Initial BUBBLES ConOps for UAS separation management delivered: first Milestone achieved

BUBBLES will build its separation management ConOps upon the U-space ConOps delivered by the SESAR2020 CORUS project. Following this approach, BUBBLES delivered its initial ConOps by the end of September 2020, thus achieving the first project Milestone.

31 Oct 2020


The first BUBBLES milestone consists of drawing up an initial Concept of Operations (ConOps) to provide separation management in the U-space. UAS are users of the airspace and, as such, lies within the worldwide-agreed ICAO framework and their operation has to be aligned with the ICAO principles. Therefore, the UAS separation management service developed by BUBBLES will be consistent with the separation management concepts laid down by the ICAO for manned aircraft, although commensurate with the risk entailed by their operations. According to the ICAO Global ATM Operational Concept, the separation management (also known as separation provision) is the second layer of the ATM conflict management component of the ATM, aiming at reducing the probability of collision to acceptably low levels.

BUBBLES separation management ConOps

The BUBBLES separation management ConOps involves the definition of a conflict horizon, separation modes, separation minima and the predetermined separator for the following hazards:

  • Unmanned aircrafts, whatever they are being flown.
  • Manned aircrafts.
  • Environmental hazards.

The ConOps also include the definition of the intervention function in charge of monitoring of the execution of the solution to ensure that the hazards are avoided by the appropriate separation minima.

For UAS operating in CORUS Y volumes, the U-space U3 Strategic conflict resolution service will tackle conflicts in the pre-flight phase and the separation management service will provide the strategic conflict management with the applicable separation minima to attain a given Target Level of Safety (TLS) with respect all the possible hazards.

For UAS operation in CORUS Za volumes, the U-space Strategic conflict resolution service will apply strategic conflict management and the separation management service will provide the ATC the applicable separation minima (taking into account the very different sizes and dynamics) applicable to attain a given TLS.

For UAS operation in  CORUS Zu volumes, the U-space Strategic conflict resolution service will apply strategic conflict management and tactical conflict management. For strategic conflict management, the separation management service will provide the Strategic conflict management with the applicable separation minima to attain a given TLS with respect all the possible hazards. In addition, for tactical conflict management, the separation management service will define conflict horizons, separation minima, separation modes and separators for the envisaged hazards.

The separation modes and separators can be:

  1. A U-space service. In this case, the separation service will issue ATC-like separation instructions and the Zu volume will be considered as controlled airspace (e.g. class B).
  2. The U-space user. In this case, the U-space will issue collision avoidance advisories. and the Zu volume will be considered as uncontrolled airspace (e.g., class G).

Each option has pros and cons:

  • Option 1 can allow higher traffic densities with smaller separation minima, but requirements on the CNS systems supporting the provision of separation management will be more demanding and can include even hardware and software certification. Moreover, liability aspects must be taken into account.
  • Option 2 is simpler for the U-space Service Provider (USSP), but separation minima should be rather cautious, traffic density relatively low and the requirements for DAA and communications will be more demanding.

BUBBLES will consider both options and will draw up requirements for each of them with the aim of supporting regulator’s decisions.

BUBBLES ConOps high level operational description

The initial conceptual architecture of the BUBBLES concept is composed of four core technical blocks:

  1. The generic ConOps Catalogue. This Catalogue will contain a set of ConOps describing from the users’ perspective how the UAS operations will occur in a given Operation Environment (OE), with risk levels linked to them following standard procedures like SORA. Since the BUBBLES targets the definition of an advanced (U3) service, this catalogue will cover BVLOS operations in high density and high complexity areas required by the envisaged U3 applications like urban air mobility. Specifically, they will include air space volumes specially conceived to this use, like corridors or vertiports and will consider the co-existence of manned and unmanned air operation in the VLL.
  2. The generic OSED Catalogue. This Catalogue will contain the generic OSED defined by the project. Each OSED will consist of assumptions and operational requirements, including the separation minima and methods assigned by the Artificial Intelligence (AI) based collision risk model developed by the BUBBLES project.
  3. The Risk Analysis Assistant. This block will correlate a given Operational Plan with the ConOps stored in the generic ConOps Catalogue assigning to it the risk level of the most similar one, using algorithms developed by the BUBBLES project.
  4. The Safety Management Assistant. This block will receive the risk level assigned to the Operation Plan by the Risk Analysis Assistant and will assign separation minima, taking into account the performance of the CNS systems. using algorithms developed by the project.

Moreover, the U-Space Separation Management service will require an enabling additional block: the CNS Monitoring tools defined by BUBBLES to monitor the actual performance of the CNS systems in the airspace volume where a particular Operation Plan will take place.

The BUBBLES initial operational baseline consists of the following sequence of operations (in bold italics we highlight those U-Space services that are going to be used as defined by the CORUS project with updated interfaces while normal bolds characters are used to denote those components or U-Space services that are going to be defined or updated by the project):


During the U-space airspace designation.
  1. The Competent Authority will perform a risk assessment using the BUBBLES Risk Analysis Assistant for a given airspace taking into account the type, complexity and density of traffic, location, altitudes or heights and airspace classification to obtain an initial generic ConOps catalogue that will be further extended with the SORA assessments performed to issue Operational Authorisations.
  2. The Competent Authority will perform a safety assessment using the BUBBLES Safety Management Assistant to establish the minimum list of U-space services and the applicable SPR, as well as the performance requirements for the CNS systems and, if necessary, the required UAS capabilities. This information will lead to define the applicable OSED that will have to be used by the UAS operators and the USSP to tailor their aircrafts capabilities and U-space services performance to the particular U-space airspace.

In the pre-flight phase.
  1. The Operation Plan Management service will pass to the Risk Analysis Assistant the Operation Plan description previously introduced by the UAS operator, including the operation area co-ordinates.
  2. The Risk Analysis Assistant will correlate the Operation Plan description received with those stored in the generic ConOps Catalogue and will assign a risk level to it.
  3. The Safety Management Assistant will receive the operation area co-ordinates along with the assigned risk level from the Risk Analysis Assistant and, taking into account the available CNS systems in the operation area and their performance (provided by the CNS Monitoring tools), will assign one generic OSED out of those stored in the generic OSED Catalogue. The assigned OSED, including the applicable separation minima and methods, will be sent to the Operation Plan Management service.
  4. The Operation Plan Management service, depending on the separation method associated to the received OSED, will send the updated Operation Plan:
      • to the Strategic Conflict Resolution service (in case of ‘procedural’ separation) and, after any possible conflict (including with manned aircrafts in Zu volumes) has been resolved, to the UAS Control system.
      • to the ATM systems through the Procedural Interface to ATM, for UAS flying in Za5 volumes.
      • to the UAS Detect and Avoid (DAA) system (in case of ‘tactical self-separated’ separation); the Remain well Clear (RWC) function will be provided by the DAA capability using the situational awareness obtained from the Traffic Information service or generated on-board, or
      • to the U-Space Monitoring service (in case of ‘tactical ground-based’ separation).

In the in-flight phase:
  1. In case of ‘tactical ground-based’ separation, the Monitoring service will receive the tracks obtained by the Tracking service (including the UAS/manned aircrafts eID), as well as the data provided Geospatial and Weather Information services and will check that all the UAS maintain the assigned separation minima. If it detects a potential breach of the separation minima, it will issue an alarm to the Tactical Conflict Resolution service and will monitor whether the conflict is resolved.
  2. The Tactical Conflict Resolution service will issue separation instructions to resolve any potential conflict detected, while preserving the overall safety level. The separation instructions will be timestamped and sent to the Legal Recording service, as well as the eID of the involved UAS/manned aircraft.
  3. In case of ‘tactical self-separation’, the UAS DAA system will check that the UAS maintains the assigned separation minima based on the situational awareness obtained from internal or external sources. If it detects a potential breach of the separation minima, it will issue separation instructions to the UAS Control system.
  4. In both cases (ground-based and self-separated), if the Monitoring service detects that the applied separation instructions are not effective, a timestamped report with the eID of the involved UAS/manned aircraft will be sent to the Accident/Incident Reporting service.
  5. Also in both cases (ground-based and self-separated), the CNS Monitoring tools will monitor the CNS systems performance and will issue warnings to the Safety Management Assistant when the values of the performance metrics change. Upon the received performance information, it will assess whether the separation minima and/or methods need to be updated in order to preserve the overall safety level. If so, the updated values will be sent to the UAS DAA system or to the Monitoring service through the Operation Plan Management service.
  6. In case that a performance degradation is detected in the surveillance systems, the values of the performance metrics will be fed into the Tracking service so that the tracking algorithms can be adapted to them.
  7. Optionally, the separation minima assigned by BUBBLES may be used by the Dynamic Capability Management service to dynamically optimise the use of the VLL.