Ice Is Ice?

MIL-STD-810D, Method 521.0, "Icing/Freezing Rain," contains guidance for testing equipment exposed to freezing rain. This method was developed around a narrow set of meteorological conditions resulting in the buildup of clear glaze ice. The icing procedures described in Method 521.0 can be applied to a wide range of equipment and will help to predict equipment operations during natural freezing rain. However, the procedures do not give any indication of the operation of equipment during exposure to rime ice. The physical properties of rime and glaze ice differ significantly, as do their effects on equipment. Until MIL-STD-810D is modified to include rime icing, program managers and environmental test engineers will find no guidance or procedures in MIL-STD-810D for half of the icing (rime vs. glaze) that equipment can be exposed to in nature.