Modeling of the Six-Degree-of-Freedom Nonlinear Ground Dynamics of the Cessna Citation X

This paper presents a detailed methodology developed at the Laboratory of Applied Research in Active Controls, Avionics, and AeroServoElasticity (LARCASE) to develop the six-degree-of-freedom ground dynamics of the Cessna Citation X (CCX) business aircraft. A highly nonlinear model for ground reaction forces (i.e., horizontal, lateral, and vertical forces) was designed based on an in-house longitudinal ground dynamics model and also considering lateral motion. Furthermore, two new ratios using the angular momentum theorem around the roll and pitch axes were developed to obtain reaction forces, first between the nose and the main landing gears and then between the right and left main landing gears. Finally, based on the landing gear model and its deflections, two trigonometric equations were used to estimate the Euler angles in both roll and pitch motions. The yaw angle was calculated using the sum of ground moments around the z-axis, incorporating the steering moment. This methodology was tested and validated using the CCX Level-D Research Aircraft Flight Simulator (RAFS). Compared with the RAFS data, the proposed model provided an excellent prediction of the CCX aircraft’s ground performance.