Modeling of the Nonlinear Takeoff Dynamics of the Cessna Citation X

This paper presents the methodology developed at the Laboratory of Applied Research in Active Controls, Avionics, and AeroServoElasticity (LARCASE) for identifying the six-degree-of-freedom takeoff dynamics of the Cessna Citation X business aircraft. A highly nonlinear takeoff dynamics model was developed using an in-house ground dynamics model. A practical nonlinear friction coefficient model, which depends on high accelerations and speeds, was defined for this approach. The landing gear model was modeled using a two-mass–spring–damper system, and two equations for stiffness coefficient deflections were proposed. In addition, a loss-of-contact model was introduced to determine ground reaction contact loads during rotation and transition phases. The equations of motion were calculated for each phase of the takeoff (i.e., ground acceleration, rotation, and transition) by considering the loss of ground contact, the total gear deflection (i.e., tire and strut), and the cumulative effects of ground, out-of-ground, and steering moments. This approach was tested and validated using a Cessna Citation X Level D Research Aircraft Flight Simulator. The model demonstrated excellent predictive accuracy in takeoff performance.