# A Survey of the Effects of Vehicle Configuration on Urban Air Mobility +
## 2 Aerial Urban Vehicle Configurations and Concepts
### Horizontal Take-Off and Landing (HTOL)
#### 2.1.1 Fixed-Wing  
A majority of AUVs are light and personal vehicles. They mostly can carry up to two passengers and are suitable for personal usage. A good example in this category is Cessna 172 which is considered to be one of the most popular personal planes in history. As well as Cirrus SR22, Cessna uses a fixed-wing configuration, which provides a simple structure and manufacturing process for it. A fixed-wing configuration provides several advantages, such as high flight endurance, the ability to operate under adverse or hazardous conditions, and low operating costs. Generally, fixed-wing AUVs have longer endurance, their flight endurance is essentially up to the efficiency of their configuration [15,19]. One of the greatest challenges related to fixed-wing aircraft is the lack of enough space for runways. As they are unable to vertically take-off and land, the applicability of using them in daily transportation would be a challenging problem specifically in big and dense cities. However, currently they are being used in UAM more than any other configuration and there are many small airports around big and small cities for small fixed-wing air taxis. The family of Cessna (like 172, 182, 206, 208, and 408) and Cirrus are good examples of fixed-wing AUVs which are able to fly up to 2000 km and 170 km/h [20]. Voltaero's Casio is also a modern fixed-wing hybrid-electric airplane that is designed to carry four to ten passengers for about 3.5 h. Its wing and canard along with twin tail boom are aerodynamically optimized to have a safe, quiet, efficient, and eco-friendly flight [21]. Other examples are very light jets (VLJs) or personal jets, which are suitable options for low-passenger solutions. Using jet propulsion provides higher speeds and range, and an increased number of passengers can cover their operational costs and make the flight more efficient. VLJs are comparatively popular in short urban air mobility. A summarization of the common advantages and disadvantages of fixed-wing configuration is provided in Table 1 but high cargo capacity (including passengers) and range are two main advantages of this configuration. Figure 3 illustrates views of some fixed-wing AUVs. There are several known faults that are well studied in fixed-wing configuration, among them we can mention: damage to the lift-generating surfaces, damage to control surfaces, and damage to/loss of efficiency of the engine(s). These faults can be caused by a plethora of reasons such as subsystem failures (as an example, failure of hydraulics and/or mechanical systems in a commercial jetliner can result in a partial or total loss of control \begin{table}
\begin{tabular}{c c} \hline \hline
**Advantages** & **Disadvantages** \\ \hline Simple structure & Need for runway and infrastructure \\ Low operating cost & \\ Flexibility in operational environment & \\ High endurance & \\ High cargo capacity & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Advantages and disadvantages of fixed-wing configuration. surface authority), external elements (such as bird strikes [22]) or even debris from damaged parts hitting other components (for example, in an airplane with aft-mounted engines, parts that fly off a damaged wing can fly into an engine intake resulting in an engine failure). Fault in any of the aforementioned components can to some extent be remedied by changing the aircraft's trim state (which refers to the throttle setting and control surface angles for a steady and level flight) and through the employment of robust/adaptive/fault-tolerant control systems [22; 23; 24]. Of course, in order for any of these methods to be effective in maintaining or restoring the stability of aircraft in case of faults, the aircraft itself needs to have some degree of \"redundancy\" and an inherent margin of safety in order for it to still be controllable in such situations.