Aviation Investigation Report A98H0003

1.14.4  Time Required to Troubleshoot in Odour/Smoke Situations

It can take time for odour or smoke to develop to the concentration necessary for the crew to cognitively establish that they are dealing with an abnormal situation. This can delay the initiation of checklist actions.

When the source of odour/smoke is not readily apparent, flight crews are trained to follow checklist troubleshooting procedures to eliminate the origin of the odour/smoke. Most of these procedures involve removing electrical power or isolating an environmental system. A variable amount of time is required to assess the impact of each action, typically to see whether the odour/smoke dissipates. For some checklists, including the MD-11 checklist, this procedure could take an extended period of time. The longer it takes to complete a prescribed checklist that is designed to de-energize a smoke source, the greater the chance that the smoke source could intensify or become an ignition source and start a fire.

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