Flight Operations Research

Airframe icing is the single most challenging obstacle to all-weather operations. Contrary to the conventional descriptions such as light, moderate and severe, rime, clear or mixed, airframe icing is not a linear, progressive or cumulative threat. Indeed, there is no type or quantity that can be considered non-hazardous. The median ice thickness found at crash sites is typically between ¼ and ½ inch of ice. The aerodynamic effects of ice are highly unpredictable, and depend on a wide range of variables including shape, location on the airfoil, the type of airfoil, and the scale of the aircraft. These effects can change quickly. 

This website contains an extensive library of accident reports, research papers and articles associated with airframe icing. Some of these documents are historical, and some present ideas that persist today, despite having been debunked decades ago. We know today, for example, that frost is dangerous, that polished ice is not acceptable, and that despite years of persistent belief, there are no accidents in which the phenomena known as ice bridging has been identified. 

More recent research details the actual pernicious effects of airframe ice, including substantial,  and often quite sudden, reductions in lift , debilitating drag effects and significant changes in aircraft stability and handling qualities. Each of these effects alone cause airframe icing to remain one of the most serious environmental threats to flight safety today.


Right: A glory, indicating liquid water in the cloud. If the temperature is near or below freezing, this is a pretty good indication of icing conditions in the cloud.


"...History is linear memory and, as such, beyond organization and indifferent to reason. The characteristic common to the modern man of reason is this loss of memory; lost or rather, denied as an uncontrollable element. And if it must be remembered, then that evocation of real events is always presented as either quaint or dangerous. The past, when it involves a failed system, disappears from the mind. The past is always ad hoc. The future is always optimistic, because it is available for unencumbered solutioneering. And the present lies helpless...just begging to be managed."

John Ralston Saul
Voltaire’s Bastards
1993


Left: A main landing gear from a Beech King Air, N41WE, showing the ice accreted after  the gear was extended. The aircraft was lost 2.5 miles from the runway on January 11, 2005; two people were killed, and one survived.

Airframe Icing Overview


Icing Accident Reports


Icing Papers and Articles


Aerodynamics of Icing


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