The Future of Advanced Air Mobility
Air Traffic Management

For the new generation of electric vertical takeoff and landing (eVTOL) aircraft looking to drive the so-called urban air mobility (UAM) revolution, it is the prospect of autonomous (i.e. no pilot on board) operations that poses serious questions about how they can be safely integrated into the air traffic management (ATM) network. In so far as the new aircraft can be flown by pilots, they will essentially be treated much like today’s helicopters from an ATM perspective. This, as well as questions about passengers’ willingness to accept autonomous operations, is the key reason why the majority of eVTOL aircraft developers seem to be looking to at least begin the service life of their new products with a pilot on board.

In recent years, the extraordinary proliferation of unmanned aircraft systems (UAS), or drones, has presented a growing ATM challenge. In Rwanda, drones are now responsible for over half of all blood deliveries, and in Australia, Google's Wing recently launched its first public drone delivery service. A spate of events in which drones, apparently operated with malicious intent, seriously disrupted commercial aviation operations at major international airports including London Gatwick and Dubai have raised the stakes, increasing pressure on the industry to solidify a sustainable plan for what is now referred to as unmanned aircraft systems traffic management (UTM).

Government agencies worldwide, supported by industry bodies and stakeholders, are making a concerted effort to develop the legal structures and infrastructures required for aircraft to be operated autonomously in regulated airspace. Progress has undoubtedly been made, but the big picture remains far from completely resolved.

The reason this is so critical to the highly ambitious UAM sector is that the eVTOL pioneers are proposing to carry passengers in autonomously-operated aircraft and to do so in dense urban areas. This raises the stakes, but fundamentally the technical and operational issues are much the same as for drones being used for all manner of other purposes, including those that will deliver pizzas or human organs for transplant. What is clear is that rules already in place to cover the limited, but fast-growing, array of commercial drone operations are not sufficient to cover what the UAM industry has in mind.

Urban Air Mobility
EHang has had permission from the Civil Aviation Administration of China to conduct operational trials with its 216 Autonomous Aerial Vehicle (shown in the foreground) in several Chinese cities. In this regard, it has enjoyed more access to public airspace than most rival eVTOL aircraft developers.

With drones performing increasingly complex operations, including beyond visual line-of-sight (BVLOS), flying over urban areas and transporting people, these safety challenges will only continue to mount. For now, in so far as there are already rules governing UAS operations, they generally impose quite a narrow scope with limitations such as the following U.S. rules for so-called "Small UAS":

  • No flights within five miles of an airport
  • Stay below 400 feet
  • Fly slower than 100 mph
  • No aircraft weighing more than 55 pounds

Current U.S. regulations define any UAS exceeding 55 pounds in weight as a "Large UAS" and these cannot be operated in the National Airspace System unless the individual operator obtains both UAS airworthiness approval and operational approval. The latter requires either a special experimental airworthiness certificate under FAA Order 8130.34D (for testing purposes only) or an exemption based on the Special Authority for Certain Unmanned Systems covered by the 49 U.S.C. Section 44807 (for either testing or commercial operations).

Integration: A Challenge and a Priority

The proliferation of drones is rapidly transforming—and disrupting—airspace as we know it, and safely accommodating these new entrants is an essential priority for the ATM industry. With decades of experience in the safe, efficient, and effective management of air transport, ATM service providers are still coming to terms with this new era of aviation and the opportunities and benefits that remotely piloted and unmanned aircraft vehicle operations can bring. 

Swedish company Saab has been developing remote air traffic control technology that allow controllers to manage flights in places where it would not be cost effective to have a control tower.

"Unmanned and autonomous aerial vehicles are challenging traditional legal paradigms, while authorities that govern safety and security in the air are struggling to keep pace with technical innovation," wrote Harrison Wolf, Lead of Drones and Tomorrow's Airspace at the World Economic Forum's (WEF) Center for the Fourth Industrial Revolution and author of the WEF’s Advanced Drone Operations Toolkit. "Transport systems must adapt to meet the increasing demands of society, but without adding additional risks."

To promote the safe and compliant use of UAS, while also preventing future drone incursions, regulators and airspace stakeholders must implement new methodologies for evaluating and mitigating potential risks, both on the ground and in the sky. "The ATM industry's primary objective is the safe and efficient separation and flow of all aircraft, manned, remote and unmanned," said Civil Air Navigation Services Organization (CANSO) spokesperson Freyja Moorhead. "Safely integrating these new entrants into our already crowded skies and ensuring equitable access to airspace for all is one of the greatest tasks facing the transport industry today."

Because UAS do not operate point-to-point between established airports, they require a more effective use of airspace than current air traffic control (ATC) services can provide. "With UAS, we're talking about automated operations without onboard pilots, meaning the standard ATM process in which ATC verbally gives instructions to a pilot who implements them is inapplicable," said Air Traffic Control Association (ATCA) president and CEO Peter Dumont. "Today's ATC was not built to handle automated operations and will definitely not be able to handle the sheer amount of volume of UAS that is being predicted."

Data-based UTC
Current air traffic control arrangements are not set up for dealing with unmanned aircraft, but technology has been developing to allow for databased exchanges between aircraft and controllers.

Further complicating the situation is the fact that many of the new players in the UAS ecosystem do not come from the traditional aviation community and often seek to accomplish tasks that are not possible using traditional aviation technology. For example, the predicted number of UAS operating in urban areas—including the planned eVTOL air-taxi services—highlights a very different future for aviation compared with today, presenting both opportunities for connectivity and potential regulatory, operational and safety challenges that must be tackled.

"Consequently, regulation, supervision, and timely air traffic services must all be considered in enabling safe and equitable access, as well as expediting and maintaining an orderly flow of air traffic," said Moorhead. "This will become even more critical given the high degree of automation associated with UAS compared to conventional air traffic management."

Understandably, most regulations favor safety over enabling advanced operations, and thus significantly restrict where and how drones can operate. UAS are typically prohibited from flying over federal facilities or people, at night, and, unless permitted to do so, within five miles of an airport. Furthermore, most regulations require UAS to operate below 400 feet, at speeds of less than 100 mph and always to yield the right of way to manned aircraft. These regulations also tend to limit UAS operations to those weighing under 55 pounds. and require that they always remain in the operators’ visual line of sight (i.e., BVLOS).

These restrictive regulations severely limit the widespread use—or full enablement—of drones. "While the technology to make and operate air taxis is available now, the integration of these aircraft into a mature aviation system will take considerable effort and public confidence," says Federal Aviation Administration (FAA) spokesperson Paul Takemoto. "While the FAA encourages and supports the development of self-flying or autonomous aircraft, the rules for operating them are not in place, and this type of operation has not yet been tested."

What is needed is a system that both keeps our skies safe and enables the increasing movement of people and goods via drones. "While many emerging technologies proliferate in the absence of fit-for-purpose regulation, innovation in the application of drone technology is limited by governments' inability to update legacy rules to meet new possibilities," writes Wolf. "Most countries are struggling to routinely enable BVLOS operations, multiple aircraft per operator or autonomous operations, and operations around people, all key conditions for realizing the full potential of drones."

While many emerging technologies proliferate in the absence of fit-for-purpose regulation, innovation in the application of drone technology is limited by governments' inability to update legacy rules to meet new possibilities.

Metropolitan New York area
Commercial eVTOL air taxi operations, like those planned by Lilium, will need to be able to share very busy airspace around major urban areas like New York City.

The challenge of safe and equitable UAS integration into the aviation system is a significant change project for the entire industry. A collaborative approach among all stakeholders is essential to ensuring efficient and effective services as new airspace users take to the skies. From the regulators, states, airlines, airports, and industry suppliers, to drone manufacturers and operators, all will need to play their part in developing, managing and enabling the technologies and regulations needed to create an effective UTM system.

At its most basic level, UTM is a system meant to keep drones and manned aircraft from hitting each other. By allowing a UAS to see and be seen by other aircraft (both manned and unmanned) and airspace stakeholders, UTM will determine how BVLOS operations can safely take place in heavily trafficked, low-altitude airspace. "The viability of eVTOLs and urban air mobility depend on the development of a secure and safe UTM system," says Northeast UAS Airspace Integration Research Alliance (NUAIR Alliance) chief technology officer Andy Thurling.

The FAA, which, along with NASA, has developed a joint UTM Research Plan that maps out the development of UTM, defines UTM as "a traffic management ecosystem for uncontrolled operations that is separate from, but complementary to, the FAA's ATM system." Meanwhile, in its UTM Guidance, the International Civil Aviation Organization (ICAO) envisions UTM as "a subset of ATM, intended to manage UAS operations safely, economically, equitably, and efficiently through the provision of facilities and a seamless set of services, in collaboration with all parties and involving airborne and ground-based functions." The U.S. Department of Homeland Security simplifies it further, saying that UTM is "like air traffic management, but automated and in the cloud."

London (shown here with VRCO’s planned NeoXcraft), is a city that has imposed tight restrictions on helicopter operations, raising questions about how it will deal with eVTOL aircraft.

UTM or U-space? Same Game, Different Name

What the U.S. calls UTM in Europe is U-space. Despite the difference in name, both UTM and U-space are working toward the same goal: the creation of a drone ecosystem based on services enabled by new technologies, information sharing and automation and all underpinned by a robust regulatory framework. What is different, however, is the method of getting there.

“The European approach is more top-down, where we have a planned set of steps that need to be defined and then implemented to cater to ever-more complex operations,” says Robin Garrity, an ATM expert with SESAR, the joint venture formed to implement the so-called Single European Sky initiative. “UTM, on the other hand, takes a more bottom-up approach by trying and testing basic services and, based on this experience, determining where to go next.”

Regardless of how it is defined, what is essential is that UTM be interoperable with existing ATM systems and be able to provide an equivalent level of safety and compliance with the applicable and forthcoming rules. "As part of the appeal for UAM is to take people quickly across town to the airport, they must seamlessly integrate with traditional ATM systems and procedures, and UTM is a key component in achieving this," said Thurling.

"What we're looking at is a new service provider, the UTM, working together with ATC via appropriate regulations," added Dumont. "In this sense, ATC won't change, we're just adding another level of coordination to the equation."

Airmap apps
Airmap has pioneered a planned to support unmanned aircraft systems traffic management, including an app showing the location of individual aircraft.

A Seamless Set of Services for Advanced Operations

UTM is not, however, a single system. Instead, it is best defined as a complex collection of both technologies and regulations that, together, will facilitate full UAS enablement. "UTM is really a seamless set of services that integrates humans and information technology to manage UAS operations safely, economically and efficiently in a collaborative environment," explained Thurling. "What this means is that UAS operators can use UTM to understand airspace, geographic, weather, and other constraints, and then use that knowledge to plan better and safer flight operations, share their intent with other UAS operators and be strategically deconflicted from constraints and other users." 

More advanced UTM capabilities will make real-time information regarding airspace constraints and other airspace users' flight paths available to UAS operators. Using this information, operators will be able to deconflict on a more tactical basis without receiving positive air traffic control services from the FAA or other air navigation service provider (ANSP). This communication will be primarily through a distributed network of highly automated systems via application programming interfaces, and not between pilot and air traffic controllers via voice.

Anyone flying in the UTM system will be required to interface to a UAS Service Supplier (USS) to submit flight intent to other users and receive authorizations for specific access. This not only allows the UAS to communicate with UTM for pre-flight schedules and to announce their airspace use, it also allows UTM operations to scale up to the levels of density envisioned by delivery providers like Wing and Amazon.

An Enabling Regulatory Environment

Achieving full drone enablement will not happen overnight, and technology is only one piece of the puzzle. "The most important ingredient that will begin the development of a long-term and sustainable drone industry is an enabling regulatory environment that provides legal use of commercial and non-commercial operations," concluded the WEF’s Harrison Wolf. "Just as a flower may not bloom without soil for its roots to take hold, neither can a drone economy take root without a stable regulatory environment."

Because the current regulatory structure is built on the philosophy of having a pilot-in-command, new operational rules and a regulatory construct for supporting autonomous flight will be needed. "The level of automation necessary to safely replace functions of human pilots and air traffic controllers will require significant changes to our regulations and operational infrastructure," said FAA’s Paul Takemoto.

One significant change already being implemented is the use of permission-based regulations (PBR). The use of permission-based access to airspace lets regulators open otherwise closed airspace to operators meeting specific requirements or operational parameters. A prime example of such a regulation is the FAA's Low-Altitude Authorization and Notification Capability (LAANC) program. Through LAANC, commercial UAS operators certified under FAA Part 107 who are flying drones less than 55 pounds in weight can submit digital requests for authorizations to fly in controlled airspace.

Whereas the multi-step manual waiver process can take up to 90 days to process, LAANC automatically authorizes flights in controlled airspace, providing approval in a matter of seconds. Operators simply apply for airspace authorization through automated applications developed by an FAA-approved USS. Requests are checked against multiple airspace data sources within the FAA's UAS Data Exchange, including temporary flight restrictions, NOTAMs and UAS Facility Maps. This check happens immediately, meaning if approved, the UAS pilot will receive authorization in near-real time.

Although LAANC's weight limitation makes it of limited use to air taxis and large delivery drones, according to David Marcontell, General Manager of Oliver Wayman's CAVOK Group, it is a very critical first step. "The important piece of LAANC is that it is a mechanism that allows a drone pilot to interact with the FAA's air traffic control system," he says.

In this respect, LAANC is much like an instrument flight rules (IFR) flight plan that is filed by commercial airlines every day. "As drones get bigger in the future—subject to certification and infrastructure issues—the LAANC, or some variation thereof, will be a part of the process," adds Marcontell.

Demos, Sandboxes, and Prototypes

Although technology and regulations are the key components to building a robust UAS ecosystem, before drones can be embraced for extensive commercial use, the risks—especially from bigger drones—must be identified, and strategies to mitigate those hazards must be developed. One way of doing this is through technology demonstrations, regulatory sandboxes, and policy prototyping.

Just as a flower may not bloom without soil for its roots to take hold, neither can a drone economy take root without a stable regulatory environment.

"Technology demonstrations, regulatory sandboxes, and policy prototyping provide an opportunity for all stakeholders to experiment with new frameworks and new enabling infrastructure like UTM that can further support and accelerate positive integration into the airspace," declared Wolf. 

Lilium and other eVTOL air taxi service providers intend for consumers to be able to book their own flights, just as they already do with ground-based ridesharing programs. However, the complexity of managing how these vehicles will safely navigate shared airspace is far more complex.

Technology demonstrators are fit-for-purpose events geared towards showing relevant decision makers that a given technology is mature enough for implementation. Prime examples of such demonstrators include the U-space Demonstration Projects in the European Union and, in the U.S., the FAA’s UAS Integration Pilot Program (IPP).

Under the mandate of the European Commission, the SESAR has been charged with conducting U-space research and development, as well as staging demonstrations. The aim of this work is to show the readiness of U-space services to manage a broad range of drone operations and related services and their interaction with manned aviation. Demonstrations range from parcel deliveries between two dense urban locations, to medical emergency and police interventions, maritime search and rescue and forestry inspections. The demonstrations also aim to showcase the different levels of automation that are possible, as well as facilitate a seamless exchange of information between multiple drone operators and service providers.  

"By de-risking implementations, accelerating the lead time to market for new services and innovative solutions, and providing a platform for regulators and public authorities to share best practices and lessons learned, the U-space Demonstration Network will establish an integrated European airspace system, attracting additional commercial UAS businesses and investments," says Paul Bosman, head of  the aviation cooperation and strategies division of air traffic control agency Eurocontrol.    

The UAS IPP operates along similar lines. The purpose of the program is to accelerate and expand the safe integration of drones into the national airspace. Under the IPP, the FAA is partnering with local, state and tribal governments, which in turn are partnering with the unmanned aircraft industry, to explore ways to safely expand and manage cutting-edge drone operations.

"This program takes collaboration to a new level by enabling governments to determine what kind of activities will occur in their jurisdictions during the period of the pilot program and subject to FAA safety oversight," said Takemoto. "It also gives a wider range of private operators and localities the chance to propose solutions to the most difficult integration challenges."

The 10 programs, which are spread across the U.S., are evaluating a range of operational concepts, including night operations, flights over people and BVLOS, package delivery, detect-and-avoid technologies, and the reliability and security of data links between pilot and UAS. The FAA expects the program to provide valuable data and acquired knowledge to accelerate its efforts to enable the UAS industry, standardize low-altitude UAS operations, and improve safety through broadly applicable procedures and rulemaking efforts.

Regulatory Sandboxes

With regulatory sandboxes, governments create small areas where advanced operations are authorized to happen. Often called flight corridors, here stakeholders can experiment with complex operations in real-use scenarios and showcase the advantages of full enablement.

In the U.S., the Northeast UAS Airspace Integration Research (NUAIR) Alliance is building the first UTM 50-mile corridor for BVLOS tests. Located in New York state, the corridor runs between Syracuse and Griffiss International Airport. Part of Central New York's strategy for stimulating communities and growing the local economy (CNY Rising), NUAIR's mission is to advance the research, development, and deployment of state-of-the-art technologies to support integrating UAS into the nation's airspace. 

One of the Alliance's top priorities is conducting UTM standards flight test validations. "Despite many top-level strategic discussions on the topic of what UTM is intended to provide, there are no published standards defining the expected level of performance," said Thurling. "We defined 'what' UTM does and 'how' it talks, but not 'how well' it should do anything!"

According to Thurling, validated performance requirements are essential to moving the UTM ecosystems past the demonstration phase. Without standards that define the level to which UTM services are effective, it is impossible to quantify the risk mitigated by using a UTM service.

Policy Prototyping

Providing a planned revision of a policy, or a continuous process for evaluating the implementation of policies for UAS technologies according to key performance indicators, is a new approach to governance requisite to achieving full enablement. "Understanding that drone technologies, including UTM, are evolving rapidly, the policies that govern these technologies must also be able to evolve consistently," said Wolf.

An example of how this looks in practice can be seen in Switzerland's Federal Office of Civil Aviation (FOCA) approach oversight. Here, drones have been used to transport time-sensitive medical laboratory samples and urgently needed medication between two hospitals in Bern. This level of enablement has been possible due in large part to FOCA's implementation of the specific operation risk assessment (SORA) issued by the Joint Authorities for Rulemaking on Unmanned Systems (JARUS). SORA creates a framework to systematically and consistently evaluate the risks of particular UAS missions, giving regulators and ATC the unprecedented ability to quantify and describe the risk a specific mission might entail.

The SORA approach analyzes the overall complexity of UAS operations, along with various risk mitigations. This allows UTM platforms to ingest risk-based data sets and provide a consistent framework for authorities to implement more automated authorizations of drone flights.

Together with UTM, SORA helps pave the way for the risk-based authorizations required by advanced operations. "As more and more countries adopt SORA and new systems come online, the performance of those systems is better understood and the needs of communities and authorities evolve," writes Wolf. 

Even with all the right technology and regulations in place, full enablement will not happen if the public doesn't buy into the benefits of drones. Without concrete engagement and involvement, the public's very real concerns about privacy, data usage and safety could be a significant roadblock to full UAS enablement.

"Specific campaigns to develop community engagement by governments, while working with company vendors that also want to operate, can address the concerns of the public when impact-driven use cases have been developed," Wolf maintained.

Building Tomorrow’s Airspace Today

Estimates vary on the volume and value of the drone industry in the future. However, according to SESAR’s Drone Outlook Study, it is estimated that the industry will be worth over $11 billion annually by 2035, with a fleet of more than 400,000 commercial and government drones expected to be in use across Europe by 2050. Airbus UTM forecasts that more than 20,000 drones will be flying above Paris each hour by 2035. And, according to Goldman Sachs, the commercial drone segment will grow to $13 billion by next year, which equates to roughly 2.7 million units and a CAGR of approximately 27 percent.

But these numbers assume that the technology, infrastructure, and regulations will all come into place. Although great strides are being made on each of these fronts, there's still considerable work to be done. On the one hand, the infrastructure required to support air taxis, or even high-density drones in urban areas, is not yet in place. And the detect-and-avoid technologies, as well as the "bad actor" contingency technologies, have not yet been standardized.

On the other hand, there are also issues with the UAS technology itself. For example, whereas commercial aircraft design is effectively based on the probability of a fatal accident being no more than 1 x10-9 (i.e. less than 0.000000001), hardware designs in current UASs have not even come close to demonstrating that level of reliability and redundancy, which would be absolutely required to make the transition from hobby or even package operations to passenger operations like air taxis.

But change takes time and, despite some stakeholders' impatience with what is seen as a go-slow approach to drones, this caution is critical to the future of the industry. "A failure to sufficiently test and validate these rapidly emerging technologies could doom the industry before it even gets off the ground with the first loss of life from a drone mishap," said Marcontell.

That being said, change is happening. Starting with the enablement of complex commercial drone operations, the industry will slowly scale up to bigger and more sophisticated services, including air taxis. In fact, the United Arab Emirates (UAE) is already conducting advanced tests with UAS hoverbikes that could soon be used by the Dubai police force.

“Private and public entities alike are making great strides in defining the standards, procedures and security concerns necessary to lay the groundwork for a robust UTM system," said Dr. Isabel Del Pozo de Poza, head of Airbus UTM. "We know the airspace of tomorrow can only deliver on its promise of full drone enablement through further industry collaboration—with regulators, manufacturers, service providers, and consumers all working together with a common understanding."

Speaking of the airspace of tomorrow, the real question on everyone’s mind is 'When can I take an Uber Air [flight]?' "This is purely my personal opinion, but I think we'll see authorized air-taxi operations in remote areas sometime around 2025, with limited urban applications to follow around 2030," predicted Marcontell.  

Remote ID: Separating the Bad Actors from the Good

As was made clear by the airport incursions of late 2018 and early 2019, for UTM to work, airspace authorities must have the ability to identify good actors from bad actors. Here, Remote Identification (Remote ID) has emerged as a critical component to achieving fully integrated UTM services. Essentially a virtual license plate, the Remote ID is a unique digital certificate for every drone and its human operator. Just as a license plate lets law enforcement know whether a vehicle is properly licensed, Remote ID allows airspace managers, law enforcement officials and, to a certain degree, the public to quickly assess whether a UAS has the right authorizations or whether it requires intervention.

In practice, when there is a drone sighting near an airport runway, instead of immediately canceling thousands of flights, as was the case at Gatwick in December 2018, security could use Remote ID to first identify the drone, determine whether it has permission to be there and, based on this information, act accordingly.

Essentially, Remote ID gives authorities clarity about what's happening in the airspace, a clarity that is essential to expanding the type of operations that UAS are allowed to perform. "Before such wide-scale drone operations as autonomous deliveries or even air taxis can take place, we need to ensure that regulators—and the public—can easily assess whether or not a particular drone belongs to a good actor or requires intervention," said Ben Marcus, co-founder and chairman of AirMap, a UTM service provider. "Remote identification applications help airspace managers enforce aviation regulations while cultivating public trust in drones."

Volocopter Prototype
In August 2019, Volocopter flew its eVTOL prototype at Helsinki International Airport using both the ATM and UTM networks as part of Eurocontrol’s u-space project.

But regulating airspace also means ensuring that UAS operators have the tools they need to know where and when they can and cannot fly. Airspace is complex and always changing, meaning an operator can inadvertently enter regulated or restricted airspace.

According to a study by Embry-Riddle Aeronautical University, this happens quite often, with the study finding 20 percent of operators flying higher than the safe altitude prescribed for their given operating area. In other words, at least one out of every five operations pose an unmitigated risk to manned aircraft. Furthermore, only 12 percent of operations took place over unimproved land or parks. This means that 88 percent of operations surveyed were taking place near or above obstructions, urban structures or other hazards.   

Using geofencing, airspace regulators can build virtual fences and establish no-fly zones around specific areas or points of areas. When using a properly equipped UAS, an operator will receive a real-time alert whenever they approach or intersect geofenced airspace where a flight is either regulated, restricted or prohibited, allowing them to correct their course. Chinese eVTOL aircraft developer EHang, which appears to enjoy a very supportive relationship with China’s aviation authorities, has established just such a geofencing experiment in its home city of Guangzhou.

Whether an airspace regulator or an airspace user, having the right information is key to airspace safety. On the one hand, authorities must be able to monitor all flights and ensure that a UAS without permission stays out of restricted airspace. On the other hand, operators must have easy-to-use, up-to-date and fully configurable airspace monitoring tools. Remote ID and geofencing are steps in the right direction.

To this end, on December 31, 2019, the FAA issued a Notice of Proposed Rulemaking for regulations covering Remote ID processes and technologies for UAS. The industry has until March 2, 2020 to comment on the proposals.

Ehang Command
EHang has established a trial command-and-control system for eVTOL operations in the Chinese city of Guangzhou as part of a pilot program approved by the Civil Aviation Administration of China.