## 3 Results  
As part of the ASSISTANCE project financed under the Horizon 2020 program, it is planned to conduct three pilots in which new technologies, including drones, will be launched and tested. The UAV usage locations and assumptions for each scenario are shown in Table 2 below [46]. This article will consider the terrorist attack scenario (Pilot 3 in Table 2.) and risk with the use of UAVs by uniformed services. The first step necessary to perform a risk analysis of a UAV operation is the definition of the concept of operation (ConOps). According to the scenario [46], a tragedy occurs during Seville Fair (a very popular Spanish event) at the bullfighting ring arena, known as Plaza de Toros de la Real Maestranza de Caballeria de Sevilla, located 2 km from the fair area (Figure 1). A truck crashed in the west part of bullring and a big explosion occurred. People responsible for the security of the event additionally reported the sighting of two unknown UAVs. Under the scenario, UAVs will be performed in VLOS (Visual Line of Sight) operation over people and infrastructure, for the following purposes:  
* Detection of gases and their toxicity;
* Recognition through the RBG camera. It is planned to use DJI Matrice 600, whose characteristic dimension (the largest distance between the rotors) is approximately 2255 mm. To determine the risk of an operation, the first element is to determine the value of the kinetic energy that the drone may have. According to the formula below and with the manufacturer's data, kinetic energy is approximately 1.5 kJ. \[E_{k}=\frac{mv^{2}}{2}\]  
\(E_{k}\)--kinetic energy [J], \(m\)--mass [kg], \(v\)--velocity [\(\frac{m}{s}\)]. \begin{table}
\begin{tabular}{l l l l} \hline \hline
**Pilot** & **The Place of Use of the UAV** & **Tasks** & **Type of Platform** \\ \hline \multirow{3}{*}{Pilot 1} & Izmir (Turkey) & \multirow{3}{*}{\begin{tabular}{l} Road reconnaissance, assessment \\ of the technical condition of the \\ building, video stream \\ \end{tabular} } & DJI Phantom 4 with an integrated \\  & Izmir Metropolitan Municipality & \multirow{3}{*}{\begin{tabular}{l} Road reconnaissance, assessment \\ of the technical condition of the \\ building, video stream \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{l} DJI Phantom 4 with an integrated \\ telemetry module based on a \\ Pixhawk autopilot \\ \end{tabular} } \\  & Fire and Natural Disaster Training & & \\  & Center & & \\ \hline \multirow{3}{*}{Pilot 2} & \multirow{3}{*}{\
\begin{tabular}{l} Rotterdam (The Netherlands) GB \\ training area \\ \end{tabular} } & Assessment of the technical & \multirow{3}{*}{
\begin{tabular}{l} DJI Matrice 200 \\ module \\ \end{tabular} } \\  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \cline{1-1} \cline{3-3}  & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Place, type of platform, and tasks performed by UAV platforms in each of the pilots of the ASSISTANCE project. Based on these data, the intrinsic UAS Ground Risk Class (GRC) can be determined. Due to the holiday, the flight conducted during the actual occurrence would have to be qualified as \"VLOS over an assembly of people\". Unfortunately, SORA does not cover this type of operation, the risk of which would be too high; therefore, the authors' team assumed that the considered type of operation would be VLOS over a populated area. The GRC for this flight type is 5 on the current 10 point scale, as shown in Table 3 below [41]. The next step is the final determination of the ground risk (final GRC determination). For this purpose, it is needed to analyze mitigation sequences of ground risk and give them an appropriate level of robustness (low/none, medium, high).