U.S. Patent Specifications

In an aircraft, a revoluble thrust‐producing system including a hub, a generally radially disposed airfoil blade pivotally secured to and carried by said hub by a corresponding single pitch‐varying blade‐root pivot whose axial line of pivotation is fixed in relation to the longitudinal axis of the blade‐root and passes outwardly from said hub on the back or pressure side of the airfoil blade in a generally radial direction and diverges from the airfoil blade as it goes outwardly from said hub, and passes through the stable region of the resultant air‐load vectors of the airfoil.