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Applicability and surrogacy of uncorrelated airspace encounter models at low altitudes
July 1, 2021
Journal Article
Published in:
J. Air Transport., Vol. 29, No. 3, July-September 2021, pp. 137-41.
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Summary
National Airspace System (NAS) is a complex and evolving system that enables safe and efficient aviation. Advanced air mobility concepts and new airspace entrants, such as unmanned aircraft, must integrate into the NAS without degrading overall safety or efficiency. For instance, regulations, standards, and systems are required to mitigate the risk of a midair collision between aircraft. Monte Carlo simulations have been a foundational capability for decades to develop, assess, and certify aircraft conflict avoidance systems. These are often validated through human-in-the-loop experiments and flight testing. For example, an update to the Traffic Collision Avoidance System (TCAS) mandated for manned aircraft was validated in part using this approach [1]. For many aviation safety studies, manned aircraft behavior is represented using the MIT Lincoln Laboratory statistical encounter models [2–5]. The original models [2–4] were developed from 2008 to 2013 to support safety simulations for altitudes above 500 feet above ground level (AGL). However, these models were not sufficient to assess the safety of smaller unmanned aerial systems (UAS) operations below 500 feet AGL and fully support the ASTM F38 and RTCA SC-147 standards efforts. In response, newer models [5–7] with altitude floors below 500 feet AGL have been in development since 2018. Many of the models assume that aircraft behavior is uncorrelated and not dependent on air traffic services or nearby aircraft. The models were trained using observations of cooperative aircraft equipped with transponders, but data sources and assumptions vary. The newer models are organized by aircraft types of fixed-wing multi-engine, fixed-wing single engine, and rotorcraft, whereas the original models do not consider aircraft type. Our research objective was to compare the various uncorrelated models of conventional aircraft and identify how the models differ. Particularly if models of rotorcraft were sufficiently different from models of fixed-wing aircraft to require type-specific models. The scope of this work was limited to altitudes below 5000 feet AGL, the expected altitude ceiling for many new airspace entrants. The scope was also informed by the Federal Aviation Administration (FAA) UAS Integration Office and Alliance for System Safety of UAS through Research Excellence (ASSURE). The primary contribution is guidance on which uncorrelated models to leverage when evaluating the performance of a collision avoidance system designed for low-altitude operations, such as prescribed by the ASTM F3442 detect and avoid standard for smaller UAS [8]. We also address which models can be surrogates for non-cooperative aircraft without transponders. All models and software used are publicly available under open source licenses [9].
Summary
National Airspace System (NAS) is a complex and evolving system that enables safe and efficient aviation. Advanced air mobility concepts and new airspace entrants, such as unmanned aircraft, must integrate into the NAS without degrading overall safety or efficiency. For instance, regulations, standards, and systems are required to mitigate the...
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Forecast confidence measures for deterministic storm-scale aviation forecasts
February 5, 2014
Conference Paper
Published in:
4th Aviation, Range, and Aerospace Meteorology Special Symp., 2-6 February 2014.
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Deterministic storm-scale weather forecasts, such as those generated from the FAA's 0-8 hour CoSPA system, are highly valuable to aviation traffic managers. They provide forecasted characteristics of storm structure, strength, orientation, and coverage that are very helpful for strategic planning purposes in the National Airspace System (NAS). However, these deterministic weather forecasts contain inherent uncertainty that varies with the general weather scenario at the forecast issue time, the predicted storm type, and the forecast time horizon. This uncertainty can cause large changes in the forecast from update to update, thereby eroding user confidence and ultimately reducing the forecast's effectiveness in the decision-making process. Deterministic forecasts generally lack objective measures of this uncertainty, making it very difficult for users of the forecast to know how much confidence to have in the forecast during their decision-making process. This presentation will describe a methodology to provide measures of confidence for deterministic storm-scale forecasts. The method inputs several characteristics of the current and historical weather forecasts, such as spatial scale, intensity, weather type, orientation, permeability, and run-to-run variability of the forecasts, into a statistical model to provide a measure of confidence in a forecasted quantity. In this work, the forecasted quantity is aircraft blockage associated with key high-impact Flow Constrained Areas (FCAs) in the NAS. The results from the method, which will also be presented, provide the user with a measure of forecast confidence in several blockage categories (none, low, medium, and high) associated with the FCAs. This measure of forecast confidence is geared toward helping en-route strategic planners in the NAS make better use of deterministic storm-scale weather forecasts for air traffic management.
Summary
Deterministic storm-scale weather forecasts, such as those generated from the FAA's 0-8 hour CoSPA system, are highly valuable to aviation traffic managers. They provide forecasted characteristics of storm structure, strength, orientation, and coverage that are very helpful for strategic planning purposes in the National Airspace System (NAS). However, these deterministic...
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Sector workload model for benefits analysis and convective weather capacity prediction
June 10, 2013
Conference Paper
Published in:
10th USA/Europe Air Traffic Management Research and Development Sem., ATM 2013, 10-13 June 2013.
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En route sector capacity is determined mainly by controller workload. The operational capacity model used by the Federal Aviation Administration (FAA) provides traffic alert thresholds based entirely on hand-off workload. Its estimates are accurate for most sectors. However, it tends to over-estimate capacity in both small and large sectors because it does not account for conflicts and recurring tasks. Because of those omissions it cannot be used for accurate benefits analysis of workload-reduction initiatives, nor can it be extended to estimate capacity when hazardous weather increases the intensity of all workload types. We have previously reported on an improved model that accounts for all workload types and can be extended to handle hazardous weather. In this paper we present the results of a recent regression of that model using an extensive database of peak traffic counts for all United States en route sectors. The resulting fit quality confirms the workload basis of en route capacity. Because the model has excess degrees of freedom, the regression process returns multiple parameter combinations with nearly identical sector capacities. We analyze the impact of this ambiguity when using the model to quantify the benefits of workload reduction proposals. We also describe recent modifications to the weather-impacted version of the model to provide a more stable normalized capacity measure. We conclude with an illustration of its potential application to operational sector capacity forecasts in hazardous weather.
Summary
En route sector capacity is determined mainly by controller workload. The operational capacity model used by the Federal Aviation Administration (FAA) provides traffic alert thresholds based entirely on hand-off workload. Its estimates are accurate for most sectors. However, it tends to over-estimate capacity in both small and large sectors because...
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Air traffic decision analysis during convective weather events in arrival airspace
September 17, 2012
Conference Paper
Published in:
12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conf. and 14th AIAA/ISSM, 17-19 September 2012.
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Decision making during convective weather events in the terminal area is shared among pilots and air traffic management, where uninformed decisions can result in wide-spread cascading delays with high-level impacts. Future traffic management systems capable of predicting terminal impacts will mitigate these unnecessary delays; however in order to realize this vision, it is important to understand the decision mechanisms behind convective weather avoidance. This paper utilizes an arrival adaptation of the Convective Weather Avoidance Model (CWAM) to investigate the catalysts for arrival traffic management decision making. The analysis is broken down by category of terminal airspace structure in addition to the type of decision. The results show that pilot behavior in convective weather is heavily dependent on the terminal airspace structure. In addition, pilot and air traffic management decisions in convective weather can be discriminated with large-scale weather features.
Summary
Decision making during convective weather events in the terminal area is shared among pilots and air traffic management, where uninformed decisions can result in wide-spread cascading delays with high-level impacts. Future traffic management systems capable of predicting terminal impacts will mitigate these unnecessary delays; however in order to realize this...
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Evaluation of the Convective Weather Avoidance Model for arrival traffic
September 17, 2012
Conference Paper
Published in:
12th AIAA Aviation Technology, Integration, and Operations (ATIO) Conf. and 14th AIAA/ISSM, 17-19 September 2012.
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The effective management of traffic flows during convective weather events in congested air space requires decision support tools that can translate weather information into anticipated air traffic operational impact. In recent years, MIT Lincoln Laboratory has been maturing the Convective Weather Avoidance Model (CWAM) to correlate pilot behavior in the enroute airspace with observable weather parameters from convective weather forecast systems. This paper evaluates the adaptation of the CWAM to terminal airspace with a focus on arrival decision making. The model is trained on data from five days of terminal convective weather impacts. The performance of the model is evaluated on an independent dataset consisting of six days of convective weather over a variety of terminal areas. Model performance in different terminal areas is discussed and the sensitivity of prediction accuracy to weather forecast horizon is presented.
Summary
The effective management of traffic flows during convective weather events in congested air space requires decision support tools that can translate weather information into anticipated air traffic operational impact. In recent years, MIT Lincoln Laboratory has been maturing the Convective Weather Avoidance Model (CWAM) to correlate pilot behavior in the...
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Estimation of New York departure fix capacities in fair and convective weather
January 23, 2012
Conference Paper
Published in:
3rd Aviation, Range, and Aerospace Meteorology, 23 January 2012.
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When convective weather impacts the New York Metro airspace, traffic managers may employ several tactics to mitigate weather impacts and maintain manageable and efficient flow of traffic to and from the airports. These tactics, which include maneuvering individual flights through weather, merging and redirecting traffic flows to avoid storms, and rerouting traffic from blocked routes onto unimpacted or less-impacted routes, all affect the capacity of the affected airspace resources (departure fixes, routes, or gates). Furthermore, the location of the weather impacts can have a great influence on the amount of leeway that traffic managers have in applying these tactics. In New York, departure fixes, the gateways to en route airspace where departure traffic from several metroplex airports are merged onto en route airways, are particularly critical. When congestion (volume of traffic in excess of capacity) occurs near departure fixes as a result of weather impacts, traffic managers must resort to airborne holding or unplanned departure stops to quickly reduce traffic over the fix to manageable levels. Nonetheless, when convective weather impacts densely packed and busy metroplex airspaces, it is inevitable that traffic will need to use impacted departure fixes and routes to keep delays in check. For this reason, predictions of the weather-impacted capacity of critical airspace resources like departure fixes that are based in the reality of commonly used impact mitigation tactics, are needed to help traffic managers anticipate and avoid disruptive congestion at weather-impacted departure fixes. The Route Availability Planning Tool (RAPT) is a departure management decision support tool that has been used in the New York operations since 2003. It predicts the weather impact on departure fixes and routes based on departure times. RAPT assigns a departure status (RED, YELLOW, or GREEN) to individual departure routes based on the departure time, the predicted severity of the convective weather that will impact the route, the likelihood that a pilot will deviate to avoid the weather along the route, and the operational sensitivity to deviations in the departure airspace that the route traverses. These blockages assist traffic managers in prompt route reopening of routes closed by convective weather impacts, as well as providing situational awareness for impeding impacts on routes. RAPT also identifies the location of weather impacts along the departure route. This paper presents an analysis of observed fair weather and convective weather impacted throughput on New York departure fixes. RAPT departure status and impact location are used to characterize the severity of departure fix weather impacts, and weather-impacted fix capacity ranges are estimated as a function of RAPT impacts. The use of traffic flow merging is identified, and weather impacted capacity ranges for commonly used merged flows are also estimated.
Summary
When convective weather impacts the New York Metro airspace, traffic managers may employ several tactics to mitigate weather impacts and maintain manageable and efficient flow of traffic to and from the airports. These tactics, which include maneuvering individual flights through weather, merging and redirecting traffic flows to avoid storms, and...
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Analytical workload model for estimating en route sector capacity in convective weather
June 14, 2011
Conference Paper
Published in:
9th USA/Europe Air Traffic Management Research and Development Sem., ATM 2011, 14-17 June 2011.
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We have extended an analytical workload model for estimating en route sector capacity to include the impact of convective weather. We use historical weather avoidance data to characterize weather blockage, which affects the sector workload in three ways: (1) Increase in the conflict resolution task rate via reduction in available airspace, (2) increase in the recurring task load through the rerouting of aircraft around weather, and (3) increase in the inter-sector coordination rate via reduction in the mean sector transit time. Application of the extended model to observed and forecast data shows promise for future use in network flow models.
Summary
We have extended an analytical workload model for estimating en route sector capacity to include the impact of convective weather. We use historical weather avoidance data to characterize weather blockage, which affects the sector workload in three ways: (1) Increase in the conflict resolution task rate via reduction in available...
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Uses for field communication data in designing air traffic management decision support
May 31, 2011
Conference Paper
Published in:
10th Conf. on Naturalistic Decision Making, 31 May 2011.
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In this paper, example uses of field communication data are provided and how these data impact the evolution of the Route Availability Planning Tool (RAPT) for air traffic management is introduced. Simple communications analyses are provided that illustrate how communications can be used to improve what decision support is provided, who it is provided to, and in what context to present the support. Communications data is also shown to aid in contextualizing the decision support to better fit within the decision support framework in existence, which is critical to the success of situation awareness systems.
Summary
In this paper, example uses of field communication data are provided and how these data impact the evolution of the Route Availability Planning Tool (RAPT) for air traffic management is introduced. Simple communications analyses are provided that illustrate how communications can be used to improve what decision support is provided...
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Route availability planning tool evaluation vizualizations for the New York and Chigaco departure flows
March 29, 2011
Conference Paper
Published in:
AIAA Infotech at Aerospace Conf. and Exhibit, 29-31 March 2011.
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When operationally significant weather affects a region of the National Airspace System (NAS) a Severe Weather Avoidance Program (SWAP) is initiated for that region. Each SWAP event is a unique mix of demand, weather conditions, traffic flow management (TFM) initiatives and traffic movement. On the day following a SWAP, the SWAP events are reviewed by FAA and airline representatives as part of the daily planning teleconference, and the TFM initiatives used are evaluated to understand their impact on the traffic flows, benefits, and disadvantages. Due to the complexity of the situation various exploratory visualizations were designed in order to evaluate aspects of the aviation environment and the responsive actions of the NAS during outbreaks of convective weather as well as to gain insights on the interaction of weather and traffic operations. From these visualizations, analyses and metrics were developed that could be used to objectively evaluate the effectiveness of TMIs. This paper will present three visualizations that have directly resulted in the development of analyses for TMIs or lead to insights into air traffic operations.
Summary
When operationally significant weather affects a region of the National Airspace System (NAS) a Severe Weather Avoidance Program (SWAP) is initiated for that region. Each SWAP event is a unique mix of demand, weather conditions, traffic flow management (TFM) initiatives and traffic movement. On the day following a SWAP, the...
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Collaborative Decision Making (CDM) Weather Evaluation Tool (WET) operational bridging for convective weather: demonstrations and implementation plans
January 25, 2011
Conference Paper
Published in:
2nd Aviation, Range and Aerospace Meteorology Special Symp. on Weather-Air Traffic Management Integration, 22-27 January 2011.
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The purpose of this manuscript is twofold. First, it provides a review of the activities of the Weather Evaluation Team (WET), which is part of a joint Industry and Federal Aviation Administration (FAA) effort called Collaborative Decision Making (CDM). Over ten years ago, the predecessor to the WET, the Weather Action Group (WAG), developed a process that involved industry and government participants in the production of the Collaborative Convective Forecast Product (CCFP). The CCFP was developed in response to the need of industry and government Air Traffic Managers to have a common forecast of convective information used in their decision making processes. In light of the concepts introduced by the Next Generation Air Transportation System (NextGen), the CCFP could be viewed as one predecessor to the Single Authoritative Source. During the period 2008 through 2010, the WET worked on a task to increase the amount of detail as well as extend its forecast time period. At the same time, new automated convective forecasts were developed and introduced to both the WET and Traffic Flow Management (TFM) community. The manuscript includes a description of how the WET has strived to integrate both Human-in-the-Loop (HITL) and fully automated products, including the Localized Aviation Model Output Statistics (MOS) Product (LAMP)/CCFP Hybrid (LCH), the Aviation Impact Guidance for Convective Weather, the Corridor Integrated Weather System (CIWS) and the Consolidated Storm Prediction for Aviation (CoSPA). The second purpose of this manuscript is to introduce the new concept called Operational Bridging. The WET first discussed Operational Bridging at the 2010 Friends and Partners of Aviation Weather (FPAW) Vision Meeting in July, 2010. Foundational materials such as a Concept of Operations (CONOPS) and a demonstration plan are now being developed by the WET. Operational Bridging is first described from within a meteorology-centric view of the CCFP forecast process. Not only does this allow the new concept to be further defined, it also lays out a transition path for the current CCFP. Operational Bridging is next described from the broader conceptual perspective of Air Traffic Management (ATM)/Weather Integration, and two key areas are explored: 1) the role of the CDM weather community in the area of automated probabilistic and deterministic convective weather forecast information and 2) the integration of probabilistic forecast information into both strategic and deterministic (tactical) ATM decision making process.
Summary
The purpose of this manuscript is twofold. First, it provides a review of the activities of the Weather Evaluation Team (WET), which is part of a joint Industry and Federal Aviation Administration (FAA) effort called Collaborative Decision Making (CDM). Over ten years ago, the predecessor to the WET, the Weather...
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