Experimental Study on Ground Interaction and Breakdown of Generic Transport Aircraft Wakes with Focus on Final Approach and Landing

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The wake vortex characteristics of large transport aircraft on final approach and during touchdown are of large interest for the aircraft industry and to the same extent for airport operations. Current efforts of Federal Aviation Administration (FAA) and Eurocontrol aim at designing a modified Wake Vortex Advisory System (WVAS) to increase the capacity of airports, while maintaining or even exceeding current safety standards.Therefore, within the framework of the international project Re-Categorization (RECAT) work is in progress, in order to establish a dynamic pair-wise separation of aircraft by 2020. Despite extensive efforts over the last years, still there is a great need for research in order to understand the complex three-dimensional phenomena, which especially occur close to the ground. In the report of the European network WakeNET3 fields of research are clearly formulated to reach these ambitious goals. As for experimental challenges, the investigation of non-linear aircraft trajectories is stated, as well as curved vortex trajectories and the investigation of the vortex behavior near the ground.Current studies on the subject considering actual landings of an aircraft are conducted numerically, and also in form of full-scale field campaigns using laser-optical measurement techniques (LIDAR). Within the framework of these studies also ground based measures (plate lines) are investigated to promote vortex breakdown close to the runway.To the knowledge of the applicant, comparable scaled experiments regarding the vortex breakdown including the actual effects of landing are currently not represented in literature. Previous studies involving two-vortex systems in ground effect have been carried out using ground parallel model trajectories. Especially end effects, which are important in this context, have been excluded intentionally.Therefore, the goal of the proposed study is to achieve novel insights into the breakdown mechanisms of landing aircraft wakes, and to enable predictions of the propagation speed of the involved secondary instabilities. For this purpose the actual landing has to be simulated as realistic as possible. Special focus is put on the model trajectory and the temporal evolution of the lift coefficient, which requires to simulate the final approach, capturing the ground effect, as well as to simulate a realistic flare and touchdown. As a result this study intends to contribute to modeling, simulation and prediction of full-scale aircraft wakes during and after landing.