The National Transportation Safety Board issued a Safety Alert titled “Activate Leading-Edge Deice Boots As Soon As Airplanes Enter Icing Conditions.”
The Safety Alert reminds pilots that
* noting that as little as 1/4 inch of ice can be deadly;
* as little as 1/4 inch of leading edge ice can increase the stall speed 25 to 40 knots; and
* early activation of the deice boots limits the effects of leading-edge ice and improves the operating safety margin.
The Safety Alert states that leading-edge deice boots should be activated as soon as icing is encountered, unless the aircraft flight manual or the pilot’s operating handbook specifically directs not to activate them. (NTSB)