## 3 Results and Discussion
### Test Results
#### 3.3.1 Test 1 Results  
The evolution of the flight is represented in Figures 10 and 11.  
When the distance threshold set for the activation of the separation assurance function was reached, the system indicated to the remote pilot the predicted loss of separation condition; at the same time, it started proposing a suitable separation assurance maneuver to be implemented by the ownship. The remote pilot, after having analyzed the proposed maneuver (that was updated at a proper rate by the ASACAS), provided his clearance for the activation and, in this specific test, requested the automatic implementation of the maneuver by the autopilot, i.e., requested ASACAS to automatically send the separation assurance maneuver reference commands to the autopilot. The separation assurance maneuver for this head-on encounter geometry consisted of a track variation of about 25 degrees, as represented in Figure 10.  
This led to a trajectory of the ownship (the conflicting intruder continued its straight-levelled flight undisturbed) that was tangent to the separation volume centered in the intruder and whose size was increased with respect to the nominal one based on the closure rate between vehicles at the moment where the maneuver was frozen by the system. The ownship trajectory represented in Figure 10 did not seem to be tangent to the separation volume due to the unavailability of some real-time trajectory data that were not correctly saved in the flight data recorder and thus not retrieved in the post flight data analysis, leading to the need for the offline computation of the separation volume dimensions with some approximation. Indeed, it is worth noticing here that the separation assurance maneuver was the one cleared by the remote pilot; nevertheless, some fine tuning of it was still possible and automatically implemented by the ASACAS during the maneuver execution if needed based on the current traffic picture.  
In Figure 11, the range distance \(r\) and the range rate \(r\)_dot_ between the two aircraft involved in the conflict situation are reported. It is worth noticing here that the range and range rate indicated in Figure 11 were only calculated during the separation assurance maneuver execution, i.e., from about 62 to about 268 s, and the null values indicated outside this time interval therefore have no meaning in the figure. An analysis of Figure 11 then, allows one to observe that, in this real-time simulation test, the conflict condition was detected by the ASACAS at about 32 s, and so the self-separation maneuver started to be proposed to the pilot few moments after that time (due to elaboration time and transmission latency). The remote pilot examined the maneuvers that were updated in real-time by the system at a proper frequency and, at about 62 s, cleared the automatic execution of the proposed maneuver by the system.  
The minimum distance between vehicles (i.e., the distance at the closest point of approach--CPA) was set to about 1800 m, consistent with the set dimension of the separation volume. Thus, the ownship trajectory was almost tangent to the separation volume. The separation assurance maneuver was completed at about 268 s, when the range rate between vehicles became positive (the vehicles started diverging).  
The separation assurance functionality of the ASACAS, therefore, was shown to perform as expected in the real-time simulation test described here.