Prediction of dynamic pairwise wake vortex separations for approach and landing

Design and performance of the Wake Vortex Prediction and Monitoring System WSVBS are described. The WSVBS has been developed to tactically increase airport capacity for approach and landing on single runways as well as closely-spaced parallel runways. It is thought to dynamically adjust aircraft separations dependent on weather conditions and the resulting wake vortex behavior without compro-mis>ing safety. Dedicated meteorological instrumentation and short-term numerical terminal weather prediction provide the input to the prediction of wake-vortex behavior and respective safety areas. LIDAR monitors the correctness of WSVBS predictions in the most critical gates at low altitude. The WSVBS is integrated in the arrival manager AMAN of DLR. Performance tests of the WSVBS have been accomplished at Frankfurt airport in winter 2006/07 and at Munich Airport in summer 2010. Aircraft separations for landings on single runways have been compared employing the concepts of either heavy-medium weight class combinations or dynamic pairwise separations where individual aircraft type pairings are considered. For the very conservative baseline setup of the WSVBS the potential capacity gains of dynamic pairwise operations for single runways appear to be very small. On the other hand, the consideration of individual aircraft types and their respective wake characteristics may almost double the fraction of time when radar separation could be applied

Numerical Optimization of Plate-Line Design for Enhanced Wake-Vortex Decay

The design of plate lines as a ground-mounted device for wake-vortex decay enhancement is investigated in this work. The most important design parameters, the aspect ratio and plate distance, are analyzed for the wake vortices generated by two aircraft: the A340 as well as the A380. Large-eddy-simulations are used to simulate the wake-vortex evolution in ground proximity for different parameter combinations. Fully rolled-up wake vortices are initialized using a Lamb–Oseen vortex model resembling the characteristics of the two aircraft. With the stochastic so-called kriging method, estimates of the performance and respective probabilistic envelopes are given for the design parameter region, spanned by the large-eddy-simulation. The vortex circulation averaged over the rapid decay phase is taken as the objective function. The large-eddy-simulation parameters are selected in the vicinity of the expected optimum. An optimal parameter combination can be localized in the A340 case, as well as in the A380 case. For both cases, statistical relevance is provided. Moreover, it can be deduced that the optimal parameters for the A380 are also well suited for smaller aircraft like an A340

Large-Eddy Simulation of Spatially Developing Aircraft Wake

Development of aircraft’s wake vortex from the roll-up until vortex decay is studied. An aircraft model and a surrounding flow field obtained from high-fidelity Reynolds Averaged Navier-Stokes simulation are swept through a ground fixed computational domain to initialize the wake. After the initialization, large-eddy simulation of the vortical wake is performed until vortex decay, i.e., 2-3 minutes after the passage of aircraft. Here, the methodology and some results from the simulations using the DLR-F6 wing-body model are presented

Plate Lines - Mitigating Wake Turbulence Risks and Increasing Runway Throughput

So-called plate lines have been developed at the DLR Institute of Atmospheric Physics in order to shorten the lifetime of wake vortices generated by landing aircraft. Installing plate lines underneath the glide path mitigates wake vortex encounter risks and prevents go-arounds. In combination with a modern separation scheme, delays can be reduced and runway capacity can be increased

Estimating Aircraft Landing Weights from Mode S Data

Aircraft weights prior to touchdown are assessed employing equations suggested for estimates of descent speeds depending on aircraft gross mass following BADA (Base of Aircraft Data). The required aircraft type, calibrated airspeed and air density data are derived from Mode S data protocols. Landing weights of 3328 aircraft approaching Vienna airport, provided by Austrian Airlines, serve as reference gross masses. Average aircraft masses during final approach vary between 85% and 93% of the maximum landing weight depending on the aircraft type. A simple correction for the observed inclination of pilots to fly somewhat faster than prescribed in reference handbooks eliminates the bias of the mass estimates in the current data base, while the respective standard deviation amounts to approximately 5%

Assessment of the Wake-Vortex Proximity to Landing Aircraft Exploiting Field Measurements

This paper examines possible wake-vortex encounters by analyzing light detection and ranging (LIDAR) field measurements conducted by DLR, German Aerospace Center and NASA at major international airports (Dallas, Denver, Frankfurt, Memphis, and Munich) comprising 8056 aircraft landings. The applied aircraft separations are analyzed, depending on the involved aircraft types and compared to the International Civil Aviation Organization and recategorization separation standards. Furthermore, the distances between the wake generated by the leading aircraft and the follower are evaluated

LES study on the shape effect of ground obstacles on wake vortex dissipation

The lingering wake vortex following a landing aircraft has long been a hazard to aviation safety. Previous studies at the German Aerospace Center (DLR) confirmed the effectiveness of applying ground-based obstacles to improve the dissipation of the wake vortex pair by triggering the onset of the vortex bursting by the artificial introduction of shortwave instability. Following the design of the plate line obstacles as proposed by DLR for vortex dissipation, we further investigate the influence of the shape of the ground obstacles on dissipating wake vortex in the present work. The secondary vortex structure, resulting from the interaction between the vortical flow and the obstacle plate, stems from the location of the obstacle and travels outward along the vortex axis, thus spreading instability to the vortex structure along the way. 3D numerical simulations were conducted using Large Eddy Simulation with OpenFOAM solver

Assessment of Aircraft Separation Reduction Potential for Arrivals Facilitated by Plate Lines

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

Vortex bursting and tracer transport of a counter-rotating vortex pair

Large-eddy simulations of a coherent counter-rotating vortex pair in different environments are performed. The environmental background is characterized by varying turbulence intensities and stable temperature stratifications. Turbulent exchange processes between the vortices, the vortex oval, and the environment, as well as the material redistribution processes along the vortex tubes are investigated employing passive tracers that are superimposed to the initial vortex flow field. It is revealed that the vortex bursting phenomenon, known from photos of aircraft contrails or smoke visualization, is caused by collisions of secondary vortical structures traveling along the vortex tube which expel material from the vortex but do not result in a sudden decay of circulation or an abrupt change of vortex core structure. In neutrally stratified and weakly turbulent conditions, vortex reconnection triggers traveling helical vorticity structures which is followed by their collision. A long-lived vortex ring links once again establishing stable double rings. Key phenomena observed in the simulations are supported by photographs of contrails. The vertical and lateral extents of the detrained passive tracer strongly depend on environmental conditions where the sensitivity of detrainment rates on initial tracer distributions appears to be low