Multibody model of the flap stop contact dynamics of an articulated rotor

Abstract

The paper discusses a multibody aeroelastic model of an articulated main rotor system. The model is developed with the specific aim to capture the main dynamic features characterising flap stop contact conditions and to provide a means to predict the associated loads. A five bladed fully articulated rotor is considered: blades flexibility is accounted for using beam modal representations and the aerodynamics is modelled with a blade element approach. Particular emphasis is given to the definition of the flap stop mechanism structural and geometrical features, by detailing the contact reaction load paths and importing the contact surfaces from verified 3D CAD geometries. The kinematics of collective and cyclic controls is accurately represented considering servo actuators, rotating and fixed swashplates with the respective scissor links, pitch links and pitch horns. Linear blade lag dampers are implemented reproducing the associated experimental operating damping curve. Special attention is addressed to the model validation activities which lead to the achievement of an encouraging level of correlation with experimental data: the findings highlighted in this paper confirm the validity of the methodology adopted and give confidence in its potential for describing the flap stop contact dynamics of fully articulated rotors.