Aircraft wake vortices constitute a potential safety concern and thus a capacity limitation at major airports. Plate Lines mitigate the risk of wake vortex encounters during final approach and may help to enhance runway capacity. They were developed by German Aerospace Center (DLR) and their benefits were demonstrated at Vienna Airport in collaboration with Austro Control.
Plate Lines accelerate the decay of wake vortices that may rebound into the flight path of following aircraft due to their interaction with the ground surface. One plate line consists of several upright plates that are installed underneath the approach glide path at the ends of runways. Plate lines are passive, cost-effective, robust and safe. They include no movable parts and do not require electricity.
Impressions of the experimental plate line installed at runway 16 of Airport Vienna (DLR, CC-BY 3.0).
Significant vortex lifetime reduction
Plate Lines reduce the lifetime of the most safety-relevant wake vortices by 22% for Medium category aircraft and by up to 37% for Heavy category aircraft. Circulation, which describes the "strength" of the wake vortex, is reduced by 50% for a typical pairing (Medium aircraft following a Heavy aircraft). Depending on the aircraft pairing, plate lines allow for a potential separation reduction of between 12% and 20% compared to the RECAT-EU separation scheme.
From the lab towards application
Since the first idea developed in the year 2008, the functionality of the patented plate lines was first demonstrated in towing tank experiments. Next, using high-performance numerical simulations, the underlying physical mechanism was analyzed in detail, the size of the plate lines was optimized, and the influence of wind was investigated. Flight tests with the DLR research aircraft HALO (Gulfstream G550) at the special airport Oberpfaffenhofen showed that the lifetime of the longest-lived vortices can be reduced by about 30%.
Numerical simulation of landing of A340 with plate line (left) and plate line overflight with research aircraft HALO at special airport Oberpfaffenhofen (right) (DLR, CC-BY 3.0).
In the year 2019, the effectivity of the plate lines was finally demonstrated in a large-scale measurement campaign at Vienna International Airport with real air traffic operations. Two temporary plate lines were installed underneath the glide path to runway 16. During a six-month period, wake vortex decay was measured for 9473 landings using lidar. After evaluating the achieved wake vortex lifetime and circulation reductions, the possible minimum aircraft separation reductions were established using the same method as used for the RECAT-EU separation scheme. This project has received funding within the framework of the SESAR Joint Undertaking “Increased Runway and Airport Throughput” project (PJ.02 EARTH) and the “Safely Optimized Runway Throughput” project (VLD3-W2 SORT) within the European Union's Horizon 2020 research and innovation programme under grant agreement Nos 731781 and 874520.
The technical design for a permanent plate line installation was developed in a three-phase process: Requirements definition, preliminary design and detailed design. First, eight main requirements were identified and weighted based on their respective importance. Then, the four most suitable designs were selected from 15 design ideas and evaluated using finite element analysis. The best design, consisting of four aluminum masts covered with honeycomb composite panels, was finally selected for installation at Vienna Airport.
Selected plate design for permanent installation at airports (DLR, CC-BY 3.0).
Certification is the next step In near future, plate lines may provide airports and air navigation service providers with a low-cost means to increase safety, resilience and fuel efficiency by avoiding go-arounds. In a next step, reduced aircraft separations may be certified for operational use at runways equipped with plate lines. This innovation would increase landing capacity, helping to make aviation more climate and environmentally friendly by reducing delays and holding patterns as well as deferring the construction of new runways.