Air Traffic Control Quarterly

Journal Information
ISSN / EISSN : 1064-3818 / 2472-5757
Total articles ≅ 363
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Nicolas Durand, Nicolas Barnier
Air Traffic Control Quarterly, Volume 23, pp 325-346; https://doi.org/10.2514/atcq.23.4.325

Abstract:
The concept of free-flight, introduced in the 1990s, opened a debate on the efficiency of letting aircraft deal with conflicts without any centralized control. Many models have been proposed for autonomous aircraft solvers, but their efficiency is not well-known. In this paper we experiment with a powerful algorithm derived from robotics, which can deal with thousands of robots in very small spaces and show how its performance plummets when speeds are constrained. We also compare this autonomous algorithm with a centralized approach using evolutionary computation on a complex example to point out their relative performance in a constrained speed environment. This comparison provides scientific arguments for the need for centralized air traffic control.
Paul U. Lee, Nancy M. Smith, Connie Brasil, Eric Chevalley, Jeffrey Homola, , Hyo-Sang Yoo, , Abhay Borade, Nathan Buckley, et al.
Air Traffic Control Quarterly, Volume 23, pp 245-273; https://doi.org/10.2514/atcq.23.4.245

Abstract:
Air traffic management in the New York (NY) metropolitan area presents significant challenges such as excess demand, chronic delays, and inefficient routes. At NASA, a new research effort has been initiated to explore Next Generation Air Transportation System (NextGen) Trajectory Based Operations (TBO) solutions to address lingering problems in the NY metroplex. One of the larger problems in NY is departure delays at LaGuardia Airport (LGA). Constant traffic demand and physical limitations in the number of taxiways and runways cause LGA to often end up with excessive departure queues that can persist throughout the day.At the Airspace Operations Laboratory (AOL) located at NASA Ames Research Center, a TBO solution for “Departure-Sensitive Arrival Spacing” (DSAS) was developed. DSAS allows for maximum departure throughput without adversely impacting the arrival traffic during the peak demand period. The concept uses Terminal Sequencing and Spacing (TSS) operations to manage the actual runway threshold times for arrivals. An interface enhancement to the traffic manager’s timeline was also added, providing the ability to manually adjust inter-arrival spacing to build precise gaps for two or even three departures between arrivals. With this set of capabilities, inter-arrival spacing could be controlled for optimal departure throughput.The concept was prototyped in a human-in-the-loop (HITL) simulation environment to determine operational requirements such as coordination procedures, timing and magnitude of TSS schedule adjustments, and display features for the tower, Terminal Radar Approach Control (TRACON), and Traffic Management Unit (TMU). An HITL simulation was conducted in August, 2014, to evaluate the concept in terms of feasibility, impact on controller workload, and potential benefits. Three conditions were compared: (1) a baseline condition using new RNAV/RNP procedures (no TSS); (2) the new procedures + TSS; and (3) new procedures + TSS + DSAS schedule adjustments. Results showed that with a maximum arrival demand (40-41 arrivals per hour), departure throughput could be increased from 38 aircraft/hour (baseline condition), to 44 aircraft/hour (TSS condition), to 47 aircraft/hour (TSS + DSAS). The results suggest that DSAS operations have the potential to increase departure throughput at LGA by up to 9 aircraft/hour with little or no impact on arrivals during peak traffic demand period.
, Murad Hossain, Fareed Al-Alawi, Fathi Al-Thawadi
Air Traffic Control Quarterly, Volume 23, pp 301-324; https://doi.org/10.2514/atcq.23.4.301

Abstract:
A majority of aircraft are now using Global Navigation Satellite System (GNSS) for navigation. This has led to an effect of reducing the magnitude of lateral deviations from the route center line and, consequently, increasing the probability of a collision, should a loss of vertical separation between aircraft on the same route occur. The International Civil Aviation Organization (ICAO) has introduced Strategic Lateral Offset Procedures (SLOP) that allow suitably equipped aircrafts to fly with 1nmi or 2nmi lateral offset to the right of airway centerline in oceanic airspace. Very few aircraft, however, are using the SLOP procedure because of the lack of understanding of its safety benefits and implementation issues in identifying correct lateral offset that can reduce the collision risk. This paper proposes an Evolutionary Computation framework using Differential Evolution process to identify optimal lateral offsets for each airway in a given airspace such that it reduces the overall collision risk. Airway specific lateral offsets are then correlated with airway-traffic features using Multiple Regression models to identify which features can explain the optimal lateral offset. The proposed approach establishes a generic mapping that can suggest optimal lateral offsets for a given airspace based on airway-traffic features to mitigate collision risk. The proposed methodology is applied to Collision Risk assessment of one-day traffic data (710 flights) in Bahrain Upper Airspace (FL290-FL410) to estimate optimal lateral offset that resulted in significant reduction of collision risk. Further, the number of flights and crossings on an airway were identified as key features affecting optimal lateral offset.
Jason Upchurch, César Muñoz, , María Consiglio, James Chamberlain
Air Traffic Control Quarterly, Volume 23, pp 275-299; https://doi.org/10.2514/atcq.23.4.275

Abstract:
A fundamental requirement for the integration of unmanned aircraft into civil airspace is the capability of aircraft to remain well clear of each other and avoid collisions. This requirement has led to a broad recognition of the need for an unambiguous, formal definition of well clear. Any such definition must be interoperable with existing airborne collision avoidance systems (ACAS). A particular class of well-clear definitions uses logic checks of independent distance thresholds as well as independent time thresholds in the vertical and horizontal dimensions to determine if a well-clear violation is predicted to occur within a given time interval. Existing ACAS systems also use independent distance thresholds; however, a common time threshold is used for the vertical and horizontal logic checks. The main contribution of this paper is the characterization of the effects of the decoupled vertical time threshold on a well-clear definition in terms of (1) time to well-clear violation, and (2) interoperability with existing ACAS. This paper provides governing equations for both metrics and includes simulation results to illustrate the relationships. In this paper, interoperability implies that the time of well-clear violation is strictly less than the time a resolution advisory is issued by ACAS. The encounter geometries under consideration in this paper are initially well clear and consist of constant-velocity trajectories resulting in near-mid-air collisions.
Lisa Fern, R. Conrad Rorie
Air Traffic Control Quarterly, Volume 23, pp 113-135; https://doi.org/10.2514/atcq.23.2-3.113

Abstract:
New performance standards for a detect and avoid (DAA) system are being developed to support the broader integration of unmanned aircraft systems (UAS) into the National Airspace System (NAS). One subset of these performance standards will address the minimum DAA display requirements to support pilot performance on maintaining well clear of other aircraft. These performance standards must take into account the current air traffic control (ATC) operational environment. In particular, the DAA system, and pilots’ interactions with that system, must account for the requirement for pilots to request a clearance for deviations from their approved instrument flight rules route. A series of human-in-the-loop (HITL) experiments were conducted to help identify the minimum information requirements for DAA displays. As part of these experiments, several pilot-ATC interaction metrics were collected, such as the amount of time it took pilots to request an ATC clearance prior to executing a maneuver to maintain well clear after the appearance of a DAA alert, and the proportion of time that pilots received an ATC clearance prior to maneuvering. The results indicate that while there was no observed effect of different display configurations on pilots’ interactions with ATC, these interactions were affected by the combination of alerting and operational procedures. When pilots received an unambiguous alert to potential well clear violations in conjunction with operational procedures that specified the expected actions to various alert levels, the time that it took for pilots to notify ATC of he need to maneuver dropped substantially, and the rate of obtaining a clearance increased. The implications of these results for developing performance standards for DAA are discussed.
Stephen P. Cook, Dallas Brooks
Air Traffic Control Quarterly, Volume 23, pp 137-156; https://doi.org/10.2514/atcq.23.2-3.137

Abstract:
A critical challenge for integrating Unmanned Aircraft Systems (UAS) is developing a means to sense and avoid (SAA) other aircraft. One of the main functions of SAA is to ensure the UAS remains well clear from other air traffic. Human pilots determine well clear subjectively, but SAA systems need a quantified alternative means of compliance. The UAS Science and Research Panel (SARP) brought together key researchers to define guiding principles for UAS Well Clear (UWC). The SARP aligned research efforts from NASA, MIT Lincoln Laboratory, and the US Air Force Research Laboratory to evaluate three UWC candidates in four simulation environments. These UWC candidates were evaluated against eight agreed operational suitability metrics, resulting in a recommended quantitative definition for UWC. This paper will describe the technical rationale for this recommendation, subsequent operational considerations, and potential to extend the work to small UAS.
Sarah K. Yenson, Rodney E. Cole, M. Sage Jessee, Chris Crowder, John Innes
Air Traffic Control Quarterly, Volume 23, pp 157-182; https://doi.org/10.2514/atcq.23.2-3.157

Abstract:
As unmanned aircraft systems (UAS) become more important to the US military and other users, the pressure to allow them to fly in the national airspace increases. The greatest impediment to this is the lack of an alternative means of compliance with federal “see and avoid” regulations to provide the capability to avoid airborne conflicts between the UAS and manned aircraft. To provide this alternative means of compliance, the US Army is leading the development of a Ground-Based Sense and Avoid System (GBSAA). The system uses ground-based radars, threat detection and alerting logic, and decision support display aids to provide an air picture of the UAS’s operating environment and follows the DO-254 and DO-178C standards for safety critical avionics hardware and software, respectively. This system will allow greater airspace access and lower cost operations by replacing ground observers in the field with a centralized system, thus consolidating the observer function. The first GBSAA deployment site is expected to go live in 2016 at Fort Hood Army Air Field, Fort Hood, TX, operating under the FAA’s Certificate of Authorization process. This paper provides an overview of the system and of a human-in-the-loop simulation-based test exercise that is a key component of the certification of the system. During this test exercise, 19 self-separation violations, in which intruders came within 1 nmi horizontally and 100 ft vertically of the ownship, and no near-mid-air collisions (NMACs) occurred during 195 hours of simulation, including many stressing multi-intruder scenarios, during which reported workload was low and situation awareness was high throughout. All participants ultimately stated that the GBSAA system was appropriate for UAS operations within the National Airspace System (NAS).
Air Traffic Control Quarterly, Volume 23, pp 203-240; https://doi.org/10.2514/atcq.23.2-3.203

Abstract:
With the increasing demand to integrate unmanned aircraft systems (UAS) into the National Airspace System (NAS), new procedures and technologies are necessary to ensure safe airspace operations and minimize the impact of UAS on current airspace users. Currently, small UAS face limitations on their use in civil airspace because they lack the ability to detect and avoid other aircraft. This article presents a framework that consists of an Automatic Dependent Surveillance-Broadcast (ADS-B)-based sensor, track estimator, conflict/collision detection, and resolution that mitigates collision risk. ADS-B offers long-range, omni-directional intruder detection with comparatively few size, weight, power, and cost demands. The proposed conflict/collision detection and planning algorithms for conflict/collision resolution are designed in the local level frame, which is the unrolled, unpitched body frame where the ownship is stationary at the center of the map. The path planning method is designed to be multi-resolutional at increasing distance from the ownship to account for both self-separation and collision avoidance thresholds. We demonstrate and validate this approach using simulated ADS-B measurements.
Thomas Teller, Evan Maki, Wesley Olson, Charles Leeper
Air Traffic Control Quarterly, Volume 23, pp 183-201; https://doi.org/10.2514/atcq.23.2-3.183

Abstract:
The Federal Aviation Administration’s (FAA’s) Traffic Alert and Collision Avoidance System (TCAS) Program Office is developing an advanced Airborne Collision Avoidance System (ACAS X) to meet the needs of both manned aircraft and Unmanned Aircraft Systems (UAS). ACAS Xu, the UAS variant, provides vertical Resolution Advisory guidance in most situations and horizontal RA guidance for cases where either surveillance quality or vehicle performance does not support vertical maneuvers. ACAS Xu is fully interoperable with TCAS II and also features new passive (ADS-B based) collision avoidance maneuver coordination techniques. To evaluate the effectiveness of ACAS Xu for collision avoidance as well as to inform interoperability requirements for integration with self-separation systems, the FAA, in conjunction with NASA, General Atomics Aeronautics Systems, Inc, and Honeywell Aerospace, conducted a proof-of-concept flight test in November 2014 with both manned and unmanned intruder aircraft. This paper describes the ACAS Xu system as well as the flight test and provides a summary of observed system performance.
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