Abstract: Structure for minimizing gap changes in a circulation control pneumatic ve. A flat, flexible ring is located below and adjacent to the plane of the nozzle of blade ducts. The flat, flexible ring is supported from beneath by an array of actuators. In one embodiment, the nozzles are immobilized relative to hub-induced displacements and thus eliminate any feedback due to hub flexing. In another embodiment, the nozzle is pivotally attached to a rotating carrier and feedback is reversed so that feedback becomes negative.

Abstract: A rotor hub for a helicopter having a hum member rotatably mounted to a rr mast stationarily attached to the fuselage of a helicopter and forming an air plenum for circulation control. A shaft, which is driven from a transmission, drives a torque plate which is attached to the top of the hub member. A flexible hub plate is attached to a flange on the hub member and has a plurality of axles to which the rotor blades are individually attached. Air from inside the plenum is piped to the rotor blades through flexible ducts. The flexible hub plate is designed to provide a high degree of stiffness in the plane of rotation and a lesser degree of stiffness in a plane normal to the plane of rotation.

Abstract: A circulation control airfoil having an edge slot formed by upper and lower uct panels. A plurality of struts are spaced along the length of the edge slot and are adjustably attached to the upper and lower duct to maintain the edge slot height. A reinforcing saddle is provided at each attachment position on the panels for distributing load applied to the struts over a large area of the duct panels. Each strut is provided with a differential lead thread system which provides high resolution adjustment capability for the edge slot.