Differentiation between Appendix O and Appendix C Icing Conditions in Flight Using the Collins Ice Differentiator System

Protecting against atmospheric icing conditions is critical for the safety of aircraft during flight. Sensors and probes are often used to indicate the presence of icing conditions, enabling the aircraft to engage their ice protection systems and exit the icing cloud. Supercooled large drop icing conditions, which are defined in Appendix O of 14 CFR Part 25, pose additional aircraft certification challenges and requirements as compared to conventional icing conditions, which are defined in Appendix C of 14 CFR Part 25. For this reason, developing sensors that can not only indicate the presence of ice, but can also differentiate between Appendix O and Appendix C icing conditions, is of particular interest to the aviation industry and to federal agencies. Developing detectors capable of meeting this challenge is the focus of SENS4ICE, a European Union sponsored project. While participating in the SENS4ICE Project, Collins Aerospace has developed an ice detection and differentiation sensor known as the Collins Ice Differentiator System (Collins-IDS). A flight test campaign evaluating the performance of the Collins-IDS in natural icing conditions was completed; the results of which are the focus of this technical paper. During the campaign, the Collins-IDS successfully detected the presence of ice and determined, with high accuracy whether that ice was Appendix C or Appendix O. Additional testing in Appendix O icing conditions, either in an icing wind tunnel or during a flight test in natural icing conditions, will benefit the future development of the Collins-IDS.