The Development and Application of an Analysis for the Determination of Coupled Tail Rotor/Helicopter Air Resonance Behavior.

摘要

An analysis and associated computer program have been developed to provide a highly sophisticated mathematical representation of coupled tail rotor/support structure systems. The coded analysis allows the consideration of an anisotropically supported flexible swashplate control system, rotor drive shaft torsional flexibility, anisotropic mounting of the gearbox about two mutually orthogonal axes, and an elastic support structure such as a fuselage-tailboom-fin structure in addition to the rotor system. As such, the analysis can also be applied to main rotor systems. The resulting analysis has the capability of predicting the air resonance (frequency, stability, and mode shape) behavior of a coupled tail rotor/support structure system in hover and forward flight where the rotor may be of a rigid, teetering, gimballed, flexstrap, or partial to fully articulated type. The blade aerodynamics representation including both quasi-steady and unsteady (Theodorsen's) terms can utilize either a uniform or a variably defined induced velocity field and up to five types of airfoil sections. All blade and fuselage-tailboom-fin structure characteristics required to adequately represent these structures in a lumped parameter form are considered, including inertia and gyroscopic damping effects. The analysis includes aerodynamic interharmonic blade coupling and interharmonic coupling due to support structure behavior.