The present invention includes a balancing system that includes a weight box, mounted substantially within the rotor-blade spar, flush with a rotor-blade spar outer surface, operably accessible from a rotor-blade tip, and retained within the rotor-blade spar by a weight-box retention pin, one or more weight-box contact surfaces bonded to a rotor-blade-spar inner surface, or a weight-box lip providing a bearing contact with an edge of a spar rotor-blade spar cutout; and a weight package attached to the weight box, the weight package including a weight-box cover, two or more weight guide-rods attached to the weight-box cover, wherein one of the two or more weight guide-rods is positioned forward of a pitch change axis or center of twist and wherein one of the two weight guide-rods is positioned aft of the pitch change axis or center of twist, and one or more balance weights mounted on the weight guide-rods.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Disclosed are systems, methods, and apparatus for actively adjusting the position of one or more propeller blade treatments of a propeller blade of an aerial vehicle during operation of the aerial vehicle. For example, the propeller blade may have one or more propeller blade treatments that may be adjusted between two or more positions. Based on the position of the propeller blade treatments, the airflow over the propeller is altered, thereby altering the sound generated by the propeller when rotating. By altering the propeller blade treatments on multiple propeller blades of the aerial vehicle, the different sounds generated by the different propeller blades may effectively cancel, reduce, and/or otherwise alter the total sound generated by the aerial vehicle.

An unmanned aerial vehicle (UAV) may emit masking sounds during operation of the UAV to mask other sounds generated by the UAV during operation. The UAV may be used to deliver items to a residence or other location associated with a customer. The UAV may emit sounds that mask the conventional sounds generated by the propellers and/or motors to cause the UAV to emit sounds that are pleasing to bystanders or do not annoy the bystanders. The UAV may emit sounds using speakers or other sound generating devices, such as fins, reeds, whistles, or other devices which may cause sound to be emitted from the UAV. Noise canceling algorithms may be used to cancel at least some of the conventional noise generated by operation of the UAV using inverted sounds, while additional sound may be emitted by the UAV, which may not be subject to noise cancellation.

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.

An acoustic abatement apparatus for an aircraft includes a layer of material disposed exterior to a fuselage of the aircraft, where the layer of material connects to the fuselage to establish a gap between the layer of material and the fuselage, a flexible container disposed in the gap, and at least one acoustic resonator connected to the flexible container. The at least one acoustic resonator is tuned to a predetermined resonator frequency.

A weight system for a rotor blade includes a weight box open in an outboard direction, a weight guide rod connected to the weight box, the weight guide rod extending in a spanwise direction through an interior of the weight box, and a span balance weight disposed within the weight box, the span balance weight being captured between the weight guide rod and the weight box.

A lift fan for use in short takeoff and vertical landing (STOVL) aircraft is disclosed and claimed. The lift fan is driven by bleed air from a main engine of the aircraft and may be controlled by an electromagnet. This eliminates the drag and torque on the main engine and reduces fuel cost and engine wear.

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.

The invention relates to an assembly for a turbine engine blade, the assembly comprising a fastener defining a well for receiving a blade root, and a clamping device for clamping the blade root against the fastener when the blade root is received in the well, wherein the clamping device comprises: at least one clamping member suitable for bearing simultaneously on the blade root and on the fastener in the well so as to exert a clamping force on the blade root, the clamping member defining a threaded hole, and a resilient layer arranged to bear in the well on the blade root, a rod comprising a thread engaging with the threaded hole so that a rotation of the rod with respect to the clamping member causes a variation in the clamping force exerted by the clamping member on the root.

Apparatus for controlling multi-rotor vehicle vibrations and related methods are disclosed herein. An example apparatus includes a vibration level detector to determine a vibration level of a frame of a vehicle based on data received from a sensor of the vehicle, the vehicle including a rotor. The apparatus includes a rotor operation analyzer to determine an operational parameter of the rotor based on the vibration level. The apparatus includes a communicator to transmit an instruction including the operational parameter to a controller of the rotor.