How Plate Lines Influence the Hazard Perception of Pilots During Wake Encounters

Abstract

Wake vortex encounter reports as well as simulations show a significantly higher encounter risk in ground proximity. This is caused by the special behavior of wake vortices in ground effect. Nevertheless, hazardous wake encounters with adverse consequences are rarely reported in reality. In order to gain more insight in the mechanisms of wake encounters close to ground a realistic flow field around an aircraft of the HEAVY category is initialized using a high fidelity Reynolds-averaged Navier-Stokes solution. The further development of the vortical wake during final approach until touchdown is investigated by large-eddy-simulation until final decay. The resulting flow fields are used for a hazard analysis of wake encounters close to the ground. Encounter simulations are performed with a simulation model of the DLR research aircraft A320 ATRA with autopilot engaged. Different wind conditions and vortex ages are considered as well as the effect of a so-called plate line. Recent studies showed increased vortex decay in case that a series of plates is positioned in front of the runway threshold. Whether such a plate line also lowers the encounter risk or its severity is analyzed in this study. Nomenclature  C = rolling moment coefficient [-] RCR = roll control ratio [-] t = time [s] V/S = vertical speed [ft/min] x,y,z = Cartesian co-ordinates [m] Φ = bank angle [deg] Θ = pitch angle [deg]

Mitigating Wake Turbulence Risk During Final Approach Via Plate Lines

“…Previous investigations of the plate line principle comprise towing tank experiments 17 , large eddy simulations 16,17,18 , and flight experiments with DLR's research aircraft HALO 15 . Encounter simulations employing LES flow fields reveal a significant reduction of the maximal vortex impact on the encountering aircraft after the installation of plate lines 19 .…”

“…Figure19 Measurements of A320 wake vortices in ±50 m safety corridor for headwinds lower than 2 m/s with both plate lines (left) and only plate line 1 (right).…”

Assessment of Aircraft Separation Reduction Potential for Arrivals Facilitated by Plate Lines Following the RECAT-EU Methodology

“…These secondary vortices lead to an accelerated wake vortex decay independent of natural external disturbances [11] [12]. Lidar measurements confirm the functionality of the plate line [13] and flight simulator tests also showed a reduction of the encounter severity through the installation of plates [14]. Although the plates of course affect all vortices, the benefits of the plate line are most obvious if the most safety-relevant longest-living and strongest vortices are considered whose lifetime can be reduced by one third [13].…”

Plate lines to enhance wake vortex decay for reduced separations between landing aircraft

“…Plate lines accelerate the circulation decay of wake vortices that may rebound into the flight path of following aircraft due to their interaction with the ground surface Stephan, Holzäpfel, & Misaka, 2013, 2014. Encounter simulations employing large eddy simulations (LES) flow fields reveal a significant reduction of the maximal vortex impact on the encountering aircraft after the installation of plate lines (Vechtel, Stephan, & Holzäpfel, 2020). Plate lines are passive, cost effective, robust and safe.…”