Publications
Aircraft encounters with thunderstorms in enroute vs. terminal airspace above Memphis, Tennesssee
May 13, 2002
Conference Paper
Published in:
Proc. 10th Conf. on Aviation, Range and Aerospace Meteorology, 13-16 May 2002, pp. 162-165.
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Summary
To date, very little attention has been given to quantifying the effects of thunderstorms on air traffic in enroute airspace. What types of storms cause pilots to deviate from their nominal flight routes? What types of storms do pilots fly through? Around? Over? When thunderstorms are forecast to affect a particular region, how many planes will need to be rerouted? Which ones? Which aspects of the storm need to be accurately forecast in order to answer those questions? How does the forecast accuracy affect the quality of airspace capacity predictions? Quantitative answers to these questions would contribute to the design of useful decision support tools. Federal Aviation Administration decision support tools are being equipped with the ability for air traffic managers to define dynamic "flow constrained areas" (FCAs). Each FCA will be a polygon in latitude/longitude space with ceiling and floor altitudes and a motion vector. One primary use for FCAs will be to define regions that do, or probably will, contain convective thunderstorm activity. These tools will help air traffic managers decide which planes to re-route around the weather and which planes have a reasonable chance of flying through, between, or over the storms. Although it will be helpful to have the ability to manually define FCAs in the traffic managers' tools, the efficiency of the solutions that will be worked out with those tools would be greatly enhanced by answers to the questions posed above. In our prior work we have attempted to quantify the behavior of pilots who encounter thunderstorms in terminal airspace during the final 60 nautical miles of flight. In this study we compare the storm avoidance behavior of pilots in enroute airspace with that of pilots who encountered the very same storms at lower altitudes, in terminal airspace. The study is preliminary, but it complements the terminal work, affords some insight into pilot behavior, and raises questions that should be addressed in a larger study.
Summary
To date, very little attention has been given to quantifying the effects of thunderstorms on air traffic in enroute airspace. What types of storms cause pilots to deviate from their nominal flight routes? What types of storms do pilots fly through? Around? Over? When thunderstorms are forecast to affect a...
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Commercial aircraft encounters with thunderstorms in the Memphis terminal airspace
September 11, 2000
Conference Paper
Published in:
Proc. Ninth Conf. on Aviation, Range, and Aerospace Meteorology, 11-15 September 2000, pp. 37-42.
Summary
Thunderstorms are dynamic obstacles to the flow of air traffic. Aircraft routing in the presence of thunderstorms is as dynamic as the position and intensity of the storms. The question of where pilots will and will not fly is relevant to the decisions made by human air traffic managers as well as to the development of automated decision aid tools. In order to accurately anticipate which routes will be useable one needs to be able to 1) forecast the relevant weather variables, and 2) convert those weather variables into a quantitative probability that pilots will request deviations from the nominal route. The Convective Weather Integrated Product Team at the FAA is improving the accuracy and lead time of forecasts of thunderstorm products. This paper provides an update on our examination of the issue of probability of deviation. In our recent examination of 63 hours of weather and flight track data from the DFW airspace (Rhoda and Pawlak, 1999a,b) we combined several weather variables (measurements, not forecasts) to correctly predict pilot deviation and penetration behavior for 70-85% of the encounters between thunderstorms and aircraft arriving at DW and Dallas Love (DAL) airports. We also found that pilots were more likely to penetrate strong precipitation when they: 1) were near the arrival airport, 2) were following another aircraft, 3) were flying after dark, 4) had been delayed in the air by 15+ minutes upstream of the DFW airspace. We did not find any statistically significant difference between the percentages of thunderstorm penetrations by various airlines. We also found that persistent penetration of storms near the airport is sometimes abruptly interrupted presumably by wind shear alerts from air traffic controllers or cautionary pilot reports from the penetrating aircraft. When the arrivals cease, aircraft on the final approach course may turn suddenly to the left or right to avoid the weather that caused the interruption. Aircraft that abort the approach sometimes fly through very intense precipitation-sometimes through downdrafts that are causing microburst outflows at the surface. The work described in this paper applies the methodology from the DFW study to data collected in the Memphis Terminal Radar Approach Control (TRACON). The methodology is described briefly here and in more detail in (Rhoda and Pawlak, 1999b). We developed several probability of deviation classifiers using a portion of the Memphis data and tested them on the remaining data to determine if it is possible to predict whether pilots will penetrate or deviate around the storms. We also tested the classifiers that were developed in the DNV study on the MEM data and vice versa. We repeated the DFW hypothesis tests for various dichotomies of encounters: near/far, leading/following, light/dark, delayed/undelayed.
Summary
Thunderstorms are dynamic obstacles to the flow of air traffic. Aircraft routing in the presence of thunderstorms is as dynamic as the position and intensity of the storms. The question of where pilots will and will not fly is relevant to the decisions made by human air traffic managers as...
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Weather sensing and data fusion to improve safety and reduce delays at major west coast airports
September 11, 2000
Conference Paper
Published in:
Ninth Conf. on Aviation, Range, and Aerospace Meteorology, 11-15 September 2000, pp. 102-107.
Summary
In this paper we present results from a recently completed study of weather sensing and data fusion to improve safety and reduce delays at major west coast airports. With the exception of a summer stratus burn-off prediction project at San Francisco, these airports have received much less attention in terms of advanced FAA terminal weather decision support systems than major airports east of Los Angeles. This is because the principal concern for terminal weather decision support to date has been microburst-induced wind shear, which is very infrequent at the west coast airports. However, three factors warrant a reexamination of weather decision support provided to these major west coast airports: 1. The increased emphasis on significantly improving aviation safety while reducing delays at major airports in the face of expected increases in operations rates within the National Airspace System (NAS), 2. New air traffic management technology such as terminal automation, collaborative decision making (CDM), and weather adaptive wake vortex spacing systems, and 3. Advances in terminal weather decision support technology represented by the Integrated Terminal Weather System (ITWS) [including various P31 enhancements to ITWS (Evans and Wolfson, 2000)] The airports considered in this study were the Los Angeles (LAX), San Francisco (SFO), Portland (PDX) and Seattle (SEA) International Airports. It should be noted that because these airports did not receive a Terminal Doppler Weather Radar, there currently is no plan to provide them with an ITWS. LAX, SF0 and PDX are scheduled to receive an ASR-9 Weather System Processor (WSP). The paper proceeds as follows. Section 2 discusses the study's methodology and provides background information on delays and weather phenomena for these airports in the context of other major US airports as well as applicable air traffic management (ATM) and terminal weather system technology. Section 3 summarizes the principal findings for the four airports. We conclude with a summary of the potential benefits of improved weather sensing and data fusion that might be provided at these west coast airports by an augmented ITWS as well as recommendations for further studies.
Summary
In this paper we present results from a recently completed study of weather sensing and data fusion to improve safety and reduce delays at major west coast airports. With the exception of a summer stratus burn-off prediction project at San Francisco, these airports have received much less attention in terms...
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Weather sensing and data fusion to improve safety and reduce delays at major west coast airports
November 30, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-290
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The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive an Integrated Terminal Weather System (ITWS). This report considers the Los Angeles (LAX), San Francisco (SFO), Seattle (SEA) and Portland, OR (PDX) international airports. A number of visits were made to the various ATC facilities to better understand their weather decision support operational needs. Analyses were made of an incident of lightning strikes to two aircraft at SEA in February 1999, and a prototype terminal winds product was developed for LAX that uses profilers as well as plane reports to update the the National Weather Service (NWS) Rapid Update Cycle (RUC) winds estimates. We found that an augmented ITWS could potentially address safety concerns for triggered lightning strikes and vertical wind shear in winter storms at Portland and Seattle. An augmented ITWS terminal winds product (that uses wind profiler data in addition to the current ITWS sensors) could provide very large delay reductions for LAX and SFO during winter storms as a component of a wake vortex advisory system. This augmented product also could provide significant delay reduction benefits at SEA. The sensors required to obtain the projected benefits at SFO do not exist currently. Portland may warrant additional sensors to address the vertical wind shear problems, and LAX would require additional sensors for a wake vortex advisory system. We recommend near-term experimental measurements at PDX to determine the optimum sensor mix and that an operational evaluation of the prototype augmented ITWS terminal winds product be carried out at LAX to determine if the current sensor mix can meet operational needs. Lightning strike data at SEA and PDX should be analyzed to determine if a proposed triggered lightning predictant is accurate.
Summary
The objective of this study was to analyze the weather sensing and data fusion required to improve safety and reduce delays at a number of west coast airports that are not currently scheduled to receive an Integrated Terminal Weather System (ITWS). This report considers the Los Angeles (LAX), San Francisco...
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The thunderstorm penetration/deviation decision in the terminal area
January 10, 1999
Conference Paper
Published in:
8th Conf. on Aviation, Range and Aerospace Meteorology, ARAM, 10-15 January 1999.
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During thunderstorm periods, terminal air traffic planners make a number of key decisions. They decide when to close and re-open arrival fixes, departure fixes, and runways; they anticipate and execute changes in runway configuration; they negotiate routing and flow rate decisions with Air Route Traffic Control Center (ART CC) traffic managers; and they set the airport acceptance rate. In making each of these decisions, the traffic planner looks at a weather radar display and makes an educated guess at answering the two following questions: - What will the weather be like in the airspace and time period in question? - Will the pilots be able and willing to fly through that airspace during that time? The same two questions will be important for advanced terminal automation systems. One key element of air traffic automation systems such as the Center-TRACON Automation System (CTAS) is the calculation of candidate trajectories for each aircraft for the time period of automation control. To make this calculation, the automation software must know which routes will be usable during the control period. The first of the two fundamental questions is being addressed by the convective weather Product Development Team (PDT) of the FAA's Aviation Weather Research program. (Wolfson, 1997; Wolfson, 1999; Hallowell, 1999; Forman, 1999; Evans, 1997) The second fundamental question is the subject of the work reported here. The state of the art answer to the second question is a widely quoted air traffic control rule-of-thumb which says that pilots generally do not penetrate precipitation that is NWS VIP level 3 (i.e. 41 dBZ) or higher. That is not to say that air traffic controllers always vector aircraft around level 3+ cells but rather that they begin to anticipate pilot requests for deviations when the weather approaches level 3. A suite of new weather sensors have become available that provide much more comprehensive information on convective weather features than was available in the past. Additionally, flight-related data such as preceding pilot behavior and whether a flight is running late are easier to obtain than in the past. In this study we develop an objective quantitative assessment of which weather and flight-related variables best explain pilot deviation decision-making.
Summary
During thunderstorm periods, terminal air traffic planners make a number of key decisions. They decide when to close and re-open arrival fixes, departure fixes, and runways; they anticipate and execute changes in runway configuration; they negotiate routing and flow rate decisions with Air Route Traffic Control Center (ART CC) traffic...
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The impact of thunderstorm growth and decay on air traffic management in class B airspace
February 2, 1997
Conference Paper
Published in:
7th Conf. on Aviation, Range, and Aerospace Meteorology, ARAM, 2-7 February 1997.
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Air traffic management is a challenging task, especially if the airspace involved is impacted by inclement weather. The high volume of air traffic which inundates the nation's major airports compounds the difficulties with which Air Traffic Control (ATC) specialists have to cope. When you add the unpredictability of thunderstorm growth and decay to the controllers workload, air traffic management becomes even more of a challenge. ATC specialists would benefit from reliable forecasts of thunderstorm growth and decay. To determine how they would use a Growth and Decay product, ATC specialists from the Memphis Air Route Traffic Control Center (ARTCC), Traffic Management Unit (TMU), and TRACON supervisors were interviewed while viewing five movie loops of Memphis weather cases. The movies consisted of the ASR-9 six-level reflectivity data, aircraft beacons, and storm motion vectors.
Summary
Air traffic management is a challenging task, especially if the airspace involved is impacted by inclement weather. The high volume of air traffic which inundates the nation's major airports compounds the difficulties with which Air Traffic Control (ATC) specialists have to cope. When you add the unpredictability of thunderstorm growth...
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Analysis of the 12 April 1996 wind shear incident at DFW airport
November 13, 1996
Conference Paper
Published in:
Workshop on Wind Shear and Wind Shear Alert Systems, 13-15 November, 1996.
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Wind shear detection algorithms that operate on Doppler radar data are tuned to primarily recognize the velocity and reflectivity signatures associated with microbursts and gust fronts. Microbursts produce a divergent pattern in the velocity field that is associated with a descending column of precipitation. Gust fronts produce a convergent pattern that is often associated with a thin-line reflectivity feature. On April 12, 1996 at Dallas-Fort Worth International Airport (DFW) three pilots reported encounters with wind shear in a five minute period (2329-33 GMT). The third pilot (AA 1352) reported an encounter with "severe wind shear", which we refer to as "the incident" throughout the paper. He used maximum throttle to keep the MD-80 in the air and reported that it was only "by the grace of God" that the aircraft did not crash (Dallas Morning News, 4/19/96). The plane, originally bound for Pittsburgh, was diverted to Tulsa where the passengers were offloaded to another aircraft, the black box was removed, and the engines were checked according to procedures required whenever maximum throttle is utilized.
Summary
Wind shear detection algorithms that operate on Doppler radar data are tuned to primarily recognize the velocity and reflectivity signatures associated with microbursts and gust fronts. Microbursts produce a divergent pattern in the velocity field that is associated with a descending column of precipitation. Gust fronts produce a convergent pattern...
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Feedback from the users of commissioned TDWR systems
November 13, 1996
Conference Paper
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Workshop on Wind Shear and Wind Shear Alert Systems,. Oklahoma City, 13-15 November, 1996.
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The primary mission of the Terminal Doppler Weather Radar (TDWR) system is to detect thunderstorm-related wind shears and microbursts that are potentially hazardous to aircraft during landing and takeoff operations (e.g.. within three nautical miles on final approach and within two nautical miles on departure). The sources of these wind shears are microbursts and gust fronts. The mechanism by which these wind shears are provided to Air Traffic Controllers is the Ribbon Display Terminal. A secondary mission of the TDWR system is to support traffic management by the detection of precipitation and detection and forecast of gust-front-induced wind shift. This information is provided to the Air Traffic managers (Supervisors and Traffic Management Coordinators) via the Situation Display. The TDWR Program Office tasked Massachusetts Institute of Technology Lincoln Laboratory to survey the first five commissioned TDWR sites in order to assess how well the system was meeting its mission goals and to measure user (Air Traffic Controllers and air traffic managers such as Supervisors, Traffic Management Coordinators, etc.) benefits achieved through deployment of the TDWR. A list of candidate questions was prepared (Appendix A). Site visits commenced on 28 November 1995 and ended 25 January 1996. At each site, interviews began with a tour of the Air Traffic Control Tower. Questions regarding airport configuration, number of operations, and weather impact on operations were asked to provide a context for controller and traffic manager interviews. Users who acted in the capacity of controller were asked questions regarding their perceptions (If the accuracy of the Ribbon Display Terminal messages and their views of the impact (if any) on the effectiveness with which they performed their duties. Users who performed the duties of traffic managers (Controllers-in-Charge, Supervisors, Traffic Management Coordinators) were asked questions about the operational benefits of the products on the Situation Display. After the interview process was completed, the benefits estimates claimed for the TDWR system were revisited.
Summary
The primary mission of the Terminal Doppler Weather Radar (TDWR) system is to detect thunderstorm-related wind shears and microbursts that are potentially hazardous to aircraft during landing and takeoff operations (e.g.. within three nautical miles on final approach and within two nautical miles on departure). The sources of these wind...
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Assessment of the delay aversion benefits of the Airport Surveillence Radar (ASR) Weather Systems Processor (WSP)
July 2, 1996
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-249
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The Weather Systems Processor (WSP) modification to existing Airport Surveillance Radars (ASR-9) significantly enhances the functionality of the radar with respect to hazardous weather detection and tracking. Dedicated alphanumeric and color graphic displays alert controllers to hazardous wind shear conditions on the runways or final approach/initial departure flight corridors, show current location and anticipated movement of thunderstorm cells, and provide short-term forecasts of operationally significant wind shifts. Operational tests of a prototype WSP and related terminal area hazardous weather detection systems (the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS)) have shown that, in addition to reducing the risk of aircraft accidents associated with wind shear encounters on landing or takeoff, the information provided by these systems is a significant aid in terminal air traffic management during adverse weather. The resulting efficiency enhancements reduce delay and associated costs. This report assesses the magnitude of the delay aversion benefits that will be realized through national deployment of the WSP. These are quantified both in terms of aircraft delay-hour reductions and corresponding dollar benefits. The analysis indicates that these benefits will total approximately $18M per year given year 2000 expected traffic counts at the 34 planned WSP airports. This exceeds, in equivalent dollar value, the safety benefits realized through WSP deployment by a factor of approximately five.
Summary
The Weather Systems Processor (WSP) modification to existing Airport Surveillance Radars (ASR-9) significantly enhances the functionality of the radar with respect to hazardous weather detection and tracking. Dedicated alphanumeric and color graphic displays alert controllers to hazardous wind shear conditions on the runways or final approach/initial departure flight corridors, show...
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