Nonlinear Modeling of the Longitudinal Ground Motion of the Cessna Citation X

This paper presents a practical approach developed at the Laboratory of Applied Research in Active Control, Avionics, and AeroServoElasticity (LARCASE) for the longitudinal ground dynamics modeling of the Cessna Citation X (CCX) business jet aircraft. A detailed analysis was conducted to calculate the ground reaction forces and their distribution among the three aircraft landing gears: nose, left main, and right main gears. For this purpose, a new methodology was proposed to determine a dynamic friction coefficient using an identification technique that considered the aircraft weight, center of gravity, velocity, and acceleration. Additionally, a nonlinear landing gear model was developed to compute the vertical forces and landing gear deflection (i.e., tire and strut) using a two-mass spring–damper dynamic model. Using the landing gear deflections, a new model for pitch angle estimation is proposed, capable of estimating the variation in pitch angle based on the aircraft accelerations and decelerations. Finally, the model is complemented with a brake model that accounts for brake pressure and pilot brake inputs. This methodology was tested and validated using the CCX Level-D Research Aircraft Flight Simulator. Based on the validation results, the proposed model can provide an excellent prediction of ground performance.