## 2 Materials and Methods
### Data Collection and Pre-Processing  
Data collection was performed in two ways. The first was derived from pilot performance measurement by means of piloting precision evaluation. The second was oriented to psychophysiological condition assessment by means of heart rate variability (HRV). Piloting precision was assessed by instructor who noted maximum deviations from predetermined flight parameters of individual manoevures (see Figure 2A). These data were subsequently used for assessment. This method was selected because of the impossibility to download aircraft flight recorder's data, especially with analogue setup. Even though other data exist and it was possible to record them in both flight simulator and aircraft equipped with an electronic flight instrument system (EFIS); with respect to the aforementioned, data obtained from the instructor were used. Efforts were spend to limit potential bias due to subjective measurement by employing only one instructor for the assessment. Additionally, assessment was partly harmonized in this way among simulated and real flying, since during real flying, apparent piloting error may have occurred due to meteorological factors, such as wind gusts. Overall, maximum deviation from constant altitude to be maintained during horizontal steady flight and horizontal 360\({}^{\circ}\) turn was assessed. Next was assessed maximum deviation from banks during horizontal, climb, and descend turns. In addition, vertical speed error was evaluated for climb and descend turns. As the last parameter, magnetic heading deviation during horizontal steady flight was evaluated. In case of psycho-physiological condition measurement, heart activity was measured and evaluated for the purpose of HRV analysis. The main reason for the choice of HRV was ease of measurement and no limitation for the pilot during his or her activity. At the same time, HRV and parameters obtained from the RR intervals analysis is perceived as significant indicator of psychophysiological condition [25; 26]. From the perspective of psychophysiological condition quantification, it is also possible to use other measurements, such as skin resistance, brain activity (EEG) or respiratory rate [27]. On the other hand, there were many limitations related to these measurements, such as complicated measurement bothering the pilot during his or her activity related to flying (EEG cap), influence of the measurement by external forces (skin resistance), unclear methodology in  
Figure 2: Example of flight pattern with marked prescribed manoeuvres (**A**) along with training schedule for Group A and B (**B**). terms of sensor location (temperature) or many artefacts following the nature of the measurement and used sensors (respiratory rate). Heart activity analysis, i.e., the HRV, is the most used and examined from all methods [26; 28]. The use of such data stems from the idea that autonomous nervous system reacting to external stimuli regulates body functions, including the heart activity, i.e., the change in psychophysiological condition leads to change in heart activity, including the HRV [25]. Based on this knowledge and many studies proving the suitability of this signal for the given purposes and ease of its measurement, including the fact that the very measurement does not limit or bother the pilot during his or her activity related to flying an aircraft, the HRV has been selected for this study. Heart activity measurements were performed by means of FlexiGuard (Czech Technical University in Prague, Prague, Czech Republic) mobile telemetry system [29; 30] dedicated to physiological parameters recording. The main monitored parameter was heart activity, so the data collection was based on recording RR intervals (time intervals between R peaks of QRS complex when measuring electrocardiogram) [31]. During particular flight, the measurement was performed with presence of an operator who manually marked beginning and end of respective manoeuvre.