Mitigating Wake Turbulence Risk During Final Approach via Plate Lines

Abstract

To mitigate the risk of wake vortex encounters during final approach, so-called plate lines have been developed. Wake vortices generated by landing aircraft induce secondary vortices at the plates’ surfaces that approach the primary vortices and trigger premature wake vortex decay. Each plate line consists of several upright plates being installed underneath the approach slope. While the plate line extends perpendicular to the flight direction, its individual plates are oriented in parallel to the runway centerline. To obtain the approval of the authorities for the installation of the plate lines at runway 16 of Vienna International Airport, the plate design had to comply with airport requirements like obstacle clearance, stability, and frangibility. During a six-month campaign, wake vortex behavior of about 9500 landings with and without plates was measured simultaneously by three lidars complemented by a comprehensive suite of meteorological instrumentation. The analysis of over 1000 measured wake vortex evolutions indicates that the plate lines reduce the lifetimes of the vortices in a safety corridor along the final approach by 22–37% depending on the aircraft type. This corresponds to a reduction of vortex circulation by about 50% for the most relevant International Civil Aviation Organization separation (Medium behind Heavy).