Originally Posted by "Boeing 717 FCOM - Vol II Operating
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SP.30.12
Cold Weather Operation (Continued)
Engine anti-ice should be ON whenever icing conditions exist or are expected. Airfoil anti-ice should also be used if conditions warrant. Engine anti-ice should be used, and airfoil icing conditions can exist, when the TAT air temperature is less than 6°C (42°F) and there is visible moisture in the air. In addition to temperatures below 6°C (42°F), be alert for ice buildup on windshield wipers or edges of the windshields as indications of airfoil icing conditions.
The bolding of TAT is mine, but TAT appears in multiple references throughout the FCOM series, as well as the AFM.
Last edited by Capt Claret; 12th Aug 2012 at 14:59.
Reason: Typo/auto correction