LESS TURBULENCE ON THE RUNWAY

Flugzeug Airbus A320 im Flug
Larger jets in particular produce a huge wake vortex behind them at take-off, causing high levels of turbulence for the aircraft landing behind them.
At Vienna International Airport, Austro Control, Austria’s air navigation service provider, and the German Aerospace Center (DLR) are currently successfully testing how these wake vortices can be reduced in the approach area with the aid of large plates on the ground. One positive side effect is that take-off and landing cycles can be consolidated.

When it comes to road traffic, safety distances are precisely regulated. As a legal requirement they must be large enough to stop even if the vehicle in front brakes suddenly. Outside built-up areas, there is a simple rule of thumb: The required distance in meters is half that on the speedometer – at 100 kilometers per hour, that’s 50 meters.

Airbus Flugzeug Bau
In aviation, however, aircraft generally have to maintain a distance of around ten kilometers from the preceding aircraft, especially if it is heavier. The reason for this is not sudden braking maneuvers in the air, which are physically impossible anyway, but the wake vortices generated by large jets. Especially when the next aircraft is about to touch down on the runway, the powerful effect these vortices unleash is often dangerous, and is almost impossible to calculate.
Marc Fontaine, Digital Transformation Officer (DTO) bei Airbus

“THE VERY FIRST EVALUATIONS OF THE NEW MEASUREMENTS IN VIENNA SHOW THAT THE WAKE VORTICES NEAR THE PLATES ACTUALLY DISSIPATE MUCH MORE QUICKLY.”

DR FRANK HOLZÄPFEL, DLR INSTITUTE FOR ATMOSPHERIC PHYSICS

POSSIBLE DAMAGE TO BUILDINGS TOO

All aircraft produce these long-lasting vortices of air in their wake. They roll up at the wingtips, where the negative pressure of the upper wing surface and the positive pressure of the underside of the wing meet. The powerful vortices can severely disrupt the flight paths of aircraft following close behind, and also cause damage to buildings on the ground. Smaller aircraft in particular are very sensitive to the wake vortices of large passenger and cargo aircraft and must therefore maintain a greater safety distance.

Austro Control and the DLR are working together with other measurement and sensor technology partners at Vienna International Airport to defuse wake vortices in the approach area and thus further increase safety. The researchers are using a DLR-patented configuration of parallel, vertically positioned ground plates known as plate lines, which disperse wake vortices much more quickly. A laser measuring device is used to record the behavior of the wake vortices in detail for later evaluation.

The aim of this project, which is called “Wake Turbulence Separation Optimisation” and is funded under the EU research program SESAR (Single European Sky ATM Research), is to prove the effectiveness of the plates in practice at a large commercial airport. Their effectiveness has in fact already been demonstrated in the water towing tank, flow simulations and previous flight tests at the DLR site in Oberpfaffenhofen.

Flugzeug Air New Zealand
This is how the plate lines work: While the vortices behind a rising aircraft usually drop quickly in higher layers of air, disperse and finally dissipate, they occasionally remain just above the ground on the runway for some time – precisely where the aircraft behind are supposed to land. In order to reduce the vortices circulating over the runway more quickly, the DLR researchers laid the plate lines in parallel and one after the other according to a very specific “pattern”. Secondary vortices are formed on the plates, which in Vienna are about nine meters long and four and a half meters high, causing the actual wake vortices to dissipate much faster.

MODEL FOR ALL LARGE AIRPORTS

“The very first evaluations of the new measurements in Vienna show that the wake vortices near the plates actually dissipate much more quickly there too,” explains Dr Frank Holzäpfel of the DLR Institute of Atmospheric Physics. “The project team has done great work to enable this unique system to be tested in full operation at a busy airport,” he continues. “The initial results are very encouraging and, if the effectiveness of the plate lines is fully confirmed as we assume it will be, they should increase safety and capacity at all airports in the future,” adds Christian Kern, Head of Air Traffic Management at Austro Control.

Background: The construction of new runways at established airports involves huge costs, with residential areas often affected by the expansion. If aircraft are able to take off and land closer together in future while fully guaranteeing safety, existing systems could be used more effectively, and runway extensions avoided.

Text by Behrend Oldenburg
Photos: Austro Control und Deutsches Zentrum für Luft- und Raumfahrt (DLR)
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