An Assessment of Current and On-The-Horizon eVTOL Technologies for a Flying Car
Creators: name:  B. SAEED 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: AERONAUTICS
FUTURE APPROACH

description: The new flying car AirCar has won the certificate of airworthiness which has reignited the debate about the future and realisation of a commercial flying car. The AirCar meets the definition of a flying car, it being air and road worthy, but lacks the key feature vertical take-off and landing (VTOL) to avoid the usual traffic on the road and be a more practical personal vehicle. It was established a decade ago [1] that a realistic future flying car must use non-jet propulsion systems, particularly ducted fans, to acquire a useful performance. Also, a true flying car should be VTOL capable, this imposes certain limitations such as the size, the current range of electric propulsion systems power-to-weight density allows smaller vehicles, such as drones, to acquire a desired performance. For a relatively larger size vehicle a thermal engine is still more appealing [2]. However, the future must be made carbon free and we need to find solutions to cater this imperative global goal, hence, the focus should be electric or other renewable energy sources. The pilot mode and safety are other challenges associated with realising a flying car [3]. Herein, current and on-the horizon VTOL technologies are explored, analysed and technology trends are highlighted to realise a useable flying car. The rise of high power density lithium batteries and efficient motor-rotor solutions are encouraging VTOL capable aerial vehicles; the large scale drones are on an upward trajectory [4]. The VTOL technologies are analysed with regard to power to weight ratio, wing loading, glide ratio and disk loading. The model developed in [1] is modified/improved to evaluate the performance of numerous VTOL technologies. The quest has shown a clear trend towards distributed propulsion system, examples include the Airbus Popup, Airbus Vahana and Lillium Jet, as lower disk loading allows higher propulsive efficiency. It is concluded that a flying car does not exist yet which could be everyones personal vehicle, however, if we define further categories for a personal flying vehicle, there are many promising technologies in the pipeline. For example, an electric VTOL vehicle such as the Airbus Popup may be feasible for city wide commute and for inter-city travel a vehicle with a higher glide ratio, such as the Lillum Jet, may be a better option. From the technologies considered the Lillium jet promises the best overall range, endurance and payload performance. The presented review, also, explores hydrogen fuel for a relatively small aircraft, so far hydrogen fuel is primarily being investigate for jetliners, and attempts a foray into on board renewable energy mechanisms to idealise a sustainable futuristic personal flying vehicle. References [1] B. Saeed and G. Gratton, An evaluation of the historical issues associated with achieving non-helicopter V/STOL capability and the search for the flying car, The Aeronautical Journal 114 (1152), 91-102 (2010). [2] T. Turcksin, P. Van Den Bossche and P. Hendrick, Battery Weight Optimisation for Hovering Aircraft, 8th European Conference for Aeronautics and aerospace Science (EUCASS), 2019. [3] G. Pan and M. Alouini, Flying Car Transportation System: Advances, Techniques, and Challenges, IEEE Access, Volume 9 (2021). [4] A. Straubinger, R. Rothfeld, M. Shamiyeh, KD. Buchter, J. Kaiser and K. O. Plotner, An overview of current research and developments in urban air mobility Setting the scene for UAM introduction, Journal of Air Transport Management, Volume 87 (2020).