ABSTRACT
In the previous chapters, it is shown that rotor forces and moments are functions of flap response and blade pitch input. In the most general case, these forces and moments will also be functions of blade lag, torsion, and perturbational hub motion. During steady flight, the trim condition or equilibrium of the helicopter requires that the mean values of the forces and moments acting at the center of the mass of the helicopter must be 0. Since there are six equations of equilibrium, which are three force and three moment equations, one can solve for six unknown quantities satisfying the equilibrium equations. For hover and level flight conditions, the six unknown quantities are the collective pitch (θ0) input of the main rotor, the cyclic pitch inputs (θ1c, θ1s) of the main rotor, the tail rotor collective pitch (θTR), the pitch attitude (α), and the roll attitude (Φ) of the helicopter. It may be recognized that the rotor loads are influenced by the blade response and the rotor inflow; hence, it becomes necessary to solve for the rotor inflow and the blade response equations. They form the intermediate stage in the solution procedure.
