed the flight attendant. A short time later, a second report of fire prompted the captain to activate the No. 2 fire extinguisher bottle. Because the aircraft had already been pushed back from the gate, he ordered an emergency evacuation through the two forward doors. The flight attendants deployed the forward escape slides, and the evacuation began. The right-side escape slide partially deflated but remained sufficiently firm. Four minor injuries occurred during the evacuation; the aircraft was not damaged.
Engine and Igniter Details
The DC-9 was powered by two Pratt & Whitney JT8D-7B turbo-fan engines mounted on the rear fuselage. Each engine had two igniter plugs (A and B systems). At the time of the incident, the left engine had one Champion AA725 plug and one Auburn JB3 plug. The wet start was caused by a defective igniter plug that had malfunctioned, preventing proper ignition. Unburnt fuel pooled in the combustion chamber. The igniter fired through a crack in the ceramic shield outside the combustion chamber, igniting the pooled fuel and causing an internal engine fire. The fire was short-lived and contained within the combustion, turbine, and tail-pipe sections; it did not pose a significant threat to the aircraft or occupants. No cockpit fire indications occurred because the fire was isolated from the fire sensor system.
Pilot Actions and Procedures
The standard engine starting procedures required specific pilot phraseology and checks. The captain did not follow the standard phraseology during the start sequence; a discussion about passenger seating appeared to take priority. Flight data recorder (FDR) data showed the starter was disengaged at a certain point, and the parking brake was set immediately after. The FDR did not show the characteristic rapid decrease in fuel flow when the fuel control lever is moved to OFF, indicating the lever was not returned to the OFF position during the start sequence. The captain likely interrupted his vital actions due to a request from the ground crew to set the brakes. Fuel continued to flow to the engine while motoring continued, augmenting fuel pooling and exacerbating any fire. After starter release, fuel continued to flow as engine rpm decreased.
Causes and Contributing Factors
The Transportation Safety Board determined that the abnormal start and tail-pipe fire were caused by a defective engine igniter plug. Exacerbating the fire was the captain's incomplete Unsatisfactory Start procedures. Contributing factors included inaccurate and untimely reports of a continuing and uncontained fire in the left engine.
Safety Actions Taken
Following the incident, Air Canada reviewed and amended their escape slide repacking procedures after discovering incorrect packing. An inspection campaign verified the serviceability of all DC-9 escape slides; only two slides were found similarly punctured. A bulletin was issued to cabin crew and servicing personnel about potential damage during ground servicing. Air Canada discontinued using Auburn igniter plugs after monitoring revealed similar ceramic cracking; no similar occurrences have been reported since. Transport Canada confirmed that Air Canada's maintenance programs for escape slides and ignition systems met requirements.
The investigation report was authorized for release on March 5, 1997.