CONCEPTUAL DESIGN OF LARGE ELECTRIC VERTICAL TAKE-OFF AND LANDING AIRCRAFT FOR URBAN AIR MOBILITY OPERATIONS
Creators: name: Biswas, Somrick Das
Publisher: name: Purdue University Graduate School
Year: 2025
Subjects: classificationCode: 400199
subject: Aerospace engineering not elsewhere classified

description: The rapid growth of urban populations and increasing congestion in surface transportation have driven the need for innovative mobility solutions. Urban Air Mobility (UAM) is proposed as a promising alternative to ground-based transportation, leveraging novel electric Vertical Takeoff and Landing aircraft (eVTOL) to provide fast point-to-point travel in metropolitan areas. Market analysis studies show the potential for greater ridership—and possibly greater profitability—through the deployment of larger eVTOL aircraft than those currently being designed and going through the certification process (typically 4-passenger aircraft), particularly in metro areas with large populations and significant road congestion. This thesis considers the Chicago, IL area as a case study to examine the market potential for such larger eVTOL aircraft. While designing any aircraft is inherently complex, eVTOLs present a distinct set of challenges. Not only are they unconventionally powered—relying on electric propulsion instead of traditional fuel-based systems—but they also integrate features from both rotorcraft and fixed-wing aircraft, leading to novel aerodynamic and structural trade-offs. Designing large eVTOLs also poses unique challenges that differ from their smaller counterparts, particularly due to the absence of historical data to inform sizing predictors, such as empty weight fractions, drag coefficients, and propulsion efficiency. Unlike conventional aircraft, large eVTOLs lack established baselines, making early-phase design and feasibility assessments highly uncertain. This amplifies the complexity of integrating aerodynamics, distributed propulsion, mission planning, and certification pathways into a coherent, scalable design. This thesis presents a computational framework for the conceptual design of large eVTOL aircraft tailored to UAM operations. At a high level, the framework combines passenger trip generation and ridesharing modeling with advanced aerodynamic and energy system analyses. A prop-rotor design module using Blade Element Momentum Theory (BEMT) is coupled with optimization routines to explore rotor sizing and power loading characteristics. Battery-sizing is performed using an energy-based approach that accounts for peak power discharge rates and pack-level safety constraints, while mission profiles include times required to transition from vertical lift to forward flight from flight test data of Archer Aviation’s Midnight aircraft. A regression model was trained on public eVTOL data to estimate empty weight ratios based on MTOW, disk loading, and configuration variables. A design of experiments (DoE) approach guided exploration of the eVTOL design space for a 19-passenger aircraft. Using a full-factorial approach, the sizing approach developed here evaluated 450 different design points, seeking the lightest weight design that meets performance and operating constraints. Based on the modeling framework and assumptions employed in this thesis, wing loading emerged as a key design variable influencing overall weight trends. Higher wing loading generally corresponded to reduced takeoff weight, though it is constrained by stall speed and aspect ratio requirements. Given the relatively short cruise segment assumed for this vehicle, performance during takeoff, hover, and landing becomes particularly critical. Furthermore, the design was found to be sensitive to the number and sizing of prop-rotors, with disk loading and power loading playing significant roles. These sensitivities were observed to be highly dependent on the vehicles overall configuration, underscoring the importance of integrated design exploration.Given the limited fidelity of the initial sizing approach used in this thesis, the results suggest that a 19-passenger eVTOL aircraft with a 50-mile design range appears feasible under the specified assumptions. To account for the inherent uncertainty in the estimation of empty weight fraction and parasite drag—key predictors in the sizing approach—a basic sensitivity analysis was conducted. This analysis indicates that the predicted takeoff gross weight for the 19-passenger configuration could range from approximately 5,591 kg (13,323 lb) to 8,583 kg (18,917 lb), depending on the degree of deviation in these input estimators. From an operational standpoint, the 19-passenger configuration was motivated by the need to improve passenger throughput and reduce per-passenger costs. Preliminary cost and ridership estimates suggest that such a capacity offers potential advantages in terms of load factor, operating economics, and infrastructure utilization compared to smaller-capacity eVTOLs. These findings highlight the potential value of higher capacity designs. These bounds emphasize the need for higher-fidelity modeling and validation as the design process matures.This work offers a credible approach for eVTOL aircraft sizing; however, challenges remain in addressing regulatory constraints, certification processes, and battery technology limitations. Future work should incorporate more physics-based modeling approaches to improve sizing accuracy, especially given the limited historical data available for large eVTOLs. For aerodynamic analysis, methods such as vortex-lattice models are required to provide better estimates than empirical correlations, offering a good balance between accuracy and computational efficiency. Similarly, higher fidelity structural mass estimation could benefit from finite element methods (FEM) or parametric structural models to more accurately capture airframe loads and material constraints. Furthermore, refining the modeling of the transition segment—which bridges vertical and forward flight—is critical for accurately estimating performance, weight, and propulsion requirements in future eVTOL designs.Additionally, noise considerations must be prioritized to ensure community acceptance and regulatory compliance, especially given the scale of operations envisioned for AAM. Larger eVTOL aircraft, by virtue of needing to move greater volumes of air, generally generate higher acoustic signatures than their smaller counterparts. While distributed electric propulsion offers potential for quieter operations compared to conventional rotorcraft, achieving noise levels acceptable to urban communities remains a significant design and regulatory hurdle. Future research should investigate the trade-offs between vehicle capacity, propulsion system architecture, and urban noise footprints to determine whether large-capacity eVTOLs can be operated at noise levels conducive to broad public acceptance. Furthermore, larger eVTOLs require more physical space for takeoff, landing, and ground operations. This necessitates a careful assessment of infrastructure availability, as the larger footprint of high-capacity eVTOLs may limit their operability to existing airports or specially designated facilities. Such constraints could reduce the flexibility typically associated with vertical takeoff and landing aircraft, potentially narrowing their advantage over electric CTOL or STOL alternatives. Compared to smaller eVTOLs, these larger vehicles may also have access to fewer landing sites, impacting network density and service coverage. These trade-offs between vehicle size, operational flexibility, and infrastructure scalability are central to evaluating the feasibility and overall value proposition of large eVTOL concepts.