A high stiffness hub assembly for a rotor system operable to rotate with a mast of a rotorcraft. The hub assembly includes a yoke and a constant velocity joint assembly. The yoke has a plurality of blade arms each configured to hold a rotor blade. The constant velocity joint assembly provides a torque path from the mast to the yoke that includes a trunnion assembly, a plurality of drive links and a plurality of pillow blocks. The trunnion assembly is coupled to the mast and has a plurality of outwardly extending trunnions. Each drive link has a leading bearing coupled to one of the trunnions and a trailing bearing coupled to one of the pillow blocks. Each pillow block is independently mounted between an upper surface of the yoke and a hub plate.

Aerial vehicles may be operated with discrete sets of propellers, which may be selected for a specific purpose or on a specific basis. The discrete sets of propellers may be operated separately or in tandem with one another, and at varying power levels. For example, a set of propellers may be selected to optimize the thrust, lift, maneuverability or efficiency of an aerial vehicle based on a position or other operational characteristic of the aerial vehicle, or an environmental condition encountered by the aerial vehicle. At least one of the propellers may be statically or dynamically imbalanced, such that the propeller emits a predetermined sound during operation. A balanced propeller may be specifically modified to cause the aerial vehicle to emit the predetermined sound by changing one or more parameters of the balanced propeller and causing the balanced propeller to be statically or dynamically imbalanced.

Toroidal propeller. The propeller includes a hub supporting a plurality of elongate propeller elements in which a tip of a leading propeller element curves into contact with a trailing propeller element to form a closed structure with increased stiffness and reduced acoustic signature.

A blade of a gas turbine engine may comprise a cavity defined, at least partially, by a first interior surface of the blade and by a second interior surface of the blade. A first rib and a second rib may extend from the first interior surface. A third rib may extend from the second interior surface and may be located between the first rib and the second rib. A bulkhead rib may traverse the cavity and may separate the cavity into a radially inward portion and a radially outward portion. A viscoelastic material may be disposed in the radially inward portion of the cavity.

Devices, systems, and related methods for balancing two or more pieces of independently rotating (e.g., not synchrophased) machinery are provided. In some aspects, the devices, systems, and methods can provide improved balancing techniques and can include providing a controller configured to simultaneously measure/receive vibration data and control balancers, one balancer at a time. In some aspects, the controller can calculate a beating cycle or a beating period using vibration data received from multiple rotating machines. In some aspects, a balance correction command can be derived in part from either one of: (a) an interpolation of an average vibration of the first rotating machine from a complex vibration of the multiple rotating machines or (b) an average vibration derived from one or more rules applied based upon the duration of the beating period or the beating cycle.

A high stiffness hub assembly for a proprotor system operable to rotate with a mast of a tiltrotor aircraft having helicopter and airplane flight modes. The hub assembly includes a yoke and a constant velocity joint assembly. The yoke has four blade arms each adapted to hold a proprotor blade. The constant velocity joint assembly provides a torque path from the mast to the yoke that includes a trunnion assembly, four drive links and four pillow blocks. The trunnion assembly is coupled to the mast and has four outwardly extending trunnions. Each drive link has a leading bearing coupled to one of the trunnions and a trailing bearing coupled to one of the pillow blocks. Each pillow block is independently mounted between an upper surface of the yoke and a hub plate with two connection members that extend through the yoke and the pillow block.

Aerial vehicles may be operated with discrete sets of propellers, which may be selected for a specific purpose or on a specific basis. The discrete sets of propellers may be operated separately or in tandem with one another, and at varying power levels. For example, a set of propellers may be selected to optimize the thrust, lift, maneuverability or efficiency of an aerial vehicle based on a position or other operational characteristic of the aerial vehicle, or an environmental condition encountered by the aerial vehicle. At least one of the propellers may be statically or dynamically imbalanced, such that the propeller emits a predetermined sound during operation. A balanced propeller may be specifically modified to cause the aerial vehicle to emit the predetermined sound by changing one or more parameters of the balanced propeller and causing the balanced propeller to be statically or dynamically imbalanced.

A rotating airfoil including a body and a vibration absorber located within the body. The body has a root end and a tip. The rotating airfoil has a natural frequency, and the vibration absorber has a natural frequency. The natural frequency of the vibration absorber is different than the natural frequency of the rotating airfoil.

An adjustable balance module for the balancing of rotatable blades. The adjustable blade balance module includes a frame that retains and covers an adjustment screw with a mass that translates along a threaded shaft of the adjustment screw. The adjustment screw is incrementally controlled by an adjustment dial that is accessible from an exterior surface of the blade.

The present invention includes a rotor-blade span-balancing system, including a span-balance pocket in a surface of a rotor blade; a cover operably configured to cover the span-balance pocket, wherein the cover is operably configured to be substantially flush with the surface of the rotor blade surface when covering the span-balance pocket, and wherein the cover includes a cover boss for reacting centrifugal force of the cover into the rotor blade; and one or more span-balance weights attached to the cover to span-balance the rotor blade.