## 2 eVTOL PAV Type  
VTOL aircraft do not require runways for vertical takeoff and landing. A rotorcraft, such as a helicopter, is capable of vertical takeoff and landing, but has the disadvantage of being noisy and unable to fly at high speed. A fixed-wing aircraft has the advantage of being able to fly at high speed but has the disadvantage of requiring a runway for takeoff. Therefore, the optimal design for VTOL is an aircraft that can take off and land vertically and also fly at high speed. In the early days, VTOL aircraft used internal combustion engines, but designers began using electric motors to avoid the high noise and environmental problems caused by fossil fuel engines. Current eVTOL aircraft can be divided into a multicopter type, a composite type, a tilt wing type, a tilt rotor type, and a tilt ducted fan type, depending on the propulsion method. Table 1 summarizes representative eVTOL PAVs for each type. The most effective eVTOL PAV is different for each given mission profile. The multicopter type is excellent for hovering performance, but it is only suitable for short-range flight because it is relatively slow and has inefficient energy consumption when cruising. The tilt rotor and tilt wing types have problems such as instability in control during transition from hovering to forward flight, but they are suitable for long-distance flight because their speed is relatively fast and energy efficient when cruising. The complex type has intermediate performance, between that of the multicopter type and the tilt rotor type. The performances of the tilted wing type Vahana, the complex type Aurora, and the multicopter type Volocopter are shown in Table 2, and the required time by mission range is shown in Figure 1. \begin{table}
\begin{tabular}{c c} \hline \hline
**PAV Type** & **Figure** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Electric vertical takeoff and landing personal air vehicle (eVTOL PAV) type. The energy required for hovering during takeoff and landing is based on the momentum theory [12]. \[\mathrm{P}=\sqrt{\frac{T^{3}}{2\rho_{sea}A_{hover}}} \tag{1}\]  
where \(T\) is the hovering thrust, \(\rho_{sea}\) is the air density at sea level, and \(A_{hover}\) is the disk actuator area. Using Equation (1), Vahana's required hovering power and maximum hovering time are shown in Table 5.  
The electric energy consumption of the aircraft is [13]  
\[E^{*}m_{butt}\eta_{t}=W\frac{D}{L}R \tag{2}\]  
where \(E^{*}\) is the battery energy density, \(m_{butt}\) is the battery mass, \(\eta_{t}\) is the consumption efficiency, \(W\) is the mass, \(L\). is the lift force, \(D\) is the drag force and \(R\) is the range. Rewriting the equation for range, it can be expressed as  
\[\mathrm{R}=0.75E^{*}\frac{m_{butt}}{m}\frac{1}{g}\frac{L}{D} \tag{3}\]  
where \(m\) is the aircraft mass, \(g\) is the gravity acceleration and \(\eta_{t}\) is assumed to be 0.75. In order to calculate the flight range in Equation (3), a drag force is calculated using Equations (4) and (5) [14]. \[\mathrm{D}=\frac{1}{2}\rho v^{2}SC_{D} \tag{4}\]  
\[C_{D}=C_{D_{v}}+C_{D_{i}} \tag{5}\]  
where \(\rho\) is the air density, \(v\) is the aircraft velocity, \(S\) is the wing area, \(C_{D_{v}}\) is the parasite drag, and \(C_{D_{i}}\) is the induced drag. The parasite drag coefficient value is expressed as the following equation, assuming an ideal elliptical lift distribution [14]. \[C_{D_{i}}=\frac{{C_{L}}^{2}}{\pi eAR} \tag{6}\]  
\[AR=\frac{b^{2}}{S} \tag{7}\]  
where \(C_{L}\) is the lift coefficient, \(e\) is the Oswald span efficiency coefficient, \(AR\) is the aspect ratio, and \(b\) is the wing span. The lift coefficient is as follows when cruising [14]. \[C_{L}=\frac{W}{\frac{1}{2}\rho v^{2}S} \tag{8}\]  
\[\mathrm{P}=\sqrt{\frac{T^{3}}{2\rho_{sea}A_{hover}}} \tag{1}\]0 \begin{table}
\begin{tabular}{c c c} \hline \hline
**Category** & **Vahana** & **Unit** \\ \hline Power required & 56.85 & kW \\ Hovering time & 0.67 & h \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Maximum hovering time for Vahana.