Helicopter Roll-Axis Instabilities induced by Pilot Cyclic Control: A Physical Explanation

The main objective of this paper is to give a basic understanding of the mechanisms through which pilot cyclic inputs in lateral cyclic interacts with high-order rotor dynamics destabilizing the helicopter roll motion. The paper will use a “Newtonian formulation” representing the main forces acting on the airframe body-rotor system as the pilot applies his/her control. It will be demonstrated that pilot lateral controls applied through his/her arm (which may involve also pilot biodynamics, i.e. the dynamics of pilot neuromuscular inputs and contraction dynamics of his/her muscles) may excite much higher-order frequency rotor dynamics than thought at the present.