The German Aerospace Center (DLR) has started trial operations at Vienna International Airport of a process designed to reduce wake turbulence during the final approach, and researchers describe first results as “very encouraging.” The researchers are using a DLR-developed and patented configuration of parallel ground plates to dissipate the circulating vortices in front of a runway more quickly. A laser-based measurement system (Lidar) records the behaviour of wake vortices in detail for subsequent evaluation.
“This project represents a major achievement in providing test results during live traffic at a highly frequented airport,” said Christian Kern, director of air traffic management at Austria’s air navigation service provider (ANSP) Austro Control.
“Early results are very encouraging and if these measures prove to be broadly effective, which we expect, this could result in improved safety and increased capacity at all airports.”
Austro Control, which carried out a safety assessment prior to the trials, supports the evaluation of the trial data and makes radar and flight plan data available. The ANSP and Vienna International Airport (VIE) have supported the construction of the plates.
For the VIE trials, DLR designed an installation consisting of two plate lines of respectively eight and nine ground plates—about 9 meters long and 4.5 meters high—placed in front of runway 16, one of two runways at the airport.
“We were able to measure about a quarter of the incoming flights,” Frank Holzäpfel of the DLR Institute of Atmospheric Physics said.
The very first evaluations show that the wake vortices near the plates decay “noticeably faster” than with approaches without the DLR plate lines and “reach our goal of reducing the lifetime of the longest wake vortices by 30 percent,” he said. The current trials, he added, show the “same very encouraging” characteristics of previous tests in the water-towing tank, flow simulations, and small-scale flight tests with the DLR HALO research aircraft, a modified Gulfstream G550, at the centre’s site in Oberpfaffenhofen, near Munich.
The VIE trials ran over three days but project leaders aim to complete 26 days of measurements over a six-month period. The research project focuses on reducing the wake turbulence of the largest-capacity passenger aircraft; however, the DLR procedure applies to all approaches as Vienna Airport hosts only one Airbus A380 movement per day. “We also aim to reduce the wake turbulence during the final approach of narrowbodies,” Holzäpfel noted. Narrowbodies account for most of Vienna Airport’s traffic. The choice of VIE stems from Austro Control’s long-term collaboration with DLR on the topic of wake turbulence and the airport’s proximity to DLR’s research centre. Researchers must be on site when the system is mounted and active.
It took a “long time” to get all the necessary safety approvals and the authorization of the Austrian minister of transport to install the plate lines in the landing area, Holzäpfel conceded.
While expressing satisfaction with the successful demonstration of the system at VIE, he cautioned it was too early to conclude the procedure will allow for a reduction of the separation between approaching aircraft, which in turn could lead to more effective use of existing runway capacity, thereby avoiding construction of additional runways. “The first objective is increasing safety,” he emphasized.
The project gets financial support from the EU’s SESAR public-private joint undertaking, the technological pillar of the Single European Sky to modernize Europe’s air traffic management.
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. The DLR has created 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.