NASA GRC UAS project communications modeling and simulation development status

Presents a collection of slides covering the following topics: unmanned aircraft systems; National Airspace System; NAS; control and non-payload communication system; CNPC system; aircraft testing; channel sounding flight tests; L-band air-ground channel propagation testing; C-band air-ground channel propagation testing; aircraft equipment; ground equipment; Rockwell Collins cooperative agreement; civil UAS communication architecture; waveform trade study; datalink technology evaluation; hardware test bed setup and NASA Glenn Research Center.

The Washington State Department of Transportation's (DOT) snow avalanche control program reduces winter roadway closure times and hazards to motorists. The University of Washington and the Washington State DOT evaluated small unmanned aircraft systems (UASs) as a tool to enhance this program. Because of military investment, UAS technology has dropped in cost as it has become increasingly capable and easier to operate. Commercially available UASs, which fly autonomously, can be operated off a roadway and can collect low-cost, real-time aerial imagery while also carrying payloads. This project conducted a series of test flights involving both fixed- and rotary-wing (helicopter) UASs over a roadway in mountainous terrain. The flights demonstrated that UASs can conduct snowpack and terrain surveillance and can accurately drop explosive charges such as those used to trigger controlled avalanches. The rotary-wing UAS was particularly usable because of its ability to hover, which provided a stable camera platform, and because it required minimal area to land. The reliability of UASs is a concern, and their capabilities may be challenged by mountainous terrain and weather. This problem may be reduced as UASs become either less expensive and more expendable or more reliable and all-weather capable. A major barrier to use of UASs is the need to obtain approval to fly from FAA, a process that can be time-consuming and restrictive. FAA is currently updating its plans to integrate UASs into the national airspace, and a number of technology-based solutions are being considered.

The ability of a flight crew to deliver their aircraft to its arrival runway on time is important to the overall efficiency of the National Airspace System (NAS). Over the past several years, the NAS has been stressed almost to its limits resulting in problems such as airport congestion, flight delay, and flight cancellation to reach levels that have never been seen before in the NAS. It is predicted that this situation will worsen by the year 2025, due to an anticipated increase in air traffic operations to one-and-a-half to three times its current level. Improved arrival efficiency, in terms of both capacity and environmental impact, is an important part of improving NAS operations. One way to improve the arrival performance of an aircraft is to enable the flight crew to precisely deliver their aircraft to a specified point at either a specified time or specified interval relative to another aircraft. This gives the flight crew more control to make the necessary adjustments to their aircraft s performance with less tactical control from the controller; it may also decrease the controller s workload. Two approaches to precise time navigation have been proposed: Time-Based Arrivals (e.g., required times of arrival) and Self-Spacing. Time-Based Arrivals make use of an aircraft s Flight Management System (FMS) to deliver the aircraft to the runway threshold at a given time. Self-Spacing enables the flight crew to achieve an ATC assigned spacing goals at the runway threshold relative to another aircraft. The Joint Planning and Development Office (JPDO), a multi-agency initiative established to plan and coordinate the development of the Next Generation Air Transportation System (NextGen), has asked for data for both of these concepts to facilitate future research and development. This paper provides a first look at the delivery performance of these two concepts under various initial and environmental conditions in an air traffic simulation environment.

In order to provide for the safe integration of unmanned aircraft systems (UAS) into the National Airspace System, the control and non-payload communications (CNPC) link connecting the ground-based pilot with the unmanned aircraft must be highly reliable and robust, based upon standards that enable certification. Both line-of-sight (LOS) links using terrestrial-based communications and beyond-line-of-sight (BLOS) links using satellite communications are required to support UAS operations. The development of standards has been undertaken by RTCA Special Committee 228 (SC-228), with supporting technical data developed by NASA under the UAS in the National Airspace (NAS) Project. As a result of this work minimum operational performance standards (MOPS) have been completed and published for the LOS CNPC system. The second phase of work, for both NASA and RTCA involves the BLOS CNPC systems. The development of technical data to support MOPS development for UAS BLOS satellite-based CNPC links has now been initiated by NASA, and RTCA SC-228 has organized itself to begin the MOPS development process. This paper will provide an overview of the work that has been completed to date by the Communications Subproject in support of LOS C2 communications for UAS followed by an update of plans and progress for the BLOS phase of the project, with the focus on the UAS C2 spectrum aspects.

To ensure and meet the future needs of the growing civil and commercial aviation community, the Federal Aviation Administration (FAA) has undertaken the development of the Next Generation Air Transportation System (NextGen). This paper presents the radio site layout design approach in support of the FAA's Automatic Dependent Surveillance-Broadcast (ADS-B) the cornerstone of NextGen. The radio site layout must be optimised to meet system performance, safety, and interference requirements while minimising the number of radio sites. In this paper, we show a practical way to achieve this optimality by developing an advanced technique such as reverse radio line-of-site (RLOS). Given that numerous radars are clustered together, we can optimise radio site selection through a process of coverage aggregation. This optimisation process across the USA's National Air Space (NAS) significantly reduces the total number of radio sites required for complete coverage.

Tracking and Monitoring Unmanned Aircraft Systems Activities with Crowd-Based Mobile Apps By Tejaswini Papireddy Dr. Ju-Yeon Jo, Examination Committee Chair Associate Professor, Department of Computer Science University of Nevada, Las Vegas An Unmanned Aircraft System(UAS) is an aircraft without human pilot onboard. They can be controlled remotely from a ground control station (GCS) or can fly autonomously based on pre-programmed flight plans. Tracking and monitoring these UASs activities in the National Airspace System (NAS) is one of the major challenges related to UAS. This system tracks a set of UASs at a given point of time based on the user-submitted tracking information. This thesis presents the basic knowledge of UAS, types of UAS, advantages, and challenges with UASs. The implemented Android application allows the users to submit the observed UAS information to a tracking database server by taking a picture of the UAS. The monitoring system is implemented in Android for retrieving and displaying the UAS activity data from the database server. This system is expected to promote safer airspace by providing the UAS activity information to manned aircraft pilots and other UAS operators to avoid collision. iii

To provide a context for the potential threat of unmanned aircraft systems (UAS) sightings on airport operations, this paper compares the characteristics of UAS sightings with two common airport threats: wildlife strikes and runway incursions. This study analyzed over 60,000 events in a three-year period (September 2016 to August 2019), including 6,551 UAS sightings from the Federal Aviation Administration (FAA) UAS Sightings Report database, 47,574 wildlife strikes from the FAA Wildlife Strike database, and 6,041 runway incursions from the FAA Runway Safety database. The results suggest both similarities and differences among the airport threats. Both UAS sightings and wildlife strikes vary by time of year and time of day. UAS sightings and wildlife strikes farther from the airport occur at higher altitudes than sightings and strikes occurring close to the airport. However, UAS sightings are reported at higher altitudes than wildlife strikes, and the distance of UAS sightings from the airport is farther than that of wildlife strikes, in general. The severities of UAS sightings and runway incursions are similar. Pilots take evasive actions in three percent of UAS sightings, and runway incursions of severity A and B are also rare. Pilots of general aviation (GA) aircraft reported the most UAS sightings, and GA operations are also involved in more runway incursions. Considering the kind of airport affected, UAS sightings and wildlife strikes are more common at primary airports, notably large and medium hub airports, whereas runway incursions are more common at reliever airports. Generally, UAS have had a minimal impact on airport operations despite their growing prevalence, which reflects the overall success of integrating this new airspace user into the national airspace system.

The goal of enabling the integration of unmanned aircraft systems (UAS) into the National Airspace System (NAS) in terms of UAS achieving routine access to the NAS has been established as a national goal in the United States. Among a number of technical barriers that must be overcome to meet this goal is the absence of standard, certifiable communications links supplying the control and non-payload communications (CNPC) function, essentially providing the link over which a pilot on the ground can control the unmanned aircraft (UA). The International Civil Aviation Organization (ICAO) has determined that the CNPC link must operate over protected aviation spectrum. Therefore protected aviation spectrum must be allocated for this function, approved through the processes of the International Telecommunications Union Radiocommunication Sector (ITU-R). Work has progressed in the definition of spectrum requirements for CNPC, and a portion of these requirements has been satisfied through new allocations approved at the ITU-R 2012 World Radiocommunication Conference (WRC-12). Additional work is ongoing or planned to satisfy the remaining spectrum requirements and define the specifications for the usage of CNPC spectrum allocations and develop supporting standards. This paper provides an overview of the status of RF spectrum for UAS CNPC. Issues that have been identified and ongoing analysis and research that will be necessary to fulfill spectrum requirements for UAS CNPC will be discussed. The results of this work will provide for the safe integration of UA into the NAS in both the LOS (Line of Sight) and BLOS (Beyond Line of Sight) realms.

One environmental issue regulated by the FAA is the noise created by aircraft. Federal Aviation Regulation (FAR) Title 14 Part 36 deals specifically with sound pressure levels (SPL) according to aircraft type when the aircraft are in close proximity to the ground. Minimizing aircraft noise helps to maintain positive relationships between the aviation community and the general public. Unmanned aircraft systems (UAS) are a very rapidly growing segment of the aviation industry within the National Airspace System (NAS); however, there is currently no regulation for UAS SPL. The UAS are regulated, as of August 29, 2016, such that they are mandated to be in close proximity to the ground (no higher than 400 ft). As with manned aircraft, UAS produce high levels of SPL, much of which is due to the rotors. The combination of close proximity to the ground, high SPL, and increasing UAS density will most certainly result in a negative public reaction. In order to minimize the audible impact of UAS, the author seeks to minimize the SPL of small UAS propellers/rotors via experimental rotor modifications. These modifications were inspired by the characteristics found on the flight feathers of certain owls. The modifications were evaluated individually and optimized on two-bladed rotors on thrust stands. The most recent phase of the project collected SPL data from a DJI Phantom 4 Pro+ UAS in flight with standard and low noise

A need exists to safely integrate Unmanned Aircraft Systems (UAS) into the United States' National Airspace System. Replacing manned aircraft's see-and-avoid capability in the absence of an onboard pilot is one of the key challenges associated with safe integration. Sense-and-avoid (SAA) systems will have to achieve yet-to-be-determined required separation distances for a wide range of encounters. They will also need to account for the maneuver performance of the UAS they are paired with. The work described in this paper is aimed at developing an understanding of the trade space between UAS maneuver performance and SAA system performance requirements, focusing on a descent avoidance maneuver. An assessment of current manned and unmanned aircraft performance was used to establish potential UAS performance test matrix bounds. Then, near-term UAS integration work was used to narrow down the scope. A simulator was developed with sufficient fidelity to assess SAA system performance requirements. The simulator generates closest-point-of-approach (CPA) data from the wide range of UAS performance models maneuvering against a single intruder with various encounter geometries. Initial attempts to model the results made it clear that developing maneuver performance groups is required. Discussion of the performance groups developed and how to know in which group an aircraft belongs for a given flight condition and encounter is included. The groups are airplane, flight condition, and encounter specific, rather than airplane-only specific. Results and methodology for developing UAS maneuver performance requirements are presented for a descent avoidance maneuver. Results for the descent maneuver indicate that a minimum specific excess power magnitude can assure a minimum CPA for a given time-to-go prediction. However, smaller amounts of specific excess power may achieve or exceed the same CPA if the UAS has sufficient speed to trade for altitude. The results of this study will support UAS maneuver performance requirements development for integrating UAS in the NAS. The methods described are being used to help RTCA Special Committee 228 develop requirements.

Any aircraft, manned or unmanned, may enter safely and legally into the US National Airspace System (NAS) provided that it has been issued an airworthiness certificate complying with Federal Aviation Administration (FAA) requirements. Unfortunately corresponding requirements, procedures and regulations for airworthiness certification of unmanned aircraft are in early development stages and flight of such systems is still restricted. This paper presents a survey of the current status of unmanned aircraft system (UAS) regulations both in the US and internationally, followed by brief overview of current manned aviation airworthiness certification procedures and requirements. Future perspectives of UAS regulation are discussed along with a proposed UAS classification for certification purposes.

Chapter 12 - An overview of unmanned aircraft systems (UAS) governance and regulatory frameworks in the European Union (EU)

The capability to properly assess the risks associated with the integration of unmanned aircraft systems (UAS) into the National Airspace System (NAS) is critical to ensuring UAS operations are introduced in a safe and responsible manner. Key to this capability is the accurate determination of the likelihood of collision between UAS and other aircraft. Likelihood of such collisions are not well understood and, in many cases, are assessed in a subjective and qualitative manner, resulting in potentially inaccurate assumptions and evaluation of risk and/or allocation of limiting mitigations that decrease the efficiency and effectiveness of UAS operations. Quantification of the likelihood of these collision risk elements will transform the way UAS integration is evaluated and approvedThis paper focuses on a methodology to quantify and analyze the likelihood of unmitigated aircraft collisions within defined airspace volumes. This methodology, developed by The MITRE Corporation (MITRE), will enable a more objective, standardized, and comprehensive assessment of the collision risk posed by the integration of UAS into the NAS with the ability to statistically assess the differences between distributions of risk across multiple airspace volumes. Leveraging this methodology will speed the determination of airspace risk associated with integration and will specifically assist in the identification of mitigations to reduce identified risk to an acceptable level.

Development of effective sense and avoid systems is a critical challenge for operation of unmanned aircraft systems (UAS) in the National Airspace. A key issue is achieving detection of potential targets at sufficient range to achieve a low probability of collision with lightweight, low cost sensors suitable for UAS. We present a closed form analytical approach to designing the minimum required sensing range based on worst-case collision encounter geometries. Using a minimum safe distance of 500 ft and known velocities for several different aircraft, this minimum required sensing range is found to be approximately 1.861 km using slack parameter of δr = 0.0354. We demonstrate that this is a feasible result by describing a radar sensor prototype that achieves the required minimum sensing range.

Safe planning for fleets of Unmaned Aircraft Systems (UAS) performing complex missions in urban environments has typically been a challenging problem. In the United States of America, the National Aeronautics and Space Administration (NASA) and the Federal Aviation Administration (FAA) have been studying the regulation of the airspace when multiple such fleets of autonomous UAS share the same airspace, outlined in the Concept of Operations document (ConOps). While the focus is on the infrastructure and management of the airspace, the Unmanned Aircraft System (UAS) Traffic Management (UTM) ConOps also outline a potential airspace reservation based system for operation where operators reserve a volume of the airspace for a given time interval to operate in, but it makes clear that the safety (separation from other aircraft, terrain, and other hazards) is a responsibility of the drone fleet operators. In this work, we present a tool that allows an operator to plan out missions for fleets of multi-rotor UAS, performing complex time-bound missions. The tool builds upon a correct-by-construction planning method by translating missions to Signal Temporal Logic (STL). Along with a simple user interface, it also has fast and scalable mission planning abilities. We demonstrate our tool for one such mission.