Aviation Investigation Report A98H0003
2.7.3 Additional Checklist Issues
The deviations noted with the Swissair Smoke/Fumes of Unknown Origin Checklist had the potential to be problematic. However, the only direct connection that could be established with the SR 111 scenario was the darkened cabin that resulted from the emergency lighting in the passenger cabin going off when the CABIN BUS switch was selected by the pilots. Working in a darkened cabin could have delayed the cabin crew preparations for an emergency landing by necessitating the use of flashlights. However, there was a cabin emergency lights switch installed at the flight attendant station normally occupied by the maître de cabine (M/C). The use of this switch would have restored the emergency lighting and eliminated the need to temporarily use flashlights. It is unknown whether this cabin emergency light switch was used.
There is no indication that the decisions made by the pilots were affected by the absence of direction in the checklist to don oxygen masks. It is unknown whether the pilots would have initiated an emergency diversion earlier if there had been a single, combined checklist with one of the first items being related to preparing to land expeditiously. It could not be determined whether they were inhibited by the size of the font or any glare from the checklist, although either of these conditions could affect the ability of flight crews to read the checklist, especially in a smoke or low-light environment.
A review of several checklists showed a lack of emphasis on treating any amount of smoke in an aircraft as a serious fire threat. For example, neither the Swissair nor the McDonnell Douglas Smoke of Unknown Origin Checklist stipulated that preparations for a possible emergency landing should be considered immediately when smoke of unknown origin appears. Rather, on both versions, the reference to landing is the last action item on the checklist. Similarly, the Swissair guidance provided to flight crews was that the aircraft was to land at the nearest emergency airport if smoke of unknown origin was "persistent."
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