Structural Dynamic and Aeroelastic Finite Element Simulation of an F-18 Tail Rudder: Impact of Adding a Control Surface

Abstract

This paper presents the findings of a Finite Element Analysis (FEA) based aeroelastic analysis performed on the F-18 tail rudder using MacNeal-Schwendler (MSC) suite of commercial FEA codes. The purpose of the study was to examine the stabilizing effects of adding a control surface to the tail wing, in this case the control surface is the tail rudder. MSC NASTRAN modal analysis and aeroelastic simulations were employed to carry out the investigation. Results are presented herein for the fundamental modes subject to a structural dynamics analysis and a series of supersonic 4G rolling maneuvers. Without a control surface, modal analysis yielded the following; 1st bending mode = 17.098 Hz, 1st torsional mode = 53.879 Hz, 2nd bending mode = 80.531 Hz, and 2nd torsional mode = 117.15 Hz. By adding the of rudder, the following is found; 1st bending mode = 17.797 Hz, 1st torsional mode = 48.266 Hz, 2nd torsional mode = 61.267 Hz, and 2nd bending mode = 81.142 Hz. Hence, adding the control surface, changes the precedence of the 2nd torsional and 2nd bending modes. Aeroelasticity predictions show that for a 100% increase in Mach number, the maximum pressure on the control surface increases by 93%.