Aviation Investigation Report A98H0003
4.3.1 In-Flight Firefighting Measures
In December 2000, the TSB issued five recommendations that identified deficiencies associated with in-flight firefighting measures. Although the Board recognizes that improved material flammability certification tests will eventually result in a decreased threat, flammable materials will remain in many aircraft for decades. In addition, initiatives aimed at reducing potential ignition sources, such as improved CB, wire inspection methods, and maintenance procedures, while encouraging, will not eliminate all potential ignition sources. Consequently, the Board believes that continuing emphasis must be placed on ensuring that aircraft crews are adequately prepared and equipped to quickly detect, analyze and suppress any in-flight fire, including those that may occur in areas such as cockpits, avionics compartments, and hidden spaces.
The Board is encouraged that the deficiencies identified in its recommendation package of December 2000 are being assessed and acted upon at various levels by manufacturers, operators, and regulatory authorities. Such activity will lead to enhanced safety, and some positive changes have already been achieved as indicated in Section 4.1 of this report. However, industry-wide progress appears to be unnecessarily slow. For example, although some airline operators have made improvements, the Board remains concerned with the pace of progress in mandating that all aircraft crews have a comprehensive firefighting plan that starts with the assumption that any smoke situation must be considered to be an out-of-control fire until proven otherwise, and that an immediate response based on that assumption is required. Regulatory authorities have not taken substantive measures to ensure that aircraft crews are provided with all necessary firefighting procedures, equipment, and training to prevent, detect, control, and suppress fires in aircraft.
In addition, there are specific aspects that remain problematic. In the recommendation package dealing with in-flight firefighting measures, the TSB expressed concern with the lack of built-in smoke/fire detection and suppression equipment in hidden areas of aircraft. For the most part, smoke/fire detection is reliant on human sensory perception, and fire suppression is dependent on direct human intervention. As shown by this accident, human sensory perception cannot be relied on to consistently detect or locate an in-flight fire. Furthermore, it is unrealistic to rely on human intervention for firefighting in areas that are not readily accessible. The Board believes that the industry, led by regulatory authorities, needs to do more to provide a higher degree of safety by enhancing smoke/fire detection and suppression capabilities.
The TSB expressed concern that there was a lack of awareness in the industry about the potential seriousness of odour and smoke events. The TSB recommended that regulatory authorities take action to ensure that industry standards reflect a philosophy that when odour/smoke from an unknown source appears in an aircraft, the most appropriate course of action is to prepare to land the aircraft expeditiously. Although the tragic events of SR 111 have served to alert the industry to the threat from in-flight fire, the Board believes that the potential for complacency may increase with the passage of time. The Board believes that regulatory authorities need to do more to enhance the regulatory environment (i.e., regulations, advisory material, etc.) to ensure that awareness remains high in the long term and appropriate plans, procedures, and training are in place industry wide.
The TSB has observed that personnel involved with maintaining and operating aircraft remain unaware of the potential existence of flammable materials in their aircraft. In general, the predominant misconception remains as it was before SR 111; that is, that the materials used in aircraft construction are "certified," and therefore are not flammable. As highlighted by this investigation, existing certification criteria do not ensure that materials used in the manufacture or repair of aircraft are not flammable. This lack of awareness continues to lead to circumstances where potential ignition sources, such as electrical anomalies, are viewed as reliability or maintenance issues, and not as potential safety issues and fire threats.
As the threat from an in-flight fire will continue to exist in many in-service aircraft, the Board believes that as a minimum, aircraft crews need to be provided with a comprehensive firefighting plan that is based on the philosophy that the presence of any unusual odour or smoke in an aircraft should be considered to be a potential fire threat until proven otherwise. The Board has yet to see significant industry-wide improvements in certain important areas, and is concerned that regulatory authorities and the aviation industry have not moved decisively to ensure that aircraft crews have adequate means to mitigate the risks posed by in-flight fire, by way of a comprehensive firefighting plan that includes procedures, equipment, and training.
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