Purpose From pilot reports, field measurements and numerical simulations, it is known that wake vortices may persist within the glide path in ground proximity, leading to an increased encounter risk. This paper aims to investigate wake vortex behaviour during final approach and landing to understand why landings can be safe nevertheless. Further, it is investigated whether and to which extent the installation of plate lines beyond the runway tails may further accelerate wake vortex decay and thus improve safety by reducing the number of wake vortex encounters. Design/methodology/approach A hybrid numerical simulation approach is used to investigate vortex evolution from roll-up until final decay during the landing manoeuvre. The simulations are complemented by field measurement data accomplished at Munich Airport and at Special Airport Oberpfaffenhofen. Findings During touchdown, the so-called end effects trigger pressure disturbances and helical vortex structures that appear to ensure vortex decay rates in ground proximity needed to guarantee the required safety targets of aviation. Light detection and ranging (LIDAR) measurements indicate that vortex decay indeed can be accelerated by a plate line installed on the ground surface. The lifetime of the most safety relevant, long-lived and strongest vortices can be reduced by one-third. Practical implications The installation of plate lines beyond the runway tails may improve safety by reducing the number of wake vortex encounters and increase the efficiency of wake vortex advisory systems. Originality/value The novel numerical simulation technique and the acquired insights into the wake vortex phenomena occurring during landing as well as the demonstration of the functionality of the patented plate line provide high originality and value for both science and operational application.

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Data from numerical simulations and two field measurement campaigns are used to investigate aircraft wake vortex evolution during final approach and landing with and without a plate line. A new hybrid simulation method is employed to capture wake vortex evolution from early roll-up to final decay in ground proximity. Vortex decay is driven by the turbulence of the aircraft wake itself, the interaction of the wake vortices with the ground, the so-called end effects triggered by the sudden loss of lift during touchdown, and it is artificially augmented by a plate line installed a few hundred meters from the runway threshold. The field experiments WakeMUC at Munich airport and WakeOP at special airport Oberpfaffenhofen corroborate and complement the findings of the simulations. The end effects together with an acceleration of the decay in close ground proximity significantly accelerate vortex decay nearby the runway. In view of the fact that the probability to encounter wake vortices is distinctly increased in ground effect, the described mechanisms ensure the required safety of air traffic operations. Experiments and simulations demonstrate that plate lines appreciably accelerate wake vortex decay and interfere favorably with end effects. This way safety can be further increased during the flight phase with most reported encounters.

Several multimodel ensemble methods are selected and further developed to improve the deterministic and probabilistic prediction skills of individual wake-vortex transport and decay models. The different multimodel ensemble methods are introduced, and their suitability for wake applications is demonstrated. The selected methods include direct ensemble averaging, Bayesian model averaging, and Monte Carlo simulation. The different methodologies are evaluated employing data from wake-vortex field measurement campaigns conducted in the United States and Germany.= forecast of ith model g i yjf i = probability density function of forecast L = likelihood PB = probability that B occurs PBjA = probability that B occurs, given that A occurs py = probability density function of the y forecast

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