Multiple rotor configurations are adopted in most electric vertical take-off and landing (eVTOL) aircraft concepts for urban air mobility. As a concept of high-speed eVTOL, this paper investigates a “Lift and Cruise” type configuration composed of multiple rotors and a thrust propeller to achieve a high-speed and compact rotorcraft design. This rotorcraft is designed for cruising flight with the fuselage and rotors in a horizontal attitude. The impact of aerodynamic interference between the rotors on the aerodynamic performance is investigated using high-fidelity CFD simulations. In the present study, the computational model consists only of the isolated quadrotors without the fuselage and the thrust propeller, and the influence of the vertical position of the rear rotors on the aerodynamics and flow field is explored. Two flight speeds, medium/high advance ratios of 0.297 and 0.594, are simulated. Different interactional effects depending on the rotor advance ratio are observed. At the high advance ratio condition, the aerodynamic performances of the rear rotors are slightly changed and obtain the highest effective lift-to-drag ratio despite at the same vertical position of the front rotor. The numerical results suggest that high advance ratio rotors can potentially reduce the interference effect between rotors.

This paper describes the control system for the Mars Airplane Balloon Experiment 2 (MABE-2). In this paper, firstly, the characteristics of this aircraft and a future Mars airplane is presented. Secondly, the constraints and flight plan of this flight mission are indicated. Based on these constraints and flight plan, the configuration of the designed control system is presented. Thirdly, we evaluate the achievement rate of the flight mission constraints using Monte Carlo Simulation (MCS) with the assumed errors and disturbances. Additionally, the error items that strongly affect the achievement rate of the flight mission are detected and evaluated from the MCS failure cases. Fourthly, the gains of the control system are determined to maximize the mission achievement rate. Finally, the achievement rate is again evaluated by MCS with the determined gains.

The purpose of this study is to validate aerodynamic measurements obtained from the 1-m Magnetic Suspension and Balance System (MSBS) using a practical model with multiple measurement data consisting of wind tunnel and flight tests. Static wind tunnel tests using 1-m MSBS were conducted on the ALFLEX model within an angle of attack range of 0 to 20 degrees, and the aerodynamic force coefficients: C_D, C_L and C_M were evaluated and compared with previous studies. Additionally, since ALFLEX has a base surface, which is known to reduce the accuracy of CFD-based aerodynamic predictions, CFD simulations were performed to estimate the aerodynamic force coefficients, and the results were also compared with previous studies. As a result, the effectiveness of wind tunnel tests using the 1-m MSBS was demonstrated for C_D and C_L, while some measurement accuracy issues were identified for C_M. For CFD, reasonable values were obtained for all coefficients.

Although it is well known that the equation of motion of T-tail transport aircraft has stable steady states at high angles of attack due to deep stall, a reliable and prompt recovery procedure has not been established. In this study, bifurcation analysis is conducted to understand post-stall nonlinear behavior of a T-tail airliner model, with deflection of rudder and elevator as parameters. The results show that it is difficult to recover from flat spin, a stable equilibrium point with a high angle of attack, by simply switching the rudder and elevator deflection. In order to propose recovery control, an optimal control problem is solved with the direct collocation method. This problem requires a transition from the flat spin to another stable equilibrium point, which is steady level flight. The optimal control input utilizes the coupling of longitudinal and lateral dynamics to make state variables cross the boundary of attraction in the nonlinear dynamical system, and recovery is achieved in a short time.