# ATC Human Factors Involved in RPAS Contingency Management in Non-Segregated Airspace
## 2 Method
### Human Factor Concerns in RPAS Operations
In some circumstances, high-workload RPAS missions may produce active fatigue, which may induce a more significant state of distress in operators. Although RPAS operation may be exempt from some of the major stressors afflicting traditional pilots, such as fear of physical injury, it may be more psychologically intense and fatiguing. In [22], the authors propose a set of human factor guidelines to avoid RPAS operator fatigue. We identify a set of RPAS flight characteristics that may affect ATCO and pilot's performances when an RPAS is operating in non-segregated airspace:  
1. Dissimilar RPAS flight performance and mission trajectory. ATCO expects certain aircraft performance levels in the airspace system in order to orchestrate traffic safely, efficiently, and under an acceptable workload. Although the training of ATCO prepares them to safely manage aircrafts that cannot meet the expected performance due to emergencies, RPAS may be especially disruptive due to their highly dissimilar performance characteristics. Besides this, RPAS may require increased controller monitoring, with necessary clearance amendments issued to move manned traffic around it (increasing fuel burn) or to decelerate traffic (leading to delays) [23]. In addition, compared to typical point-to-point operations, an increase in mission-oriented flight trajectories may also increase the controllers' workload. 2. Loss of natural sensing. Without a rich set of sensory cues related to RPAS, operations may decrease the situational awareness of the PiC. For example, RPAS pilots cannot accept instructions from air traffic controllers to acquire and separate from other aircrafts visually. ATCO requires positive acknowledgement that one pilot has the other aircraft in sight. These visual operations are beneficial to the controller in high-workload situations. ATCO should manage the airspace, including some RPAS missions, in a comparable way to situations where the flight of a conventional aircraft proceeds under instrumental meteorological conditions. 3. Human-machine interface issues. Air traffic controllers need to use the proper HMI interfaces to access specific flight data about the traffic they monitor and control and RPAS may introduce further information requirements. Using those new interfaces must prevent the ATCO from becoming confused about the automation's current and future status (i.e., operating mode), thus avoiding incorrect interactions. For example, controllers may have access to information such as aircraft identification, aircraft type, and specific on-board equipment for manned aircrafts. However, it is still unclear what additional information controllers would require properly supervising RPAS operations properly; flight-intent technology may be a mechanism that could increase ATCO situational awareness. However, at the same time, such new interfaces may increase the ATCO workload by requiring the operation of a new source of information. From an opposite perspective, early standardisation discussions emphasised transparency so that controllers would not necessarily know if an aircraft is manned or unmanned. However, it may seem obvious that there are unique aspects to RPAS operations and that controllers may need to be aware of those RPAS-specific characteristics to maintain safety, efficiency, and an acceptable workload level. 4. Communication issues. Ineffective communication and other communication-related factors are the underlying causes of most ATCO workload increases. In a controlled airspace, communication between PiC and ATCO may occur through the relay of  
Figure 1: Yerkes and Dodson Law [21]. traditional very-high-frequency radio transmitted through the unmanned vehicle. However, such a relay may introduce significant latencies, especially if implemented via satellite links that may be sufficient to disrupt verbal communication. Besides this, there are common mistakes in radio use associated with operational factors, such as using the wrong phraseology or the incorrect understanding of the required commands.