61ST ANNUAL CONFERENCE, 23-27 May 2022
WP No. 57
General Considerations on the Impact of U-Space Dynamic Airspace Reconfiguration on ATS Units
Presented by IFATCA RPATF Coordinator (Eugenio Diotalevi)
Unmanned Aircraft System (UAS) are one of the most promising business opportunities worldwide and are evolving rapidly. The current Air Traffic Management (ATM) system is not able to accommodate and manage UAS operations entirely due to reasons connected both to their specificities and different technologies used and to the shortage in Air Traffic Control (ATC) capacity.
UAS Traffic Management (UTM) has been specifically designed and developed to securely, economically, and efficiently manage UAS operations. U-space is the European UTM concept and it will become applicable on 26th January 2023 within specific portions of airspace identified by Member States called “U-space airspace”.
Despite UTM being separate from ATM, the two systems require exchanging information and data to safely manage their own traffic, while maintaining separate responsibilities. In particular, the European Commission (EC) has mandated that manned traffic in controlled airspace and unmanned traffic in U-space airspace established within controlled airspaces have to be segregated. To ensure this, a dynamic airspace reconfiguration concept has been developed. It requires ATC units to coordinate with proper U-space Service Providers (USSP) the deactivation or the boundary reconfiguration of specific parts of the U-space airspace.
Such reconfiguration is an additional workload source for ATC units that might affect the ATC capacity. This document analyses the possible dynamic airspace reconfiguration procedure from the ATC point of view and identifies possible sensitive areas for the workload to be further explored. Furthermore, it proposes a methodology to evaluate the procedure and the workload to help Air Navigation Service Providers (ANSP) and other U-space stakeholders to improve the efficiency of the entire ATM/UTM combined system.
1.1. It is recommended that this paper is accepted as information material.
GENERAL CONSIDERATIONS ON THE IMPACT OF U-SPACE DYNAMIC AIRSPACE RECONFIGURATION ON ATS UNITS
Unmanned Aircraft System (UAS) (see list of definitions in Appendix A) with their associated technologies, design, and business concepts are evolving rapidly. States are hence being challenged with the safe, secure and efficient integration of unmanned operations into volumes of airspace in which highly regulated and well-established manned aircraft activities have taken place for decades.
ICAO lists 4 main requirements  for integration of manned and unmanned traffic in the same volume of airspace:
a) The integration of UAS shall not imply a significant impact on current users of the airspace;
b) UAS shall comply with the existing and future regulations and procedures laid out for manned aviation;
c) UAS integration shall not compromise existing aviation safety levels nor increase risk more than an equivalent increase in manned aviation would;
d) UAS operations shall be conducted in the same way as those of manned aircraft and shall be seen as equivalent by ATC and other airspace users.
UAS Traffic Management (UTM) (see list of definitions in Appendix A) is envisaged to be the response to the need to accommodate high volumes of UAS traffic in airspace regions so far underutilised (e.g. below 1000 ft AGL above metropolitan areas). In addition, UTM aims at also solving the issue of how manned and unmanned aviation can coexist within the same portion of airspace. UTM, named U-space (see list of definitions in Appendix A) in the European Union (EU), is considered a separate, but a potentially complementary, system to the Air Traffic Management (ATM) system (see list of definitions in Appendix A) . UTM is structured as a set of collaborative facilities and digital services to manage UAS operations safely, securely, economically, and efficiently. However, as it will be detailed later in this document, UTM implementation implies additional requirements for interacting stakeholders, for example mandating the electronic conspicuity for manned aviation in regions of airspace mainly used by UAS. In addition, in a broader vision, ISO DIS 23629-12  states that UTM serves all properly equipped aircraft (i.e. both manned and unmanned) in the Designated Operational Coverage (DOC).
The need to implement UTM (U-space) derives principally from the high volume of UAS operations expected in the coming decades. At the current pace, the number of UAS operations will surpass conventionally piloted aircraft (CPA) operations within a few years at Very Low Level (VLL) in particular above urban areas (see note below), in which case operations may largely occur below the coverage of VHF radio-telephony and Secondary Surveillance Radars (SSR). The current ATM system, with its technologies and declared capacity (see list of definition in Appendix A), is unable to accommodate such new demand. Furthermore, differently from ICAO requirements, experiences have shown that UAS cannot be completely handled as traditional manned aviation because types of operation, technical characteristics, performances, dimensions, and the absence of the pilot on board make CPA’s regulations not applicable in most of the cases.
Readers may however note that, based on Art. 40 of the Chicago Convention, ICAO is tasked to standardise only international aviation (i.e. large Remotely Piloted Aircraft (RPA) flying under Instrument Flight Rules (IFR) along controlled airways also used by conventional airlines). Conversely, ICAO does not have the mandate to standardise operations of small UAS at VLL below the minimum heights in Annex 2 to the Chicago Convention.
Analysing research and development activities, it has to be noted that studies on UTM are mainly focused on UAS integration requirements in terms of collision avoidance and to overcome limitations introduced by the absence of a pilot on board. Few of them, at least until 2021, are investigating the relationship between ATC and UTM in terms of workload inducted to the ATC system.
This document hence points out some elements that are essential to try to understand the role Air Traffic Controller Officers (ATCO) in relation to U-space and which are the sensitive key areas that should be taken into consideration in developing procedures and tools in that respect.
First of all, how can the community make U-space able to operate without impacting on ATCOs workload? Or, an alternative question would be, is ATC capacity affected by UAS operations?
NOTE: VLL is the airspace below that used by VFR flights (see list of definition in Appendix A). In ICAO Annex 2  and SERA  there are statements about the minimum height for VFR. For example in SERA section 5005 is written:
(f) Except when necessary for take-off or landing, or except by permission from the competent authority, a VFR flight shall not be flown:
(1) over the congested areas of cities, towns or settlements or over an open-air assembly of persons at a height less than 300 m (1 000 ft) above the highest obstacle within a radius of 600 m from the aircraft;
(2) elsewhere than as specified in (1), at a height less than 150 m (500 ft) above the ground or water, or 150 m (500 ft) above the highest obstacle within a radius of 150 m (500 ft) from the aircraft.
1.1. To fly a drone, UAS operators (see list of definitions in Appendix A) shall respect all requirements and limitations posed by the airspace structure. Art. 15 of EC Implementing Regulation (EU) n°2019/947  enables the Member States to establish UAS “geographical zones” (see list of definitions in Appendix A), or “geozones”, where there are needs to facilitate, restrict or exclude UAS operations. These geozones may be established in controlled airspace or not (see list of definitions in Appendix A) and they are essential to address risks pertaining to safety (see list of definitions in Appendix A), privacy, protection of personal data, security or the environment, arising from UAS operations. For example, through Circular ATM 09A , ENAC has established that in Italy, inside aerodrome traffic zone (ATZ) or control zone (CTR) (see list of definitions in Appendix A), UA may fly, under certain conditions, below the Obstacle Free Zone (OFZ) (see list of definitions in Appendix A) protecting manned traffic around the aerodrome. In this way, due to the very limited maximum height allowed to UAS, there is no possible conflict between manned and unmanned traffic.
1.2. In circumstances described above, UAS Operators have no help in managing their missions in such UAS geographical zones. All work remains under the responsibility of UAS Operators, from the planning phase to execution, including deconfliction with other traffic. With the number of operations that is continuously rising, and the consequent possible coexistence of drones under control by different operators in the same geozone, there is the need to establish a UTM system (see list of definitions in Appendix A) to manage and coordinate all UAS operations in a given geozone.
1.3. SESAR Joint Undertaking, in coordination with EASA, proposed that U-space « is a set of services provided in an airspace volume designated by the Member State to manage a large number of UAS operations in a safe and efficient manner» . U-space services (see list of definitions in Appendix A) are provided within specific geographical zones that are called U-space airspaces (see list of definitions in Appendix A). These zones can either be established inside or outside controlled airspaces as per Standardised European Rules of the Air (SERA) .
1.4. The first European “blueprint” for the U-space was published by the SESAR JU in 2017 , followed by a more comprehensive CONOPS (see list of definitions in Appendix A) developed by the EU-funded Project CORUS . Based on this concept and on the subsequent EASA Opinion 01/2020  the U-space has been initially regulated through a package of Commission Implementing Regulations that will be applicable from 26th January 2023. Such package is composed of Reg. (EU) 2021/664 , Reg. (EU) 2021/665 , and Reg. (EU) 2021/666 .
1.5. In late 2018, EUROCONTROL developed the UAS ATM Integration Operational Concept  in partnership with EASA. This document, in line with ICAO 2016-2030 Global Air Navigation Plan (GANP) , highlighted the need to adopt a step approach towards the full integration of UAS activities into the ATM environment.
1.6. Following the suggested approach, in its initial stage, the U-space has been regulated in the EU as a stand-alone system that serves only UAS traffic. Despite its isolation, U-space requires information and interactions with ANSPs Air Traffic Services units (ATS units) (see list of definitions in Appendix A), UAS operators, and manned aircraft operators (see list of definitions in Appendix A). These interactions are even more important if manned traffic intends to operate inside the U-space airspace, such as manned helicopters in emergency services. For this reason, the EC has set two different procedures to manage mixed traffic according to whether U-space airspace is inside or outside controlled airspace.
1.7. To cross or to operate into U-space airspace established outside controlled airspace, manned aircraft operators have to fulfil requirements of electronic conspicuity as per Reg. (EU) 2021/666 . It means that they shall make themselves continuously electronically visible to the U-space service providers (USSP). This requirement is essential for the correct provision of the Traffic Information Service (TIS) to UAS operators from the competent USSP.
1.8. In case of U-space airspace inside controlled airspace, the competent ATC unit (see list of definitions in Appendix A) is responsible for the dynamic airspace reconfiguration (see list of definition in Appendix A) of the U-space airspace ensuring that, at any time, segregation exists between manned and unmanned traffics . Thus, the ATC unit has to change three-dimensionally the u-space airspace’s limits, as well as completely deactivate it, to avoid proximity between UAS operating into it and manned aircraft. The concept is similar to the Temporarily Reserved Areas (TSA) in the Flexible Use of Airspace (FUA) .
2. Airspace classification and UAS operations
2.1 A global ATM system  should provide an operating environment that ensures that all airspace users have the right of access to the ATM resources needed to meet their specific operational requirements and that the shared use of airspace by different users can be achieved safely. Furthermore, a global ATM system should ensure equity for all users that have access to given airspace or service, whether the involved aircraft is manned or unmanned.
2.2 The airspace is a strategic resource and the possibility to share it among different users, regardless of the type of operations they want to conduct is essential for all the States. It allows new business models to emerge on the market and economic development as well as military operations. UAS are only the new actors that claim for it.
2.3 The volume of available airspace is usually not sufficient to accommodate with total freedom the total traffic demand. Markets and business opportunities are based on reliable, predictable, and sustainable operations with an Acceptable Level of Safety Performance (ALoSP) (see list of definitions in Appendix A). The ALoSP is defined in ICAO Doc 9859  and implemented by safety regulatory authorities in terms of the combination of the frequency (probability) of an occurrence and its associated level of severity. Airspace users are hence prepared to accept limitations and conditions if these are fair, known, safe, and predictable.
2.4 To meet safety objectives defined by ALoSP, operations, air traffic services airspace (ATS airspace) (see list of definition in Appendix A) and its structures shall be managed and organised in accordance. For this reason, art.3 of Reg. (EU) 2021/664  requires Member States to perform an airspace risk assessment (see list of definitions in Appendix A) before implementing the U-space airspace. There is limited information available for UAS operations unlike for manned aviation. Consequently, there are many unknown factors and new risks that need to be identified and assessed, especially those connected to mixed manned and unmanned operations.
2.5 Having considered that EC has adopted two different approaches in allowing manned and unmanned traffic in the same portion of airspace simultaneously, the determining factor is the classification of ATS airspace where the U-space airspace is set and consequently, the type of Air Traffic Services (ATS) (see list of definitions in Appendix A) provided therein.
2.6 Outside controlled airspaces, only flight information service (FIS) (see list of definitions in Appendix A) and alerting service (ALS) (see list of definitions in Appendix A) are currently provided . For manned aviation, “see and avoid” is the primary means of ensuring safety and preventing collisions . Pilots increase such capabilities through information provided by FIS and no separations are provided by ATS units. On the other hand, mainly due to the relatively small size of UAS, see and avoid is hardly applicable for manned aviation pilots to detect and solve possible conflicts with UAS. For these reasons, the responsibility to avoid UA colliding with manned and unmanned aircraft and to maintain the overall safety lies on the UAS operator, through the remote pilots it employs. This is easy to achieve until the UAS operation is in Visual Line-of-Sight (VLOS) (see list of definitions in Appendix A). But less trivial for operations Beyond VLOS (BVLOS) (see list of definitions in Appendix A). Therefore, to allow the community to safely manage UAS operations in BVLOS, the competent USSP has to provide UAS Operators with all traffic information about any other conspicuous air traffic that may be in proximity to the position or intended route of the UAS flight.
2.7 In controlled airspace, alongside FIS and ALS, air traffic control service (ATC) is also provided. ATC service is defined  as «a service provided for the purpose of:
a) preventing collisions:
I. between aircraft, and
II. on the manoeuvring area between aircraft and obstructions; and
b) expediting and maintaining an orderly flow of air traffic. »
2.8 Furthermore, «in order to provide ATC service, an ATC unit shall:
a) be provided with information on the intended movement of each aircraft, or variations therefrom, and with current information on the actual progress of each aircraft;
b) determine from the information received, the relative positions of known aircraft to each other;
c) issue clearances and information for the purpose of preventing collision between aircraft under its control and of expediting and maintaining an orderly flow of traffic;
d) coordinate clearances as necessary with other units:
i. whenever an aircraft might otherwise conflict with traffic operated under the control of such other units;
ii. before transferring control of an aircraft to such other units.» 
2.9 From the paragraphs above it is clear that ATC requires a comprehensive situational awareness as well as the possibility to interact with all traffic under control to issue ATC clearances to prevent collisions. Interactions are primarily made by bi- directional radio communication that requires equipment and certification of airborne elements in addition to the declaration of verification signed by the ATS Provider for the ground elements .
2.10 The cost to obtain such capabilities in all geozones at VLL have been deemed too high and EC and UAS Operators are considering such costs a limiting factor for the expansion of the UAS market. In addition, ATC units can be in the position of benign overloaded by the amount of information and communication to handle if the volume of UAS operations will progress as expected, if applying the same enablers and procedures traditionally used. The effectiveness of the service would be degraded to a point where manned aviation won’t receive any useful information to support their detection of possible conflict and the safety of operations.
2.11 Considering also these reasons, EC has decided to segregate the two different flows of traffic operating into controlled airspaces and, consequently, dynamic airspace reconfiguration is the means through which manned aviation can use a portion of airspace normally reserved for UAS operations. As the airspace, also responsibilities to manage traffic are divided and the ATC unit will remain responsible to provide ATS to manned aviation that is crossing the deactivated portions of U-space airspace.
3. Dynamic airspace reconfiguration procedures
3.1. Dynamic airspace reconfiguration means the temporary modification of the volume of the U-space airspace in order to accommodate short-term changes in manned traffic demand, by adjusting the geographical limits of that U-space airspace .
3.2. This definition was explained by EASA in Notice of Proposed Amendment (NPA) 2021-14  containing draft Acceptable Means of Compliance 8AMC) and Guidance Material (GM) related to Regulation 2021/664. In particular, the NPA clarifies that since U-space airspace would be established by the competent authority based on Art. 15 of Reg (EU) 2019/947 , there are needs to facilitate, restrict or exclude UAS operations in order to address risks pertaining to safety, privacy, protection of personal data, security or the environment, arising from UAS operations. Even if not explicitly reported in regulations, this leads to the conclusion that in nominal situations UAS has priority on utilizing the U-space airspace. Dynamic reconfiguration should be applied as an exception or during periods of low demand by UAS.
3.3. Examples given by EASA NPA 2021-14  as reasons to apply dynamic airspace reconfiguration are ranging from clearing the path of an aircraft in emergency or distress, to accommodating unexpected traffic demand due to any contingency situation or allowing a shorter route for an individual flight, as well as potential U-space airspace restrictions to enable military and State operations. Furthermore, AMC2 ATS.TR.237(a) proposed by same NPA  recommends that dynamic airspace reconfiguration causing the forced landing of unmanned aircraft should only be applied when so dictated by safety reasons connected to manned traffic, in order to avoid unnecessary risks.
3.4. Based on in the provisions of Reg. (EU) 2021/665  complemented by EASA NPA 2021-14 , figure 1 presents a possible overview of the dynamic airspace reconfiguration procedure. However, it is not detailed and, at this stage, different implementations are even possible. In particular, Letter of Agreements (LoA) between ATC unit and USSP should specify conditions for every possible strategic scenario.
3.5. The flowchart is subdividing different tasks among the actors involved in the procedure and it is clear that the decision on initiating the procedure lays on the ATCO on duty (see list of definitions in Appendix A). The ATCO has to evaluate the request according to several factors: operational and safety conditions, current status of the U- space airspace (for example if it is deactivated from a previous request or it has a low demand for UAS operations) and according to all additional information available. It is also clear that the ATC clearance cannot be issued to manned aviation before UAS operators have vacated the U-space airspace as instructed by the competent USSP (this condition might not be respected in case of emergency or if so coordinated in the LoA).
4. Impact of dynamic airspace reconfiguration on ATC capacity
4.1. ICAO, in DOC 4444 PANS-ATM , states that «the number of aircraft provided with an ATC service shall not exceed that which can be safely handled by the ATC unit concerned under the prevailing circumstances». In fact, ICAO Annex 11  defines declared capacity as « a measure of the ability of the ATC system or any of its subsystems or operating positions to provide service to aircraft during normal activities. It is expressed as the number of aircraft entering a specified portion of airspace in a given period of time, taking due account of weather, ATC unit configuration, staff and equipment available, and any other factors that may affect the workload of the controller responsible for the airspace».
4.2. ImplementingRegulation(EU)2021/665establishes new obligations to be fulfilled by ANSP and ATC units in relation to U-space. Evaluation of the request, coordination and the application of dynamic airspace reconfiguration procedure represent sources of additional workload. Consequently, increased workload directly affects ATC capacity.
4.3. Even if the dynamic airspace reconfiguration is expected to be exceptionally applied by the ATC unit, situations are quite common in daily work. An example is a helicopter emergency medical service (HEMS) that has its target inside the U-space airspace. Although pre-coordination activities and agreements would be possible and recommended among ATC unit, manned aircraft operators and USSP , these will relieve only partially the workload on the ATC unit since timing and traffic situation cannot be precisely described in advance.
4.4. To preserve ATC capacity for manned traffic, time used in dynamic airspace reconfiguration and coordination should be minimised. Two possible methods can be suggested for this scope:
i. procedure and airspace structure optimisation and/or,
ii. task sharing.
4.5. For sure, the procedure has to be as simple as possible and avoid unnecessary tasks, information, and side effects on workload. LoA as well as a U-space airspace sub- structure that allows easy and quick activation/deactivation of some areas are essential to reduce as much as possible the strategic workload.
4.6. In particular, human machine interface (HMI) for coordination between ATC units and USSP plays an essential role. In addition to ergonomics and human factor considerations, it has to be studied if data has to be managed in a separate way or they have to be integrated into systems in use. This aspect is extremely important, especially if the procedure has to be solely applied by the ATCO responsible for the airspace. Timewise, this is the worst-case scenario and the dynamic airspace reconfiguration procedure has the biggest impact.
4.7. A second option could be to share the burden among all components of the ATC unit. Tasks can be distributed to minimise the workload on the ATCO on duty and they can be assigned to other operating positions, such as coordinators and/or supervisors. Establishing a dedicated position operated by specialised operators could be another possible option. Above all, it has to be ensured that coordination tasks inside the ATC units are affordable and minimised.
4.8. In the absence of parameters that might be used to evaluate UAS (such as parameters applicable to VFR flight) (see list of definition in Appendix A) and due to scarce data related to a procedure not yet implemented, it is not easy to determine the impact of dynamic airspace reconfiguration on capacity. In fact, there is no evidence in international documents that elements outside the number of IFR flights (see list of definition in Appendix A) and airport layout are used in such calculation . Attempting to give numerical data, a starting value might be provided by the Capacity Analysis methodology (CAPAN) . It reports that the Theoretical Sector Capacity is attained when controller workload reaches 70% of the absolute working time. It means the ATCO spends 42 minutes in an hour doing discrete events: speaking, writing, typing, or coordinating, for example. The remaining 30% represents tasks that cannot be captured by discrete events, such as general monitoring of the radar screen or recuperation time.
Figure 1: example of possible dynamic reconfiguration procedure
4.9. From these values, it is possible to calculate that for each minute actively dedicated to the dynamic airspace reconfiguration procedure, ATCO uses 2,4% of the maximum theoretical sector capacity. Namely, it means that theoretical sector capacity usable for manned aviation is reduced by 2,4% for each minute spent on accomplishing UAS related tasks.
4.10.This data is only an estimate based on general information. Since different procedures and interfaces will be implemented, the value does not give any quantitative indications on the number of operations manageable per minute. However, this could be a starting point to be considered by ANSPs, that are constantly looking for increasing ATC capacity, by the Member States, that have to support UAS operations establishing U-space airspaces and by ATCOs themselves, that have to decide if and when to apply the dynamic airspace reconfiguration procedure.
5. NASA TLX
5.1. As described, ATC capacity, workload and time are interdependent variables. Even if the overall picture is becoming even more detailed and defined, real implications on applying the dynamic airspace reconfiguration are not available at the time this document is written. This is because U-space regulations will be applicable from 26th January 2023 . During past years, several projects have investigated UAS related matters but only a few of them have focused on ATM-UTM coordination.
5.2. Further analysis and simulations are therefore necessary and, in particular, the correct HMI should be developed. A possible methodology to evaluate human performances and workload experiences is the one developed by the Human Performance Group of NASA’s Ames Research Centre called NASA Traffic Load Index (NASA-TLX) . The TLX is «a multi-dimensional rating procedure that provides an overall workload score based on a weighted average of ratings on six subscales: Mental Demands, Physical Demands, Temporal Demands, Own Performance, Effort, and Frustration» (see definitions in Appendix B).
5.3. It is worth underlining that, in addition to common items used to study workloads, such as Mental Demand and Temporal Demand, the TLX explores particular aspects. For example, under the definition of Physical Demand it considers aspects of ergonomic and usability of the HMI that have a direct impact on performance and on the time spent to accomplish the task.
5.4. It would be very interesting to explore the Frustration Level subscale in relation to the dynamic airspace reconfiguration. Two different results might be expected depending on the role of the person tested. On the one hand, if dedicated positions and personnel are used, the reconfiguration task is the main (and sole) task. Consequently, the frustration level would produce no other factors to be considered apart from the procedure itself. On the other hand, for example, should the procedure be performed by the ATCO responsible for the airspace, several tasks would become interrelated and would have to be carried on by the same person. In this case, it is expected that the level of frustration would depend on how the reconfiguration task interferes with other activities (maybe with higher priorities) and how it is considered urgent and important.
5.5. The overall workload score provided by the TLX would be an indication of how productive, applicable, and understandable procedures and interfaces are. ANSPs could use these data to balance internal procedures, to set up the correct ATC unit layout configuration, and to provide other U-space stakeholders with indications on how to improve coordination tasks and information exchange.
U-space is essential to support and protect UAS operations. It is also the first essential step towards the integration of manned and unmanned traffic. UAS specificities, capabilities and technologies require a dedicated system that is able to provide UAS Operators with all necessary services and information for safe operations, including information to prevent collision with manned traffic. These services will be available in dedicated areas called U- space airspaces.
Regulations developed for manned aviation barely support unmanned activities. Therefore, it is essential to develop procedures that take into consideration different services provided in different airspaces. Outside controlled airspaces, manned aviation allows UAS Operator to prevent a collision by making themselves electronically conspicuous while crossing U-space airspaces. In controlled airspaces, EC has established that manned aviation and UAS operating in U-space airspace established within controlled airspace shall be segregated. This is because ATC units are responsible for manned aviation safety. In exceptional circumstances where manned aviation has to use portions of controlled airspace identified as U-space airspace, the ATC unit has to dynamically reconfigure the U-space airspace in order to ensure that prescribed segregation is maintained.
Coordination tasks and the dynamic reconfiguration procedures are new tasks that add up to those already performed by ATC units. They have an impact on workload and, since the workload is strictly connected to ATC capacity, they negatively affect such capacity.
To preserve ATC capacity, time spent by the ATC unit to perform tasks related to UAS operations should be minimised. This objective requires adequate procedures, interfaces, and, if deemed preferable, to establish a dedicated position with dedicated personnel.
NASA TLX is a possible methodology to evaluate human performances and perceived workload on applying the dynamic reconfiguration tasks. This might help ANSPs to correctly evaluate the preferred configuration case by case.
Even if the U-space concept was initially presented in 2017, operationally-wise it has never been implemented before. It will become applicable on 26th January 2023. This has as a consequence that regulations supporting its implementation, although promulgated, may still be not sufficiently mature, inter alia because no real data are presently available to evaluate the actual impact on ATC. So far, only a few studies have been conducted on this. It is therefore not excluded that U-space regulations and related AMC/GM and industry standards would evolve in the future.
In any case it is essential that ATCOs are involved during the U-space implementation process, especially in situations where, with their deep knowledge of every local situation, they can provide useful inputs to allow the entire process to start at the right pace.
Appendix A – Definitions
Acceptable level of safety performance (ALoSP) – The level of safety performance agreed by State authorities to be achieved for the civil aviation system in a State, as defined in its State safety programme, expressed in terms of safety performance targets and safety performance indicators (ICAO Doc 9859 ).
Aerodrome traffic zone (ATZ) – An airspace of defined dimensions established around an aerodrome for the protection of aerodrome traffic (ICAO Annex 2 ).
Air traffic – All aircraft in flight or operating on the manoeuvring area of an aerodrome (ICAO Annex 11 ).
Air traffic control clearance – Authorization for an aircraft to proceed under conditions specified by an air traffic control unit.
Note 1.— For convenience, the term “air traffic control clearance” is frequently abbreviated to “clearance” when used in appropriate contexts.
Note 2.— The abbreviated term “clearance” may be prefixed by the words “taxi,” “take-off,” “departure,” “en route,” “approach” or “landing” to indicate the particular portion of flight to which the air traffic control clearance relates (ICAO Annex 11 ).
Air traffic control service (ATC) – A service provided for the purpose of:
a) preventing collisions:
1) between aircraft, and
2) on the manoeuvring area between aircraft and obstructions; and
b) expediting and maintaining an orderly flow of air traffic (ICAO Annex 11 ).
Air traffic control unit (ATC unit) – A generic term meaning variously, area control centre, approach control unit or aerodrome control tower (ICAO Annex 11 ).
Air traffic management (ATM) – The dynamic, integrated management of air traffic and airspace including air traffic services, airspace management and air traffic flow management — safely, economically and efficiently — through the provision of facilities and seamless services in collaboration with all parties and involving airborne and ground-based functions (ICAO Doc 4444 ).
Air traffic management system – A system that provides ATM through the collaborative integration of humans, information, technology, facilities and services, supported by air and ground- and/or space-based communications, navigation and surveillance (ICAO Doc 4444 ).
Air traffic service – A generic term meaning variously, flight information service, alerting service, air traffic advisory service, air traffic control service (area control service, approach control service or aerodrome control service) (ICAO Annex 11 ).
Air traffic services airspaces – Airspaces of defined dimensions, alphabetically designated, within which specific types of flights may operate and for which air traffic services and rules of operation are specified.
Note.— ATS airspaces are classified as Class A to G as described in 2.6 (ICAO Annex 11 ).
Air traffic services unit – A generic term meaning variously, air traffic control unit, flight information centre or air traffic services reporting office. (ICAO Annex 11 ).
Airspace risk assessment – An evaluation of operational, safety and security risks that takes into account the required levels of safety performance as defined in the European Plan for Aviation Safety and the State Safety Programme referred to in Articles 6 and 7 of Regulation (EU) 2018/1139, the type, complexity and density of the traffic, the location, altitudes or heights and the airspace classification (Reg. (EU) 2021/664 ).
Alerting service (ALS) – A service provided to notify appropriate organizations regarding aircraft in need of search and rescue aid, and assist such organizations as required (ICAO Annex 2 ).
Beyond visual line of sight operation (BVLOS) – A type of UAS operation which is not conducted in VLOS (Reg. (EU) 2019/947 ).
Concept of operations (CONOPS) – A document describing the characteristics of a proposed system from the viewpoint of an individual who will use that system (Wikipedia ).
Controlled airspace – An airspace of defined dimension within which air traffic control service is provided in accordance with the airspace classification.
Note.— Controlled airspace is a generic term which covers ATS airspace Classes A, B, C, D and E (ICAO Annex 11 ).
Control zone (CTR) – A controlled airspace extending upwards from the surface of the earth to a specified upper limit (ICAO Annex 11 ).
Declared capacity – A measure of the ability of the ATC system or any of its subsystems or operating positions to provide service to aircraft during normal activities. It is expressed as the number of aircraft entering a specified portion of airspace in a given period of time, taking due account of weather, ATC unit configuration, staff and equipment available, and any other factors that may affect the workload of the controller responsible for the airspace (ICAO Annex 11 ).
Duty – Any task that an air traffic controller is required by an air traffic services provider to perform. These tasks include those performed during time-in-position, administrative work and training (ICAO Annex 11 ).
Dynamic airspace reconfiguration – The temporary modification of the U-space airspace in order to accommodate short-term changes in manned traffic demand, by adjusting the geographical limits of that U-space airspace (Reg. (EU) 2021/664 ).
Flexible use of airspace (FUA) – An airspace management concept based on the principle that airspace should not be designated purely as civil or military, but rather as a continuum in which all user requirements are accommodated to the greatest possible extent (ICAO Doc 10088 ).
Flight information service (FIS) – A service provided for the purpose of giving advice and information useful for the safe and efficient conduct of flights (ICAO Annex 11 ).
IFR flight – A flight conducted in accordance with the instrument flight rules. (ICAO Annex 11 ).
Obstacle free zone (OFZ) – The airspace above the inner approach surface, inner transitional surfaces, and balked landing surface and that portion of the strip bounded by these surfaces, which is not penetrated by any fixed obstacle other than a low-mass and frangibly mounted one required for air navigation purposes (ICAO Annex 14, Vol.1 ).
Operator – A person, organization or enterprise engaged in or offering to engage in an aircraft operation (ICAO Annex 11 ).
Safety – The state in which risks associated with aviation activities, related to, or in direct support of the operation of aircraft, are reduced and controlled to an acceptable level (ICAO Annex 19 ).
Temporary reserved area (TRA) – An airspace that is temporarily reserved and allocated for the specific use of a particular user during a determined period of time and through which other traffic may or may not be allowed to transit under air traffic control clearance (ICAO Doc 10088 ).
UAS geographical zone – A portion of airspace established by the competent authority that facilitates, restricts or excludes UAS operations in order to address risks pertaining to safety, privacy, protection of personal data, security or the environment, arising from UAS operations (Reg. (EU) 2019/947 ).
Unmanned aircraft system (UAS) – An unmanned aircraft and the equipment to control it remotely (Reg. (EU) 2019/947 ).
Unmanned aircraft system operator (UAS operator) – Any legal or natural person operating or intending to operate one or more UAS (Reg. (EU) 2019/947 ).
Unmanned aircraft system traffic management (UTM) – A specific aspect of air traffic management which manages UAS operations safely, economically 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 (ICAO UTM Framework ).
Unmanned aircraft system traffic management (UTM) system – A system that provides UTM through the collaborative integration of humans, information, technology, facilities and services, supported by air, ground or space-based communications, navigation and surveillance (ICAO UTM Framework ).
U-space – A set of services provided in an airspace volume designated by the Member State to manage a large number of UAS operations in a safe and efficient manner (EASA Opinion 01- 2020 ).
U-space airspace – A UAS geographical zone designated by Member States, where UAS operations are only allowed to take place with the support of U-space services (Reg. (EU) 2021/664 ).
U-space service – A service relying on digital services and automation of functions designed to support safe, secure and efficient access to U-space airspace for a large number of UAS (Reg. (EU) 2021/664 ).
VFR flight – A flight conducted in accordance with the visual flight rules (ICAO Annex 11 ).
Visual line of sight operation (VLOS) – A type of UAS operation in which, the remote pilot is able to maintain continuous unaided visual contact with the unmanned aircraft, allowing the remote pilot to control the flight path of the unmanned aircraft in relation to other aircraft, people and obstacles for the purpose of avoiding collisions (Reg. (EU) 2019/947 ).
Appendix B – NASA TLX Rating Scale Definitions
Acronyms and abbreviations
ALoSP: Acceptable Level of Safety Performance
ALS: Alerting Service
ANSP: Air Navigation Services Provider
ATC: Air Traffic Control
ATCO: Air Traffic Controller
ATM: Air Traffic Management
ATS: Air Traffic Services
ATZ: Aerodrome Traffic Zone
BAT: Buster Air Traffic
BVLOS: Beyond Visual Line of Sight
CAPAN: Capacity Analysis
CONOPS: Concept of Operations
CPA: Conventionally Piloted Aircraft
CTR: Control Zone
EASA: European Union Aviation Safety Agency
EC: European Commission
ENAC: Ente Nazionale Aviazione Civile
EU: European Union
FIS: Flight Information Service
FUA: Flexible Use of Airspace
GANP: Global Air Navigation Plan
HEMS: Helicopter Emergency Medical Service
HMI: Human Machine Interface
ICAO: International Civil Aviation Organisation
IFR: Instrument Flight Rules
ISO: International Organization for Standardization
LoA: Letter of Agreement
NPA: Notice of Proposed Amendment
OFZ: Obstacle Free Zone
SARPS: Standard and Recommended Practices
SERA: Standardize European Rules of the Air
SESAR JU: Single European Sky ATM Research Joint Undertaking
SSR: Secondary Surveillance Radar
TLX: Traffic Load Index
TRA: Temporary Reserved Area
UA: Unmanned Aircraft
UAS: Unmanned Aircraft System
USSP: U-space Service Provider
UTM: UAS Traffic Management
VFR: Visual Flight Rules
VLL: Very Low Level
VLOS: Visual Line of Sight
1. ICAO, Unmanned Aircraft Systems Traffic Management (UTM) – A Common Framework with Core Principles for Global Harmonization, edition 3, October 2020.
2. ISO, UAS traffic management (UTM) — Part 12: Requirements for UTM service providers, edition 1 (under development).
3. ICAO, Annex 2 to the Convention on Civil Aviation, Rules of the Air, tenth edition, July 2005.
4. Commission Implementing Regulation (EU) No 923/2012 of 26 September 2012 laying down the common rules of the air and operational provisions regarding services and procedures in air navigation and amending Implementing Regulation (EU) No 1035/2011 and Regulations (EC) No 1265/2007, (EC) No 1794/2006, (EC) No 730/2006, (EC) No 1033/2006 and (EU) No 255/2010, as lastly amended by Commission Implementing Regulation (EU) 2020/886 of 26 June 2020.
5. Commission Implementing Regulation (EU) 2019/947 of 24 May 2019 on the rules and procedures for the operation of unmanned aircraft, as lastly amended by Commission Implementing Regulation (EU) 2021/1166 of 15 July 2021.
6. ENAC, Circolare ATM-09° “UAS-IT: Criteri d’implementazione e procedure per zone geografiche”, Ed. 1 del 24 marzo 2021.
7. ICAO, Annex 14 to the Convention on Civil Aviation, Aerodrome, Volume 1 Aerodrome design and operation, eight edition, July 2018.
8. SESAR Joint Undertaking: U-space Blueprint, 2017.
9. Wikipedia definition of ConOps in English: https://en.wikipedia.org/wiki/Concept_of_operations
10. SESAR Joint Undertaking, The Concept of Operations for European Unmanned Traffic Management (UTM) Systems (CORUS), 2019.
11. European Aviation Safety Agency, Opinion No 01/202020 High-level regulatory framework for the U-space, 13th March 2020.
12. Commission Implementing Regulation (EU) 2021/664 of 22 April 2021 on a regulatory framework for the U-space.
13. Commission Implementing Regulation (EU) 2021/665 of 22 April 2021 amending Implementing Regulation (EU) 2017/373 as regards requirements for providers of air traffic management/air navigation services and other air traffic management network functions in the U-space airspace designated in controlled airspace.
14. Commission Implementing Regulation (EU) 2021/666 of 22 April 2021 amending Regulation (EU) No 923/2012 as regards requirements for manned aviation operating in U-space airspace.
15.EUROCONTROL & EASA: Unmanned Aircraft Systems (UAS) ATM Integration Operational Concept, edition 1.0, 27th November 2018.
16. ICAO, 2016–2030 Global Air Navigation Plan, ICAO DOC 9750, first edition, 2016.
17. ICAO, Manual on Civil-Military Cooperation in Air Traffic Management, DOC 10088, first edition, 2021.
18. ICAO, Global Air Traffic Management Operational Concept, DOC 9854, first edition, 2005.
19. ICAO, Safety Management Manual (SMM), DOC 9859, Fourth edition, 2018.
20. ICAO, Annex 11 to the Convention on Civil Aviation, Air Traffic Services, fifteenth edition, July 2018.
21. Regulation (EC) No 552/2004 of the European Parliament and of the Council of 10 March
2004 on the interoperability of the European Air Traffic Management network (the interoperability Regulation), as lastly amended by Regulation (EU) 2018/1139 of the European Parliament and of the Council of 4 July 2018.
22. European Union Aviation Safety Agency (EASA), Notice of Proposed Amendment 2021- 14, 16th December 2021.
23. ICAO, Procedures For Air Navigation Services, Air Traffic Management, ICAO DOC 4444, sixteenth edition, 2016.
24. ICAO, Manual on Collaborative Air Traffic Flow Management, second edition, 2014.
25.EUROCONTROL, CAPAN Methodology Sector Capacity Assessment, Air Traffic Services System Capacity Seminar/Workshop, Nairobi, Kenya, 8 – 10 June 2016.
26. NASA Human Performance Research Group, NASA Task Load Index (TLX), version 1.0.
27. ICAO, Safety Management Manual (SMM), DOC 9859, Fourth edition, 2018.
28. ICAO, Annex 19 to the Convention on International Civil Aviation, Safety Management, second edition, July 2016.
Last Update: August 1, 2022