# A Study on Finding Partners through Patent Network Analysis of UAM (Urban Air Mobility)
## 2 Theoretical Background and Hypothesis
### UAM Concept  
Urban Air Mobility (UAM) refers to urban aviation mobility, or the entire air traffic industry that seeks to transport passengers and cargo in the city center, and according to the latest development trend, electric vertical take-off and landing (eVTOL)-type aircraft manufacturing is gaining momentum [10]. There are several ways to distinguish between varieties of UAM, and the criteria are summarized as follows:  
The first is a UAM classification method by aircraft type [10]. Table 1 shows that the fixed-wing-type is mainly used in the military, and is suitable for high speed and long distance, but requires a runway/launcher. A rotary-wing aircraft can have vertical takeoff and landing and hovering, but its speed range is not as high as the fixed-wing-type. Combining the advantages of both fixed and rotary wing is the hybrid-type, which has high energy efficiency, high-speed flight, and vertical landing [11; 12]. Figure 1: Construction cost per 1 km of public transportation (Seoul metro, 2017, Ministry of Land, Infrastructure and Transport, 2018). Second is a UAM classification based on weight [13]. Table 2 shows that it divides airplanes and lightweight helicopters, etc. with 600 kg as the threshold, and classifies air vehicles that weigh 115 kg as ultra-light. In the case of UAM, the weight is estimated to be around 600 kg, which is the equivalent of a manned rotary aircraft. Third is another UAM classification method that classifies aircrafts according to the shape of the wings [14]. Figure 2 shows that this classification is based on the shape of the wings as defined on the TransportUP website, and UAM classification is possible in an intuitive manner. Finally, as shown in Figure 3, this is another UAM classification method based on the operating altitude, which can be divided into low altitude (0.15 km), medium altitude (14 km), high altitude (20 km), and stratosphere (up to 50 km); UAM can be seen as corresponding to low and medium altitude [15; 16]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Category** & & \multicolumn{2}{c}{**Key Characteristics**} \\ \hline Fixed-wing & - & Ideal for high-speed and long-haul flights \\  & - & Take-off using runway/launcher \\  & - & Primarily used in military \\ Rotary & - & Vertical take-off and landing and hovering design \\  & - & Low-speed, troubling compared to fixed-wing \\  & - & Includes properties of fixed- and rotary-wing \\ Hybrid & - & High-speed flight, vertical landing possible \\  & - & High energy efficiency compared to rotational income \\  & (tension) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: UAM classification by aircraft type, KIAST. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Category** & **600\(\uparrow\)** & **600** & **180** & **150** & \multicolumn{2}{c}{**115 (kg)**} \\ \hline  & & & - & lightweight & - & powered aircraft \\  & - & airplane & & helicopter & - & powered paraglider \\ Manned & - & rotary & - & power parachute & - & hang glider \\ aircraft & & aircraft & - & weight-dyed plane & - & paraglider \\  & & - & steerable airplane & - & fixture \\  & - & airplane & & - & urltra-light airship \\ Drone & - & rotary flyer & & & (unmanned aerial vehicle) \\  & - & unmanned aerial vehicle (airship) & - & ultra-light flight (drone) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: UAM classification by weight, KIAST. Figure 2: UAM classification by wing shape ([[https://transportup.com/](https://transportup.com/)]([https://transportup.com/](https://transportup.com/)) (accessed on 7 March 2022)). Comparing the development schedule of the eVTOL manufacturing system, one company that launched the commercialization model is Ehang [17], and the technological gap was confirmed to be approximately 1-2 years, which is not considered significant [18]. The launch plan differed over several years by company, but the comparison between large companies that are developing multiple models in parallel and startups that are developing one model did not lead to much significant difference [19].