STRUCTURAL QUALIFICATION OF A MAIN ROTOR YOKE USING THE FINITE-ELEMENT ANALYSIS METHOD

This paper presents an analysis approach that was used to structurally certify a re-designed main rotor yoke. The finite-element method was the analysis technique used. Two yokes were analyzed-an existing “old design” and a functionally and geometrically similar “new design” yoke. To “prove” the analysis, the yoke of the old design was analyzed first and the results were then compared with the available strain-gage readings of the previous testing. Having made an acceptable comparison between test data and analysis, the finite-element analysis on the new design yoke would be considered valid since the redesigned yoke was of the same basic design of the old design yoke. The objective of the finite-element analysis was to assist in structural certification of the new design yoke promptly, and to do so without the necessity of expensive fatigue testing. Analysis data for the old design yoke and the new design yoke would be submitted to the Federal Aviation Administration. The basis for approval was acceptable correlation between test strain-gage data and the analysis on the old design yoke, the design similarity of the two yokes, and analysis data showing lower stresses for the new design yoke. The results obtained showed acceptable correlation with the old design test data and a decrease in stress for the new design yoke. The redesigned new yoke was approved by the Federal Aviation Administration and has been in production for over two years.