July 2, 2019 | DLR-patented technique tested at Vienna Airport

Plate lines reduce wake vortices during landing approaches

  • DLR-patented configuration of parallel ground plates speeds up the dissipation of wake vortices.
  • Laser-based wake vortex measurement system documents the effects during trial operations at Vienna Airport.
  • In the long term, it might be possible to reduce the separation between approaching aircraft.
  • DLR and Austro Control are partnering with Leonardo Germany GmbH and RPG Radiometer Physics GmbH to increase flight safety.
  • Focus: Aeronautics

Small and medium-sized aircraft currently have to maintain a safety separation of approximately 10 kilometres from larger aircraft flying ahead of them. The reason for this is wake vortices that are created by the preceding aircraft, which creates wake turbulence and can potentially destabilise the aircraft behind. Austro Control and the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) are now working together with other partners at Vienna International Airport to reduce the lifetime of wake vortices in the approach area and thus further increase safety. The researchers are using a DLR-patented configuration of parallel ground plates, which causes wake vortices to dissipate more quickly. A laser measurement system (lidar) is used to record the behaviour of wake vortices in detail for subsequent evaluation.

The aim of 'Wake turbulence separation optimisation' project, which has received funding from the SESAR Joint Undertaking under the European Union's Horizon 2020 research and innovation programme under grant agreement No 731781, is to demonstrate the effectiveness of the plate lines at large airports. During trials in the water towing tank, flow simulations and previous flight tests at the DLR site in Oberpfaffenhofen, the favourable effects of the plates have already been shown. "The very first evaluations of the new measurements in Vienna show that the wake vortices near the plates decay noticeably faster there as well," says Frank Holzäpfel of the DLR Institute of Atmospheric Physics. The partners plan to work on the specification and installation of a permanent facility incorporating these plates during the next two years.

"The project team has done a great deal to enable this unique system to be tested during full-scale operations at a busy airport. Initial results are very encouraging, and if the effectiveness of the plate lines is fully confirmed, as expected, they will be able to provide increased safety and capacity at all airports in the future," says Christian Kern, Director of the Air Traffic Management Department at Austro Control.

How plate lines work

High up in the air, wake vortices usually descend quickly, drift away and finally dissipate. Near the ground, they can hover for some time, a short distance upstream of the runway threshold. This is exactly where subsequent aircraft finish their approach. A system of plates arranged in parallel one behind the other, referred to as a plate line, can be set up to attenuate the circulating vortices in front of a runway more quickly. Secondary vortices form on the plates, which are about nine metres long and 4.5 metres high in this test installation. This causes the wake vortices to decay much more quickly.

More effective use of existing airport infrastructure

The construction of new runways at established airports is associated with an immense effort, with inhabited areas often affected by the expansion. If, in future, aircraft are able to land with reduced separation distances while maintaining the required level of safety, existing facilities could be used more effectively, thus eliminating the need for additional runways.

Wingtip vortices

Wake vortices are long-lasting, rotating airflows that are generated by every aircraft. They are formed by air 'rolling' up over the tips of the wings as it moves from the higher-pressure region beneath the wing to the lower-pressure area above. These powerful vortices can have severe effects on aircraft following closely behind and can also cause damage to structures on the ground. Smaller aircraft are particularly sensitive to the wake turbulence from wide-body passenger jets and have to maintain extended separation distances for safety reasons.


The project is the result of many years of cooperation between Austro Control and DLR on the subject of wake turbulence. DLR developed the plate lines and carries out measurements of wake turbulence on site.

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 radar and flight plan data available. Together with its partners, Austro Control is testing the effectiveness of the plates during live operations. Additional, extensive meteorological measurement equipment is being provided by the companies Leonardo Germany GmbH and RPG-Radiometer Physics GmbH.

The RPG microwave radiometer supplies the vertical temperature and humidity profile and thus measures the atmospheric stability, including low-level temperature inversions and heated profiles leading to more convection. The novel cloud radar is being tested for the first time at an airport and provides in-depth view into cloud dynamics, such as wind direction and shear in otherwise obstructed heavy clouds and precipitation scenarios.

In addition to these novel sensors, the meteorological situation is constantly monitored by a combination of a whole set of sensors: a combination of a scanning Doppler Lidar (LEOSPHERE) and a dual polarisation Doppler Radar (LEONARDO Germany), a visual and infrared (FLIR) camera, all provided by LEONARDO Germany, as well as a Sodar/RASS complementing the standard AWOS sensors operated by Austro Control.

SESAR Joint Undertaking

As the technological pillar of the Single European Sky (SES) to modernise Europe's air traffic management (ATM) system, SESAR is now making significant progress in transforming the performance of Europe's ATM network. The SESAR Joint Undertaking (SESAR JU) was established in 2007 as a public-private partnership to support this endeavour. It does so by pooling the knowledge and resources of the entire ATM community in order to define, research, develop and validate innovative technological and operational solutions. The SESAR JU is also responsible for the execution of the European ATM Master Plan, which defines the EU priorities for research and development (R&D) and implementation. Founded by the European Union and EUROCONTROL, the SESAR JU has 19 members, who together with their partners and affiliate associations represent over 100 companies working in Europe and beyond. The SESAR JU also works closely with staff associations, regulators, airport operators, airspace users, the military and the scientific community.

Developed within the framework of SESAR, the 'Wake turbulence separation optimisation' solution (PJ.02-1) aims to demonstrate the effectiveness of the plate lines at large airports. The SESAR Solution is one of several solutions developed within the framework of the SESAR JU 'Increased Runway and Airport Throughput' project (PJ.02 EARTH), which has received co-funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731781.


Falk Dambowsky

Head of Media Relations, Editor
German Aerospace Center (DLR)
Corporate Communications
Linder Höhe, 51147 Cologne
Tel: +49 2203 601-3959

Frank Holzäpfel

German Aerospace Center (DLR)
Institute of Atmospheric Physics
Cloud Physics and Traffic Meteorology
Münchener Straße 20, 82234 Oberpfaffenhofen