Mixed-Phase Icing Conditions: A Review

This report reviews publicly available evidence bearing upon possible safety hazards due to flight in mixed-phase conditions. Recent investigations with modern instrumentation suggest that these conditions are more frequent and widespread than had been realized. However, information characterizing these conditions which is suitable for addressing questions of aviation safety is very limited. Facility simulation of mixed-phase conditions is difficult and well-controlled simulations have been done in very few facilities in the world. It is not known how well the various methods that have been used actually simulate the natural environment, nor with what degree of fidelity it needs to be simulated for the investigation of some safety questions. The limited data available from research flights does not indicate that there is any difference in performance effects caused by structural icing resulting from flight in mixed-phase cloud rather than in purely liquid supercooled cloud.