A Case Study on the Aircraft Icing in Various Flight Pathways in Iran

Deposition of ice on external surfaces of flying airplanes is one of the major meteorological aviation hazards. Icing is an atmospheric phenomenon, which is not easily predicted. In this study, a number of reported icing cases by pilots were investigated. Moreover meteorological reports, weather charts corresponding to ground surface and¬¬ 500 & 850 Millie-Bar Pressure levels plus upper air sounding data were studied. Analysis of weather charts and synoptic patterns effective on icing, verification of icing intensity using liquid water content of clouds, determination of freezing level height based on surface temperature and applying -8D method for occurrence of icing and also the instability indices were studied. The results indicate that the maximum number of icing events occurred in April, while the most intensive icing events occurred in January and April. In most cases, the dynamical low-pressure levels, synoptic patterns, trough and cold frontal regions are the most probable patterns for icing to occur over the country. Intensive icings are associated with deep cumulonimbus (CB) clouds with high extension. Moreover the -8D method is an acceptable procedure in determination of severe icing possibility in Jan & Apr, while in other cases the method does not seem to indicate good results in determining icing possibility in the corresponding surfaces reported by pilots.