The prediction of the vibratory airloads of helicopter rotors in forward flight

Abstract

The determination of the vibratory airloads generated by helicopter rotors in forward flight presents a difficult problem in unsteady aerodynamics. However, their analytical prediction in the design phase is essential if the vibration level is to be controlled and rotor fatigue loads minimized. Recent advances in developing free-wake vortex theories for rotors in forward flight which are sufficiently compact for design purposes, yet agree well with the experimentally-determined blade loads, are discussed. The effects of modifications in blade geometry and of blade elasticity on the vibratory loads are shown.