## 3 Research Environment and Plan of Experiment
### Flight Plan and Its Realisation for Estimating Head-on Gusts  
During the simulation, the aircraft descended from an altitude (ALT) of 14,000 ft (4267.2 m) to 6000 ft (1828.2 m). The flight was fully automated with the pilot operating the autopilot and autothrottle systems in LVL CHG and HDG SEL modes. A constant IAS 250 kt (128.6 m/s) was set on the MCP. Basic flight parameters are presented in Figure 11. Significant IAS fluctuations occurred between 50 s and 340 s of the recording (Figure 12B), caused by variable atmospheric gusts. These gusts also had a substantial impact on the aircraft's vertical speed (VVI), which varied from a stabilized 6 m/s at the start of descent to values ranging between 3 and 12 m/s.  
The wind conditions were calm above 14,000 ft (4267.2 m) and below 6000 ft (1828.2 m). As the airplane descended below 4000 m, the headwind speed Ug began to increase, as shown in Figure 12A,B. When wind speeds exceeding 3 m/s, sudden gusts with peak velocities up to 22 m/s were observed. These occurred between the 50 th and 320 th seconds of the simulation. From 320 to 350 s, both headwind and gust intensity gradually decreased, eventually returning to calm conditions below 1828.2 m.  
Figure 11: (**A**) Altitude, (**B**) IAS, and (**C**) VVI recorded during simulated flight—descent phase.  
A subsequently simulated level flight was conducted within a wind layer containing head-on gusts at a constant altitude of 10,000 ft (Figures 13 and 14). Due to limited simulator environment capabilities there were no possibilities to set the wind layer at a specific location in the horizontal plane. As a result, the recording does not include calm wind conditions at the beginning or the end of the flight segment. The level flight was executed automatically using the autopilot ALT HLD mode with MCP selected speed of 250 kt (128.6 m/s). Due to the presence of strong head-on gusts ranging from 5 to 22 m/s, significant variations in IAS were observed. Despite this, the altitude stabilized within 20 m, while the vertical speed fluctuated between \(-2\) and 2 m/s.  
Figure 14: Registered ideal gust measurements from simulation weather section—level flight; wind speed as a function of time.  
Figure 12: Registered ideal gust measurements from simulation weather section—descent phase; (A)—wind speed as a function of time, (**B**)—wind speed as a function of altitude.  
Figure 13: (**A**) Altitude, (**B**) IAS, and (**C**) VVI recorded during simulated level flight.  
The next simulation was conducted for an aircraft climbing through a layer of head-on gusts, from 6000 ft (609.6 m) to 14,000 ft (4267.2 m) (Figures 15 and 16). Wind conditions were calm below 6000 ft (1828.2 m) and above 14,000 ft (4267.2 m). During the climb the speed of head-on wind increased with maximum gusts up to 19 m/s. After passing 3750 m, the wind speed decreased until reaching windless conditions and the end of climb.  
The climb was performed using the autopilot LVL CHG mode with a constant IAS 250 kt (128.6 m/s) set on MCP. At the start of the climb, the vertical speed stabilized at about 25 m/s, then it started to fluctuate due to atmospheric gusts. The total simulation time was approximately 50% shorter compared to the descent scenario, owing to the significantly higher vertical speed enabled by the high thrust setting.