## 3 Results
Mitigations are divided into three levels: M1--strategic mitigations for ground risk, M2--effects of ground impact are reduced, M3--an Emergency Response Plan is in place, validated by operator, and effective, as shown in Table 4 below [41]. At first, we limit the number of people who may get hurt from a breakdown or a UAV error. To this end, use should be made of the criteria for strategically identifying M1 risk. Its elements are the level of integrity and the level of assurance. The first risk mitigation criteria for the overall level is the application of a basic risk buffer with at least a 1 to 1 rule, i.e., if the UAV is flying at a height of 50 m, the horizontal distance from any bystanders should be at least 50 m.  
Application of this method for rescue operations envisaged in this scenario is almost impossible due to a large number of people. Since the low method cannot be used in this case, attention should be focused on the more complex level methods of the medium. They are concerned with mitigation methods that would lead to an operation outside of the operational volume; they mainly cover:  
* Meteorological conditions (e.g., wind);
* UAS delays (e.g., delays that affect the ability of the UAS to maneuver at the right time);
* The behavior of the UAV during the activation of the technical security measure;
* The UAV's performance. For this risk analysis, optimal weather conditions prevailing over the site of UAV's operations are assumed, delays do not affect the UAS's maneuverability, and emergency systems such as RTH have been checked. This allows us to assume an average level of \(-2\) for the level of integrity. The application of the second criterion (evaluation of people at risk) for the low level assumes the transfer of flights to a different time, when due to the schedule of the day, the density of people may be smaller (e.g., at night, when there are no employees in the buildings). The nature of rescue operations make it impossible to fully apply this criterion. It is possible to partially meet these requirements, because of the evacuation of victims and the presence of only an FR who is aware of drone operations and involved in the operation. What is more, at the medium level, there is compliance because the flight will be a UAV weighing less than 25 kg and flying at a speed slower than 89.5 m/s. When it comes to the level of assurance, the medium level is reached. The evidence which supports this claim in criterion 1 is this article and analyses which it includes. To strengthen the evidence, it is additionally recommended to perform some simulations and inspections before flights. In the case of criterion 2, density data has been taken from a reliable source [47] and the path of flight will be performed in conjunction with other authorities (e.g., city police, office of civil protection, crisis response team). Summing up, we obtain with robustness: level of integrity (medium) and level of assurance (medium). So we can subtract \(-2\) from the ground risk level. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & & & **Robustness** & \\ \hline
**Mitigation** & **Mitigations for Ground Risk** & Low/None & Medium & High \\
**Sequence** & & & & \\ \hline
1 & M1—Strategic mitigations for ground risk & 0: None & \(-1\): Low & \(-2\) & \(-4\) \\
2 & M2—Effects of ground impact are reduced & 0 & \(-1\) & \(-2\) \\
3 & M3—An Emergency Response Plan (ERP) is in place, & 1 & 0 & \(-1\) \\  & operator validated and effective & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Mitigations for final GRC determination. Then we move on to M2--this is the part relating to the limitation of the effects of the UAV accident. The UAV envisaged in the scenario meets the medium level of integrity, because, in the event of damage to one of the six driving elements, it can enter autorotation (hexacopter). This allows for resignation from other methods of risk mitigation, such as the use of a parachute.