Publications
Corridor Integrated Weather System
June 1, 2006
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 16, No. 1, June 2006, pp. 59-80.
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Summary
Flight delays are now a major problem in the U.S. National Airspace System. A significant fraction of these delays are caused by reductions in en route capacity due to severe convective weather. The Corridor Integrated Weather System (CIWS) is a fully automated weather analysis and forecasting system designed to support the development and execution of convective weather impact mitigation plans for congested en route airspace. The CIWS combines data from dozens of weather radars with satellite data, surface observations, and numerical weather models to dramatically improve the accuracy and timeliness of the storm severity information and to provide state-of-the-art, accurate, automated, high-resolution, animated three-dimensional forecasts of storms (including explicit detection of storm growth and decay). Real-time observations of the Federal Aviation Administration (FAA) decision making process during convective weather at Air Route Traffic Control Centers in the Midwest and Northeast have shown that the CIWS enables the FAA users to achieve more efficient tactical use of the airspace, reduce traffic manager workload, and significantly reduce delays. A real-time data-fusion architecture to assist in national deployment of CIWS is under development, and the CIWS products are being used in integrated air traffic management decision support systems.
Summary
Flight delays are now a major problem in the U.S. National Airspace System. A significant fraction of these delays are caused by reductions in en route capacity due to severe convective weather. The Corridor Integrated Weather System (CIWS) is a fully automated weather analysis and forecasting system designed to support...
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Integrating advanced weather forecast technologies into air traffic management decision support
June 1, 2006
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 16, No. 1, June 2006, pp. 81-96.
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Explicit integration of aviation weather forecasts with the National Airspace System (NAS) structure is needed to improve the development and execution of operationally effective weather impact mitigation plans and has become increasingly important due to NAS congestion and associated increases in delay. This article considers several contemporary weather-air traffic management (ATM) integration applications: the use of probabilistic forecasts of visibility at San Francisco, the Route Availability Planning Tool to facilitate departures from the New York airports during thunderstorms, the estimation of en route capacity in convective weather, and the application of mixed-integer optimization techniques to air traffic management when the en route and terminal capacities are varying with time because of convective weather impacts. Our operational experience at San Francisco and New York coupled with very promising initial results of traffic flow optimizations suggests that weather-ATM integrated systems warrant significant research and development investment. However, they will need to be refined through rapid prototyping at facilities with supportive operational users.
Summary
Explicit integration of aviation weather forecasts with the National Airspace System (NAS) structure is needed to improve the development and execution of operationally effective weather impact mitigation plans and has become increasingly important due to NAS congestion and associated increases in delay. This article considers several contemporary weather-air traffic management...
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Operational evaluation of runway status lights
June 1, 2006
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 16, No. 1, June 2006, pp. 123-146.
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To maintain safe separation of aircraft on the airport surface, air traffic controllers issue verbal clearances to pilots to sequence aircraft arrivals, departures, and runway crossings. Although controllers and pilots work together successfully most of the time, mistakes do occasionally happen, causing several hundred runway incursions a year and, less frequently, near misses and collisions in the United States. With this rate of incursions, it is imperative to have an independent warning system as a backup to the current system. Runway status lights, a system of automated, surveillance-driven stoplights, have been designed to provide this backup function. The lights are installed at runway-taxiway intersections and at departure points along the runways. They provide a clear signal to pilots crossing or departing from a runway, warning them of potential conflicts with traffic already on the runway. Existing FAA-installed radar surveillance is coupled with Lincoln Laboratory-developed algorithms to generate the light commands. To be compatible with operations at the busiest airports, the algorithms must drive the lights such that during normal operations pilots will almost never encounter a red light when it is safe to cross or depart from a runway. A minimal error rate must be maintained even in the face of inevitable imperfections in the surveillance system used to drive the safety logic. A prototype runway status light system has been designed at Lincoln Laboratory and installed at the Dallas/Fort Worth International Airport, where Laboratory personnel have worked with the FAA to complete an operational evaluation of the system, demonstrating the feasibility of runway status lights in the challenging, complex environment of one of the world's busiest airports.
Summary
To maintain safe separation of aircraft on the airport surface, air traffic controllers issue verbal clearances to pilots to sequence aircraft arrivals, departures, and runway crossings. Although controllers and pilots work together successfully most of the time, mistakes do occasionally happen, causing several hundred runway incursions a year and, less...
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Surveillance accuracy requirements in support of separation services
June 1, 2006
Journal Article
Published in:
Lincoln Laboratory Journal, Vol. 16, No. 1, June 2006, pp. 97-122.
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The Federal Aviation Administration is modernizing the Air Traffic Control system to improve flight efficiency, to increase airspace capacity, to reduce flight delays, and to control operating costs as the demand for air travel continues to grow. Promising new surveillance technologies such as Automatic Dependent Surveillance Broadcast and multisensor track fusion offer the potential to augment the ground-based surveillance and controller-display systems by providing more timely and complete information about aircraft. The resulting improvement in surveillance accuracy may potentially allow the expanded use of the minimum safe-separation distance between aircraft. However, these new technologies cannot be introduced with today's radar-separation standards, because they assume surveillance will be provided only through radar technology. In this article, we review the background of aircraft surveillance and the establishment of radar separation standards. The required surveillance accuracy to safely support aircraft separation with National Airspace System technologies is then derived from currently widely used surveillance systems. We end with flight test validation of the derived results, which can be used to evaluate new technologies.
Summary
The Federal Aviation Administration is modernizing the Air Traffic Control system to improve flight efficiency, to increase airspace capacity, to reduce flight delays, and to control operating costs as the demand for air travel continues to grow. Promising new surveillance technologies such as Automatic Dependent Surveillance Broadcast and multisensor track...
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Evaluation of proposed changes to the ACAS modified tau calculation
May 1, 2006
Conference Paper
Published in:
Int. Civil Aviation Organization Aeronautical Surveillance Panel Working Group, 1 May 2006.
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Modified tau is a parameter computed by ACAS to estimate the earliest time at which a collision could occur should an intruder aircraft accelerate toward the own aircraft. A concern with the modified tau calculation has been raised in a class of encounters where intruders are already close and converging slowly. In these problem cases, ACAS may induce a Near Mid-Air Collision by generating RAs with inappropriate timing or initial sense or failing to reverse sense when necessary. Performance in some problem encounters is greatly improved when using several proposed changes to the modified tau equations. These changes are outside CP112E, which focuses only on RA reversals. Although changes to modified tau resolve some problem encounters, aggregate risk-ratio results do not support implementing the existing proposals. There remains a concern about mid-air collision risk due to vulnerability in the existing modified tau equations, yet a robust solution to the problem has not been developed.
Summary
Modified tau is a parameter computed by ACAS to estimate the earliest time at which a collision could occur should an intruder aircraft accelerate toward the own aircraft. A concern with the modified tau calculation has been raised in a class of encounters where intruders are already close and converging...
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Update on the analysis of ACAS performance on Global Hawk
May 1, 2006
Conference Paper
Published in:
Int. Civil Aviation Organization Aeronautical Surveillance Panel Working Group, 1 May 2006.
Summary
Initial results are presented from a Lincoln Laboratory study of ACAS performance on the Global Hawk UAV. The study has been applying the process outlined in the ICAO ACAS Manual which involves developing UAV airspace encounter models and running fast-time Monte Carlo simulations of encounters. ACAS performance was examined in conventional aircraft vs. conventional aircraft, conventional aircraft vs. non-ACAS Global Hawk, and conventional aircraft vs. ACAS-equipped Global Hawk cases. The existing ICAO and ACASA encounter models were modified to reflect Global Hawk flight characteristics. ACAS performance on Global Hawk was also assessed parametrically across reaction latencies from 0 - 20 s. Global Hawk flight characteristics were shown to have a small but measurable negative impact on collision risk. Assuming no system failures or visual acquisition effects occur, performance with ACAS on Global Hawk is significantly better than without ACAS if response latencies (from the moment an RA is issued to the moment maneuvering begins) are less than 10 s. Performance drops off rapidly at latencies greater than 10 s. The needs for improved airspace models and a more in-depth study of the interaction between visual acquisition and ACAS are noted.
Summary
Initial results are presented from a Lincoln Laboratory study of ACAS performance on the Global Hawk UAV. The study has been applying the process outlined in the ICAO ACAS Manual which involves developing UAV airspace encounter models and running fast-time Monte Carlo simulations of encounters. ACAS performance was examined in...
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Multifunction phased array radar pulse compression limits
April 25, 2006
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-327
Summary
An active phased array radar with distributed low-peak-power transmit modules requires pulse compression to provide high sensitivity and fine range resolution. A long transmitted pulse, however, has accompanying problems such as a near-range blind zone for the transmitting channel and a loss of other gate data (dead gates) in other channels for a multichannel system. In this report the trade-off between the benefits and costs of pulse compression (lengthening) for multifunction phased array radars (MPARs) are analyzed. Specific results are presented for a three-channel MPAR and a two-channel terminal-area MPAR (TMPAR) that have been proposed as replacement systems for current U.S. civil-sector aircraft anad weather surveillance radar systems. The recommended maximum compression ratio is 130 ofr the MPAR and 80 for the TMPAR. The results are independent of radar peak power and antenna gain, and represent upper bounds. Acutal pulse compression ratios that would be employed are likely to be somewhat less tha these values, based on fulfilling specific sensitivity and scan-time requirements with specific radar physical parameters.
Summary
An active phased array radar with distributed low-peak-power transmit modules requires pulse compression to provide high sensitivity and fine range resolution. A long transmitted pulse, however, has accompanying problems such as a near-range blind zone for the transmitting channel and a loss of other gate data (dead gates) in other...
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An exploratory study of modeling enroute pilot convective storm flight deviation behavior
February 2, 2006
Conference Paper
Published in:
12th Conf. on Aviation Range and Aerospace Meteorology, 2 February 2006.
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The optimization of traffic flows in highly congested airspace with rapidly varying convective weather is an extremely complex problem. Aviation weather systems such as the Corridor Integrated Weather System (CIWS) provide weather products and forecasts that aid en route traffic managers in making tactical routing decisions in convective weather, but traffic managers need automated decision support systems that integrate flight information, trajectory models and convective weather products to assist in developing and executing convective weather mitigation plans. A key element of an integrated ATM/wx decision support system is the ability to predict automatically when pilots in en route airspace will choose to deviate around convective weather and how far they will deviate from their planned path. The FAA Aeronautical Information Manual suggests that pilots avoid thunderstorms characterized by intense radar echo in en route airspace by at least 20 nautical miles (40 km). However, a recent study (Rhoda, et. al., 2002) of pilot behavior in both terminal and en route airspace near Memphis, TN suggested that pilots fly over high reflectivity cells in en route airspace and penetrate lower cells whose reflectivity is less than VIP level 3. Recent operational experience with CIWS supports the Rhoda findings (Robinson, et. al., 2004). This study presents initial results of research to develop a quantitative model that would predict when a pilot will deviate around convective weather in en route airspace. It also presents statistics that characterize hazard avoidance distances and weather penetrations. The results are based on the analysis of more than 800 flight trajectories through two Air Traffic Control (ATC) en route super-sectors (geographical regions that include several adjacent ATC en route sectors) on five days in the summer of 2003. One supersector from the Indianapolis Air Route Traffic Control Center (ZID ARTCC) encompassed southern Indiana, southwestern Ohio and northern Kentucky (ZID); the other, located in the Cleveland ARTCC (ZOB), included northern Ohio, along the southern shore of Lake Erie (ZOB). The weather encountered along the flight trajectories was characterized by the CIWS high-resolution precipitation (VIL) and radar echo tops mosaic (Klingle-Wilson and Evans, 2005) and NLDN lightning products. Flight trajectories were taken from the Enhanced Traffic Management System (ETMS).
Summary
The optimization of traffic flows in highly congested airspace with rapidly varying convective weather is an extremely complex problem. Aviation weather systems such as the Corridor Integrated Weather System (CIWS) provide weather products and forecasts that aid en route traffic managers in making tactical routing decisions in convective weather, but...
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A "demand pull" approach to short term forecast development and testing
January 30, 2006
Conference Paper
Published in:
86th AMS Annual Mtg., 1st Symp. on Policy Research, January 2006.
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We discuss two specific short term aviation weather forecasts - convection and ceiling - to illustrate the issues that arise in thinking about the overall decision support system, key users, and training needed to generate benefits. We also consider reducing weather-related fatal accidents. Second, what is the preexisting "baseline" of aviation forecasts/decision processes that already exists to address the user needs? In most cases, there are already various weather information sources that can be viewed as providing a short term forecast (e.g., a Center Weather Service Unit (CWSU) meteorologist, persistence, or animation loops of the past weather). How well do we understand how the "baseline" forecast and the associated user decision support system operate? How will the new forecast and its decision support compare? What are the training implications if the new forecast is rather different than the "baseline"? Third, how will we measure the change in system performance? For example, if the new forecast claims to help reduce delays and/or accidents, how will one address differences in the weather between the "before" and "after" time periods? How will one determine whether the new forecast is in fact the key factor, if there was a change? The paper concludes with some suggestions for development and testing of new aviation forecasts to improve safety and reduce delays.
Summary
We discuss two specific short term aviation weather forecasts - convection and ceiling - to illustrate the issues that arise in thinking about the overall decision support system, key users, and training needed to generate benefits. We also consider reducing weather-related fatal accidents. Second, what is the preexisting "baseline" of...
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Upgrade and technology transfer of the San Francisco Marine Stratus Forecast system to the National Weather Service
January 30, 2006
Conference Paper
Published in:
86th AMS Annual Mtg., 1st Symp. on Policy Research, January 2006.
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The local airspace surrounding the San Francisco International Airport (SFO) is prone to regular occurrences of low ceiling conditions from May through October due to the intrusion of marine stratus along the Pacific coast. The low cloud conditions prohibit dual parallel landings of aircraft to the airport's closely spaced parallel runways, thus effectively reducing the arrival capacity by a factor of two. The behavior of marine stratus evolves on a daily cycle, filling the San Francisco Bay region overnight, and dissipating during the morning. Often the low ceiling conditions persist throughout the morning hours and interfere with the high rate of air traffic scheduled into SFO from mid-morning to early afternoon. The result is a substantial number of delayed flights into the airport and a negative impact on the National Air Space (NAS). Air traffic managers face a continual challenge of anticipating available operating capacity so that the demand of incoming planes can be metered to match the availability of arrival slots.
Summary
The local airspace surrounding the San Francisco International Airport (SFO) is prone to regular occurrences of low ceiling conditions from May through October due to the intrusion of marine stratus along the Pacific coast. The low cloud conditions prohibit dual parallel landings of aircraft to the airport's closely spaced parallel...
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