Chapter 7 Dynamic Ground Testing: Ground Vibration Tests Through Control Surface Excitation G. Osmond, A. Azzat, S. Leroy, and O. Delverdier Abstract Flutter flight tests are a crucial step in aircraft certification. The typical approach to flutter flight testing is to excite the aircraft using its control surfaces at several stabilized test points and to measure the corresponding structural response. Before beginning the flight test campaign, however, a preliminary ground vibration test (GVT) performed on the prototype is necessary in order to ensure the reliability of the flutter predictions. These tests are currently costly in terms of preparation time, hardware, resources and time spent in the final assembly line. Due to the high development costs, each day that can be saved in the test program is crucial. As AIRBUS’ current strategy is to develop more derivative aircraft from its flagship projects as opposed to completely new aircraft, a reduction in the number of measurements can be considered. A lighter GVT (or DGT) can therefore be used to save costs. The DGT approach proposed in this paper also relies on the adaptation of in-flight excitation techniques in order to reduce the need for external exciters. These tests would be achieved through sine sweep excitations performed with the control surfaces on ground. However several challenges have to be addressed. Keywords Structure • Vibration • Dynamics • Aircraft • Certification Abbreviations DGT Dynamic Ground Tests FAL Final Assembly Line OGT Optimized Ground Tests ADIS Aircraft systems in charge of generating c/s orders TLM Telemetry tools C/S control Surfaces OMA Operational modal analysis 7.1 Introduction In the past few years, AIRBUS has launched several derivative developments based on existing programs. Economic pressure has led to a reduction of the lead time dedicated to get the type certification for these new derivative programs. These efforts are primarily made possible by the fact that the development does not start from a blank page, meaning that knowledge gained from the legacy product can be used to efficiently update the theoretical models. Even if the time slot devoted to ground vibrations tests have been greatly reduced on the A350-900 compared to the previous programs (9 days vs. 14 days), the challenge has been raised to reduce these tests to only one day for the derivative programs. In addition to the aforementioned challenges, a consolidated modal base has to be transmitted quickly to the design office after the end of the test. This point requires a drastic optimization of the modal filtering and validation process. Thus, this test would be used to validate the theoretical model when we already have a good level of confidence in it. The tests would no longer be performed during the FAL period but under the flight test team responsibility, only a couple of days before the first flight. The requested reduction is so significant that it could not be addressed by an evolution of the G. Osmond • A. Azzat • S. Leroy ( ) • O. Delverdier Airbus, Flight and Integration Test Centre, EVAAA – Vibrations Tests, 31060 Toulouse Cedex, France e-mail: stephane.leroy@airbus.com © The Society for Experimental Mechanics, Inc. 2015 A. Wicks (ed.), Shock & Vibration, Aircraft/Aerospace, and Energy Harvesting, Volume 9, Conference Proceedings of the Society for Experimental Mechanics Series, DOI 10.1007/978-3-319-15233-2_7 55
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