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Wind prediction to support reduced wake separation standards for closely spaced parallel runway departures
October 4, 2004
Conference Paper
Published in:
11th Conf. on Aviation, Range and Aerospace Meteorology, 4-8 October 2004.
Summary
Wake vortices are a by-product of lift generated by aircraft. The vortices from the wings and other lift surfaces such as flaps spin off and trail behind an aircraft (see Figure 1). These vortices can be a hazard to other aircraft, especially lighter aircraft that are following at low altitude. For this reason, numerous air traffic control standards require increased aircraft separation when wake vortex avoidance is a concern. These separation standards provide the required safety: there has never been a fatal accident in the U.S. due to wake vortices when wake vortex separations were provided by air traffic controllers. Wake vortex behavior is strongly dependent on atmospheric conditions, giving rise to the possibility that wake behavior can be predicted with enough precision to allow reduced use of wake vortex avoidance separations. Because vortices can not be seen, and their location and strength are not currently known or predicted, separation standards and air traffic procedures are designed to account for the worst case wake behavior. Because of this, the imposed aircraft separations are larger than required much of the time, reducing terminal capacity and causing increased traffic delay. If procedures or technologies can be developed to reduce the use of wake avoidance separations, terminal area delay reduction may be achieved. A prototype wind dependent wake separation system is operating in Frankfurt, Germany for arrivals into closely spaced parallel runways. The system uses wind prediction at the surface to determine when separation for wake vortex avoidance must be used and when the extra separation does not need to be used [Konopka, 2001][Frech, et al., 2002]. This led the FAA to ask the question: does the wind prediction algorithm used in Frankfurt, or perhaps another algorithm, have sufficient performance to consider it for possible use in the US for a closely spaced parallel runway departure system? This paper reports on a research effort to answer that question. This is part of a larger FAA and NASA research effort [Lang et al., 2003].
Summary
Wake vortices are a by-product of lift generated by aircraft. The vortices from the wings and other lift surfaces such as flaps spin off and trail behind an aircraft (see Figure 1). These vortices can be a hazard to other aircraft, especially lighter aircraft that are following at low altitude...
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Designing a terminal area bird detection and monitoring system based on ASR-9 data
August 27, 2001
Conference Paper
Published in:
3rd Joint Annual Meeting Bird Strike Committee, 27-30 August 2001.
Summary
Conflicts between birds and commercial aircraft are a noteworthy problem at both large and small airports [Cleary, 1999]. The risk factor for United States airports continues to increase due to the steady rise in take-off/landings and bird populations. There is a significant bird strike problem in the terminal area as shown by the incidents reported in the National Bird Strike Database [Cleary and Dolbeer, 1999]. The focus of bird strike mitigation in the past has centered primarily on wildlife management techniques. Recently, an Avian Hazard Advisory System (AHAS) has been developed to reduce the risks of bird strikes to military operations [Kelly, 1999]. This system uses a mosaic of data obtained from the Next Generation Weather Radar (NEXRAD). This sensor serves as an excellent tool for enroute bird advisories due to the radar coverage provided across the majority of the United States. However, its utility in the airport terminal environment is limited due to the slow update rate and the fact that the distance of most NEXRADs from the airport results in beam heights that are too high to detect low-altitude birds over the airport. The Federal Aviation Administration (FAA) operates two radar systems – the Terminal Doppler Weather Radar (TDWR), and the Airport Surveillance Radar (ASR-9) -- that could be used to help monitor bird activity at an airport in order to: 1. Provide continuously updated information on locations and approximate numbers of birds in flocks roosting or feeding on or near an airfield; 2. Generate real-time warnings of bird activity for dissemination to pilots of landing or departing aircraft by air traffic controllers or by direct data link. The TDWR provides wind shear warnings in the terminal area to enhance safety, while the ASR-9’s primary function is air traffic control. Both of these systems have been shown to detect biological echoes as well. Characteristics of the two radar systems have been examined and compared to determine capabilities for bird detection. Amongst other favorable factors, the high update rate and on-airport locale makes the ASR-9 a highly desirable platform for a bird detection and warning system for the terminal area. Data from an ASR-9 at Austin TX (AUS) equipped with a Weather Systems Processor (WSP) have been analyzed to assess the ASR-9's capability to detect and monitor bird activity. The WSP add-on provides a variety of radar base data products similar to those that would be available on all ASR-9s as part of an ASR-9 Service Life Extension Program (SLEP) currently underway. The Austin airport area is subject to large flocks of wintering migratory birds as well as a resident population of bats in close proximity to the airport. Radar data, visual observations and bird strike information during periods of active bird/bat movements have been collected for this study. An automated processing algorithm called the Terminal Avian Hazard Advisory System (TAHAS) is being developed to detect and track roosting and migratory birds using ASR-9 data. A key challenge will be the ability to discriminate biological from non-biological targets based on variables such as vertical continuity, variance or spectral width, and horizontal velocity distribution.
Summary
Conflicts between birds and commercial aircraft are a noteworthy problem at both large and small airports [Cleary, 1999]. The risk factor for United States airports continues to increase due to the steady rise in take-off/landings and bird populations. There is a significant bird strike problem in the terminal area as...
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Rotating a weather map
June 1, 1999
Journal Article
Published in:
Dr. Dobb's J., Vol. 24, No. 6, June 1999, pp. 80-88.
Summary
Introduction: I was recently part of a project developing a system for aircraft pilots to access the national ground weather-radar database while in flight. This weather-radar graphical database is generated from the outputs of the FAA and National Weather Service network of radars covering the continental United States and is updated every five minutes. Each pixel in the database covers a square measuring two kilometers (about one nautical mile) on a side. The content of each data pixel is a measure of the radar reflectivity measured at that location - radar reflectivity is proportional to the water content in the atmosphere (the precipitation rate). This graphical database is available through several commercial vendors - it's what you see displayed on The Weather Channel or during typical TV weather reports. Our system, on the other hand, provides a low-speed digital datalink connection from an FAA ground computer to an avionics computer/display located in the aircraft cockpit.
Summary
Introduction: I was recently part of a project developing a system for aircraft pilots to access the national ground weather-radar database while in flight. This weather-radar graphical database is generated from the outputs of the FAA and National Weather Service network of radars covering the continental United States and is...
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A comprehensive system for measuring wake vortex behavior and related atmospheric conditions at Memphis, Tennessee
January 1, 1997
Journal Article
Published in:
Air Traffic Control Q., Vol. 5, No. 1, January 1997, pp. 49-68.
Topic:
R&D area:
R&D group:
Summary
Models of vortex behavior as a function of atmospheric conditions are being developed in an attempt to improve safety and minimize unnecessary airport capacity restrictions due to wake vortices. Direct measurements of vortices and the relevant meteorological conditions in an operational setting, which would serve to improve the understanding of vortex behavior, are scarce and incomplete. A comprehensive vortex, meteorological, and aircraft measurement system has been constructed at Memphis International Airport and operated in two I-month periods during 1994 and 1995. A 10.6 um continuous-wave (CW) coherent lidar was used to measure vortex parameters with high fidelity. This lidar features a number of improvements over previous systems, including an automatic vortex detection and tracking algorithm to ensure efficient scanning. Meteorological data were collected from a 45 m instrumented tower, balloon soundings, a wind profiler/radio acoustic sounding system (RASS), sonic detection and ranging (SO DAR), and other sensors. This paper presents ensemble distributions of the conditions under which the over 500 aircraft were measured, and samples of vortex and atmospheric measurements. These data will be compared with theoretical predictions of vortex behavior as part of the development of an operational system designed to reduce aircraft spacings in the terminal area.
Summary
Models of vortex behavior as a function of atmospheric conditions are being developed in an attempt to improve safety and minimize unnecessary airport capacity restrictions due to wake vortices. Direct measurements of vortices and the relevant meteorological conditions in an operational setting, which would serve to improve the understanding of...
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1995 wake vortex program at Memphis, TN
January 5, 1996
Conference Paper
Published in:
AIAA 34th Aerospace Sciences Meeting and Exhibit, 15-18 January 1996.
Summary
This paper describes wake vortex field measurements conducted during August, 1995 at Memphis, TN. The objective of this effort was to record wake vortex behavior for varying atmospheric conditions and aircraft types. Wake vortex behavior was observed using a mobile CW coherent lidar. This lidar features a number of improvements over previous systems, including the first-ever demonstration of an automatic wake vortex detection and tracking algorithm. An extensive meteorological data collection system was deployed in support of the wake vortex measurements, including a 150-ft instrumented tower, wind profiler/RASS (radio acoustic sounding system), sonar and balloon soundings. Aircraft flight plan and beacon data were automatically collected to determine aircraft flight number, type, speed, and descent rate. Additional data was received from airlines in postprocessing to determine aircraft weight and model. Preliminary results from the field measurement program are presented illustrating differences in wake vortex behavior depending on atmospheric conditions and aircraft type.
Summary
This paper describes wake vortex field measurements conducted during August, 1995 at Memphis, TN. The objective of this effort was to record wake vortex behavior for varying atmospheric conditions and aircraft types. Wake vortex behavior was observed using a mobile CW coherent lidar. This lidar features a number of improvements...
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MDCRS: aircraft observations collection and uses
August 2, 1993
Conference Paper
Published in:
5th Int. Conf. on Aviation Weather Systems, 2-6 August 1993, pp. 317-321.
Topic:
R&D area:
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Summary
The Meteorological Data Collection and Reporting System (MDCRS) was designed for the Federal Aviation Administration (FAA) and the National Weather Service (NWS) to collect, decode, store and disseminate aircraft meteorological observations. The system, targeted primarily at improving upper air wind forecasts, was fielded in 1991.
Summary
The Meteorological Data Collection and Reporting System (MDCRS) was designed for the Federal Aviation Administration (FAA) and the National Weather Service (NWS) to collect, decode, store and disseminate aircraft meteorological observations. The system, targeted primarily at improving upper air wind forecasts, was fielded in 1991.
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Multisensor surveillance for improved aircraft tracking
January 1, 1989
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 2, No. 3, Fall 1989, pp. 381-396.
Summary
Cross-range measurements of aircraft travelling at distances of 50 to 200 miles include significant errors. Therefore, heading estimates for medium-to-long-range aircraft are not sufficiently accurate to be useful in conflict-detection predictions. Accurate crossrange measurements can be made-by using two or more sensors to measure aircraft position-but such measurements must compensate for the effects of system biases and aircraft turns. A set of algorithms has been developed that are resistant to system biases, that detect turns, and that track successfully through both biases and turns. These algorithms can be incorporated into a complete multisensor system, with good intersensor correlation of aircraft tracks and no added delays to the air traffic control processing chain.
Summary
Cross-range measurements of aircraft travelling at distances of 50 to 200 miles include significant errors. Therefore, heading estimates for medium-to-long-range aircraft are not sufficiently accurate to be useful in conflict-detection predictions. Accurate crossrange measurements can be made-by using two or more sensors to measure aircraft position-but such measurements must compensate...
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MLS Multipath Studies, Phase 3 Final Report, Volume III: Application of Models to MLS Assessment Issues, Part 1
June 8, 1981
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-88,III,PT-1
Topic:
R&D area:
R&D group:
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new approach and landing guidance system. The first two volumes of the report presented an overview of the simulation effort as well as describing in detail the propagation and MLS technique mathematical models and their validation by comparison with experimental data. In this volume, we describe the results of comparative simulations for the various MLS techniques in various scenarios and analyze in detail certain multipath performance features which were found to be significant in the scenario simulations. Simulation results are presented for several scenarios, and shadowing of the MLS azimuth by taxiing and overflying aircraft is analyzed. The remainder of the report focuses on multipath performance factors specific to various individual techniques. These include: (1) the effects of angle data outlier tests and filtering in the TRSB receivers, (2) the effects on the DMLS system due to receiver AGC, receiver motion-induced Doppler shifts, and the use of commutated reference systems, and (3) acquisition/validation algorithms for all three techniques. The report concludes with a summary and suggestions for future work. Part I of this volume consists of Chapters I through IV; Part II contains Chapters V through VIII and the Appendices.
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new...
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MLS Multipath Studies, Phase 3, Volume I: Overview and Propagation Model Validation/Refinement Studies
April 25, 1979
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-88,I
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new approach and landing guidance system. This first volume of the report presents an overview of the overall simulation results as well as a description of the refined mathematical models and validation of the propagation portion of the simulation. Specific propagation topics include: 1) preliminary results for validation of models for reflections from rough and/or rising terrain based on L-band field data. 2) validation of the models for building reflections based on field measurements at a number of operational airports. 3) validation and refinement of the models for angle guidance system shadowing by obstacles such as buildings and other objects.
Summary
This report presents work done during phase 3 of the US national Microwave Landing System (MLS) program toward developing a computer simulation model of the MLS multipath effects, the experimental validation ot the model, and the application of the model to investigate multipath performance of ICAO proposals for the new...
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Airborne measurements of ATCRBS fruit
October 3, 1978
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-84
Summary
Airborne measurements of ATCRBS fruit (asynchronous replies from ATCRBS transponders) are described. These measurements were undertaken to provide a more firm basis for assessing the interference impact of ATCRBS fruit on airborne 1090 MHz receivers (as in BCAS). Fruit rate measurements were performed with an instrumented aircraft flying along the East Coast from Boston to Washington and in the Los Angeles Basin. The results of these measurements are reported here, with fruit rates given as a function of altitude, geographical location, and receiver threshold, for receptions on both top-mounted and bottom-mounted aircraft antenna. The highest observed fruit rates, approximately 10,000 replies/sec, occurred in the LA Basin. To complement the measurements, a first-order fruit prediction model is defined. Predictions of this model are compared with the measurements, generally showing favorable agreement in absolute fruit rate, in power distribution, and in the functional dependence on traffic density.
Summary
Airborne measurements of ATCRBS fruit (asynchronous replies from ATCRBS transponders) are described. These measurements were undertaken to provide a more firm basis for assessing the interference impact of ATCRBS fruit on airborne 1090 MHz receivers (as in BCAS). Fruit rate measurements were performed with an instrumented aircraft flying along the...
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