A summary of meteorological conditions associated with aircraft icing and a proposed method of selecting design criterions for ice-protection equipment

Data from various sources on the observed values of meteorological variables, liquid-water content, mean-effective droplet size, and temperature, which are pertinent to aircraft icing, are summarized; and a method is proposed for the selection of design criterions for iceprotection equipment.•The data are divided according to two broad cloud types, namely, stratiform and cumuliform clouds, because the physical dimensions, the formation and development processes, the frequency of encounter, and the severity of icing conditions are very different for the two cloud types.The data are summarized in such a manner as to give the frequency of occurrence of observed icing conditions according to two of the pertinent meteorological variables.The summarized data indicate that statistical relations exist between liquid-water content, meaneffective droplet diameter, temperature, and pressure altitude.The proposed method of selecting values of liquid-water content and mean-effective droplet diameter as design criterions for iceprotection equipment is based upon the collection efficiency of an airfoil as a function of droplet size and the frequency of occurrence of icing situations with various liquid-water-contents and mean-effective droplet diameters.The method provides a convenient means of calculating the percentage of icing encounters in which the water-collection rate exceeds the design rate for the ice-protection equipment and also illustrates the desirability of sometimes designing ice-protection equipment for water-collection rates which are less than the maximum rate expected.The method is illustrated by the selection of design criterions for ice-protection equipment for a hypothetical, 12-percent thick, low-drag airfoil with a chord length of 15.8 feet; however, the method may be employed for any airfoil provided the collection efficiency is known. is