Renewed interest in aircraft icing has arisen because o the recent realisation of the significant hazard posed by supercooled large drops (diameter > 100 mu m). The processes governing the occurrence of supercooled water are reviewed. The two mechanisms for producing supercooled large drops (SLD) are described These are the melting of ice crystals followed by the resultant drop falling into a sub-zero layer and the coalescence of cloud drops to produce supercooled drizzle drops. The latter mechanism is now thought to be more widespread than the former. The EC funded EURICE project is described. This has involved the establishment of two data bases, one cntaining accident/incident reports and the other microphysical data. The existing microphysical data have been found to be mainly compatible with JAA/FAA Appendix C. Analysis of selected accidents/incidents over Europe suggests SLD involvement in many. New flights havealso been undertaken on most of which some SLD were sampled. Thesee are mainly associated with convection embedded in layer cloud or with gravity waves in layer cloud. Finally, recent work on forecasting is summarised.
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