Midterm Report - Multi-Disciplinary Design and Optimisation of a Long-Range eVTOL Aircraft

Midterm Report of the Design, Synthesis and Exercise (DSE) carried on during the Spring DSE 2021, group 06, assignment "Multi-Disciplinary Design and Optimisation of a Long-Range eVTOL Aircraft".

Tutor: Saullo Giovani Pereira Castro
Coaches: Davide Biagini and Ali Nokhbatolfoghahai
Institution: Delft University of Technology
Place: Faculty of Aerospace Engineering, Delft
Submission Date: Thursday 27th May, 2021

Summary

The issue of adequate transportation is widespread. Not only are many modes of transportation expensive, but they often require dedicated infrastructure and are prone to traffic and congestion. In an attempt to attenuate this costly problem an electrical Vertical Takeoff and Landing (eVTOL) aircraft concept is proposed. To be precise, three such concepts are proposed. One with a tandem wing configuration, another with a box wing and a third with a single wing. While there can be three such solutions, the objective remains the same, which is to provide sustainable, personal aerial transportation for inter-city travel that is competitive with the current transportation methods while requiring minimal infrastructure. In order to accomplish this goal, several steps are taken, which are hereby explained.

In Chapter 2 the organisational structure of the group is explained, which allows for the project plan to be explicated in Chapter 3. After the planning is complete the trade-off criteria is listed in Chapter 4 and possible solutions can be graphed by means of a design option tree in Chapter 5.

However, out of the realm of possibility, one is likely to be the most suitable for the problem at hand. The purpose of this report is to select the concept which performs the best under the requirements previously formulated, that state what the solution shall do and how it shall do it. Through these requirements, it is possible to establish the relevant trade-off criteria and thereby create a trade-off matrix. That being said the criteria of the trade-off matrix have yet to be defined, for which preliminary values are necessary. For these, Chapter 6 outlines the method used to size the vehicle, using a set of statistical models after the concepts are illustrated. In this, the stall speed, climb rate, turning load factor, and other parameters pertaining to the aircraft is estimated, including the mass.

Then the flight performance is discussed in Chapter 7. Therein the aircraft is analysed during the different phases of flight. This leads to its energy consumption being considered during different phases. Thereafter its climb performance is evaluated as well as aspects of the passengers. After that the aerodynamics of the aircraft is explicated in Chapter 8. This includes estimations of the lift and drag coefficients, the design of the wing (if applicable) and the selection of airfoils for the concepts. Once that is complete the drag estimation can be concretised and a more accurate version of the drag polar can be made.

The discussion of the design continues with the Propulsion & Power subsystem in Chapter 9, the crux of which lies in selecting a proper and adequate source of power. Several options were considered, including a variety of hydrogen fuel cells and batteries. The design of the propulsion subsystem of the vehicle also presented itself as a challenge, but it could be overcome with Actuator Disk Theory, which exploits the relationship between the area of a propeller and the weight of the aircraft.

The stability and control of any aircraft not only constitutes passenger comfort, but also governs their safety during flight, an essential discipline that is presented in Chapter 10. In this chapter, the controllability is explained in hover, through a set of state space models that govern the output of a system, given the inputs. An aircraft is only as good as the loads it is capable to withstand, which implicates another crucial aspect of the design of an aircraft, namely the structure thereof. Chapter 11 presents the structural design envelope. These are done with the critical failure modes: fatigue and yield. This is coupled with the estimation of the aircraft weight and centre of gravity, as well as its crash-worthiness.

After the technical aspects of the design are discussed, the finances can then be planned, as in Chapter 13. In this, the unit cost analysis is performed as well as the direct operational cost. Upon completion of this analysis the project development and design is also discussed, as well as the plan for sustainability in Chapter 14. The Reliability, Availability, Maintainability and Safety characteristics are then elucidated in Chapter 15. The Technical Risk Analysis is also performed in Chapter 16 in order to determine any foreseeable malignant circumstances and plan for all contingencies.

With all of the above in mind, the trade-off can then be conducted in Chapter 17. Wherein the selection criteria and weights are defined, as well as how well it complies to its constraints. Thereafter the Trade-Off matrix is generated. With all of this done, the purpose of this is thereby fulfilled and the final design is presented in Chapter 18, wherein the Tandem configuration is selected.