Innovative Approach to Full Scale Fatigue Testing using Hybrid Methodologies

The lack of adequate fatigue life verification for rotorcraft airframe structures leads to costly in service repairs being required in order to maintain structural integrity. The current established methodology does not test the airframe to the synergistically harmful combination of high cycle fatigue (HCF) vibratory load cycles superimposed on low cycle fatigue (LCF) caused by g maneuvers and airloads. Dayton T Brown, Inc. (DTB), a leader in aircraft system engineering and testing services, has developed a comprehensive solution to improve structural testing methods by incorporating combined HCF and LCF testing. Our approach is based upon combining our years of experience in vibration (HCF) testing with our aerospace structural qualification (LCF) testing using servo hydraulics. DTBs familiarity with multiple testing methodologies, instrumentation techniques and our previous investigations into combined HCF & LCF fatigue testing have enabled us to identify areas requiring additional development; namely control system design and the application of the LCF loads to the airframe in a way that allows the airframe vibration loads to remain unimpeded. Our baseline concept integrates existing technologies to address this requirement.