# ATC Human Factors Involved in RPAS Contingency Management in Non-Segregated Airspace
## 2 Method
### Nominal RPAS Conditions and Contingencies into Non-Segregated Airspace
#### 2.3.3 RPAS Engine Failure Contingency  
Engine failure is a critical emergency as most RPAS have just a single engine and the electric generator coupled with that engine would leave the RPAS entirely dependent on its internal batteries without any auxiliary power unit available. So, the capability of the RPA to remain airborne would depend on its gliding capacity, the altitude at the time of the failure, and the vehicle's capacity to remain controllable when operating under battery power. This type of emergency should tackle the closest airport or at least within gliding distance, sometimes requiring off-airport landings or even terminating the flight by controlled grounding, ditching, parachute descent, or other methods. The PiC and ATCO should be in continuous contact in order to achieve a safe gliding and emergency landing without endangering the surrounding traffic. In case of engine failure contingency, the pre-programmed operational procedure is activated through the following three steps. 1. Airport selection: Assuming an engine contingency, the safest line of action is to determine the available landing locations safely accessible within the gliding capabilities of the RPAS. Low-traffic secondary airports/airfields would be a priority, with further alternatives being flat fields, waterways, etc. The PiC may determine if the safest action is to divert to a more distant airfield instead of the nearest airfield, taking into account not only the pre-planned trajectories but also the actual vehicle state, wind direction, weather conditions, etc. Airfields and airports should have preliminary agreements with the ATM authority to specify if the RPAS is accepted in case of emer \begin{table}
\begin{tabular}{l p{227.6 pt}} \hline \hline \(\bullet\) & The RPAS on-board system must check for further vehicle degradation and redirect the lost-link trajectory to the closest pre-planned airfield to minimize the total RPAS flight time. \\ \(\bullet\) & An ADS-B-equipped aircraft having radio communication failure must set up its transponder and ADS-B into emergency mode (Mode-A Code 7600). An aircraft equipped with other communication systems (including ADS-C) must indicate the loss of air-to-ground communication by all available means. \\ \(\bullet\) & The RPAS operator must carry out all checks to attempt to recover the link (maintaining the last assigned speed and level for a period of 7 min). \\ \(\bullet\) & Lost-link contingency will be confirmed after a 2 min period has elapsed. Then, the RPAS should follow the pre-planned manoeuvre to re-join the originally planned return flight plan route and altitude. Afterwards, the RPAS should proceed to the designated IAF that serves as the destination aerodrome. \\ \(\bullet\) & The RPAS should complete a standard instrument approach procedure and land after 30 min of holding time at the IAF. \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Flight-specific procedures for a C2 lost link or general loss of communications. gency conditions. In this sense, airports should be able to manage potential runway accidents and remove the RPAS after a successful landing, crash landing, or failure of taxi capabilities. Some airports may have an alternative area to perform controlled RPAS crashes to avoid damage to people or properties. As a final factor, on each landing site, some waypoints must be assigned to guide the landing procedure, such as the Initial and Final Approach Fix. Figure 2 depicts the emergency airport selected in one of our engine failure contingency experiments. Note that a small portion of the northwest trajectory has no viable coverage; thus, additional contingency landing sites may need to be included. 2. Alternative trajectories: In case of RPAS engine failure, any change in the predefined trajectories must consider the area of operation, gliding capabilities, and traffic volume. We assume that the RPAS flight range is limited by its gliding ratio, disregarding other factors such as battery life and limitations in the actuators.