Facing the Challenges of Supercooled Large Droplet Icing: Results of a Flight Test Based Joint DLR-Embraer Research Project 2019-01-1988

Today’s airplanes are well equipped to cope with most common icing conditions. However, some atmospheric conditions consisting of supercooled large droplets (SLD) have been identified as cause of severe accidents over the last decades as existing countermeasures on modern aircraft are not necessarily effective against SLDs. In 2014, the new Appendix O to the certification regulations had been issued to guarantee the safe operation of future aircraft when encountering SLD-icing conditions. But as the SLD topic is quite new for the majority aircraft manufactures and research institute in a same way, German Aerospace Center (DLR) and Embraer established a joint research cooperation to gain a better understanding of the distinct influences of SLD-ice shapes on aircraft characteristics in 2012; for both, a better basic understanding physics and to evaluate proper ways for future aircraft certification under Appendix O. Furthermore, one additional scientific goal of the cooperation was to develop and test new tools for in-flight monitoring of aircraft characteristics as well as directly identifying simulation models. During the 4 years of the project, a distinct way to better understand icing-induced degradations on a specific aircraft was followed: first, the data of clean aircraft was gathered in flight test to identify a dynamic simulation model as base for the subsequent evaluations. Second, data of test flights with artificial App. C ice configurations were analyzed and used for the development of distinct modifications of the base aircraft simulation model. A first evaluation of the icing-induced changes of aircraft characteristics was conducted. Third, after the generation of SLD-ice shapes, wind tunnel testing and flight clearance, a second flight test campaign with these artificial SLD-ice shapes delivered the data for an additional model modification and identification. The results of the final data and model evaluation show the detectable degradation of SLD-ice in flight.