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![Cross-section of wake vortices defining the dimensions of a wake plane [10]](profile/Jd-Powell-2/publication/3922819/figure/fig1/AS:651182490001408@1532265412035/Cross-section-of-wake-vortices-defining-the-dimensions-of-a-wake-plane-10.png)
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Over the coming decades, aviation operations are predicted to rise
steadily, increasing the burden on already congested and constrained
airports and terminal areas. It has long been recognized that a major
factor governing the safe minimum separation distance between aircraft
is the hazard associated with the wake generated by the preceding
aircraf...
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International regulations require aircraft to be separated in approach phase of flight by up to six nautical miles (11.12 km) due to the potential hazard caused by the swirling air left in their wakes. This 'wake vortex' is now the subject of intense worldwide research to understand the nature of the phenomenon and find ways of making air travel sa...
In air traffic control - and in many other domains - decisions are frequently based on uncertain information, most obviously where they involve predictions of future system states. Eliminating the uncertainty completely will not be possible and may in some cases not be desirable, for example where it restricts the flexibility of the human operator...
This air traffic management study designed a cockpit tool for assisting pilots to achieve a constant time delay behind a lead aircraft. A system architecture for manual and automatic `merge' and `remain' modes was proposed with required design and performance requirements. A manual `merge' guidance mode suggesting calibrated airspeed was developed...
In this simulator study, we evaluated the benefits and limitations of a collision warning system for flight according to visual flight rules (VFR). Pilots were confronted with single and multiple traffic, visible both on a moving map display and on the visual system of a simulator. The results demonstrate the benefits of the collision warning syste...
We propose a discrete time probabilistic model for predicting the future position of airliners, based on information about their current positions and flight plans. The model is used to derive an algorithm for detecting possible conflicts between aircraft, situations where the aircraft may come closer than a certain distance to one another with hig...
Citations
... The results presented assume that the transition from a VMC to an IMC capability at airports has been completed (refs. [21][22][23][24][25][26][27][28][29][30][31][32][33]. For numerous operational reasons, success with wake-avoidance technologies is achieved when the safe zone for the alongtrail separation distance, or time between the two aircraft, can be safely increased from nearly simultaneous (or 5 s, i.e., about 1000 ft or 305 m) to as much as 10 s (about 2000 ft or 610 m) or more. ...
This paper proposes a reliable method for estimation of the movement and spread of lift-generated vortex wakes as a function of time to better enable aircraft arriving at airports to avoid the hazards associated with the wakes of preceding aircraft. Operations on closely-spaced parallel runways illustrate how the method may be applied. An overview presents the aerodynamic mechanisms that cause the hazardous parts of lift-generated wakes to spread as a function of time. A computational method developed for determination of the spread of vortex wakes as a function of time is then applied to operations of aircraft as they approach closely-spaced parallel runways. The results suggest guidelines for efficiently and effectively avoiding the vortex wakes of preceding aircraft. Because the theoretical tools developed and the measurements of the components of the time-averaged wind and its gust magnitudes contain uncertainties, flight tests are recommended to confirm and to refine the guidelines presented, and to verify the techniques used to measure the atmospheric parameters that control wake intrusion.
... Except in cases of severe updrafts, wake turbulence will only descend; lateral movement is possible, but even in these cases, reporting the highest nearby point gives a conservative prediction. This is opposed to more high fidelity models, like those explored in[30,31].Nearby can be abstracted to mean " within some intersection volume, within some recent time interval. " For this prototype, two different intersection volumes have been tested. ...
... " Furthermore, we would like to enhance the synthetic world to quickly give the pilot wake turbulence information for all local air traffic which will decrease necessary aircraft spacing, increase airport capacity, minimize airport congestion, and relieve wake turbulence related air traffic control responsibilities while improving overall safety. Finally, we intend to incorporate more advanced wake turbulence models, such as those found in[30,31], and compare trade offs between the additional aircraft density allowed by these models and safety. ...
A flying aircraft disturbs the local atmosphere through which it flies creating a turbulent vortex at each wing tip known as a wake vortex. These vortices can persist for several minutes and endanger other aircraft traversing that turbulent airspace; large vortices are essentially invisible horizontal tornadoes and are a grave threat to smaller aircraft, especially during landing and take off. Accidents related to wake turbulence have resulted in both loss of life and aircraft destruction in the United States and around the world. Currently no cockpit instrumentation exists that tracks wake vortices and enables a pilot to sense and avoid wake turbulence in real-time. This paper presents a prototype of a novel, flight tested instrument that tracks wake vortices and presents this information to a pilot in real time using a synthetic virtual world augmented with wake turbulence information.
... However, their measurement is local: it does not cover the entire approach corridor. This partly explains why on-board systems are being contemplated to directly warn pilots [9] and to be one of the components to airport-wide wake vortex management. On-board integration of a LiDAR system was demonstrated in [10] and since then has been the subject of several studies, from atmospheric particle backscatter experiments [11] [12] to in situ measurements of wake encounters [13] [14]. ...
This paper describes the first successful attempt to detect wake vortices axially using an on-board infrared pulsed Doppler LiDAR (light detection and ranging) is described. On-board axial detection is more complex than the classic ground-based tangential approach, because the axial air speed in vortices is low and the atmospheric particle density is reduced, yielding a poorer SNR. To provide meaningful results in such unfavorable conditions we have developed a new flexible signal processing method based on a two-primitive model fitting the spectrum of the Doppler return. This new spectral estimation successfully detects wake vortices with an admissible SNR that is lower than other on-board state-of-the-art approaches. It was validated through flight tests.
... The results presented assume that the transition from a VMC to an IMC capability at airports has been completed. [21][22][23][24][25][26][27][28][29][30][31][32][33] For a number of operational reasons, success with wake-avoidance technologies will have been achieved when the safe zone for the along-trail separation distance, or time between the two aircraft, can be safely increased from nearly simultaneous (or 5 s, i.e., about 1000 ft or 305 m) to as much as 10 s (about 2000 ft or 610 m) or more. The larger along-trail separation distances facilitate wave-off operations and accommodate required aircraft-grouping combinations. ...
This paper proposes a reliable method for estimation of the movement and spread of lift-generated vortex wakes as a function of time to better enable aircraft arriving at airports to avoid the hazards associated with the wakes of preceding aircraft. Operations on closely-spaced parallel runways illustrate how the method may be applied. An overview presents the aerodynamic mechanisms that cause the hazardous parts of lift-generated wakes to spread as a function of time. A computational method developed for determination of the spread of vortex wakes as a function of time is then applied to operations of aircraft as they approach closely-spaced parallel runways. The results suggest guidelines for efficiently and effectively avoiding the vortex wakes of preceding aircraft. Because the theoretical tools developed and the measurements of the components of the time-averaged wind and its gust magnitudes contain uncertainties, flight tests are recommended to confirm and to refine the guidelines presented, and to verify the techniques used to measure the atmospheric parameters that control wake intrusion.
... The method chosen here to study the problem differs from previous approaches [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] in that it concentrates on the use of additional parallel runways and measurements in the airport environment to more accurately track the spread and motion of vortex wakes as a function of time. [21][22][23][24][25][26][27][28][29] When the ability to control the flight paths of aircraft accurately through the use of the Global Positioning System (GPS) and precise guidance of aircraft is coupled with knowledge of the locations of vortex wakes, runway operations can be expedited because vortex wakes can then be safely avoided by careful management of the time and location of aircraft. On this basis, the purpose of the study presented here is to first provide the information needed to extend current technology in wake prediction for nearly simultaneous operations on parallel runways. ...
... The method must also include an evaluation of the probabilistic uncertainties associated with the various components of the predictive method to insure that the level of safety is adequate. Previous guidelines [21][22][23][24][25][26][27][28][29] have shown that acceptance rates for closely-spaced parallel runways depend primarily on the longitudinal (in-or along-trail) time intervals between aircraft operations. As indicated in Fig. 2, two regions are safe from wake-vortex encounters when parallel runways are available. ...
... A wake-hazardous region is defined as that part of the atmosphere that must be avoided by aircraft because hazardous elements of a lift-generated wake shed by a preceding aircraft are located there to within a high degree of certainty. [21][22][23][24][25][26][27][28][29] Ideally, the definition should state that, if the centerline of a following aircraft is outside of such a hazardous region, any disturbances induced on the aircraft by the vortex wake of a preceding aircraft is indistinguishable from an encounter with ambient turbulence in the area. At this time, the technology is not sophisticated enough to specify the distance that the centerline of a following aircraft must be from the centerline of the wake for such a specification to be valid. ...
... Wake predictions and/or observations could be presented to pilots through a Synthetic Vision System (SVS) [4] or a Cockpit Display of Traffic Information (CDTI), using on board sensors and computation or a data-link to a ground based system. This concept, studied in [5], would place the burden of wake avoidance back on the pilots in all meteorological conditions. This is not a large paradigm shift in terms of wake avoidance procedures since currently under VMC pilots remain clear of a preceding aircraft's wake by adjusting the flight path based on a crude understanding (mental prediction) of wake behavior and assessment of the current weather conditions. ...
NASA Langley Research Center has a long history of aircraft wake vortex research, with the most recent accomplishment of demonstrating the Aircraft VOrtex Spacing System (AVOSS) at Dallas/Forth Worth International Airport in July 2000. The AVOSS was a concept for an integration of technologies applied to providing dynamic wake-safe reduced spacing for single runway arrivals, as compared to current separation standards applied during instrument approaches. AVOSS included state-of-the-art weather sensors, wake sensors, and a wake behavior prediction algorithm. Using real-time data AVOSS averaged a 6% potential throughput increase over current standards. This report describes a Concept of Operations for applying the technologies demonstrated in the AVOSS to a variety of terminal operations to mitigate wake vortex capacity constraints. A discussion of the technological issues and open research questions that must be addressed to design a Wake Vortex Advisory System (WakeVAS) is included.
The human pilot is typically required to control aircraft in which the dynamics of the vehicle vary with time. This variation may occur naturally as the aircraft changes flight condition, it can be deliberately induced by changes in the stability and command augmentation system (SCAS), or it may result from airframe damage or control system failures. A computer simulation in which the structural pilot model controlled a model of a UH-60 rotorcraft is considered next. Including rotor degrees of freedom, actuator, and SCAS dynamics, the rotorcraft model was of 42nd order. The piloting task was to maintain position in hover in turbulence. A pilot?model-based framework for approaching the problem of human pilot detection of time variation in aircraft dynamics can be offered. The pilot model that was employed was the structural pilot model that has been previously introduced in the literature and used in a variety of pilot/vehicle analyses, from handling qualities studies to investigations of flight simulator fidelity.
In order to avoid the hazard posed by the vortex wakes of preceding aircraft during landing and take-off operations, certain minimum in-trail and across-trail spacings are mandated. Since the minimum spacings are usually more than those required for other purposes, the wake-vortex hazard is a factor that now limits the capacity of airports. As part of an ongoing effort to increase airport capacity, an individual-flight-corridor concept is being studied as a possible way by which both lateral and in-trail spacings of aircraft operations can be reduced. In the concept, a wake-advisory system is used to indicate the time-dependent locations of the hazardous regions posed by the vortex wakes of preceding aircraft. A separate or individual vortex-free flight corridor is then designed for each aircraft operation. Since runways will be required for these newly defined flight corridors, existing and/or new closely-spaced parallel runways need to be available. In this way, all active vortex wakes shed by preceding aircraft are safely avoided, and delays due to the wake-vortex hazard can be reduced. Some steps toward implementation and problems to be encountered are described.
A preliminary study of a Cockpit Display of Traffic and Wake Information for closely-spaced parallel approaches was conducted at the NASA Ames Research Center. With the advent of the navigational precision of the Global Position System, data-link, and the operational procedures of Required Navigational Performance, the possibility exists for simultaneous instrument operations to runways with separations approaching those used for simultaneous visual operations. In addition, new algorithms for predicting wake vortex movement may allow these instrument operations to be conducted with greater safety than for present visual operations. The study developed a cockpit display for traffic and wake information and developed operational procedures for a mix of conventional and runway-independent aircraft to closely spaced landing areas. Results showed that very small Total System Errors were obtained using pursuit displays and manual flight control. For aircraft with different approach speeds, a small increase in paired aircraft approach spacing was found to be necessary for wake separation over that for aircraft with similar approach speeds. Performance at decision height was compatible with CAT II/IIIA operations. Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc.
