Aircraft trailing vortices, generated as an unavoidable consequence of lift, pose a potential risk to following aircraft. The highest risk of encountering wake vortices prevails in ground proximity, where the vortices cannot descend below the glide path but tend to rebound because of the interaction with the ground surface. Weak crosswinds may compensate the self-induced lateral propagation of the upwind vortex, such that it may hover over the runway directly in the flight path of the following aircraft.
DLR has developed patented plate lines that shall accelerate wake vortex decay and thus increase flight safety during final approach. Together with Austro Control the Institute of Atmospheric Physics has installed two plate lines at the end of runway 16 of Vienna International Airport that shall demonstrate the functionality of the plates in the environment of an international airport. One plate line consists of 8 plates, erected with a separation of 20 m, where each plate is 4.5 m high and 9 m long. Three lidars are used to measure the vortex behaviour simultaneously. The evaluation of first measurements is promising; the lifetime of the vortices is notably reduced by the plates. Further, the characteristics of the evolution of the vortex strength is similar to what was found in previous towing tank experiments, numerical simulations (hybrid LES) and flight trials with the HALO research aircraft.
Austro Control made it possible to construct the plate lines and carried out a safety assessment prior to the trials. In addition, they support evaluation of the trial data and make Mode-S data and meteorological data available. Additional, extensive meteorological measurement equipment is being provided by the companies Leonardo Germany GmbH and RPG-Radiometer Physics GmbH. The 'Wake turbulence separation optimisation' project has received funding from the SESAR Joint Undertaking under the European Union's Horizon 2020 research and innovation programme under grant agreement No 731781.
The wake vortices of the huge A380 are also weakened by the plates. (Photo: Frank Holzäpfel, DLR, CC-BY 3.0)
Final approach above Plate Line at localizer. (Photo: Frank Holzäpfel, DLR, CC-BY 3.0)
A Plate Line consists of eight elements, each 4.5 metres tall and nine metres long. (Photo: Frank Holzäpfel, DLR, CC-BY 3.0)