*4.5. Summary*

Though many design proposals have been made and research papers have been published, there are no vertiports existing yet except of two single FATO designs such as the 2019's demo *VoloPort* in Singapore and Coventry's first *urban-Air Port*. However, the collection of vertiport designs displayed in Section 4.1 offer a wide range of ideas and approaches how to integrate UAM into urban and sub-urban environment and how to use already existent infrastructure. Keywords like *scalability*, *acceptance* and *sustainability* were raised frequently in this context. For those considered contributions, important topics influencing the vertiport design like energy grid capabilities, VTOL aircraft storage during non-operational hours, safety and security measures, contingency operations, check-in procedures, passenger flow and guidance from gate to the vehicle and operational weather dependencies are, if at all, described very briefly and not in detail. It is also unclear yet, on what basis a vertiport will be dimensioned; is it designed to accommodate peak hours, to fit the overall daily demand, or is the vertiport configuration dynamically adjustable to serve varying demand flows as proposed by [186]. Additional discrepancy is provided by the claimed footprint required for processing one vehicle per hour (cf. [102,126,128]). Vertiport throughput capacity has been studied both analytically as well es through simulation (cf. Section 4.2). There is a wide range of ana-

lyzed throughput addressing up to 1400 movements per hour. Various vertiport topologies, positioning pads, gates, and terminals, have been proposed such as satellite, linear and pier topologies. The ratio of gates to pads can vary from 2 to 8. It appears that vertiports will have strongly differing shapes and capacities depending on their location and demand profile they have to process. A novelty of vertiports compared to conventional heliports is the expected use of ground taxiing. Three types of taxiing are defined, namely hover taxiing, passive ground taxiing and active ground taxiing. Lastly, the turnaround at gates, which is driven by passenger de-/boarding and VTOL vehicle re-fueling will be of significant influence for the overall available capacity provided by the vertiport; the latter will depend on the primary energy source, which could be fully electric, hybrid-electric or LNG-powered. Transitioning from airside ground to airside air operations, high-density UAM operation itself is a challenging endeavor in terms of traffic management. But taking into account other airspace users such as commercial and general aviation, helicopter emergency and medical services will increase complexity immensely. This is even aggravated by first implementing piloted UAM operations and, over time, transitioning to automated and autonomous operations. The importance of harmonization between strategic and tactical measures of arrival and departure traffic is highlighted throughout Section 4.3. Different approaches how to structure a vertiport network airspace as well as a vertiport's local airspace and fair access to it was discussed. CNS and ATM capabilities are not only crucial for managing UAM traffic around vertiports, but also when merging UAM traffic with already existing airspace users and conventional traffic especially in airport environment. A need for a thorough strategic planning is discovered, but tactical measures cannot be neglected. The scientific publications discussed in Section 4.3 tend towards a FCFS scheduling and sequencing approach. However, it was clearly highlighted that certain parameters such as remaining endurance and agglomerated delay may impose critical constraints which may favor a priority-based sequencing concept. The transition from piloted to automated to autonomously operating UAM may impose additional implementation challenges especially in terms of traffic management, the distribution of roles and responsibilities, the way of communication and exchanging information while ensuring the highest standards for safety and cyber-/security. In Section 4.4, the prediction of vertiport costs was addressed, which seems to be not really part of scientific papers nor discussed frequently in the public. Neither are UAM and vertiport operations existent yet, nor does Europe has a mature high-volume urban air commuting market from which historic experience may provide reliable cost estimations. Current European research as well as UAM industry does not know what the real operation and traffic densities will look like. Existing aviation infrastructure like airports and heliports may be used initially. But, retrofitting and upgrading them to meet UAM needs and future standards, and integrating UAM traffic at those already existing traffic junctions may be limited and may result into even more additional investments.

#### **5. Weather Impact on Vertiports**

*"Moreover, the weather enterprise needs champions in the aviation industry to embrace and promote weather as an integral component in the design, certification, and operation of aerial vehicles like eVTOLs or unmanned aerial systems (UAS)" [187]*

Airborne operations performing in urban environment do not only face challenges due to a complex obstacle environment, but also due to so far unknown weather conditions arising in highly and densely built-up areas. Every operating environment in which UAM services should be offered, needs to be evaluated locally and regionally depending on the vertiport network size.

Other than for vertiports, STOL contributions are "more conscious" about weather influencing the placement and orientation of the take-off and landing strip. Based on an initial airpark placement which focused on identifying the largest vacant area [82], subsequent contributions like [188,189] use historical weather observation data together with a detailed obstacle analysis to determine the location and orientation of the runway

within those areas of interest. For a single runway, its orientation needs to be defined so that the emerging crosswind vector does not exceed 10.5 kts (5.4 m/s) more than 95% of the time [188].

From a European regulatory perspective, EASA's *SC-VTOL-01* provides the requirement "[. . . ] the applicant must demonstrate controllability in wind from zero to a wind limit appropriate for the aircraft type" [21]. In the subsequent *MOC-2 SC-VTOL*, performance data was considered under wind conditions defining "take-off until reaching VTOSS (see *MOC VTOL.2115*) and from below VREF (see *MOC VTOL.2130*) to landing (i.e., the ground referenced phase), at least 17 kts of relative steady wind should be considered" [38]. Additional high-level requirements regarding visibility during falling and blowing snow are displayed in [38]. Other than that, no further requirements are yet provided.
