Urban air mobility (UAM) is an emerging innovation and research area and is one of the key pillars enabling
future vertical mobility. UAM specifically focuses on air travel within and around urban areas. In recent years, more studies have been performed on the acceptability and performance of UAM vehicles. However, a research gap is present on the dynamic rollover tendencies for UAM lift plus cruise vehicles, a type of Vertical Take-Off and Landing (VTOL) multirotor vehicle. Dynamic rollovers are known to be a risk for helicopters, another type of VTOL. A dynamic rollover occurs when the center of gravity of an aircraft rotates around a pivot point. The pivot point is the contact point of the surface and the aircraft’s landing gear. This causes the aircraft to roll and eventually crash. There are multiple situations in which a rotary aircraft can roll over, such as sloped landings or due to strong crosswinds.

This thesis research aims to investigate the susceptibility of dynamic rollover for a lift plus cruise vehicle during landing through computational simulations. Investigating this susceptibility is achieved by identifying the flight conditions that influence the dynamic rollover behaviour of the vehicle and testing design alterations to the lift plus cruise model. To model the rollover susceptibility, a base scenario is introduced in which an eight-rotor lift plus cruise vehicle makes a vertical landing of eight meters and reaches a landing surface. During this descent, the vehicle encounters a wind gust. The model was developed using the equations of motion with five degrees of freedom, which include: roll, pitch, surge, sway and heave.

From this research it can be concluded that the wind gust influences the rollover susceptibility of the vehicle. The stronger the wind gust, the more prone the vehicle is to roll over and the more time the wind gust has to develop, the less chance the vehicle has to roll over. In comparison to the helicopter, the multirotor is more stable and less prone to rolling over. Design alterations have been applied to the model to investigate whether improvements are possible in the design of the lift plus cruise vehicle to decrease its tendency to roll over. It was found that a smaller disc loading is beneficial, as well as a smaller lateral distance between the rotors. To reduce the wingspan of the vehicle and therefore, reduce the angle at which the rotor can touch the ground. When investigating a reduction in the number of rotors, in all cases, a reduction would not benefit the susceptibility to rollover in a positive sense. The influence of the landing gear structure is small, therefore, the development of a new type of landing gear does not have a priority.

In conclusion, this thesis explores the factors influencing rollover susceptibility in a UAM multirotor vehicle. By systematically analysing the dynamics of vehicle behaviour under various conditions, key insights into rollovers were uncovered.