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

Abstract

Wake vortex related minimum aircraft separations for arrivals were evaluated utilizing plate lines. A plate line consists of a series of vertical plates placed in front of the runway that accelerate the decay of wake vortices. This study evaluates the potential to reduce minimum aircraft separations and the potential to increase safety due to the accelerated vortex decay. The presented method follows the methodology of the proposal for revised wake turbulence categorization RECAT-EU as much as possible in order to be compliant with the respective certified safety assessment. Wake vortex data measured by lidar with and without plates during a measurement campaign at Vienna International Airport, Austria, were used to generate generic non-dimensional decay curves for all captured aircraft types under so-called reasonable worst-case weather conditions with and without plates. The observed wake vortex behavior without plates was fitted to the generic decay curve from RECAT-EU. The application of the same method to the measurements with plates yields a generic decay curve representing the accelerated decay triggered by the plates. Applied to the RECAT-EU minimum separation scheme potential separation reductions ranging from 12% to 15% were evaluated. The same method was applied to the RECAT-EU-PWS pairwise separations, yielding a potential separation reduction due to the plates of 12% to 24% (average 14.8%) or a potential circulation reduction of about 20% to 30%. An assessment of the associated encounter risk showed significant benefits from plate lines indicating that the collaborative introduction of RECAT-EU-PWS together with plate lines may bring about increased airport capacity and safety at the same time when comparing it to the RECAT-EU scheme which is already operational at four European airports. Nomenclature1, 2 = decay coefficients (-)  = vortex circulation (m²/s)  = initial vortex circulation (m²/s)   = normalized vortex circulation (-)  = wing aspect ratio (-)  = air density (kg/m³) b = wing span (m) b0 = initial vortex spacing (m) g = gravitational acceleration (m/s²)  = altitude (m)

Optimised Pairwise Aircraft Separation Minima Applying Plate Lines

“…In the next step, for each individual combination of leader and follower aircraft type, the RMC is calculated that would result OGE when applying the reduced IGE separation with Plate Lines also for OGE. The reduced IGE separation when using Plate Lines (IGE-PL separation) had been calculated previously as published in [11] and described in section 2. This IGE-PL separation and the resulting RMC for the OGE case are shown in Fig.…”

“…The results of that previous study shall only be recapitulated as far as required to understand the combined analysis in and out of ground effect as presented in section 3. Details on the previous study can be found in references [11] and [12].…”

“…6 show the absolute and percental reduction of the minimum aircraft separations for each considered aircraft pair. As a depiction of each aircraft name would make the gures barely readable, only an index number of each aircraft is depicted (as de ned in [11]) with increasing number for decreasing maximum take-off mass (MTOM).…”

“…The current manuscript deals with use case III, which applies the RECAT-EU(-PWS) methodology to convert the accelerated wake vortex decay facilitated by the Plate Line into some potential for an additional reduction of the aircraft separations without compromising safety. In contrast to the previous investigations of use case III [11], [12], which were focusing on the effects in ground proximity, the current analysis investigates to which extent the reduced separations in ground proximity can also be safely applied along the glide slope. This previous work is summarized in section 2 together with other pre-requisits that have been used for the current investigations.…”

Aircraft wake vortices affecting airport wind measurements

“…In addition to RECAT, other current research includes work on plate lines, also with the ultimate goal of increasing capacity. Plate lines are an array of vertical plates placed in front of a runway to accelerate the decay of wake vortices and, thus, to reduce the required wake separation [7]. Overall, the physics of wake vortices is well researched and understood and the field is still active.…”