Structural dynamic characterization of the horizontal tail section of a civil aircraft iron bird test rig

Abstract

A shell-element finite element model of the horizontal tail section of a civil aircraft iron bird test rig was developed in HyperMesh. Natural frequency extraction and modal effective mass fraction (MEFFMASS) analysis were performed using Nastran SOL 103, static strength assessment was carried out using SOL 101, and a parameter sensitivity study was conducted on the wall thicknesses of three key lug-region components with respect to the two localised lug-assembly modes. The first six natural frequencies (16.5–38.4 Hz) fall within the elevator sinusoidal sweep excitation band; however, the cumulative Y-directional modal effective mass fraction of these six modes is only 0.47%, and the dominant Y-directional mode is Mode 13 (69.80 Hz) with a frequency margin of 74.5%, confirming negligible resonance risk within the sweep band. Under the maximum actuator load, the peak structural displacement is 16.1 mm, and the von Mises stress distribution satisfies the Q235A yield criterion. Thickness variations of the three lug-region components alter the two localised lug-assembly mode frequencies by no more than 5.8%, demonstrating that the dynamic safety of the rig is robust to maintenance and modification activities in the lug region.