CORRELATION OF EXPERIMENTAL FLAP-LAG-TORSION DAMPING - A CASE-STUDY

In 1982, carefully done experiments measured the flap-lag-torsion damping of hingeless rotor at various RPM's and for several combinations of flexure geometry and stiffness. The best elastic-blade stability codes of that time were unable to predict this damping and typically gave errors of the order of 100% (as percentage of the largest measured damping, 5 rad/s). Through the past ten years, various unsuccessful efforts have been made to improve those predictions. Now, improved correlation has been performed with errors of 0% to 20% of 5 rad/s. The results show that most of the former discrepancies can be attributed to aerodynamic effects, the largest of which is the dynamics of the three-dimensional wake.