# Modeling and Analysis of Noise Emission Using Data from Flight Simulators
## 3 Comparative Analysis
### Parameters for Single-Factor Impact Analysis  
Factors distinguished in Table 1 for which the influence on noise and other substance emissions are the subject of analysis, can be divided into two categories:  
* Random factors: variables independent of the flight crew's choice. These include the aircraft mass and atmospheric conditions;
* Non-random factors: all other factors influenced to some extent by the crew or the appropriate flight management system. These include the wing mechanization configuration (selection of flap positions for takeoff), engine power setting for takeoff, and thrust reduction and acceleration. It should be emphasized that although the influence of both random and non-random factors will be analyzed, any potential optimization of selecting their appropriate values should focus only on non-random factors. In practice, it should also consider other unmentioned aspects specific to each airport, special conditions, and the airline operator. In order to conduct such an analysis, a number of reliable metrics or parameters shall be defined, the most useful of which are as follows:  
* An area \(S_{\geq 85}^{SEL}\), which contains all the observers, for which the \(SEL\) noise metric is equal to or greater than 85 dB. The calculation of these area boils is a matter of counting the number of observers whose \(SEL\) level meets the criteria and multiplying this number by the area of a single tile on the defined grid, which is a rectangle of 100 \(\times\) 50 m;
* Change in \(CO_{2}\) emissions relative to the baseline procedure expressed in [%];  
Figure 4: Profile view of procedures NADP1 and NADP2 and differential noise maps of the \(L_{Amax}\) and \(SEL\) parameter, respectively. * The values of the \(SEL\) noise metric for the three observers, for which the position in relation to the start of the roll point is specified in Figure 5. Although their specific positions are not relevant, they are selected to allow for the analysis in both \"close-in\" and \"distant\" areas. The axis system is anchored to the starting position of the simulation, located on the beginning of the departure runway, with the X-axis aligned parallel to the runway track. As an example, the influence of take-off thrust reduction is provided. It is perceived as one of the most common methods for emission reductions at the source. However, it needs to be emphasized that the lower engine thrust setting will result in reduced excess thrust, which will negatively impact the climb gradient during the initial climb phase, thus reducing the distance between the aircraft and observers on the grid. During the simulation, the thrust reduction was achieved by de-rating the thrust from 26,000 to 24,000 pounds of force, further reducing it by means of the Assumed Thrust Reduction. A comparison between scenarios 6 and 1 (NADP1), as well as 12 and 7 (NADP2), is presented in the profile view in Figure 6.  
It is worth noting that the almost level flight segment corresponding to the acceleration phase is significantly extended for the solid red NADP1 trajectory in comparison with the  
Figure 5: Specific observers’ coordinates on the defined grid. Figure 6: Profile view of the trajectories (baseline scenarios—dashed line, reduced thrust—solid line). solid blue NADP2 trajectory. Both scenarios have a visibly reduced climb profile gradient, which in turn moves the crossover point by almost 1 km further away from the start of the roll point. Behind the crossover point, a greater difference in height between trajectories is observed in comparison with the baseline scenarios (dashed line). For the observers \(O_{1},\ O_{2},\ O_{3}\), whose position was specified in Figure 5, the following values of the SEL metric can be listed (Figure 7):  
In compliance with the previous analysis, it can be seen that the values of \(SEL\) for observers \(O_{1},\ O_{3}\) located underneath the aircraft's trajectory are increasing for up to 1.5 dB. Observer \(O_{2}\), located aside, benefits from the reduced thrust.