The SENS4ICE team successfully mastered to collect valuable experimental flight data in natural icing conditions during a one-month campaign based in Toulouse, France, in April 2023. The campaign was very challenging with numerous different instruments and technologies involved (several under development) and an international team from different organisations that targeted very specific and rare weather conditions requiring high priority flight safety considerations. What has been achieved is beyond expectations! Relevant icing conditions have been encountered during many flights particularly in the dedicated flight test airspace regions. Icing conditions and ice accretion on the aircraft were observed during almost every flight and also supercooled large droplet (SLD) conditions were detected in several cases. In total 15 flights with a total of about 50 flight hours have been successfully conducted collecting icing data.

This great achievement was made possible by the excellent work and collaboration of all involved partners, partly working on-site/in-flight and remotely, bringing together SENS4ICE internal and external project partners, to make best use of weather situations in order to find mixed phase and liquid cloud conditions but also to overcome technical problems and handle operational limitations.

The experimenters of the SENS4ICE project for this campaign comprised teams from Safran, the French Aerospace Lab (ONERA), Instituto Nacional de Técnica Aeroespacial «Esteban Terradas» (INTA) and German Aerospace Center (DLR). The French facility for airborne research Safire operating the ATR 42 research aircraft provided great support and flexibility with a dedicated team to find best solutions. As icing conditions, particularly including SLD conditions, are rare and difficult to find, dedicated weather forecast support was needed which was provided by the forecast teams of Météo France, German Weather Service DWD and Leading Edge Atmospherics (LEA; Ben Bernstein). In particular, the continuous and committed on-site support by the Météo France team for both forecasting and in-flight guidance was facilitating to find these rare conditions even at higher flight levels in southern Europe. Without these team efforts the great success of the campaign would never have been possible!

Several hours of valuable measurement data was acquired, supplemented by extensive image/video documentation and observations regarding aircraft icing status. While data evaluation and sensor validation will take place within the next months, the in-flight and preliminary post-flight data evaluation of sensor performance showed good agreement of detected icing situations in comparison with the different forecast weather conditions and reference sensors. The data will provide a valuable basis for the validation of icing forecast products, sensor evaluation and satellite nowcasting products after a detailed analysis.

SENS4ICE project results will be presented in the upcoming months, including the SAE International Conference on Icing of Aircraft, Engines, and Structures, June 20-22, 2023 in Vienna, Austria.