*2.2. European Union Regulatory Framework*

Until 2020, the Member States regulated civil drones with an operating mass of less than 150 Kg, and the EASA handled civil drones with an operating mass of over 150 Kg. The fragmentation in the extent, content, and level of national detail led to unreached conditions for the joint recognition of operational authorization between the EU Member States [91]. Fortunately, the EASA is providing uniform regulation for the EU legal framework of UASs since 2020 [96]. Figure 1 presents an overview of European Union regulatory framework progress over time.

**Figure 1.** Chronological evolution of the European Union regulatory framework.

2.2.1. Access Rules for Unmanned Aircraft Systems (Regulations (EU) 2019/947 and 2019/945)

The operational framework for civil drones in the Europian Union (EU) is Regulations 2019/947 and 2019/945. These regulations conduct a risk-based approach, considering the weight, specifications, and intended operation of civil drones [97]. Regulation 2019/947 was expected to be implemented on 1 July 2020; however, due to the COVID-19 crisis, it was delayed to 31 December 2020 [96].

Civil Drone Operation Categories in the European Union Regulatory Framework

Regulation 2019/947 presents three risk-based categories for civil drone operations, shown in Figure 2: the open, specific, and certified categories [97]. The definition of each category is as follows:

**Figure 2.** Categorization of UAS operations under EU regulation.


Overall, drone operations with any of the below conductions are certainly in the certified category:


Operational Risk Assessment for Drones in Specific Category

UAS operational risk assessment is divided into three categories: standard scenarios (STSs), predefined risk assessment (PDRA), and specific operation risk assessment (SORA) [93]. The definition of each category is as follows:

### 1. Standard scenario (STS): Due to the lower risks in UAS operations in STSs listed in Table 1, a declaration may be submitted.

**Table 1.** List of standard scenarios (STSs) [93.].


<sup>1</sup> Maximum take-off mass. <sup>2</sup> Beyond visual line of sight/visual line of sight. <sup>3</sup> Airspace observer.

2. Predefined risk assessment (PDRA): PDRA is considered the most common operation in Europe, and instead of conducting a full risk assessment, an authorization request may be submitted based on the PDRAs listed in Table 2. PDRAs are described in a generic way to provide flexibility, while STSs are detailed. The two types of PDRAs are PDRAs derived from STSs (a UAS operator conducts similar operations without the UAS class label mandated in STSs) and generic PDRAs. A PDRA with the letter "G" is a generic PDRA, and those with an "S" are PDRAs derived from STSs [93].

**Table 2.** List of predefined risk assessments (PDRAs) [93].



<sup>1</sup> Acceptable means of compliance.

3. Specific operation risk assessment (SORA): SORA evaluates the UAS operation risks, considering any class, size, and type of operation [93]. Figure 3 demonstrates the SORA methodology.

SORA defines risk as "the combination of the frequency (probability) of an occurrence and its associated level of severity". Risk mitigations and operational safety objectives (OSOs) can be demonstrated at different robustness levels presented by SORA: low, medium, and high. SORA focuses on the assessment of air and ground risks. Figure 4 presents the required workflow to conduct SORA. Ten steps are required to conduct SORA, and some of these steps may be repeated in different environments [22]. It is important to verify the operational feasibility before starting SORA. The operation must not be categorized as the open category or certified category, must not be covered by an STS or a PDRA, and not be subjected to a specific NO-GO from the competent authority [93].

To ensure safety in UAS operations, especially in populated areas, the design verification of drones by the EASA is needed depending on the risk level of operations [101]:

• In high-risk operations (i.e., SAIL V and VI according to SORA), the EASA will issue a type certificate according to Part 21 (Regulation (EU) 748/2012). Easy Access Rules for Airworthiness and Environmental Certification (Regulation (EU) No. 748/2012) contains the applicable rules for the airworthiness and environmental certification of aircraft and related products, parts, and appliances, as well as for the certification of design and production organizations [102].

• In medium-risk operations (i.e., SAIL III and IV according to SORA), a design verification report will be applied [101].

2.2.2. Commission Implementing Regulation (EU) in U-Space (Regulations (EU) 2021/664, 2021/665, and 2021/666)

U-space is a set of services and procedures to ensure safe and efficient airspace accessibility for a large number of UAS operations, with the purpose of achieving automated UAS management and integration. The European Commission adopted and published a regulatory framework for U-space in April 2021. This regulatory package is going to implement three regulations as of January 2023 [103]:


2.2.3. EASA Artificial Intelligence Roadmap (Autonomous and Automatic UASs)

Autonomous and automatic UASs are reaching a level of complexity and development such that they are expected to conduct safe operations in urban air mobility (UAM). Automatic UAVs operate on predetermined routes, and remote pilots intervene in the case of unforeseen events. In autonomous UAVs, artificial intelligence (AI) must conduct a safe flight (without a pilot's intervention) and cope with unforeseen conditions as well as unpredictable emergencies. Automatic UAV operations are allowed in all categories. Autonomous UAVs only operate in the specific category and certified category (where the Regulation includes more flexible tools to verify requirements and the level of robustness); they are not allowed in the open category [107].

One of the key research questions is how these operations can safely be used in UAM [108]. In 2020, the EASA published a human-centric approach for the safe use of AI in aviation, entitled "EASA AI roadmap". Figure 5 presents the trustworthy AI building blocks: AI trustworthiness analysis, learning assurance, AI explainability, and AI safety risk mitigation [109]. The EASA AI roadmap's deliverables timeline foresees the first approvals of AI in 2025 [110].

**Figure 5.** EASA trustworthy AI building blocks [109].
