# Reinventing Mobility Paradigms: Flying Car Scenarios and Challenges for Urban Mobility
## 2 Main Features of Flying Cars and Air Urban Mobility Cases
### Flying Car Main Features  
Flying cars' main features have been identified in: (_i_) architecture; (_ii_) range, endurance and speed; (_iii_) vertical position and main flight rules; (_iv_) take-off and landing requirements; (_v_) automation level; (_vi_) communication technologies. As for architecture, current flying car prototypes have suitable sizes that allow them to also be used on road lanes or parked in available slots as standard cars. Compared to standard cars, their aerodynamic shapes improve performances during the flying stage and, at the same time, are conceived to be suitable for ground mode [28]. Currently, helicopter-like prototypes are more common than airplane-like ones, because of their capability to take off and land (almost) vertically, to hover and to fly forward, backward, and laterally with greater flexibility than airplane-like vehicles [29]. Furthermore, as they do not require long runways for take-off and landing, they are more suitable to be used in reduced spaces. Range and endurance are, respectively, the maximum flight distance--measured on the ground--that can be travelled for a given amount of fuel/charge and the maximum flight time, still in relation to the available fuel/charge. Range and endurance are specific aerodynamic features roughly depending on [30]: (_a_) the vehicle weight, which may change during the journey for fuel-powered vehicles; (_b_) the specific fuel/battery charge consumption, which in turn depends on the kind of engine; (_c_) the engine power or the thrust; (_d_) the weather conditions. Depending on the required performances, range could be more important than endurance and vice versa. For example, range estimate is relevant to move between origin and destination points. On the contrary, a good endurance is preferred for surveillance or security control tasks. Speed performances refer to two drive conditions: (_i_) on the road and (_ii_) in-flight. The first value depends mainly on the \"Rules of the road\", which may change among countries. The second value depends on aerodynamic features, such as combinations of maximum speed and the angle of attack (this latter is the angle between the airfoil chord, wing or blade, and the vector representing the relative motion between the object and the fluid through which it is moving), weight, load factor and the center of gravity, among others [31; 32; 33]. When flying, vertical separations are required to avoid collisions with other oncoming traffic. Height, altitude and flight level (see Figure 1) are generally used to identify the vertical position of flying objects. Height is the vertical distance of the object, measured from a specified datum, expressed in feet AGL (Above Ground Level). Altitude is the vertical distance of the object measured from the Mean Sea Level (MSL). Flight Level (FL) is a surface of constant atmosphere pressure and identifies the vertical distance of an object above the isobaric surface of 1013.25 hPa, which is the zero level. Two flying conditions are currently operating [34]: Visual Flight Rules (VFR) and Instrument Flight Rules (IFR). VFR flights apply to Visual Meteorological Conditions (VMC) and are freely operated below 900 m (3000 ft) from the ground or water without any particular cruising altitude, although they are not allowed above FL200. IFR flights apply to Instrument Meteorological Conditions (IMC), defined as weather \"below the minimums prescribed for flight under VFR\". Navigation is made by referring to on-board instruments rather than on visual references. For flying car scenarios, VFR conditions are expected to be realized at Very Low Level (VLL) airspace, usually defined as 0-500 ft AGL. In addition, below 7000 ft--which in principle could be an expected maximum vertical position for a flying car--it is possible to fly without cabin pressure plants. As for take-off and landing, flying cars could require runways (Conventional Take-off and Landing, CTOL, procedure) or only short spaces for vertical operations (Vertical Take-off and Landing, VTOL, procedure).