Predicting Glaze or Rime Ice Growth on Airfoils

A droplet trajectory analysis model is combined with calculations of heat transfer to provide predictions of glaze or rime ice during e ight. Such a prediction is not currently available and could prove useful for e ight planning. The droplet trajectory model is used to determine the collection efe ciency of various sized cloud droplets on representative airfoils. This information is included in ice accretion and growth calculations to determine whether wet (usually glaze or mixed icing ) or dry (rime icing) growth is expected for combinations of outside air temperature, liquid water content, and impinging droplet size. The calculations produced critical liquid water contentsfortherimeto glazetransitionthatvariedfrom0 .15 § 0.051g/m 3 foraCessnaT-37Bto 0 .38 § 0.154g/m 3 for a Beechcraft Queen Air at their typical airspeeds and for atmospheric conditions 700 hPa, i 10 ± C, and 15-πm impinging droplets. For larger droplets, lower atmospheric pressure, and higher airspeeds these critical values decreased, making glaze more likely. Suggestions for adaptation of the calculations as guidelines for forecasting icing type are presented. Nomenclature