Common Themes

Organizational Lapses

Prior to this accident, Embraer issued an AFM revision to recommend increases in minimum operating speeds in icing, and to advise immediate activation of the ice protection system, rather than the delayed activation specified in existing versions of the AFM. The Brazilian regulatory authority and the FAA did not issue airworthiness directives to require adoption of the modified procedures, and Comair, citing conflicts with existing procedures and training and a concern that the revised procedures would promote ice bridging, elected not to incorporate the revision into their AFM or into operating procedures. Further, while background information was available that substantiated the safety enhancements associated with early activation of deicing boots, this information was not widely distributed or known.

Flawed Assumptions

At the time of this accident, there was a prevalent belief throughout the industry that deicing boots would be ineffective if operated too early during an icing encounter. The concern was centered around the formation of an ice bridge over the boot that would prevent removal of ice. Accordingly, procedures related to operation of boot systems required delaying system activation until a sufficient thickness of ice (normally from ¼ to ½ inch) had accumulated. Following the accident, procedures were modified to require activation of deicing boots at the first indication of icing.

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