page_title: Air Canada Flight 797
section_title: Investigation
hierarchical_section_title: Air Canada Flight 797 / Investigation
caption_attribution_description: English: Fire damage of DC-9 C-FTLU (Air Canada Flight 797).
context_page_description: Air Canada Flight 797 was an international passenger flight operating from Dallas/Fort Worth International Airport to Montréal–Dorval International Airport, with an intermediate stop at Toronto Pearson International Airport. On 2 June 1983, the McDonnell Douglas DC-9-32 operating the service developed an in-flight fire behind the lavatory that spread between the outer skin and the inner decor panels, filling the plane with toxic smoke. The spreading fire also burned through crucial electrical cables that disabled most of the instrumentation in the cockpit, forcing the plane to divert to Cincinnati/Northern Kentucky International Airport. Ninety seconds after the plane landed and the doors were opened, the heat of the fire and fresh oxygen from the open exit doors created flashover conditions, and the plane's interior immediately became engulfed in flames, killing 23 passengers who had yet to evacuate the aircraft.
  The accident became a watershed for global aviation regulations, which were changed in the aftermath of the accident to make aircraft safer.
context_section_description: Because the accident occurred in the United States, it was investigated by the National Transportation Safety Board (NTSB).
  Although the fuselage was nearly destroyed by the intensity of the fire, the cockpit voice recorder (CVR) and flight data recorder (FDR) were still in good condition and produced vital data for the NTSB investigation. On the CVR, NTSB investigators heard eight sounds of electrical arcing beginning at 18:48.  The arcing sounds repeated each time the crew tried to reset the lavatory circuit breakers. Both pilots testified that they did not hear any arcing, and the NTSB concluded that these sounds would be inaudible to the flight crew.  Although a number of wires in the lavatory section were later found with insulation stripped away, NTSB investigators were unable to determine whether this insulation damage was the cause of the fire or was caused by the fire.
  This particular DC-9 had experienced a number of problems over the months leading up to the incident; 76 maintenance reports had been filed in the plane's logs in the previous year, and the CVR records Cameron telling Ouimet to "put [the tripping breakers] in the book there" when the breakers fail to respond to the first reset attempt at 18:52. Cameron attempted once more to reset the breakers at 18:59. The CVR records arcing sounds followed by the popping sound of the breakers continuing to trip again after each reset over the next 60 seconds. Nearly four years earlier, on 17 September 1979, the plane, then serving as Air Canada Flight 680 (Boston, Massachusetts, to Yarmouth, Nova Scotia), 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 back of the plane; Cameron later noted that the Air Canada maintenance crew "did a heck of a job getting everything put back together" after the decompression incident. Investigators were unable to find signs of arcing in any of the wire splices from the repairs done four years earlier, though much of the wiring in the rear of the plane was severely damaged or destroyed by the fire itself.
caption: Fire damage in the rear of the aircraft around the aft lavatory.
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