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

Abstract

To mitigate the risk of wake vortex encounters during final approach, so-called plate lines have been developed. Data collected during a six-month measurement campaign at Vienna International Airport are used to assess the potential for reducing minimum aircraft separations facilitated by plate lines during approach and landing following the re-categorisation (RECAT-EU) methodology for revised wake turbulence categorisation. To ensure that no other parameters controlling wake vortex decay bias the analysis, it is verified that wind speed, atmospheric turbulence, thermal stratification and flight altitude reside in similar ranges with and without the plates. The analysis follows the steps of the RECAT-EU method to generate non-dimensional so-called reasonable worst-case circulation decay curves; one as a reference for nominal operations without plates and one representing the accelerated wake vortex decay brought about by the plate lines. The difference between the two circulation decay curves corresponds to the non-dimensional time-based aircraft separation reduction potential that can be translated into distance-based separation gains. Depending on the particular RECAT-EU category combination, the attained aircraft separation reduction potential ranges between 12% and 15%. Constricting the analysis to wake vortices generated by one aircraft type representing the Upper Heavy RECAT-EU category, the separation reduction potential amounts up to 24%.

Optimised Pairwise Aircraft Separation Minima Applying Plate Lines

“…For some aircraft pairings, even higher bene ts of more than 1 NM or 20% seem to be possible with Plate Lines. Landing aircraft with Plate Line at Vienna International Airport Figure 3 P2P prediction of circulation evolution for a number of heavy aircraft types under reasonable worst-case conditions Figure 4 The generic reasonable worst-case decay curves with and without Plate Line and the reference generic decay curve from RECAT-EU [12] Figure 5 Absolute reduction of minimum separations due to the Plate Line based on RECAT-EU-PWS seperations (IGE consideration only) [11] Figure 6 Percental reduction of minimum separations due to the Plate Line based on RECAT-EU-PWS seperations (IGE consideration only) [11] Figure 7 Separations and RMCs for the Learjet 35 as an exemplary follower aircraft Figure 8 Results of the combined analysis for IGE-PL and OGE when using RECAT-EU-PWS as reference (absolute values) Figure 9 Results of the combined analysis for IGE-PL and OGE when using RECAT-EU-PWS as reference (percental values)…”

“…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].…”

“…However, as the lifetime of vortices with plates is much shorter, it makes no sense to use the same lifetime criterion as without plates. For this reason, the same percental number of longest-lived vortices was used for the measurements with plates as without plates, while it was assured that the relevant parameters controlling wake vortex decay, such as wind speed, atmospheric turbulence, thermal strati cation and ight altitude above ground, reside in similar ranges for both cases [12].…”

“…The results of that analysis shall only be summarised here. Detailed descriptions can be found in the references [11] and [12]. In that assessment, the method as described in the RECAT-EU-PWS safety case report [2] was followed as closely as possible in order to be most compliant with the RECAT-EU-PWS method.…”

“…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.…”