Citation: Piancastelli, L.; Sali, M.; Leon-Cardenas, C. Basic Considerations and Conceptual Design of a VSTOL Vehicle for Urban Transportation. Drones 2022, 6, 102. https://doi.org/10.3390/ drones6050102 Academic Editor: Abdessattar Abdelkefi Received: 15 March 2022 Accepted: 15 April 2022 Published: 21 April 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). drones Article Basic Considerations and Conceptual Design of a VSTOL Vehicle for Urban Transportation Luca Piancastelli *, Merve Sali and Christian Leon-Cardenas Department of Industrial Engineering, University of Bologna, Viale Risorgomento, 2, 40136 Bologna, BO, Italy; merve.sali2@unibo.it (M.S.); christian.leon2@unibo.it (C.L.-C.) * Correspondence: luca.piancastelli@unibo.it; Tel.: +39-335-331187 Abstract: On-demand air transport is an air-taxi service concept that should ideally use small, autonomous, Vertical Short Takeoff and Landing (VSTOL), “green”, battery-powered electric aircraft (eVSTOL). In addition, these aircraft should be competitive with modern helicopters, which are exceptionally reliable machines capable of the same task. For certification and economic purposes, mobile tilting parts should be avoided. The concept introduced in this paper simplifies the aircraft and makes it economical to build, certify and maintain. Four contrarotating propellers with eight electric motors are installed. During cruise, only two of the eight rotors available are not feathered and active. In the first step, a commercial, certified, jet-fueled APU and an available back-up battery are used. A second solution uses a CNG APU and the same back-up battery. Finally, the third solution has a high-density dual battery that is currently not available. A conceptual design is shown in this paper. Keywords: electric–thermal hybrid aerial; vertical short takeoff landing; attitude control; cost-effectiveness 1. Introduction On-demand air transport is an air-taxi service concept that should use small, Vertical Short Takeoff and Landing (VSTOL), battery-powered, electric aircraft (eVTOL). These aircraft should be competitive with modern helicopters, which are exceptionally reliable and cost-effective aerial vehicles designed for the same task. These new vehicles should be more efficient, less expensive, eco-friendly, and quieter than helicopters and autogiros. A few considerations are necessary before the introduction of an innovative design concept for the task. First, autonomous flying is possible [1] and relatively straightforward, with the aid of today’s machine learning technologies [2–4]. Most commercial airplanes have the capability of fully autonomous flight from takeoff to landing [4]. Many Unmanned Aerial Vehicles (UAVs) have the capability to fly a mission autonomously even in controlled airspace and in airports. Nevertheless, unmanned flight is rarely considered for civil air transportation [5]. This is because most passengers would refuse to use a pilotless airplane. Therefore, from the perspective of an individual who communicates with their destination via an app, the notion of securing their seatbelt, closing the door, and taking off for a fully autonomous flight is physiologically uncomfortable. What would happen in case of an emergency? The air-taxi would be controlled by an emergency ground station. How would the control authority expect such an aircraft to fly over a crowded city, with other aerial vehicles? For this reason, it is important to design an optionally piloted vehicle. In this case, at least for an initial period, a pilot could transport the passengers to their destination. Theoretically, electric propulsion introduces the potential to alter the design of vertical lift vehicles for reduced cost. Experts theorize a substantive operating cost improvement because of lower energy costs, reduced maintenance time, mass production, and increased part commonality [6]. In fact, energy coming from the electrical grid costs less than one third of that obtained on-board from aviation fuel. Only for this reason, a Drones 2022, 6, 102. https://doi.org/10.3390/drones6050102 https://www.mdpi.com/journal/drones