Unmanned Aircraft Systems Traffic Management (UTM)
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This article introduces two related topics receiving attention from flight operations experts interested in manned, unmanned and autonomous aviation. Unmanned aircraft system traffic management (UTM) essentially is an initiative undertaken in various ways by national aviation authorities (NAAs). A common aspect of UTM is the NAA’s collaboration with — and dependence on — private-sector operators that cooperatively separate their small remotely piloted aircraft (RPAs) from those of other operators in uncontrolled airspace.
Urban air mobility (UAM) is a futuristic concept for a narrow group of RPAS operations — most prominently, scheduled/on-demand flights of “passenger drones.” In UAM, RPAs will be capable of routinely flying published routes above cities (and their aerodromes) at low levels, or conducting short-range flights between metropolitan areas.
The following technical details serve as examples, not necessarily matching developments in every country or envisioned by individual RPAS operators.
UTM' — This initiative primarily will mitigate the risk of collision among small unmanned aircraft systems (sUAS), a subset of RPAS, flying below 400 ft in uncontrolled airspace. UTM concepts also will segregate the participating sUAs from manned aircraft and other types of RPAs being controlled by air navigation service providers (ANSPs).
The International Civil Aviation Organisation’s (ICAO’s) Annual Report 2017 contains a section titled “New and Emerging Activities — Unmanned Aerial System Traffic Management (UTM).” The section said, “UAS traffic management is a concept that brings an automated ATM-like [system to very low level airspace, which will be occupied primarily by unmanned aircraft weighing less than 25 kg (commonly referred to as drones). Development of this concept is underway in many States, at universities and by large aviation corporations and new start-up tech companies.”
The section said that in September 2017, in the context of the ICAO Assembly’s request to include “all unmanned aircraft” in the organisation’s work programme, UTM became the main theme of the Drone Enable — ICAO Unmanned Aircraft Systems (UAS) Industry Symposium. “The focus was on UAS traffic management (UTM) and fundamental requirements needed for implementation, these being [drone] registration, identification and tracking; communications systems; and geo-fencing like systems,” ICAO said.
Among countries pursuing UTM systems, the U.S. Federal Aviation Administration (FAA) created its UTM Pilot Program (UPP) in April 2017. The program has been identifying an initial set of industry-provided and FAA-provided capabilities that will be required to support low-altitude sUAS operations (i.e., aircraft less than 55 lb/25 kg flying below 400 ft) that will depend on new, cooperative traffic-separation standards. The UPP ends in September 2019.
The final set of capabilities will define services to be provided by FAA and by private-sector UAS service suppliers (USSs), their respective roles and responsibilities, information architecture, data-exchange protocols, software functions, and performance requirements for managing these low-altitude sUAS operations without intervention by air traffic control (ATC) facilities. In January 2019, FAA selected three FAA UAS Test Sites for tests and demonstrations in conjunction with the National Aeronautics and Space Administration (NASA) and industry partners.
Explaining the impetus for UTM, the FAA said, “Currently, there is limited infrastructure available to manage the widespread expansion of sUAS or drone operations within the National Airspace System (NAS). A safe and efficient [UTM] system is needed to help ensure this quickly growing industry is able to integrate into the NAS safely and efficiently. … The primary goal for the UPP is to develop, demonstrate, and provide enterprise services, using a cloud service infrastructure which will support the implementation of initial UTM operations.
“These enterprise services will support the sharing of information that promotes cooperative separation and situational awareness. … UTM services to be demonstrated in the UPP include sharing of flight intent between operators, the ability for a UAS service supplier (USS) to generate a UAS volume reservation (UVR) — a capability providing authorized USSs the ability to issue notifications to UAS or drone operators regarding air or ground activities relevant to their safe operation – and [to] share it with stakeholders (e.g., other USSs, [FAA’s Flight Information Management System (FIMS) and] UAS operators).”
UAM — As in UTM, the airspace concepts, logistics, technologies and protocols for UAM would cooperatively separate the participating RPAs and autonomous/non-piloted aircraft (i.e., “passenger drones”) without traffic control by ANSPs. The typical UAM operator will fly missions between vertical takeoff and landing sites in a defined area (e.g., airport shuttles and air taxi services, emergency response aircraft or package-delivery aircraft).
Such missions would rely on precise navigation and timing through three-dimensional corridors of uncontrolled airspace. The benefits envisioned include high-speed transport, avoidance of motor vehicle traffic, and reduction of traffic congestion on streets, freeways and highways. Local UAM airspace will be designed to accommodate RPAs and autonomous/non-piloted aircraft used for intra-city flights (less than 100 km/62 mi) and short-range inter-city flights (more than 100 km), according to some researchers.
Roland Berger LLC, a consultancy based in Germany, expects to see electric propulsion systems on most UAM aircraft. The firm’s initial prediction of UAM-suitable RPA types includes the following designs: quadcopters, multicopters (distributed-propulsion and coaxial multirotor), hybrid-propulsion, tilt-wing/convertible-aircraft, fixed-wing vectored thrust and electrical vertical take-off and landing (eVTOL) types.
This consultancy concentrated its research on the following UAM segments in 2018 and 2019: passenger transport; package/cargo delivery (e-commerce transport); emergency medical transport and security-related operations; aerial inspection and motor vehicle traffic control; and research, development and testing of UAM aircraft, systems and safety.
- UTM — Parts of several FAA documents, combined here, define the U.S. UTM initiative as follows: “UTM is a traffic management ecosystem for uncontrolled operations that is separate but complementary to the FAA's ATM system.
“The FAA, NASA, other federal partner agencies, and industry are collaborating to explore concepts of operation, data exchange requirements, and a supporting framework to enable multiple, beyond visual line-of-sight [BVLOS] drone operations at low altitudes (under 400 ft above ground level [AGL]) in airspace where FAA air traffic services are not provided. …
“UTM relies on industry’s ability to supply services under FAA’s regulatory authority where these services do not currently exist. It is a community-based traffic management system, where operators are responsible for the coordination, execution and management of operations, with rules of the road established by the FAA.
“With UTM, there will be a cooperative interaction between drone operators and the FAA to determine and communicate real-time airspace status. The FAA will provide real-time constraints to the UAS operators, who are responsible for managing their operations safely within these constraints without receiving positive air traffic control services from the FAA.
“The primary means of communication and coordination between the FAA, drone operators, and other stakeholders is through a distributed network of highly automated systems via application programming interfaces (API), and not between pilots and air traffic controllers via voice.”
- UAM — In the absence of a standard definition, this term can be summarized as current aspirations for RPAS of various mass categories to be capable of flying published low-level routes above cities (and their aerodromes), and in some cases, using short-range RPA flights to connect nearby metropolitan areas (and their aerodromes).
Current UTM Areas of Focus
According to reports from EUROCONTROL, the SESAR Horizon 2020 PODIUM project began demonstrating UTM services, procedures and technologies in 2018 and 2019 at four operational sites in Denmark, France and the Netherlands. The project supports U-Space — a term defined as “the European vision for the safe, secure and efficient handling of drone traffic.” (The acronym PODIUM stands for Proving Operations of Drones with Initial UTM. The acronym SESAR stands for Single European Sky ATM Research Joint Undertaking.)
As leader of the consortium conducting the project, EUROCONTROL is responsible for this work’s alignment with overall strategies affecting European ATM and RPAS.
European stakeholders predict that UTM will be a key initial solution to what PODIUM project leaders call “increasing and unmanaged drone traffic and their relatively small size [that] can pose a threat to manned aviation.”
Their areas of focus include:
- Documenting how UTM provides mutual traffic situational awareness for the local participants;
- The role of ATM in facilitating operators’ day-to-day drone management;
- Reducing risks inherent in UTM deployments through “a comprehensive Web-based UTM system, using tracking systems based on Mode-S, L-Band and GSM networks for real-time tracking of RPAs;
- Demonstrating U-Space services;
- Communicating conclusions about the maturity of U-Space services and technologies;
- Issuing recommendations about future UTM deployments, regulations and standards.
The PODIUM project is scheduled to produce its final report in late 2019.
Current UAM Areas of Focus
According to a March 2019 study of UAM innovators, 100 UAM projects worldwide reflect significant progress by a diverse community of competitors and investors. The competitors comprise aviation-related companies and non-aviation-related companies that expect to apply RPAS capabilities to address complex transportation needs already identified by the world’s cities. As noted, urban “commercial passenger drone services” have been widely touted, and often characterized as imminent, by news media.
For example, Roland Berger LLC said, “Manufacturers of airplanes, helicopters and vehicles are represented, alongside mobility and delivery service providers. But there are also plenty of non-industry players involved, such as consumer goods producers, pharmaceutical companies, telecommunications firms, research institutes, as well as city authorities, nations and supranational entities. … The ecosystem is complex, and the challenges in urban air mobility projects are extensive.”
The consultancy’s interactive world map of UAM project sites specifically focuses on “projects that primarily target the use of autonomous drones to transport passengers, goods/parcels/mail and medication/first aid supplies around urban areas.”
Airspace Issues Confronting New Entrants
From the perspectives of EUROCONTROL and the European Aviation Safety Agency (EASA), UTM and UAM initiatives may warrant treatment as “new entrants” because they expand the list of reasons why flight rules need to be changed to accommodate low-level RPAS/UAS operations.
In a November 2018 discussion document titled UAS ATM Flight Rules, Edition 1.1, the agencies said, “At present, due to absence of flight rules for VLOS [UAS flights with visual line of sight] and BVLOS and their coexistence with manned aviation, it is not possible to safely integrate drones at altitudes below the lowest VFR [visual flight rules] altitude. The only way forward in this stepped approach is either through segregation of airspace or through the use of procedures where, in principal, drones remain clear of manned aircraft.
“As one of the principal objectives of flight rules is to ensure the safety of aircraft, crew, passengers and cargo through effective understanding and execution of responsibilities, a major problem that arises from the introduction of UAS into the airspace is the definition of priorities and rights of way, taking into account the vastly different speeds and capacities of different aircraft. … If and when every drone in a UTM environment is cooperative at all times, a potentially more efficient set of right-of-way rules than the current Standard European Rules of the Air (SERA) requirements permit could be developed, particularly for high-density environments. … UTM is key to the effective application of UAS Flight Rules and should also be part of the gathering and sharing of traffic situation data.”
The UTM environment has been specifically mentioned as a driver of flight rules revisions.
The agencies explained, “When commercial [UAS] operations commence in 2019, initial procedures must be established that exclude other traffic from the paths these drones will take, and perhaps require certain equipage to enable people’s awareness of these types of operation. Once this is done, the UTM environment must be treated. In the end, full cooperation between BVLOS and other traffic will be necessary. However, although outside the city or in low-density areas, the cooperative parts of flight rules might work perfectly, this might not be the case in urban areas with a large amount of interference.”
- “Autonomous urban transportation in the air: 100 projects have taken off globally” by Manfred Hader, Roland Berger LLC consultancy, Hamburg Office, March 25, 2019.
- NASA UTM Website.