Synopsis

On June 2, 1983, Air Canada Flight 797 using a McDonnell Douglas 9 was scheduled for a trans-border flight from Fort Worth to the final destination of Montreal. A fire started from the toilet cubicle at the rear of the aircraft releasing toxic gases and smoke, causing passengers on the aircraft to feel unwell. The fire also burned electrical cables which were part of the flight instrument and control circuitry, resulting in a loss of control authority and instruments, forcing the aircraft to land at an alternative airfield. While the landing was successful, after the doors were opened on the ground for evacuation, the influx of air provided sufficent oxygen to allow a flashover fire to occur. The toxic fumes and fire resulted in the deaths of 23 passengers. All 5 crews were uninjured, with the Captain being the last one to get out of the aircraft before the fire began to “flashover”.

In 1979, 4 years before the fire onboard Flight 797 happened, it was reported that the aircraft had suffered an explosive decompression in the rear bulkhead that required rebuilding the tail section and replacing or splicing most of the wiring and hydraulic lines in the aft section of the fuselage. As a result of the fire most of the wiring in the aft area was damaged and the investigators were unable to identify the exact origin of the fire.

While the fire wasn’t immediately life threatening during the initial phases of the incident, 90 seconds after the evacuation began enough oxygen became avaliable to the fire to allow a flashover. The flashover was made worse because the toxic and noxious fumes provided additional accelerants to the air mixture. Oxygen is a highly reactant with many noxious fumes produced by chemical reactions. Given the nature and location of the fire there was nothing that the flight crew could do to stop the chemical reaction from happening.

Recommendations after the accident included improved minimum fire fighting procedures, more immediate flight crew reactions and training and improved safety briefings.