## 4 Results: Optimized Configurations
### Overall Performance Comparison at the Design Point  
An overall summary of the comparison between the couples of optimal BW-TW configurations, for each value of the MTOW considered, is reported in Figure 10, which provides a complete overview of the results of the optimization process. In this context, the comparison is expressed in the form of radar charts showing the percentage differences between TW and BW of the following metrics: MTOW, OEW, block fuel, wingspan, battery mass, DOC, CO\({}_{2}\) in the three CO\({}_{2}\) scenarios, evaluated at the design point. The comparison at the design point of the optimized TW and BW configurations provides interesting insights. Indeed, as mentioned above and as demonstrated in [29], the BW configurations save significant amounts of block fuel. These advantages also reflect in a less CO\({}_{2}\) emissions in all three CO\({}_{2}\) scenarios for the BW with respect the TW, but with different quantitative impacts; in the case of the current scenario, the CO\({}_{2}\) reductions for BW are noteworthy but anyway do not exceed 17%, as the impact of emissions related to electricity production significantly mitigate the reductions due to lower fuel consumption. The differences increase in the intermediate scenario, while in the CO\({}_{2_{max}}\) scenario the percentage differences coincide with those for \(m_{fb}\), as there are no emissions related to electricity production. It becomes even more interesting to assess this comparison between hybrid-electric configurations and the thermal benchmark. Indeed, it is this trend that makes it clear whether the proposed technological solutions have a positive impact on greenhouse emissions. The comparison, in percentage terms of CO\({}_{2}\) emissions, for the three CO\({}_{2}\) scenarios, between the TW and BW hybrid-electric configurations and the thermal benchmark is shown in Table 6. From this data it is apparent that, if the electricity production scenario remains as it is today (CO\({}_{2_{max}}\)), introducing hybrid-electric propulsion on TW aircraft does not produce any reduction in greenhouse emissions. Furthermore, although increasing MTOW results in substantial reductions in \(m_{fb}\), these do not introduce any benefit in greenhouse emissions, which on the contrary are in clear opposite trend. In correspondence with fuel consumption reductions of 54%, CO\({}_{2}\) emission increases of more than 33% are \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline  & \multicolumn{10}{c}{**Design Variables**} & \multicolumn{1}{c}{**Constraint**} & **Obj.** \\ \cline{2-13}  & \multicolumn{1}{c}{**W/S [kg\(\mu\)/m\({}^{2}\)]**} & \multicolumn{1}{c}{\(H_{\text{P}}\)} & \multicolumn{1}{c}{\(\Phi_{CL}^{ice}\)} & \multicolumn{1}{c}{\(\Phi_{CR}^{ice}\)} & \multicolumn{1}{c}{\(\Phi_{DE}^{ice}\)} & \multicolumn{1}{c}{**MTOW [kg\(\mu\)]**} & \multicolumn{1}{c}{\(m_{fb}\) [kg]**} \\ \hline
**Tag** & **BW** & **TW** & **BW** & **TW** & **BW** & **TW** & **BW** & **TW** & **BW** & **TW** & **BW** & **TW** & **BW** & **TW** \\ \hline
23t & 320 & 325 & 0.38 & 0.27 & 0.23 & 0.33 & 0.35 & 0.33 & 0.17 & 0.22 & 22,976 & 22,962 & 705 & 907 \\ \hline
30t & 314 & 305 & 0.40 & 0.39 & 0.15 & 0.29 & 0.21 & 0.30 & 0.16 & 0.30 & 30,117 & 30,000 & 523 & 816 \\ \hline
40t & 311 & 325 & 0.59 & 0.45 & 0.19 & 0.11 & 0.13 & 0.20 & 0.15 & 0.13 & 40,132 & 39,913 & 320 & 631 \\ \hline
50t & 309 & 325 & 0.46 & 0.40 & 0.11 & 0.13 & 0.01 & 0.10 & 0.10 & 0.11 & 50,160 & 50,019 & 113 & 525 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Main outcomes of optimized hybrid-electric TW and BW (data taken from [29]).