AbstractThe ambition of the CA3ViAR project is to design an open test case fan that experiences instability mechanisms, which are representative for ultra-high bypass ratio (UHBR) fans of civil aircrafts, and to perform a comprehensive experimental investigation to measure aerodynamic, aeroelastic and aeroacoustic performance in a wide range of operational conditions. Experimental tests will be performed in the Propulsion-Test-Facility (PTF) of the Institute of Jet Propulsion and Turbomachinery (IFAS) of Technische Universität Braunschweig, Germany. The final objective of the project is to provide an open test case for the entire research community, with geometries, numerical and experimental results to establish a new reference for composite UHBR fan design. This will support the development of new methods and tools for the development of safer, lighter and more efficient composite fans for greener UHBR engines. In this work the preliminary design of the low transonic fan (LTF) to be used as test article, whose main requirement is to be operated in a safe and controlled way in conditions of aerodynamic and/or aeroelastic instability during wind tunnel operations, is presented. More in particular, consolidated aerodynamic design, strategy adopted to drive the structural design, flutter analysis taking into account acoustic reflection at the intake, dynamic and stress analyses, as well as aeroacoustic measurement optimization are presented and discussed. The preliminary mechanical design of composite blades and the rotor hub, together with the rotor instrumentation and related studies to embed sensors in the composite blades, are also part of this article, and complemented by manufacturing trials and demonstration tests give the full picture of all the project activities up to the preliminary design review.