NTSB Issues Deicing Safety Alert

As winter approaches, the National Transportation Safety Board (NTSB) has issued Safety Alert SA-097 reminding pilots about the dangers of flying in icing conditions—namely the adverse effects of airframe and propeller icing on aircraft performance.

SA-097 emphasizes that “as little as 1/4-inch of wing-leading edge ice accumulation can increase the stall speed by 25 to 40 knots and cause sudden departure from controlled flight.” The alert also warns that ice buildup on pitot tubes can lead to instrument failure, impacting readings for airspeed, altitude and vertical speed.

The NTSB acknowledges that some pilots have been taught to wait for a certain amount of ice to accumulate on the leading edges before using deice boots due to concerns about ice bridging. However, the FAA’s recent tests show that modern deicing boots, from aircraft manufactured after 1960, are not prone to ice bridging. The NTSB warns that performance issues may arise if deice boots are not engaged promptly when icing begins and advises pilots to refer to their operating handbooks for specific procedures on boot activation and use.

The alert also cites several accidents where failure to follow operating handbook instructions led to in-flight loss of control, underscoring the critical importance of adhering to recommended deicing practices.