The EU Horizon 2020 project SENS4ICE addresses reliable detection and discrimination of supercooled large droplets (SLD) icing conditions. These conditions are considered as particularly safety-relevant and have been included in airplane certification specifications. The SENS4ICE project comprises technology development, icing wind tunnel upgrading/testing and flight testing. A novel hybrid approach for icing detection combines direct sensing (atmospheric conditions / ice accretion) with an indirect technique based on changing aircraft characteristics. The first part of the project was devoted to the development and maturation of icing detection technologies, with a focus on Appendix O (of 14 CFR Part 25 and CS-25) icing conditions. Furthermore, several icing wind tunnel facilities have improved capabilities to represent Appendix O conditions. Icing wind tunnel testing (including Appendix O) of several icing detection sensors developed in the SENS4ICE project concluded the first part of the project. Examples of initial results are presented. The second part of the project is dedicated to flight testing of icing technologies in natural icing conditions including Appendix O. Two flight test campaigns in early 2023 served to test and demonstrate eight of the direct ice detection technologies under development as well as the hybrid ice detection system, including the indirect ice detection system. Extensive meteorological and climatological analysis was done in order to have the best chances to encounter icing conditions including Appendix O conditions.
