# Parametric Analysis for Hybrid-Electric Regional Aircraft Conceptual Design and Development
## 3 Simulation Results and Discussion
### Battery Technology Impact on Hybrid-Electric Regional Aircraft Design  
#### 3.1.1 Reference Design Range: 600 nm  
The impact of battery technology maturity on overall hybrid-electric aircraft feasibility has been assessed by means of a \(BED\) sensitivity analysis, varied in the (200, 500) \(\text{Wh}/\text{kg}\) interval [38], considering the complete battery pack. Note that in this range, the lower value is close to the state of the art [39; 40; 41], whereas the upper value represents a consolidated forecast for 2035 [42; 43]. The reference full-thermal regional aircraft, designed with the same procedure and by enforcing the condition \(H_{P}=0\), exhibits MTOW = 15,780 kg, \(m_{\text{fp}}=1103\) kg, and \(PREE=0.869\), while Table 1 shows the data for \(m_{\text{fp}}\)-optimised configurations as a function of the \(BED\) value in the selected range. Figure 1: Conceptual sketch of hybrid–electric aircraft power supply strategy (adapted from [36]). These numerical results highlight two key aspects: (i) Given the state of the art of batteries (but also for incremental technology steps up to 100% with respect to the current achievable value of the _BED_), no significant benefits can be expected from the utilisation of electric power as the weight increases related to the batteries are overwhelming, so the optimal solutions show low in-flight electric power supply; (ii) With an entry-into-service horizon of 2035, the use of hybrid-electric powertrains can contribute to substantial reductions in \(m_{fb}\), but sharp increases in MTOW must be taken into account. Indeed, for the reference \(BED=500\) Wh/kg, the advantage in the implementation and utilisation of electrical power, which can be observed from the values of \(H_{P}\) and \(\Phi_{k}^{t}\), respectively (see Table 1), results in reductions in \(m_{fb}\) but at the expense of a significant increase in MTOW. On the other hand, for lower values of the \(BED\), the search for power electrification does not introduce a tangible benefit. To better highlight these trends, the optimisations previously described have been carried out by introducing the constraint MTOW = \(W_{c}\), with \(W_{c}\) varied in the (15, 50) \(\times\) 10\({}^{3}\) kg\({}_{\text{f}}\) interval. In this context, Figure 2 shows the trend of the optimal \(m_{fb}\) obtained as a function of the value of \(W_{c}\). From a technical standpoint, increasing the value of \(W_{c}\) allows for an increase of the amount of the on-board battery power, hence allowing for the growth of the in-flight electrical power utilisation. The simulations results show a worsening trend in terms of \(m_{fb}\) as \(W_{c}\) increases for values of the \(BED\) equal to 200 and 300 Wh/kg, bringing to light the fact that with these levels of battery technology, the penalties resulting from the weight increases due to the batteries are definitely greater than the benefits of using a share of electrical power to satisfy the energy required for the flight. For a value of the \(BED\) equal to 400 Wh/kg, the beneficial and detrimental effects seem to offset each other, resulting in no noticeable benefit in terms of \(m_{fb}\) as the possible number of batteries on board increases. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline \(BED\) & \(m_{fb}\) (kg) & \(\dfrac{\text{MTOW}}{\text{(kg_{f})}}\) & \(\dfrac{\text{H}_{P}}{\text{(kg_{f}/m^{2})}}\) & \(\dfrac{\text{W/S}}{\text{(kg_{f}/m^{2})}}\) & \(\dfrac{\text{\Phi}_{el}^{t}}{\text{\Phi}_{el}^{e}}\) & \(\dfrac{\text{\Phi}_{cr}^{t}}{\text{\Phi}_{cr}^{t}}\) & \(\dfrac{\text{\Phi}_{de}^{e}}{\text{\Phi}_{de}^{e}}\) & \(\dfrac{\text{\Phi}_{de}^{e}}{\text{\Phi}_{de}^{e}}\) \\ \hline
200 & 1097 & 17,031 & 0.139 & 325 & 0.548 & 0.434 & 0.466 & 0 & 0.239 & 0.412 \\
300 & 1073 & 17,462 & 0.209 & 325 & 0.559 & 0.417 & 0.471 & 0 & 0.172 & 0.580 \\
400 & 967 & 30,116 & 0.458 & 325 & 0.151 & 0.908 & 0.433 & 0.208 & 0.148 & 0.220 \\
500 & 525 & 50,211 & 0.459 & 325 & 0.088 & 0.946 & 0.131 & 0.524 & 0.104 & 0.195 \\ \hline \hline \end{tabular}
\end{table}