A Mission Synthesis Procedure for Sine-on-Random Excitations in a Helicopter Application

Abstract

This paper considers a so-called “Mission Synthesis” procedure where a qualification test specification is derived for an electronic component (i.e., a VHF radio) mounted on a console inside a helicopter cockpit. The environmental vibrations, which are measured during various flight maneuvers, consist of deterministic sine tones superimposed on Gaussian random excitations, i.e. so-called “Sine-on-Random” (SoR) vibration. The Fatigue Damage Spectrum (FDS) model is utilized for analyzing the fatigue damage potential of these SoR excitations. A particular objective in this application example is to assess the induced fatigue damage for two design alternatives of the radio console, which is achieved by means of an FDS comparison. Furthermore, it is demonstrated that experimental modal analysis can provide valuable insights on the physical root causes for large induced fatigue damage, such that appropriate design modifications can be prescribed. Finally, the Mission Synthesis procedure enables the derivation of an accelerated but damage-equivalent shaker qualification test. For the component considered in this example it is demonstrated that the derived test specification is more severe than a MIL-STD standardized SoR test specification.