Flutter flight testing: Using operational modal analysis to identify, track and predict flutter for safe and efficient flight test campaigns

Kurzfassung

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.