Drone flights are inherently an activity prone to multiple risks. In open-field conditions, there are multiple parameters that constantly interact with each other, often in unpredictable ways, and can ultimately disrupt the safe operation of the aircraft in use. To this end, drone flight safety is the desired optimum state in which drone operations are executed after certain preparatory measures have been taken by the pilot(s), to mitigate or even completely eliminate potential hazards and ensure the safe deployment and completion of each flight mission. These measures vary, from simple safety checks before take-off, to fully fledged risk management strategies that are initiated several months before the day of flight.
EASA SORA Methodology
The SORA Methodology
The risk assessment SORA (Specific Operations Risk Assessment) methodology is a 10 steps process developed by the European Aviation Safety Agency (EASA) for the description of the operation and the evaluation of ground risk and air risk in drone flights. The SORA methodology considers parameters such as the type of the operation, the size of the aircraft and the density of air traffic in the airspace, allowing drone operators to identify operational limitations and technical requirements, and ultimately assisting them in selecting the appropriate preparatory procedures to eliminate risks. Until now, qualitative factors were used to assess ground and air risk. With the new update of the methodology in 2022, in the future to provide more accurate results, quantitative factors will be required by EASA to be used by operators as part of the application process.
Use Cases: Risk assessment in practice
Use Case 2: Drone Spraying
Use Case 2 assessed as a B2B case that will utilise drone services to explore all benefits of automatic pesticides spraying, collecting data, and evaluating the economic indicators of crop production.
The experiment takes place in the experimental vineyard of the Agricultural University of Athens in Spata, Greece. The scope of ICAERUS Use Case 2 (UC2) is to test and assess various configurations for optimal drone spraying applications in field conditions. To this end, the experimental design focuses on both the evaluation of spraying quality (i.e. deposition, canopy penetration and spray drift) achieved through various operational configurations (i.e. spraying altitude, speed, nozzle flow and liquid deposition rates) for spraying drones, as well as their comparison with existing conventional spraying machinery, such as conventional terrestrial mist sprayers.
Use Case 5: Rural Logistics
Use Case 5 is described as both a B2B and B2C case that offers drone services aiming to provide an overall improvement of the supply chain in goods, small packages, and medical products in rural conditions.
The implementation of drone logistics for the Use Case 5 (UC5) will be realised in two selected regions of North Macedonia (Ohrid lake and the surrounding rural areas of Kuklish town, respectively). The main target of the UC5 is to design, develop and deploy an innovative drone-delivery fleet management system that will act as an alternative fast response process for delivering small parcels of importance (e.g., medical supplies, documentation, etc.) in remote and rural areas of Europe. Thus, various types of drones (multirotor, fixed-wing, etc.) mounted with different payloads (cargo from hundreds of grams to a few kilograms) will be tested, in order to define the configurations for drone logistics optimal efficiency.
The Risk Assessment Model
Use Case 2: Drone Spraying
As drone spraying is an open-field, low-altitude agricultural operation, numerous parameters can intervene with the experimental iterations of UC2, and it is therefore critical that potential risks should be carefully considered and mitigation steps are taken in a timely and robust manner, e.g. by creating and implementing a detailed risk management plan and by following all existing safety guidelines. A safety risk assessment model for spraying drones would involve assessing the potential risks associated with the use of drones for spraying applications and implementing mitigation measures. This could include factors such as the safety of the chemicals used, the possibility of the drone malfunctioning and causing damage, and the possibility of the drone losing control and crashing. The aim of the model would be to identify and address potential hazards to prevent such accidents and ensure the safe operation of spraying drones.
The first step is to identify potential hazards associated with using drones for spraying applications. This could include spraying operations, the drone itself, technological components or experimental materials and the environmental conditions in which the drone will be operating. The next step is to evaluate the risks associated with each identified risk. This could involve considering the likelihood of the risk occurring, as well as its potential impact in case it manifests. Once the risks have been identified and evaluated, the next step is to develop control measures to mitigate those risks. This could include implementing safety protocols for flights and spraying operations, conducting regular maintenance on the drones, purchase all consumables while the logistics chain is operating normally (considering that this does not include chemicals or other substances that potentially expire or degrade with time) and the operators stay updated on the most recent regulatory updates and guidelines on how to safely use spraying drones. The final step is to integrate all devised control measures into the experimental pipeline. This could involve implementing safety procedures and regular inspections and maintenance, while also considering various micro-optimisations in case a risk occurs (e.g. the spare drone is located near the experimental site, so in case of a crash of the primary UAV, the secondary aircraft can be deployed in a few hours). Finally, it is important to regularly review and update the risk management plan to ensure that it remains effective and addresses any new or changing risks/hazards. This is achieved by conducting regular research checks and frequently consulting with other experts and stakeholders of the sector.
Use Case 5: Rural Logistics
Drone logistics operations that will be tested in UC5 are focused on rural, remote and generally non-urban areas, hence a plethora of parameters could potentially affect the final outcome. In particular, the process of risk assessment involves identifying the potential risks or hazards, as well as the evaluation of their impact to drone operations. A safety risk assessment model for drone logistics in rural areas involves several factors, such as the safety of the drone operations in relation with the environmental conditions and field terrain, the possible drone malfunctioning before take-off or during the flight, and the possibility to lose control of the drone, leading to a crash.
Inside the EU regulatory framework, delivery operations lie in “specific category”, as they need to be performed outside Visual Line Of Sight (VLOS) conditions to enable enough range for the benefits to be significant. Operations outside VLOS conditions are performed in either Beyond Visual Line Of Sight (BVLOS) or in Extended Visual Line Of Sight (EVLOS), the latter employing visual observers who must keep track of the drone. The BVLOS operations, lacking visual contact with the drone, require the use of detect and avoid (DAA) systems to avoid collisions with obstacles or other aircraft. Furthermore, specific operations are subject to a risk assessment using a dedicated methodology, such as the SORA or using a Predefined Risk Assessment (PDRA). Both of these risk assessment procedures must represent a predefined, standardised Concept of Operations (ConOps) or alternatively be submitted for approval to the civil aviation authority of the corresponding country. Alternately, EASA through National Aviation Authority (NAA) can accredit organisations with Light UAS operator Certificate (LUC) that allow the organisation to self-authorise operations without applying for authorisation. Nevertheless, the main risks associated with drone logistics activities are listed below:
- Drone crushes. The main mitigation measure is to deploy an additional operational-ready drone.
- Extended period of extreme weather conditions.
- Malfunction of various drone components (e.g., rotors) and/or payloads (e.g., sensors). To eliminate this risk, the purchase of spare components is required.
- Decrease of UAV battery life over time. For the elimination of this risk, the strategy is to purchase multiple spare batteries for the aircrafts (both for primary and secondary drones).
- Poor signal reception. This risk can be mitigated through the use of multiple telecommunication service providers.
- Drone operations by inexperienced pilots. To eliminate this risk, all UAV operators within UC5 are highly experienced certified pilots.
Overall, the SORA risk assessment methodology provides the applicant, the competent authority and the service provider with a well described process which includes a series of mitigations and safety objectives to be considered to ensure an adequate level of confidence that the operation can be safely conducted. In addition, the operator should address any other requirements not identified by the SORA process and identify the relevant stakeholders to coordinate with.
