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Detect and Avoid (DAA) system is an essential part of Remotely Piloted Aircraft System (RPAS) for the safe operations within civil airspace. This paper investigates the performances of a DAA system in a fast-time simulation environment. A pilot decision model was developed to enable fast-time simulation using the Detect and AvoID Alerting Logic for Unmanned Systems that computes the range of maneuvers that are free of conflicts. In addition, realistic constraints about the DAA sensors are applied. Sensor’s limits are set with azimuth angle, vertical angle, and distance as well as update rates. A realistic encounter scenario was generated based on the recorded traffic in a congested terminal area. DAA Sensor performances and update rates as well as alerting criteria were varied to have the total of 24 different configurations. The results revealed that the developed model reasonably resolves conflicts in arrival procedure junctions, but it struggles when the conflict geometry is complicated near a holding pattern. In addition, increasing the update rate was not effective in preventing Loss of Well Clear in these situations.

드론이 농업 및 산업 운송 분야에 이용되기 위해서는 큰 탑재 하중과 긴 운용시간이 필요하다. 현재의 배터리 기술로는 탑재 하중과 체공 시간을 늘리는 데에 한계가 있고, 특히 현장에서 지속적인 운용이 필요할 때에 배터리의 충전 또는 교환이 번거로운 문제가 있다. 본 연구에서는 내연기관과 발전기, 그리고 배터리와 전기모터가 결합된 복합적인 추진기관을 사용하는 드론의 동력시스템을 최적화하는 과정을 제시한다. 운반과 운용의 제약을 고려하여 이륙중량 200kg 급의 기체를 선정하였다. 내연기관과 직접 연결된 2개의 주 로터가 기체 중량의 대부분을 담당하고, 내연기관으로 구동되는 발전기의 전력을 사용하는 4개의 모터가 자세제어를 담당하도록 시스템을 구성하였다. 드론의 에너지 흐름을 파악하여, 기존의 상용품 중 최적의 모터와 프로펠러를 선정하는 기법을 제시하고, 내연기관의 측정 데이터를 이용하여 최적의 운용 점과 기어비를 도출하는 기법을 제시한다.

This paper describes the process of establishing lost C2 link contingency procedures in a busy terminal area and the assessment of the proposed procedures through Human-in-The-Loop simulations. Two contingency procedures, one for departure and the other for arrival, were developed based on existing procedures and historic traffic data analyses. A total of six 30-minute simulation sessions were performed with three controllers. By analyzing the safety using Detect and Avoid Well Clear metrics that are being developed for terminal areas, combined with two controller workload surveys, it was discovered that the lost C2 link situations with a single Remotely Piloted Aircraft were manageable without any noticeable safety or workload issues. The methodology of developing and assessing contingency procedures presented in this study will be useful for establishing such procedures in different areas to reflect their own traffic characteristics.

This paper describes the extended first-come first-served scheduler that is being developed for integrated departure and arrival management at airports. The previously developed scheduler with route assignment capability has been enhanced to handle actual wake turbulence separation requirements at runways instead of simple departure and arrival rate constraints. The scheduler is tested with recorded surface traffic data gathered for three days in April 2015 at Incheon International Airport. Three prioritization strategies of nominal, arrival, and partial arrival priorities, are compared. Both the arrival and partial arrival priorities decrease overall delays with significant reduction in arrival delays. The adverse impacts on departure delay are minimal.

In this paper, DAA Well Clear (DWC) standards suitable for the terminal area are analyzed using Automatic Dependent Surveillance-Broadcast (ADS-B) data received in the Republic of Korea. A route-finding algorithm was developed to remove the controller intervention portion from the recorded trajectory. The analyses were performed using 100 days of data processed through the route-finding algorithm. It is discovered that the previously proposed DWC thresholds for terminal areas are also applicable to the Korean National Airspace. By applying these criteria, DAA sensor requirements are investigated. Regardless of the required detection rate, the azimuth limit of ±90° is sufficient, which is smaller than the limits proposed by DAA-MOPS. This is likely to be caused by the operations being tightly restricted by jet routes and instrument flight procedures. The tradeoff between sensor elevation limit and range limit can be observed. For a fixed detection rate, minimum elevation limit, minimum range limit, and optimal elevation and range limits are presented.

In this paper, Human-in-the-Loop (HiTL) simulations of Remotely Piloted Aircraft System (RPAS) operations in two different Air Traffic Management (ATM) concepts, conventional radar vectoring and Trajectory Based Operations (TBO), were performed to assess the impacts of RPAS integration in the future ATM environment. TBO concept maximizes the throughput by planning and sharing 4-D trajectories between pilots and controllers, and it is considered one of the key concepts to enable RPASs to operate with manned aircraft in congested airspaces. RPASs are characterized by having communication delay or temporary loss of communication. TBO capability was added to the integrated air traffic simulation system for this study, which was developed in the Inha University. HiTL simulations were performed by a trainee air traffic controller with three scenarios, and the data were analyzed using safety, efficiency, and controller workload metrics. The results suggest that TBO were effective in reducing delays and controller workload while maintaining the level of safety.

Korea Aerospace Research Institute (KARI) and National Aeronautics and Space Administration (NASA) are investigating scheduling algorithms that will be a part of an integrated arrival and departure management system. Inha University, one of the Korean collaborators of KARI, developed an Extended First-Come First-Served (EFCFS) algorithm that is robust and efficient. However, since the EFCFS algorithm sequentially computes the schedule based on priority, the end results may not be optimal for system efficiency. The approach based on Mixed Integer Linear Programming (MILP) originally developed by NASA and modified by KARI is known to produce better schedules at the expense of computational cost. In this paper, the two different scheduling approaches are compared using common traffic scenarios and constraints at Incheon International Airport. Capabilities to apply weight class based wake turbulence runway separation minima and Miles-in-Trail (MIT) restrictions at selected meter fixes are added to the previously developed EFCFS scheduler. Based on historic data, 40 departures and 20 arrivals are chosen in a one-hour period and 100 scenarios were created by randomly assigning gate numbers, gate departure times, and runway landing times. With the current runway separation requirements, MILP resulted in about ten to twenty percent smaller average delays depending on the constraints. With artificially increased separation minima, the difference between MILP and EFCFS became more noticeable. However, the EFCFS was about ten times faster with smaller variations among different scenarios and constraints. The comparison suggests that the MILP-based algorithm has a small advantage at the current traffic level; however, has potential to be more effective in higher demand or severe weather situations. The EFCFS algorithm may be better suited for real-time applications or investigating larger scale scheduling problems.

With the rapid growth of technologies and demand of remotely piloted aircraft systems (RPASs), integration of such systems into the existing airspace is becoming an issue in many countries. To assess the impact of integrated operations of manned and remotely piloted aircraft (RPA), it is necessary to perform Human-in-The-Loop (HiTL) simulations of likely situations with an integrated simulation system. This paper defines several operational concepts for the integrated simulation. Several probable scenarios were developed including a traffic pattern at a small airport and an altitude maneuver at a route crossing. HiTL simulations were performed according to the developed scenarios. The simulation results are analyzed focusing on the impacts of different communication, safety, performance, and human machine interface (HMI) characteristics of RPA.

With rapid growth in the technologies and demand of Remotely Piloted Aircraft Systems (RPASs), integration of such systems into the existing airspace system is becoming an issue in many countries. RPAS have different flight performances, communication characteristics, separation assurance mechanisms, and human machine interfaces from manned aircraft. To establish rules and regulations for RPAS integration, it is important to understand the impacts of RPASs on the airspace system. A simulation system that integrates manned aircraft, air traffic control, and RPASs is developed in Inha University to investigate these impacts through Human-in-The-Loop (HiTL) simulations. Three conflict resolution scenarios between a manned aircraft and a Remotely Piloted Aircraft (RPA) were constructed and tested. Human factors such as the response times of pilots and controllers were measured and analyzed as well as the risk of each maneuver.

U NMANNED aircraft systems (UASs) are becoming increasingly popular, encompassing awide variety ofmissions ranging from military reconnaissance to wildfire monitoring. However, there are inherent safety concerns with UAS due to the lack of an onboard human pilot. Currently, to operate UAS in the National Airspace System, the operators must obtain either a Certificate of Authorization or Waiver or a special airworthiness certificate from the Federal Aviation Administration (FAA) [1]. One of the important steps in obtaining the approval is a proof that the UAS operation can be conducted at an acceptable level of safety [1]. Many past studies assessing the safety of UAS operations used uniform traffic densities. Anno [2] investigated midair collision risk using a random collision theory and compared the results with historic collision data from 1969 to 1978. McGeer et al. [3,4] performed hazard estimation studies of the Aerosonde UAS. In these studies, two different constant densities were used for the UAS and the background traffic. A comprehensive system-wide study performed byWeibel and Hansman [5] used a ratio of the volume swept by the background aircraft to the total airspace volume. Lum and Waggoner [6] conducted a study on both midair collision and ground impact based on the collision model of gas molecules. These approaches are adequate for obtaining a general idea of the risk around a given region but do not consider traffic patterns that are specific to the region of interest. Lum et al. [7] used actual UAS trajectories for a ground impact analysis. In this study, a realistic distribution of average glide angle was used to calculate the expected value of ground fatalities. Sheridan [8] proposed a model to estimate the relative collision probability between two aircraft at the closest point of approach based on Gaussian density functions. Maki et al. [9] created a method to efficiently estimate the probability of near midair collision using Gaussian probability distributions of proposed UAS trajectories and historic track data. In thiswork, the nearmidair collision probabilities are expressed as confidence intervals. Some of the work is related to quantitatively establishing the boundary of “well clear” for sense-and-avoid systems. Weibel et al. [10] used conditional probability to develop a separation standard model based on uncorrelated encounter model [11]. Asmat et al. [12] developed a UAS-specific collision-avoidance system that can communicate with the existing traffic alert collision and avoidance system. In this work, a distributed traffic model similar to Maki et al. [9] is constructed using actual traffic data collected over a one-year period to enable a probabilistic approach to risk assessment. The radar data provided by the U.S. Air Force contains not only the cooperative traffic data but also the noncooperative traffic data with altitude information. Inclusion of noncooperative traffic, mostly general aviation (GA) traffic, is important because they tend to fly at lower altitudes where the UAS are likely to operate, and it is harder to implement collision mitigation measures with them. The current study computes the collision rates, which are defined by the number of collisions per unit time of UAS operation, based on UAS tracks flying through the continuous background traffic model. The procedures and results are explained in detail throughout the following sections. Following the introduction, the area around the Grand Forks Air Force Base where the U.S. Air Force is planning to operate UAS is described in Sec. II. Then, the description of the continuous-traffic model is presented in Sec. III. In Sec. IV, mathematical formulations for the continuous-traffic model and for the computation of conflict and collision probabilities are presented. Section V reviews the air traffic characteristics of the given area in terms of average aircraft counts and their spatial distributions, and Sec. VI presents the collision risk computed for a potential mission scenario. Finally, the results and recommendations are summarized in Sec. VII.

A study analyzing the economic cost and benefit impacts of different flight routing methods in the National Airspace System is presented. It compares wind-optimal routes and filed flight routes for 365 days of traffic, from 2005 to 2007, in class A airspace. Routing differences are measured by flight time, fuel burn, sector loading, conflict counts, and airport arrival rates. From the results, wind-optimal routes exhibit an average per-flight time saving of 2.7 min and an average fuel saving of 210 lb, compared to filed flight routes. In addition, the airport arrival rates at the top 73 U.S. domestic airports do not show notable differences between wind-optimal routing and filed flight routing. The study shows an average of 29% fewer conflicts. Finally, wind-optimal routes have, at most, one high-altitude sector with increased sector workload than filed flight routes at any time instance.

This paper presents the impacts of Unmanned Aircraft System (UAS)-specific sector capacity constraints on the delay of UAS and the number of encounters between UAS and manned aircraft. The capacity constraints – represented by a limit placed on the number of aircraft allowed in a given sector – are satisfied by delaying the departure times of UAS that would otherwise exceed the constraint while preserving the intended routes of flights. A first-come first-served departure scheduler is used to determine departure times delays for UAS that satisfy the UAS-specific sector capacity constraints. In this paper, using both time-based and distance-based criteria for determining the aircraft encounters, the conflict risk for different UAS-specific capacity constraints is analyzed. Fast-time simulation results show that the number of encounters generally decreases as the UAS-specific sector capacity is reduced. When the capacity constraints are two times tighter, the number of encounters is reduced by up to 42%. The results also show a general trend toward increased departure delay for UAS as the capacity constraints get tighter.

The interaction of partitioning the airspace and delaying flights in the presence of convective weather is explored to study how re-partitioning the airspace can help reduce congestion and delay. Three approaches with varying complexities are employed to compute the ground delays. In the first approach, an airspace partition of 335 high-altitude sectors that is based on clear weather day traffic is used. Routes are then created to avoid regions of convective weather. With traffic flow management, this approach establishes the baseline with per-flight delay of 8.4 minutes. In the second approach, traffic flow management is used to select routes and assign departure delays such that only the airport capacity constraints are met. This results in 6.7 minutes of average departure delay. The airspace is then partitioned with a specified capacity. It is shown that airspace-capacity-induced delay can be reduced to zero at a cost of 20 percent more sectors for the examined scenario. While the first two approaches investigate the upper and lower bounds in terms of delay and number of sectors, the third approach investigates the tradeoff between the number of sectors and the delay by re-applying the traffic flow management using the re-partitioned sectors. In this approach, the weather constraints are reflected in the sector partitions, and the delay is shared between airspace and airports. The solutions discovered by this approach are 6.9 minutes of average delay with a 312 sector configuration and 8.1 minutes of delay with a 253 sector configuration. Results show that a sector design that is tailored to the traffic and weather pattern can reduce delay while reducing the number of sectors at the same time. However, airspace partitioning can only address the delays caused by airspace congestion. Even in the presence of convective weather, the airport capacity constraint causes the majority of the delay.

This paper discusses a novel approach to associate and rene aircraft track data from multiple radar sites. The approach provides enhanced aircraft track accuracy and time synchronization that is compatible with modern air trac management analysis and simulation tools. Unlike existing approaches where the number of aircraft in the radar data must be assumed, this approach requires no such prior knowledge. While commercial aircraft provide ID tags captured in the radar data in the form of Mode 3 transponder codes, general aviation often lacks such transponders, which precludes using the number of codes sensed to count the number of aircraft in the data. To meet this challenge, an approach to track an unknown number of unidentied aircraft using a clustering algorithm is proposed. The paper presents a method to relate aircraft between consecutive time frames and rene the trajectories of those vehicles. Experimental results from evaluating the algorithm and demonstrating its viability are provided.

A Precision Departure Release Capability concept is being evaluated by both the National Aeronautics and Space Administration and the Federal Aviation Administration as part of a larger goal of improving throughput, efficiency and capacity in integrated departure, arrival and surface operations. The concept is believed to have the potential of increasing flight efficiency and throughput by avoiding missing assigned slots and minimizing speed increase or path stretch to recover the slot. The main thrust of the paper is determining the impact of early and late departures from the departure runway when an aircraft has a slot assigned either at a meter fix or at the arrival airport. Results reported in the paper are for two scenarios. The first scenario considers flights out of Dallas/Fort Worth destined for Hartsfield-Jackson International Airport in Atlanta flying through the Meridian meter-fix in the Memphis Center with miles-in-trail constraints. The second scenario considers flights destined to George Bush Intercontinental/Houston Airport with specified airport arrival rate constraint. Results show that delay reduction can be achieved by allowing reasonable speed changes in scheduling. It was determined that the traffic volume between Dallas/Fort Worth and Atlanta via the Meridian fix is low and the departures times are spread enough that large departure schedule uncertainty can be tolerated. Flights can depart early or late within 90 minutes without accruing much more delay due to miles-in-trail constraint at the Meridian fix. In the Houston scenario, 808 arrivals from 174 airports were considered. Results show that delay experienced by the 16 Dallas/Fort Worth departures is higher if initial schedules of the remaining 792 flights are kept unaltered while they are rescheduled. Analysis shows that the probability of getting the initially assigned slot back after perturbation and rescheduling decreases with increasing standard deviation of the departure delay distributions. Results show that most Houston arrivals can be expected to be on time based on the assumed zero-mean Normal departure delay distributions achievable by Precision Departure Release Capability. In the current system, airport-departure delay, which is the sum of gate-departure delay and taxi-out delay, is observed at the airports. This delay acts as a bias, which can be reduced by Precision Departure Release Capability.

Takeoff weight is an important parameter for computing accurate aircraft trajectories. Most systems used for simulating air traffic and for providing air traffic management decision support use takeoff weights that depend only on the aircraft type. This paper proposes a closed-form algorithm for estimating takeoff weights based on flight plan and aircraft performance data. The algorithm is derived by combining the constantaltitude-cruise range equation with the weight estimation procedure commonly used in aircraft design. The model first determines whether the payload is limited by payload capacity, maximum takeoff weight, or fuel tank capacity, and then calculates the takeoff weight accordingly. The model is verified against manufacturer provided payload range diagrams for a jet and a turboprop aircraft. Accurate and fast takeoff weight estimation with negligible computational overhead will enhance large scale air traffic simulations by improving the accuracy of trajectories and fuel burn estimates. Improvement in trajectory and fuel burn estimates will benefit the assessment of noise and emissions as well as improve the accuracy of automated conflict detection and resolution algorithms.

To ensure that air traffic demand does not exceed airport and airspace capacities, traffic management restrictions, such as delaying aircraft on the ground, assigning them different routes and metering them in the airspace, are implemented. To reduce the delays resulting from these restrictions, revising the partitioning of airspace has been proposed to distribute capacity to yield a more efficient airspace configuration. The capacity of an airspace partition, commonly referred to as a sector, is limited by the number of flights that an air traffic controller can safely manage within the sector. Where viable, re-partitioning of the airspace distributes the flights over more efficient sectors and reduces individual sector demand. This increases the overall airspace efficiency, but requires additional resources in some sectors in terms of controllers and equipment, which is undesirable. This study examines the tradeoff of the number of sectors designed for a specified amount of traffic in a clear-weather day and the delays needed for accommodating the traffic demand. Results show that most of the delays are caused by airport arrival and departure capacity constraints. Some delays caused by airspace capacity constraints can be eliminated by re-partitioning the airspace. Analyses show that about 360 high-altitude sectors, which are approximately today s operational number of sectors of 373, are adequate for delays to be driven solely by airport capacity constraints for the current daily air traffic demand. For a marginal increase of 15 seconds of average delay, the number of sectors can be reduced to 283. In addition, simulations of traffic growths of 15% and 20% with forecasted airport capacities in the years 2018 and 2025 show that delays will continue to be governed by airport capacities. In clear-weather days, for small increases in traffic demand, increasing sector capacities will have almost no effect on delays.

Currently, few detailed airport surface models for air transportation system simulation and analysis exist, because the models are complex to develop and maintain. An improved method of generating detailed models is needed to expand the set of detailed airport surface and terminal airspace models. In this paper, an efficient means to automate the procedures to develop airport surface node-link graph models is proposed. Node-link graphs were created by connecting the centroids of the polygons from geographic information system data. A principal axis-based algorithm was formulated to identify and divide complex polygons. The graph was further improved by adjusting node positions, using the known centerlines from rectangular polygons and removing redundant nodes and links. The procedures were tested on 79 United States airports and proved to be robust, accurate, and efficient.

Miniature trailing edge effectors (MiTEs) are small flaps, typically around 1% chord, actuated with deflection angles up to 90 degrees. Their small size, combined with low required power and good control authority, enables the devices to be used for high bandwidth control as well as conventional attitude control. However, some of the aerodynamic characteristics of these devices are complex and poorly understood. This paper describes time accurate computations that were performed using the INS2D flow solver to resolve unsteady characteristics including transient response and vortex shedding phenomena. The frequency response was studied to identify the dynamics of moving MiTEs, an important aspect of these new control devices.

Miniature trailing edge effectors (MiTEs) are small flaps (typically 1% to 5% chord) actuated with deflection angles up to 90 degrees. The small size, combined with little required power and good control authority enables the device to be used for high bandwidth control. Numerous experiments and computational simulations have been conducted for two dimensional airfoils with miniature flaps. However the three-dimensional effects of these devices haven’t been extensively investigated. The present study examines the steady three dimensional aerodynamics of MiTEs using incompressible Navier-Stokes flow solver. Preliminary contents • Spanwise lift distribution Preliminary computation shows that the influence of a single MiTE is widely distributed along the entire span of a wing. Spanwise lift distribution will be investigated. • Spanwise length of a individual actuator Since MiTEs do not usually encompass full span, it is necessary to investigate the effect of the spanwise length, in addition to the height. The influence of the length of MiTE on the control effectiveness will be examined. • Gap If more than two MiTEs are actuated separately, Gaps are required between the MiTEs, especially when the wing is flexible. Changes in the control effectiveness and drag due to the gaps between the actuators will be investigated. Doctoral Candidate, Department of Aeronautics and Astronautics, AIAA Student Member Professor, Department of Aeronautics and Astronautics, AIAA Fellow 1 2nd AIAA Flow Control Conference 28 June 1 July 2004, Portland, Oregon AIAA 2004-2693 Copyright © 2004 by Hak-Tae Lee. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.