eVTOL Air Taxi Energy per Trip

Out-of-ground-effect actuator-disk momentum theory gives $A=N\pi d^2/4$, $W=mg$, $v_i=\sqrt{W/(2\rho A)}$ and $P_{i}=Wv_i$. Divide ideal power by hover figure of merit and battery-to-shaft efficiency, then add auxiliary load. Leishman, Helicopters, sections Induced Velocity, Power Required to Hover, and The da Vinci Aerial Screw, gives the derivation and worked checks. NASA RVLT (2018), PDF p. 1, defines figure of merit and effective L/D; Table 3 on PDF p. 12 supplies geometry and cruise consistency checks.

For wing-borne level cruise, $D=W/(L/D)$ and $P_c=DV/(\eta_p\eta_d)+P_{aux}$. Use aerodynamic L/D for normal inputs. NASA's effective $L/D_e=WV/P$ already includes a power effect, so the reference case alone sets efficiencies to unity to avoid counting those losses twice.

Each phase consumes $E_j=P_jt_j$. Departure and arrival propulsion powers are empirical multiples of hover propulsion power, with auxiliaries added separately. Reserve is $E_r=P_rt_r+E_{cont}$ and is not consumed on the planned flight. With $C=C_{nom}SOH$, landing SOC is $s_0-E_{trip}/C$; surplus above reserve and floor is $C(s_0-s_{floor})-E_{trip}-E_r$. The cruise-distance limit solves the same budget with fixed non-cruise phases. The animation integrates these constant phase powers exactly.

Discharge-power validation counts only flight phases with positive duration. The selected reserve power is checked separately whenever timed reserve duration is positive; energy sufficiency alone does not establish power capability.

• Winged battery-electric aircraft, constant mass, equal independent lift disks and steady out-of-ground-effect hover. No ground-effect credit or regeneration.
• L/D is aerodynamic and valid at the selected true airspeed. Constant efficiencies and auxiliary load; air density changes only hover power because cruise aerodynamics are supplied as inputs.
• Transition/climb and descent powers are phase averages entered as factors; no altitude, climb-rate, acceleration or descent aerodynamics are solved. Their route distance is outside the level-cruise input.
• Capacity state of health scales full-charge energy. SOC is approximated as energy fraction, rather than electrochemical or coulomb-counted SOC. Nameplate energy and floor must use a consistent basis.
• All defaults, including 5 kWh additional contingency energy and 700 kW discharge capability, are illustrative assumptions, not manufacturer data or regulatory allowances.

Preliminary mission energy and sensitivity estimates, not an aircraft sizing optimizer or dispatch tool. The energy-only battery requirement holds aircraft mass fixed. Active flight-phase average powers and any positive-duration timed-reserve power are compared with the entered available battery power, but rotor, motor, transient, voltage, temperature, stall and failure limits are not resolved. Overlapping/coaxial disks and rotor-borne cruise require another model. Negative surplus indicates a budget shortfall; a negative SOC is an extrapolated energy deficit, not a physical battery state.

Regulatory example: FAA SFAR 120 / 14 CFR 194.306(ss), as explained by AC 194-1 (October 7, 2024), section 5.7, PDF p. 32, allows the helicopter-equivalent 20-minute VFR provision only with the applicable vertical-landing capability along the route. Other operations may require different reserves or authorized deviations. Context reviewed October 28, 2026; check against the rules in force, aircraft flight manual and operator approvals. The calculator does not establish eligibility or model an emergency descent or diversion.