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Due regard encounter model version 1.0

Published in:
MIT Lincoln Laboratory Report ATC-397

Summary

Airspace encounter models describe encounter situations that may occur between aircraft in the airspace and are a critical component of safety assessment of sense and avoid (SAA) systems for Unmanned Aircraft Systems (UASs). Some UAS will fly in international airspace under due regard and may encounter other aircraft during these operations. In these types of encounters, the intruder aircraft is likely receiving air traffic control (ATC) services, but the UAS is not. Thus, there is a need for a due regard encounter model that can be used to generate these types of encounters. This report describes the development of a due regard encounter model. In order to build the model, Lincoln Laboratory collected data for aircraft flying in international airspace using the Enhanced Traffic Management System (ETMS) data feed that was provided by the Volpe Center. Lincoln processed these data, and extracted important features to construct the model. The model is based on Bayesian networks that represent the probabilistic relationship between variables that describe how aircraft behave. The model is used to construct random aircraft trajectories that are statistically similar to those observed in the airspace. A large collection of encounters generated from an airspace encounter model can be used to evaluate the performance of a SAA system against encounter situations representative of those expected to actually occur in the airspace. Lincoln Laboratory has previously developed several other encounter models. There is an uncorrelated encounter model that is used to generate encounters with an intruder that does not have a transponder, or between two aircraft using a Mode A code of 1200 (VFR). There is also a correlated encounter model that is used when both aircraft have a transponder and at least one aircraft is in contact with ATC. Both of these models were built from radar data collected from the National Airspace System (NAS). There is also an unconventional encounter model that is used to generate encounters with unconventional intruders such as gliders, balloons, and airships--these vehicles have different flight characteristics than conventional aircraft. The framework used to construct the due regard encounter model described in this paper is similar to the prior models. The primary difference is that a different data feed is used and the model covers encounters in international flight where the aircraft of interest is flying due regard, which were not within the scope of prior models. Separate electronic files are available from Lincoln Laboratory that contain the statistical data required to generate encounter trajectories.
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Summary

Airspace encounter models describe encounter situations that may occur between aircraft in the airspace and are a critical component of safety assessment of sense and avoid (SAA) systems for Unmanned Aircraft Systems (UASs). Some UAS will fly in international airspace under due regard and may encounter other aircraft during these...

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A safety driven approach to the development of an airborne sense and avoid system

Published in:
AIAA Infotech at Aerospace Conf. and Exhibit, 19-21 June 2012.

Summary

Sense and avoid is the primary technical barrier to increased unmanned aircraft system airspace access. A safety assessment driven approach to sense and avoid system design and requirements validation is being employed to ensure safety and operational suitability. The foundation of this approach is a fast-time modeling and simulation architecture originally used to support the certification of the Traffic Alert and Collision Avoidance System. This paper describes the safety assessment methodology, including the architecture and evaluation metrics, and presents preliminary results for key system architecture and design tradeoffs.
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Summary

Sense and avoid is the primary technical barrier to increased unmanned aircraft system airspace access. A safety assessment driven approach to sense and avoid system design and requirements validation is being employed to ensure safety and operational suitability. The foundation of this approach is a fast-time modeling and simulation architecture...

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Establishing a risk-based separation standard for unmanned aircraft self separation

Published in:
11th AIAA Aviation Technology, Integration, and Operations (ATIO) Conf., 20-22 September 2011.

Summary

Unmanned Aircraft Systems require an ability to sense and avoid other air traffic to gain access to civil airspace and meet requirements in civil aviation regulations. One sense and avoid function is self separation, which requires that aircraft remain well clear. An approach is proposed in this paper to treat well clear as a separation standard, thus posing it as a relative state between aircraft where the risk of collision first reaches an unacceptable level. By this approach, an analytically-derived boundary for well clear can be derived that supports rigorous safety assessment. A preliminary boundary is proposed in both time and distance for the well clear separation standard, and recommendations for future work are made.
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Summary

Unmanned Aircraft Systems require an ability to sense and avoid other air traffic to gain access to civil airspace and meet requirements in civil aviation regulations. One sense and avoid function is self separation, which requires that aircraft remain well clear. An approach is proposed in this paper to treat...

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Establishing a risk-based separation standard for unmanned aircraft self separation

Published in:
9th USA/Europe Air Traffic Management Research and Development Sem., ATM 2011, 14-17 June 2011.

Summary

Unmanned Aircraft Systems require an ability to sense and avoid other air traffic to gain access to civil airspace and meet requirements in civil aviation regulations. One sense and avoid function is self separation, which requires that aircraft remain "well clear." An approach is proposed in this paper to treat well clear as a separation standard, thus posing it as a relative state between aircraft where the risk of collision first reaches an unacceptable level. By this approach, an analytically-derived boundary for well clear can be derived that supports rigorous safety assessment. A preliminary boundary is proposed in both time and distance for the well clear separation standard, and recommendations for future work are made.
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Summary

Unmanned Aircraft Systems require an ability to sense and avoid other air traffic to gain access to civil airspace and meet requirements in civil aviation regulations. One sense and avoid function is self separation, which requires that aircraft remain "well clear." An approach is proposed in this paper to treat...

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Airspace encounter models for estimating collision risk

Published in:
J. Guidance, Control, and Dynamics, Vol. 33, No. 2, March-April 2010, pp. 487-499.

Summary

Airspace encounter models, providing a statistical representation of geometries and aircraft behavior during a close encounter, are required to estimate the safety and robustness of collision avoidance systems. Prior encounter models, developed to certify the Traffic Alert and Collision Avoidance System, have been limited in their ability to capture important characteristics of encounters as revealed by recorded surveillance data, do not capture the current mix of aircraft types or noncooperative aircraft, and do not represent more recent airspace procedures. This paper describes a methodology for encounter model construction based on a Bayesian statistical framework connected to an extensive set of national radar data. In addition, this paper provides examples of using several such high-fidelity models to evaluate the safety of collision avoidance systems for manned and unmanned aircraft.
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Summary

Airspace encounter models, providing a statistical representation of geometries and aircraft behavior during a close encounter, are required to estimate the safety and robustness of collision avoidance systems. Prior encounter models, developed to certify the Traffic Alert and Collision Avoidance System, have been limited in their ability to capture important...

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Encounter models for unconventional aircraft version 1.0

Published in:
MIT Lincoln Laboratory Report ATC-348

Summary

Airspace encounter models, covering close encounter situations that may occur after standard separation assurance has been lost, are a critical component in the safety assessment of aviation procedures and collision avoidance systems. Of particular relevance to Unmanned Aircraft Systems (UAS) is the potential for encountering general aviation aircraft that are flying under Visual Flight Rules (VFR) and are not in contact with air traffic control. In response to the need to develop a model of these types of encounters, Lincoln Laboratory undertook an extensive data collection and modeling effort involving more than 96,000 unconventional aircraft tracks. The outcome of this effort was nine individual models encompassing ultralights, gliders, balloons, and airships. The models use Bayesian networks to represent relationships between dynamic variables and to construct random trajectories that are statistically similar to those observed in the data. The intruder trajectories can be used in fast-time Monte Carlo simulations to estimate collision risk. The model described in this report is one of three developed by Lincoln Laboratory. A correlated encounter model has been developed to represent situations in which it is likely that there would b e air traffic control intervention prior to a close enounter. The correlated model applies to encounters involving aircraft receiving Air Traffic Control (ATC) services and with transponders. TAn encounter with an intruder that does not have a transponder is uncorrelated in the sense that it is unlikely that there would be prior intervention by air traffic control. The uncorrelated model described in this report is based on global databases of pilot-submitted track data. This work is a follow-on to an uncorrelated conventional model developed from recorded radar tracks from aircraft using a 1200 transponder code. A byproduct of this encounter modeling effort was the extraction of feature distributions for unconventional aircraft. This provides an extensive collection of unconventional aircraft behavior in the airspace.
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Summary

Airspace encounter models, covering close encounter situations that may occur after standard separation assurance has been lost, are a critical component in the safety assessment of aviation procedures and collision avoidance systems. Of particular relevance to Unmanned Aircraft Systems (UAS) is the potential for encountering general aviation aircraft that are...

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Airspace encounter models for conventional and unconventional aircraft

Published in:
8th USA/Europe Air Traffic Management Research and Development Sem. (ATM 2009), 25 March 2009.

Summary

Collision avoidance systems play an important role in the future of aviation safety. Before new technologies on board manned or unmanned aircraft are deployed, rigorous analysis using encounter simulations is required to prove system robustness. These simulations rely on models that accurately reflect the geometries and dynamics of aircraft encounters at close range. These types of encounter models have been developed by several organizations since the early 1980s. Lincoln Laboratory's newer encounter models, however, provide a higher-fidelity representation of encounters, are based on substantially more data, leverage a theoretical framework for finding optimal model structures, and reflect recent changes in the airspace. Three categories of encounter model were developed by Lincoln Laboratory. Two of these categories are used for modeling conventional aircraft; one involving encounters with prior air traffic control intervention and one without. The third category of encounter model is for encounters with unconventional aircraft -- such as gliders, skydivers, balloons, and airships -- that typically do not carry transponders. Together, these encounter models are being used to examine the safety and effectiveness of aircraft collision avoidance systems and as a foundation for algorithms for future manned and unmanned systems.
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Summary

Collision avoidance systems play an important role in the future of aviation safety. Before new technologies on board manned or unmanned aircraft are deployed, rigorous analysis using encounter simulations is required to prove system robustness. These simulations rely on models that accurately reflect the geometries and dynamics of aircraft encounters...

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