International audienceIn this work, we seek to understand the needs of interaction designers involved in industrial system engineering processes. While current research offers a set of methods and tools for them, we believe that more empirical user studies focusing on designers are needed, in particular to support how model-based activity analysis may inform their decisions. Our designers’ need analysis is conducted through participatory design and contextual inquiry, and applied through a real use-case project: a distributed tactile tool for airborne maritime surveillance. Thanks to this study, we report on our insights on the usability problems and needs related in particular to scenario-based modeling, model-based design rationales and design-based model refinement