As a general rule, UAV flights are carried out in three categories – open, specific and certified. The simplest operations, i.e. those performed in the open category, do not require an operating permit or a declaration of operation from the operator. The situation is different for operations performed in the special category – these require a permit issued by the President of the Civil Aviation Authority or a declaration by the unmanned aircraft system operator to comply with one of the Standard Scenarios (STS) or National Standard Scenarios (NSTS). The permit is issued by the President of the Civil Aviation Authority upon submission of an application containing a risk analysis, which should be performed in accordance with the SORA methodology.
A standard scenario is a type of operation using an unmanned aircraft system in the ‘specific’ category, as defined in Appendix 1 of the Annex to Regulation 2019/947, for which a detailed list of risk mitigation measures is indicated such that declarations in which operators declare that they will apply risk mitigation measures when conducting this type of operation may suffice for the competent authority. Two standard scenarios have now been published and will be effective from 1 January 2024. The first is STS-01 – Operations in visual line of sight VLOS over a controlled terrestrial area in a populated environment. The second is STS-02 – Operations beyond visual line of sight BVLOS with airspace observers over a controlled ground area in a sparsely populated environment.
Prior to the start of STSs, it is possible to use National Standard Scenarios (NSTSs). Statements based on them can be made until 31 December 2023 with validity until 1 January 2026. 8 NSTSs have been issued in the form of guidelines by the President of the Civil Aviation Authority, for example Guideline No. 15 of the President of the Civil Aviation Authority of 29 December 2020. on National Standard Scenario NSTS-01 for visual-line-of-sight (VLOS) or first-person view (FPV) operations using an unmanned aircraft with a take-off mass of less than 4 kg, or Guideline No. 20 of the President of the Civil Aviation Authority of 29 December 2020. on National Standard Scenario NSTS-06 for Beyond Visual Line of Sight (BVLOS) operations using multi-rotor (MR) category unmanned aircraft with a take-off mass of less than 25 kg , at a distance of not more than 2 km from the pilot of the unmanned aircraft.
In addition to the standard scenarios, the possibility of using PDRA (The Predefined Risk Assessment) is also envisaged. This is an operational scenario for which the EASA (European Union Aviation Safety Agency) has already carried out a risk assessment and has been published as an Acceptable Means of Compliance (AMC) in relation to Article 11 of Regulation 2019/947. The PDRA requires an operational authorisation issued by the national aviation authority (in Poland by the President of the Civil Aviation Authority), but the process will be significantly simplified. If the planned operation is covered by one of the published PDRAs, instead of conducting a risk assessment, the UAS operator can simply fill in the PDRA table, prepare an operator’s manual and submit an application to the President of the ULC. The PDRA table is in fact a kind of checklist on how to develop the procedures that must be included in the operator’s manual.
While STSs and NSTSs are described in detail, the provisions and mitigation measures in PDRAs are described in rather general terms to provide flexibility for UAV system operators and competent authorities of the State to establish restrictions and provisions tailored to the specifics of the intended operations. There are two types of PDRAs: 1. those derived from the STS, which allow an operator to conduct similar operations but using, for example, an unmanned aircraft without the class label that is required by the STS (e.g. privately built unmanned aircraft systems); 2. more general PDRAs.
Thus, when performing an operation not covered by either a standard scenario or a PDRA, applicants are required to carry out a risk assessment, identify mitigation measures and comply with safety objectives. To this end, a risk assessment methodology known as SORA (Specific Operations Risk Assessment) has been developed. EASA has published SORA as an acceptable means of compliance (AMC) from Article 11 of Regulation (EU) 2019/947.
The SORA method is a standardised process developed by JARUS (Joint Authorities for Rulemaking on Unmanned Systems), which is an international working group of experts on unmanned aerial systems representing civil aviation authorities. The main objective of JARUS is to develop recommendations on requirements for drones for their safe integration into the general aviation system. JARUS focuses on developing recommendations for operational procedures, equipment certification and personnel qualification. The SORA method created by JARUS was subsequently implemented by EASA, the European Union Aviation Safety Agency.
By design, SORA is intended to properly assess planned operations in a specific category, in particular to bring about a reduction to an acceptable level of risk associated with the performance of a specific drone operation (a specific flight) or a larger number of them. It is therefore inherently specific and relates to a specific unmanned aircraft, operator and pilot(s) and the intended route.
As noted in AMC1 to Article 11 of Regulation 2019/947, SORA is intended to provide a vision for the safe establishment, assessment and conduct of UAS operations. The SORA is a method to assist both the UAS operator and the competent authority in determining whether a UAS operation can be conducted in a safe manner. This document should not be used as a checklist, nor should it be expected to provide answers to all the challenges of integrating UAS in airspace. SORA is an adaptation guide that allows the UAS operator to find the best-fit mitigation measures and thus reduce the risk to an acceptable level. For this reason, it does not contain prescriptive requirements, but rather safety objectives to be achieved at different levels of reliability, commensurate with risk.
In accordance with EASA guidance, the SORA analysis is based on the principle of a holistic risk assessment model based on total system safety, used to assess the risks associated with a particular UAS operation. The model considers the nature of all hazards associated with a particular hazard, the appropriate design and proposed operational mitigation measures for a specific UAS operation. SORA facilitates a systematic risk assessment and defines the limits required for a safe operation. This method allows the applicant to identify acceptable levels of risk and confirm that these levels are adhered to by the proposed operations. The competent authority of the State, i.e. in the case of Poland, the President of the Civil Aviation Authority, may also use this method to obtain assurance that the UAS operator can safely conduct the operation.
The SORA analysis method is designed to assess the safety risks associated with the operation of unmanned aircraft systems of any class, size or type (including military, experimental, R&D and prototype). It is particularly suitable for, but not limited to, special category operations for which a hazard and risk assessment is required.
At the outset, some basic definitions related to the issue at hand should be given.
Firstly – above used – is unmanned aircraft system (SBSP): it refers to an unmanned aircraft and the equipment to remotely control it. It is therefore a broader term than just unmanned aircraft alone.
Another term to be recalled is unmanned aircraft system operator, meaning any legal or natural person operating or intending to operate one or more SBSPs. This term should not be confused with pilot defined as the natural person responsible for the safe execution of the flight of an unmanned aircraft either by manually controlling the flight or, in the case of automatic flight, by monitoring its course and maintaining the ability to intervene and change course at any time.
In terms of risk analysis, furthermore, it is important to cite the definition of robustness, which denotes the property of risk mitigation measures that results from a combination of the degree of safety improvement through the application of risk mitigation measures and the level of assurance and integrity that the safety improvement has been achieved.
Robustness is defined by the level of integrity, which indicates the safety performance (safety enhancement), and the level of assurance, which indicates the methods and means of ensuring that the specified safety performance is met. Specific solutions are assigned to each level of integrity to increase the level of security in the area under consideration. A distinction is made between three levels of integrity: low, medium and high.
SORA consists of assessing the input conditions, identifying the risks to the safe execution of the operation (i.e. the level of risk that will be acceptable) and defining the mitigation (reduction – mitigation) of these risks to an assumed level. Achieving a level of complete safety is an unattainable goal and pursuing it generates extremely high costs, which is why the concept of an acceptable level of safety has been adopted.
Terms that are often misunderstood are payload and maximum take-off weight. The first means instruments, mechanisms, equipment, parts, apparatus, instrumentation or accessories, including communication devices, installed on or attached to the aircraft, which are not used or intended to be used in the operation or control of the aircraft in flight and are not part of the airframe, engine or propeller. The second – maximum take-off mass (MTOM) – means the maximum mass of an unmanned aircraft, including payload and fuel, specified by the manufacturer or constructor, at which the unmanned aircraft can be operated.
Above all, however, to properly understand the SORA process, it is important to introduce the key concept of robustness, also referred to as resilience. Any risk reduction or operational safety objective (OSO) can be demonstrated at different levels of robustness. The SORA process proposes three different levels of robustness: low, medium and high, commensurate with risk. The robustness designation is derived from both the level of integrity (i.e. the safety gain) provided by each mitigation measure and the level of confidence (i.e. the method of proof) that the claimed safety gain has been achieved.
The SORA analysis uses a definition of risk understood as a combination of the frequency (probability) of an event and the associated level of severity. The consequence of an event will be a specific type of damage. A number of different categories of harm may result from each event.
SORA focuses on harmful events (e.g. unmanned aircraft system crashes) that are sudden, short-lived and usually result in either serious injury or loss of life. Chronic events (e.g. toxic emissions over a period of time) are explicitly excluded from this assessment. Damage categories include, firstly, fatal injuries to third parties on the ground, secondly, fatal injuries to third parties in the air or, thirdly, damage to critical infrastructure. Notwithstanding this, it is recognised that additional damage categories may be considered by aviation authorities (e.g. community disruption, environmental damage, financial loss, etc.). The SORA method may also be applied to these damage categories. An additional risk assessment of the critical infrastructure should also be carried out, in cooperation with the institution responsible for the infrastructure.
