Aeroelastic design of a drone for research on active flutter control

Within the project CONCERTO, funded by the European research program Clean Aviation, ONERA is responsible of the aeroelastic design of a flying demonstrator, aimed at providing a suitable platform for the test of active control techniques to delay the onset of the flutter instability. This leads to very peculiar specifications for the nominal flutter behaviour of the aircraft and, therefore, to adapted solutions in the design process. The flutter behaviour of the drone has to be adjustable; in particular, three configurations are expected. First, a reference configuration is required without any flutter occurrence in the flight domain and any coupling between flight mechanics and structural dynamics. For the second one, the first flexible mode’s frequency is low enough to interact with the flight dynamics, still being flutter stable. Finally, the third one presents a flutter instability for a specific range of velocities in the flight domain. Thus, the design has to include a way to tune separately the flexional and torsional natural vibration modes of the wing. To this end, a system of movable masses positioned at the tip of the wing is introduced, providing the degrees of freedom to pilot the structural dynamic and, hence, the aeroelasticity of the drone. Along these design parameters, the wing structure is also tailored to ensure the necessary sensitivity of the structural dynamics to the above-mentioned movable masses. This paper summarises the design process: starting from the baseline structural configuration, some structural parameters are tuned to comply with the above-mentioned specifications. Finally, a thorough analysis of the (linear) aeroelastic behaviour is presented, to verify and document the expected performance of the drone.