# A Conceptual Design Methodology for e-VTOL Aircraft for Urban Air Mobility
## 5 Preliminary Design of a Tilt-Wing Air Taxi with Box-Wing Architecture
### Sensitivity Analysis to the Typical Mission  
As anticipated, for this analysis it has been decided to change the main requirements by targeting the maximum number of missions without recharging the batteries on short routes (hereafter called 'typical missions') and to evaluate a posteriori the maximum achievable range with a single recharge at maximum payload (hereafter called 'harmonic mission'). Moreover, in this case, the approach adopted follows a sensitivity analysis aimed at identifying the design space, in terms of _T/A-W/S_ combinations, when the variables are the number of rides the air taxi has to perform (\(N\)), and the distance to be covered, assumed as the typical range. In order to indicate reasonable intervals for such parameters, two different cities, Milan and Beijing, have been used as reference scenarios. For Milan, where the implementation of Urban Air Mobility can have a promising growth, the typical distance to be covered is considerably smaller than the design missions used as a reference in Section 4.2. Referring to Figure 16a, it can be observed that the maximum air distance from a generic point within the urban area and a relevant peri-urban destination, such as the Linate airport, is about 12 km (6.5 nm). In this scenario, an air taxi would be asked to cover such a short route as \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Current** & **Future** & **\(\Delta\%\)** \\ \hline Cruise speed & 45 m/s & 45 m/s & = \\ \hline Range & 50 nm & 50 nm & = \\ \hline Payload & 400 kg (4 px) & 400 kg (4 px) & = \\ \hline \(W/S\) & 90 kg/m\({}^{2}\) & 90 kg/m\({}^{2}\) & = \\ \hline \(T/A\) & 55 kg/m\({}^{2}\) & 55 kg/m\({}^{2}\) & = \\ \hline MTOW & 2212 kg & 1408 kg & \(-\)36\% \\ \hline Battery mass & 500 kg & 146 kg & \(-\)71\% \\ \hline Wingspan & 12.6 m & 10.1 m & \(-\)20\% \\ \hline Propeller diameter & 2.53 m & 2.02 m & \(-\)20\% \\ \hline Electric motor power & 8 \(\times\) 82.6 kW & 8 \(\times\) 52.6 kW & \(-\)36\% \\ \hline Installed specific power & 299 W/kg & 299 W/kg & = \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Comparison of two _TiltOne_ configurations with same \(T/A\) (55 kg/m\({}^{2}\)) and \(W/S\) (90 kg/m\({}^{2}\)) and different technological levels. many times as possible, without the need to recharge the batteries. In the second scenario (Figure 16b), concerning a bigger city such as Beijing, for a transport service similar to the one considered for Milan, the range increases to about 57 km (31 nm). Figures 17 and 18 represent the trends of the main outputs as the global wing loading (_W/S_) and the disk loading (_T/A_) vary. The number of repeated missions with a single battery charge (_N_) is instead introduced as a new parameter. The graphs are arranged in a 3 \(\times\) 3 grid, in which the number of rides increases along the rows (_N_ = 6, 8, 10), whereas the typical range is increased in the column direction (11, 13, 15 nm). Each possible combination on the map of _W/S_ and _T/A_ represents a _TiltOne_ configuration designed according to the workflow depicted in Figure 2.  
Figure 16: Pictures of potential UAM scenario: (**a**) Milan; (**b**) Beijing. Figure 17: _W/S_ vs. _T/A_ charts of MTOW (future technology) varying number of rides and typical range of missions. Each plot shows a highlighted area, which identifies the design space compliant with the constraints.