Choosing Critical Ice Shapes on Airfoil Surface for the Icing Certification of Aircraft

There is no explicit definition for critical ice shapes, and it is only mentioned in some ACs. Here, a rational and applicable definition for critical ice shapes is given based on well understanding of present literatures. Then, the available icing certification guidance concerning the various “critical ice shapes” is outlined. Different methods for determination of ice shapes as well as procedures are presented, and their characteristics are compared and analyzed. Based on the Combination Airfoil Assumption first presented by Glahn et al and developed by Farooq Saeed, we suggest a simple and useful method to determine the critical ice shapes on a normal airfoil which can be called combination airfoil comparison method. This method can be used to quickly get a preliminary ice shape for icing certification, but its criticality should be verified by other means of determining critical ice shapes. In order to examine the availability of this method, examples of Airbus aircraft types that have passed icing certification will be given. We hope that our findings and recommendations will be helpful to the applicant and icing certification team during aircraft icing certification.