Tiltwing Multi-Rotor Aerodynamic Modeling in Hover, Transition and Cruise Flight Conditions

The paper discusses the aerodynamic modeling of a multi-rotor, tandem tiltwing aircraft called Vahana. Vahana is an all-electric, fully-autonomous aircraft being built by A3 by Airbus LLC. Vahana can take off and land vertically using eight fans, and can transition into cruise using fans and tilting wings. Vahana is designed to be able to trim at any speed during transition, even with the failure of any one of its eight motors. Aerodynamic modeling of Vahana is a challenging problem because of the interactions between multiple fans and wings during transition. In the present work, a medium-fidelity aerodynamic modeling tool is used for solving the flow around Vahana in any arbitrary flight condition. The trim involves finding the optimum settings of Vahana's multiple actuators, which include variable speed electric motors, variable pitch fans, tilting wings, and control surfaces. An optimization procedure is developed to find trim solutions through the transition maneuver while minimizing the vehicle total power. To speed up the analyses, surrogate aerodynamic models of the vehicle are created using Gaussian processes, which are then used in the optimization to compute the aerodynamic loads given a set of vehicle states and actuator settings as inputs. The results present a transition trimline for Vahana. A cross-check on the trim solutions is performed using a high-fidelity CFD solver. A comparison of the loads and flow fields predicted by the medium-fidelity tool and the CFD solver is presented.