Nonlinear Longitudinal Aerodynamic Analysis at Low Speed Delta Jet Fighter

Abstract

This study examines the application of the bifurcation theory to the reduced-order of longitudinal flight dynamic systems. An investigation of steady and unsteady longitudinal aerodynamic coefficients is carried out, including an extended range of pitch up and down reduced frequencies from 0 - 0.06 values. An aircraft with a general delta wing with a 1.5 aspect ratio is chosen for the present analysis. Different elevator control deflection from -28.6 to 0 degrees is used to determine the equilibrium points α and q. The unsteady aerodynamic load results increase the requirements for control power as well as thrust vectoring during pitch up than steady longitudinal one. The flow unsteadiness effect improves the vehicle stability during pitch up corresponding a loosing of it during pitch down. A positive pitch rate is required to point the nose of the fighter. This improvement in pointing will help in the close maneuvering missions.