Aircraft longitudinal unsteady aerodynamic modeling using indicial function

To describe the unsteady aerodynamics in high angle-of-attack maneuvers, a novel unsteady model based on indicial function is established for aircraft longitudinal dynamics. This model involves unsteady state expressed by first-order differential equation and squared terms of pitch rate, which effectively reflects the hysteresis characteristics and enhances the nonlinear representation ability. The static and dynamic data of large amplitude forced-oscillation test are employed to identify the parameters. Through using maximum likelihood principle and engineering experiences, the modeling procedure is significantly simplified and the reliance on dynamic derivative test is also removed simultaneously. Strong generalization performance and effectiveness of the developed unsteady model are verified by test data and dynamic derivative simulation results.