Publications
Lessons learned designing an alternative CHI for en route air traffic control
April 27, 1999
Conference Paper
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Controller Centered HMI, 27-29 April 1999.
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Summary
MIT Lincoln Laboratory is supporting the FAA-sponsored effort to design an operationally suitable Computer Human Interface (CHI) for the recently upgraded En Route Air Traffic Control Centers. All centers will soon receive new control consoles with state-of-the-art 20 square (2K by 2K resolution) color displays (currently operating in Seattle as of January 1999). The future CHI is being modeled on Eurocontrol's Operational Display and Input Development (ODID) CHI, as requested by active controllers in the US. The ODID-like CHI, with its minimal information display and color coded guidance, provides increased efficiency and productivity through employment of a modern graphical user interface. Lessons learned during the on-going design process, including research of look and feel issues in conjunction with data analysis from controller-in-the-loop testing of a prototype ODID-like CHI will be discussed. The Laboratory plans to model the alternative ODID-like CHI on the best of the European ODID, Denmark Sweden Interface (DSI) and EATCHIP CHI features, while cognizant of the FAA?s DSR capabilities and limitations to support an improved user interface. Human factors issues need resolution to provide a consistent look and feel across the Free Flight Phase 1 products and platforms, the Center TRACON Automation System (CTAS) and the User Request Evaluation Tool (URET). MIT Lincoln Laboratory has built a CHI Requirements Engineering Model (CREM) to support controller-in-the-loop testing of the ODID-like CHI, validate CHI requirements and determine applicable standards for the design of an integrated CHI. The CREM provides a means to assess various CHI alternatives and the capability to iterate options with controller teams to address user concerns. Lessons learned from the ODID-like CHI specification process will also be shared.
Summary
MIT Lincoln Laboratory is supporting the FAA-sponsored effort to design an operationally suitable Computer Human Interface (CHI) for the recently upgraded En Route Air Traffic Control Centers. All centers will soon receive new control consoles with state-of-the-art 20 square (2K by 2K resolution) color displays (currently operating in Seattle as...
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A 9PAC system and application programmer's guide
February 16, 1999
Project Report
Published in:
MIT Lincoln Laboratory Report ATC-267
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The ASR-9 Processor Augmentation Card (9PAC) is a custom processing card that provides the ASR-9 system with increased beacon and radar processing performance. This paper describes the system and application software that executes on the prototype board, with an emphasis on the interaction between software modules. The application software on the 9PAC determines the position of radar and beacon target reports, replacing software that previously ran on the ASR-9 Array Signal Processor (ASP). The software is organized as a set of cooperating tasks executing under the control of a real-time operating system, PAC/OS, which provides all the services typical of an embedded kernel such as interrupt handling, pre-emptive multitasking, queues, signals, semaphores, mailboxes, and memory management. The deployment of 9PAC will occur in two phases. The Phase I application replaces only the beacon target detector (BTD) and radar/beacon target merge (MRG) functions of the ASP. The Phase I application consists of two executable programs since Phase I uses only two of the C44 processors on the 9PAC. One program, the housekeeping processor, is responsible for all I/O functions and performs the radar/beacon merge operation. The second progam, the beacon processor, is dedicated to processing the raw beacon replies and generating beacon targets which are then returned to the first processor for the merge operation. The Phase II application consists of three executable programs, one for each of the C44 processors on the 9PAC and performs much of the Phase I functionality and adds primary radar processing. The intent of this paper is to provide the 9PAC software support personnel with sufficient information to implement future enhancements without unintentionally compromising some aspect of the overall system.
Summary
The ASR-9 Processor Augmentation Card (9PAC) is a custom processing card that provides the ASR-9 system with increased beacon and radar processing performance. This paper describes the system and application software that executes on the prototype board, with an emphasis on the interaction between software modules. The application software on...
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A case study of mid-level turbulence outside regions of active convection
January 10, 1999
Conference Paper
Published in:
8th Conf. on Aviation, Range, and Aerospace Meteorology (ARAM), 10-15 January 1999.
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Historically, the principal focus of research on clear-air turbulence of concern to aircraft has been on jet stream and mountain (orographic) induced turbulence. Relatively little research has focused on the turbulence hazard outside of, but in the vicinity of, convective storms, known as Convective Induced Turbulence (CIN). In this paper, we present our analysis requested by the National Transportation Safety Board (NTSB) of the meteorological conditions leading to severe turbulence and near loss of flight control of a commercial passenger jet and find that they fall into the CIN category. On 12 May 1997, at approximately 1929 UT, an American Airlines Airbus A300 en route from Boston, MA to Miami, FL encountered severe turbulence off the coast of West Palm Beach, FL. Near the time of the incident the crew had been directed to hold at 16,000 ft because of weather and traffic near Miami International. While approaching the holding position, the aircraft experienced severe turbulence and dropped over 3000 vertical feet in 30 seconds. A detailed postevent analysis by the NTSB failed to find any causal evidence for the turbulence and no single sensor, data set, or pilot report examined by the NTSB provided justification for the magnitude of the event. Our independent analysis of the incident was conducted primarily using recorded Miami WSR-88D base data. The analysis revealed a small-scale vertical shear zone may have emanated from a thunderstorm upstream of the Airbus. Animated cross-sectional images also suggested that a rotor may have propagated with the mean wind and intersected the flight path at the time the severe turbulence was reported. This paper will focus on meteorological conditions that led to the upset and provide evidence for several possible causes of the turbulence.
Summary
Historically, the principal focus of research on clear-air turbulence of concern to aircraft has been on jet stream and mountain (orographic) induced turbulence. Relatively little research has focused on the turbulence hazard outside of, but in the vicinity of, convective storms, known as Convective Induced Turbulence (CIN). In this paper...
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The thunderstorm penetration/deviation decision in the terminal area
January 10, 1999
Conference Paper
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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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A refinement of thunderstorm climatology for the terminal radar control airspace
January 10, 1999
Conference Paper
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8th Conf. on Aviation, Range and Aerospace Meteorology, ARAM, 10-15 January 1999.
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Convective storms pose a significant threat to aviation safety, and often result in substantial fl ight delays for the commercial aviation industry. The overall impact of these storms is typically based on thunderstorm climatologies and are often one of the factors used in decisions by the US government regarding the operational benefits and allocation of its weather surveillance resources. These climatologies are based on the average number of days that a thunderstorm is observed at a particular airport. Due to the nature of the criteria used to identify a thunderstorm, the climatological statistics often do not accurately represent the number of thunderstorms that impact an airport's operations. The present study utilizes data from the Dallas Ft. Worth International Airport (DFW) and the Orlando International Airport (MCO) to identify deficiencies in the climatological data as it applies to aviation applications. A spatially representative climatology is presented as a more accurate climatology for use in evaluating the impact of convection on an airport's operations. This type of climatological estimate of thunderstorm frequency significantly increases the estimated number of thunderstorms impacting an airport and their associated costs.
Summary
Convective storms pose a significant threat to aviation safety, and often result in substantial fl ight delays for the commercial aviation industry. The overall impact of these storms is typically based on thunderstorm climatologies and are often one of the factors used in decisions by the US government regarding the...
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Addressing the weather delay problems of the New York City airports with the Integrated Terminal Weather System
January 10, 1999
Conference Paper
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8th Conf. on Aviation, Range, and Aerospace Meteorology, 10-15 1999.
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The three major New York City (NYC) air carrier airports (Kennedy, LaGuardia, Newark) currently experience high delays due to adverse terminal weather, both in an absolute sense and relative to other major airport complexes. Significantly expanding the NYC airports (e.g., by adding new runways) to reduce delays is not feasible. One alternative is to provide aviation weather decision support systems to air traffic, airline, and airport operations personnel to help them operate more safely and effectively with the existing runway/taxiway complexes. Under an innovative partnership between the Port Authority of New York and New Jersey and the Federal Aviation Administration (FAA), Massachusetts Institute of Technology, Lincoln Laboratory has installed and is currently operating a functional prototype Integrated Terminal Weather System (ITWS) to conduct research on improving the safety and efficiency of operations at the NYC airports during adverse weather. The New York terminal area provides a stringent test of the ITWS ability to safely reduce delays due to both the meteorology and the operational usage challenges not found at the earlier ITWS test locations of Orlando, Memphis, and Dallas. In this paper, we describe key features of the New York terminal environment and the ITWS prototype, the initial experience in addressing the meteorological and operational usage challenges of the New York terminal area, and describe plans for the coming years.
Summary
The three major New York City (NYC) air carrier airports (Kennedy, LaGuardia, Newark) currently experience high delays due to adverse terminal weather, both in an absolute sense and relative to other major airport complexes. Significantly expanding the NYC airports (e.g., by adding new runways) to reduce delays is not feasible...
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Study of Network Expansion LLWAS (LLWAS-NE) fault identification and system warning optimization through joint use of LLWAS-NE and TDWR data
January 10, 1999
Conference Paper
Published in:
8th Conf. on Aviation, Range, and Aerospace Meteorology (ARAM), 10-15 January 1999.
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Low level wind shear has been identified as an aviation hazard which has caused or contributed to a significant number of aircraft accidents (Soffer, 1990). To protect aircraft from hazardous wind shear, the Federal Aviation Administration (FAA) developed a system called the Low Level Wind Shear Alert System (LLWAS), containing a collection of anemometers as well as data processing logic (Wilson and Gramzow, 1991). The LLWAS has undergone several advancements in both design and algorithmic computation. The latest deployment, known as the Network Expansion Low Level Wind Shear Alert System (LLWAS-NE), consists of additional sensors to the original LLWAS network, providing better coverage of the airfield. In addition, the LLWAS-NE is capable of providing runway-oriented wind shear and microburst alerts with loss and gain values. The alerts from LLWAS-NE will be integrated with those from the Terminal Doppler Weather Radar (TDWR) and the Integrated Terminal Weather System (ITWS) at locations where all systems are available (Cole, 1992; Cole and Todd, 1994). An analysis was undertaken at Orlando (MCO) and Dallas/Ft. Worth (DFW) International Airports to assess the accuracy of wind shear alerts produced by LLWAS-NE and the TDWR/LLWASNE integration algorithm. Identifying improvements that can be made to either system is important, as LLWAS-NE alert information is anticipated to be integrated with ITWS in an ITWS/LLWAS-NE integration algorithm. As currently specified, the ITWS/LLWAS-NE integration algorithm will work the same as the TDWR/LLWAS-NE version. The ITWS/LLWAS-NE algorithm is an area where additional work is necessary to ascertain if the integration parameters should be modified to account for performance differences between the ITWS and TDWR algorithms. We suggest that ongoing assessment of the LLWAS-NE should use both LLWAS-NE data and TDWR base data, when possible. Comparing both data sets also will facilitate optimization of LLWAS-NE parameters used in the computation of the alerts.
Summary
Low level wind shear has been identified as an aviation hazard which has caused or contributed to a significant number of aircraft accidents (Soffer, 1990). To protect aircraft from hazardous wind shear, the Federal Aviation Administration (FAA) developed a system called the Low Level Wind Shear Alert System (LLWAS), containing...
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Aviation user needs for convective weather forecasts
January 10, 1999
Conference Paper
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8th Conf. on Aviation, Range, and Aerospace Meteorology (ARAM), 10-15 January 1999.
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The prediction of convective weather is very important to aviation, since almost half of the serious delay at major airports in the warm season is caused by thunderstorms. The need for accurate 0-6 hr forecasts for NAS users has been the subject of extensive publications, forums, and advisory committees in the aviation weather community over the last several years (Wolfson, et al; 1997). The Convective Weather Product Development Team (PDT), a core team of scientists and engineers from NCAR, NSSL, and MIT LL, was formed in 1996 as part of the reorganization of the FAA Aviation Weather Research Program. The team is developing convective weather forecast algorithms that produce operationally useful products for both the terminal area and enroute airspace. The products are designed to meet specific users' air traffic planning and safety needs. Before major algorithm development began, PDT members visited terminal and enroute Air Traffic (AT) personnel and airline dispatchers to understand the forecast products that were currently available to them and their needs for a near future product. Also, in order to reach the pilot community, a pilot survey about existing convective weather information and how to improve it, was created and distributed at the OshKosh Fly-In in August of 1997. This needs assessment took advantage of interviewees that had extensively used state-of-the-art weather information products (ITWS) in an operational setting for years. Their requirements, based on personal experiences with operational products during convective weather events, were less stringent than those reported in the recent requirements document pertaining to ARTCC TMUs (Browne, et al; 1999). The results of these investigations were used in the creation of the DFW Terminal Convective Weather Forecast (TCWF) product and the National Convective Weather Forecast (NCWF) products that were demonstrated throughout the summer of 1998 (Hallowell, et al; 1999; Mueller, et al; 1999). These demonstrations also provided additional insight into user needs. In this paper we describe Air Traffic users and their specific responsibilities. We then summarize AT and airline needs based on interviews conducted in 1997 and 1998. Information on pilots' needs for convective weather information is presented at the end.
Summary
The prediction of convective weather is very important to aviation, since almost half of the serious delay at major airports in the warm season is caused by thunderstorms. The need for accurate 0-6 hr forecasts for NAS users has been the subject of extensive publications, forums, and advisory committees in...
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Thunderstorm induced gravity waves as a potential hazard to commercial aircraft
January 10, 1999
Conference Paper
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8th Conf. on Aviation, Range and Aerospace Meteorology, ARAM, 10-15 January 1999.
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Under certain atmospheric conditions, thunderstorm development can induce a phenomenon known as gravity waves (i.e., buoyancy or density waves). These waves are characterized by alternating regions of convergence and divergence over a relatively short distance. Such aerodynamic shear can become hazardous to air traffic if the shear contained within the waves surpasses the threshold for air traffic safety. Gravity waves are particularly hazardous because they develop in seemingly benign weather surrounding the parent thunderstorm and in many cases are not associated with any visual storm feature. Several cases have been studied in which commercial aircraft have encountered gravity waves and have been adversely affected by their encounters. The purpose of this study is to show how gravity waves can have a detrimental effect on aircraft in flight, how gravity waves can be detected, and that need for a detection algorithm exists. With the development of the National Weather Service's Next Generation Radar (WSR–88D NEXRAD) and the Federal Aviation Administration's Terminal Doppler Weather Radar (TDWR), the ability to detect gravity waves exists near many of America's major airports. Since gravity waves are a low–level phenomenon (generally below 2 km), their presence should be of interest to aircraft in the takeoff and landing stages of flight. During operations at Lincoln Laboratory's Integrated Terminal Weather System (ITWS) prototype field site in Dallas, there have been at least two incidents in which commercial aircraft experienced wind shear of at least 40 knots on takeoff, possibly caused by single or multiple gravity wave bands. This study will look at 57 cases of gravity wave formation within the terminal areas of Dallas–Ft. Worth International, Memphis International, and Orlando International airports. Statistics will be compiled to determine the frequency and severity of the gravity waves as well as their duration. The study will include Pilot Reports (PIREPS) from a few of these cases in which aircraft experienced wind shear due to suspected encounters with gravity waves. It is the hope of the author that this study will lead to the development of a detection algorithm that will increase the safety of America's commercial air traffic.
Summary
Under certain atmospheric conditions, thunderstorm development can induce a phenomenon known as gravity waves (i.e., buoyancy or density waves). These waves are characterized by alternating regions of convergence and divergence over a relatively short distance. Such aerodynamic shear can become hazardous to air traffic if the shear contained within the...
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Nowcasting requirements for the aircraft vortex spacing system (AVOSS)
January 10, 1999
Conference Paper
Published in:
8th Conf. on Aviation, Range, and Aerospace Meteorology, 10-15 Jan. 1999, pp. 340-344.
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Aircraft wake vortices are counter-rotating tubes of air that are generated from aircraft as a consequence of the lift on the aircraft. The safety concern of wake vortices, particularly when lighter aircraft are following heavy planes, has caused the Federal Aviation Administration (FAA) to enact minimum separation requirements during the arrival phase of flight. These separation standards are imposed at the arrival threshold during Instrument Flight Rules (IFR) and are a significant constraint on arrival capacity at the largest U.S. airports. Any movement toward increasing air traffic efficiency, such as concepts toward free-flight, must address increasing runway capacity if they are to be fully effective. Decades of past wake vortex measurements clearly show that current wake vortex separations are overconservative in many weather conditions, and that adapting the separations to the current weather state could safely reduce these separations...This paper describes the known meteorological influences on vortex behavior and gives an overview of AVOSS. Airport climatology is studied to discuss the prevalence of conditions that are conducive to capacity increases with AVOSS technology. Finally, additional constraints on AVOSS nowcasts are discussed.
Summary
Aircraft wake vortices are counter-rotating tubes of air that are generated from aircraft as a consequence of the lift on the aircraft. The safety concern of wake vortices, particularly when lighter aircraft are following heavy planes, has caused the Federal Aviation Administration (FAA) to enact minimum separation requirements during the...
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