Aviation Investigation Report A98H0003
1.16.7 Statistics for Occurrences Involving Smoke or Fire
The Boeing Company performed an analysis of reported in-service events, occurring between November 1992 and June 2000, that involved smoke, fumes, fire, or overheating in the pressurized areas of Boeing-manufactured aeroplanes. The events under study were assigned one of three general source categories: air conditioning, electrical, or material. Boeing attributed 64 per cent of the events under study to electrical sources, 14 per cent of the events to air conditioning sources, and 12 per cent of the events to material sources. The remaining 10 per cent of the reported events did not include sufficient information to determine the source of the smoke, fumes, fire, or heat. For those events involving MD-11 or DC-10 aircraft, 51 per cent were classified as being electrical in nature, 21 per cent were attributed to air conditioning, and 15 per cent were associated with material causes.
The Boeing study concluded that "larger airplanes with more complex systems show a predominance of smoke events of electrical origin, compared with air-conditioning and material smoke events." The Boeing study also concluded that "for smoke events in which the flight crew could not determine the smoke source, most were subsequently determined by maintenance crews to be of electrical origin."
The TSB reviewed data on in-flight fires that occurred between January 1967 and September 1998 to determine the average time between when an in-flight fire is detected and when the aircraft either ditches, conducts a forced landing, or crashes. The review was limited to fires in commercial transport aircraft with a maximum take-off weight of more than 50 000 lb. Included in the review were any fires that took place inside the fuselage. Events involving engine fires, wheel well fires, and explosions were not considered, nor were events that concluded with a successful landing. The data showed that in 15 representative occurrences, between 5 and 35 minutes transpired between the detection of the first fire symptoms and the crash of the aircraft. Although the circumstances varied in each of these occurrences, the research indicates that when an in-flight fire continues to develop, it can, in a very short time, lead to catastrophic results. In the case of SR 111, the elapsed time between when the unusual odour was first noticed in the cockpit and when the aircraft struck the water was approximately 20 minutes.
The Boeing study, referred to in Section 126.96.36.199, had similarly observed that "[r]eview of historical data on the rare fire events that resulted in hull loss indicates that the time from first indication of smoke to an out-of-control situation may be very shorta matter of minutes."
 The results of this analysis were reported in issue number 14 of Boeing's Aero Magazine (http://www.boeing.com/commercial/aeromagazine/aero_14/index.html).
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