13:30   Flutter testing Chair: Holger Mai 13:30 30 mins Flight flutter test modal identification by using nature inspired algorithms: A classical mathematical modeling Demian Gomes da Silva, Guilherme Castrignano Tavares Abstract: The aviation industry is coming under increasing pressure from governments, regulatory organizations and the general public to reduce emissions. To address this, the industry has come together and pledged to cut net carbon emissions to zero by 2050. To help meet this goal, EMBRAER is exploring a wide range of bold but viable aircraft designs in the Energia concepts, evaluating a range of sustainable concepts to carry up to 50 passengers, considering a number of energy sources, propulsion architectures and airframe layouts. In addition, the company is active member of FutPrint50 Project together with an international consortium of universities, SMEs and organizations to accelerate the technologies needed to deliver a hybrid-electric aircraft that could enter service in 2035-40. From aeroelastic standpoint, the Green Aviation will impose additional challenges in design, development and certification, mainly from lighter structures in unusual configurations, with multiple engines and more electrification. Consequently, it is important the evolution of aeroelastic industrial process in both prediction and testing. The present paper is focused on an innovative approach to Flight Flutter Testing modal identification by using Nature Inspired Algorithms to solve the nonlinear identification problem without using gradients. The performance of this innovative approach is valuated based on theoretical benchmarks and real Flight Flutter Testing data. The results encourage the future use of more representative, adaptive or complex mathematical models during identification process. 14:00 30 mins Lessons Learned from Flight Testing Active Flutter Suppression Technologies Julius Bartasevicius, Daniel Teubl, Thomas Seren, Fanglin Yu, Mirko Hornung, Balint Vanek, Daniel Balogh, Szabolcs Toth, Mihaly Nagy, Balazs Fritsch, Keith Soal, Thiemo Kier, Özge Süelözgen Abstract: Active flutter suppression (AFS) was demonstrated in real-life conditions during the project FLIPASED (Flight Phase Adaptive Aero-Servo-Elastic Aircraft Design Methods). It was done by passing the flutter speed with a subscale demonstrator called P-FLEX. Two different flutter suppression controllers were used in this case, both of which proved to dampen the flutter modes, allowing the demonstrator to further increase the airspeed. This article presents the background of the demonstrator, its systems, and the testing, the challenges faced during the tests and finally the important lessons learned during the process. 14:30 30 mins Flutter flight testing: Using operational modal analysis to identify, track and predict flutter for safe and efficient flight test campaigns Keith Soal, Jan Schwochow, Robin Volkmar, Martin TANG, Carsten Thiem, Yves Govers, Marc Böswald, Thiemo Kier, Özge Süelözgen, Nicolas Guerin, Daniel Teubl, Julius Bartasevicius, Balint Vanek, Szabolcs Toth, Misi Nagy Abstract: Flutter flight testing is an important, challenging and safety critical part of aircraft flight envelope expansion. Since flutter is a complex phenomenon influenced by aerodynamics, structural dynamics, and control systems, understanding and modeling these interactions accurately can be difficult. Furthermore, the prediction of the flutter boundary is challenging (both numerically and in flight) due to the interaction of many variables such as airspeed, altitude, control surface positions, excitation amplitudes etc. The critical parameter for flutter monitoring is the aeroelastic damping. The damping also remains the most difficult parameter to identify and simulate accurately. In order to demonstrate state-of-the-art testing, simulation and active control methods, a technology demonstrator was designed and built in the EU FLIPASED project. The UAV demonstrator with 7 m wing span and weighing 70 kg was designed to flutter in the achievable flight envelope. Ground Vibration Testing GVT was conducted, and the results were used to perform a flutter simulation. A flutter flight test campaign was then carried out with Operational Modal Analysis OMA running in real time on miniaturized hardware to identify and track the modal parameters. In this paper an overview of the flutter monitoring system will be presented, together with the simulation results and flutter flight test results. Finally, a comparison of the flight test and simulation results will be presented, together with the outlook of future work. 15:00 30 mins Wind tunnel experiment for body freedom flutter of flying wing unmanned aerial vehicle Hao Wei, Elijah Ang, Jieli, Daryl Leo, Jun Kang Tan, Chien Ming, Jonathan Tay, Yongdong Cui, Bing Feng Ng Abstract: Body Freedom Flutter (BFF) has always been known to be a potentially catastrophic event for any flying aircraft. BFF is a dynamic instability that is the result of strong coupling between rigid-body and elastic modes of the aircraft. In this presentation, we demonstrate how different parameters affect the speed and frequency at which BFF occurs using a wind tunnel with a novel test rig. The novel test rig was designed to allow the degrees of freedom needed for BFF to occur, which is then fabricated using 3D printing to optimise weight savings. Different flying wing profiles are considered and the UAV is subject to the different parameter variations. The mount allowed the wing profile to freedom in both the pitch and plunge movement. It is found that BFF characteristics are affected by the wing swept angle, additional wing tip weights, and spanwise weight location. These parameters directly affect the centre-of-gravity for the wing profile, its wing inertia, and its structural properties. The results and trends obtained can then be potentially used to further understand the BFF phenomenon in the future.

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