Abstract: A blade pitch control system for a rotary wing aircraft which incorporates a mast and rotor which is pivotally adapted for movement of the mast between a generally horizontal stored position and a vertical position for operation in a helicopter mode. The pitch control system incorporates a motion amplification mechanism such as a star gear arrangement connected to the pitch horn to amplify control motions which are transmitted to the pitch horns through a push-pull control tube generally parallel to the folding axis of the rotor blade. In another embodiment, the push-pull tube inputs parallel to the mast axis. A locking mechanism retains the blades so pitch changes cannot be made during a predetermined portion of the blade coning cycle.

Abstract: Hub flexures affording beamwise flapping (i.e. flapping perpendicular to the original tip-path plane), mount aircraft propellers through a hub assembly to a drive shaft of a fixed wing aircraft for increasing propulsive efficiency. The hub flexures permit the propeller blades of the fixed wing aircraft to exhibit advantageous beamwise flapping and reach equilibrium positions in response to loading conditions which would otherwise result in efficiency loss. The flexures permit only flapping perpendicular to the original tip-path plane and provide blade rigidity in radial, in-plane and torsional loading. The propeller blades may also be of the variable pitch variety wherein the flexures are advantageously inboard of the blade pitch change bearings. The flexures further facilitate both passive, or responsive flapping in response to actively induced cylic pitch to achieve maximum propulsive efficiency under any given loading conditions.