NTSB: Don’t Wait For Ice Buildup Before Inflating Boots

 - December 23, 2008, 8:17 AM

The NTSB released a new safety alert warning pilots not to wait for ice to build before inflating de-icer boots. “As little as one quarter inch of ice can be deadly,” the alert warns; “as little as a quarter inch of leading-edge ice can increase the stall speed 25 to 40 knots;” and “early activation of the de-ice boots limits the effects of leading-edge ice and improves the operating safety margin.” The NTSB said some OEMs still advise pilots to wait for ice to build and that pilots should follow AFM or POH directions. Cessna’s Citation V AFM, for example, requires pilots to wait for ice to build to between a quarter and half an inch before boot deployment during normal operations. According to Cessna, “Our extensive research has shown activation of de-ice boots with a quarter- to half-inch buildup of ice on the wing is the most effective way to shed ice. It is significant to note that if our procedure was shown to be outdated and no longer acceptable, we would expect an AD [airworthiness directive].” In fact, in the 1990s the FAA did attempt to issue an AD that would have forced OEMs to tell pilots not to wait for ice to build before deploying boots, but the FAA withdrew that proposed AD before it could become law.