# A Conceptual Design Methodology for e-VTOL Aircraft for Urban Air Mobility
## 6 Conclusions  
This paper described a design methodology suitable for the conceptual design of \"air taxi\", here intended as electric VTOL (Vertical Take-Off and Landing) aircraft conceived for Urban Air Mobility. The proposed methodology deals with the main aspects of the aircraft design and integrates the relevant aspects of electrical systems sizing. The main features implemented in the proposed methodology are:  
* aerodynamic and flight mechanics characteristics computed by means of the vortex-lattice method, which allows to analyse aircraft with different architectures (wing-tail, tandem wing, box-wing, etc. );
* drag polar estimated by using AVL and component build-up method;
* electric motor sizing performed by means of the matching chart built for the case of VTOL aircraft using physics-based equations;
* simulation of every phase of the mission by using fixed-wing and rotary-wing flight mechanic equations;
* accurate mass break-down estimation by means of literature data (for structural components, for example) properly adapted for the electrical powertrain components. The methodology is first validated with test cases taken from the literature, providing good results for different architectures, such as wing-tail and tandem wing. The novelty of the research is twofold; on the one hand, the introduction of a novel e-VTOL architecture exploits box-wing configuration features as its enhanced aircraft aerodynamic efficiency and its capability to increase the battery mass (for a given payload) due to the higher lifting capability of the configuration without exceeding the prescribed footprint limits. On the other hand, the introduction of a different design approach aiming at maximising aircraft operability by exploiting the main features of the box-wing configuration and fulfilling a set of design constraints, lays the foundation for the initialization of the design of a viable e-VTOL configuration. The design workflow is applied to a specific case of interest: the _TiltOne_, an air taxi with box-wing architecture and VTOL capabilities from a tilt-wing solution. During take-off and landing, the _TiltOne_ flies as a multi-rotor, whereas during climb, cruise and descent, it flies as a fixed-wing aircraft. To initialize the design process, a preliminary exploration of the design space has been performed, first indicating the wing loading and disk loading as the main design parameters and then by performing sensitivity analyses to them as well as to speed and range requirements. In a first step, such analyses have been performed considering the current technology level for electrical powertrain components, identifying the feasible design spaces given by the constraints on maximum take-off weight, maximum wingspan and minimum propeller clearance. In the second step, the same analyses have been repeated, introducing assumptions on the future (2035) technological improvement of electrical powertrain components, above all, in terms of battery energy density. The resulting significant expansion of the design space has been used to move the investigations along a different direction, assuming an alternative concept of operations. In fact, whereas in the previous analyses the _TiltOne_ has been designed according to a given design range, long enough to cover the urban distances, for the future scenario a \"multi mission\" approach has been introduced. In this case, the aircraft is designed to perform a shorter typical mission and maximise the number of rides it can perform without recharging the batteries. Two _TiltOne_ configurations are selected, one for the \"single mission\" and one for the \"multi mission\" case and for both of them benefits and drawback are highlighted. At this conceptual level, with a market still to be defined, and with a rapid technological development of electrical equipment, it is not possible to define which is the best solution between the two selected solutions.