Flight characteristics of coaxial-rigid-rotor helicopter during deck landing

A coaxial-rigid-rotor helicopter flight dynamics model, which can be coupled with unsteady ship airwake, was developed to investigate flight characteristics of the rotorcraft during deck landing. In the numerical simulation of ship flowfield, the detached eddy simulation method was used to obtain high-precision data of the flowfield. In building the flight dynamic model, an interaction factor of coaxial twin rotor was introduced to develop the induced velocity model of the coaxial rigid rotor, and the concept of equivalent flapping was adopted to establish the flapping movement function of coaxial rigid rotor. Then, a strategy which can transmit computational fluid dynamics (CFD) data to the flight dynamics model was established based on the “one-way” coupling idea. The accuracies of the flight dynamics model and the data transfer strategy were verified by analyzing the XH-59A coaxial-rigid-rotor helicopter and the combination of UH-60A/SFS2, respectively. Next, the combination of SFS2 ship model and XH-59A coaxial-rigid-rotor helicopter was chosen to investigate the influences of the ship airwake on the helicopter in terms of control margins and unsteady loading level. The time-averaged results showed that due to the differences in disturbance between the upper and lower rotor, pilots had to reduce the differential collective pitch to maintain the direction of the helicopter nose, while increasing the collective pitch to maintain the altitude at the same time. Furthermore, the unsteady level results indicated that for coaxial configuration, the disturbances in its thrust and pitch moment are the primary causes of pilot workload. © 2023 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.