A general mounting method for ducted fan propulsors is disclosed. This mounting method uses extremely slender stators that connect the duct ring to the propulsor which is mounted in the middle and drives the rotor, fan or propeller. The slender stators take the form of spokes and as such are so slender that the midspan stresses within the spokes are dominated by axial tension loads rather than the shear loads experienced by conventional stators. The spokes may have an aerodynamic shape and damping methods may be used to retard spoke vibrations and transmission of engine vibrations to the duct and force. The duct itself is also stiffened by the spoke arrangement, thereby reducing low frequency vibration modes.

A propeller system combines innovative strategies to create a new methodology to reduce propeller or rotor noise. The propeller is specifically aimed for ultra-quiet electrically powered aircraft for use in high proximity aviation, but its low-noise advantages will extend to other purposes. The propeller blade includes geometries, along with size and operational limitations that minimize rotational and vortex noise, vibration and span-wise air flow on the blade. To further reduce noise, the propeller provides greater relative thrust on the inboard portions of the blade than do conventional propellers and provides less than conventional relative thrust including negative thrust at the outermost portions of the blade. The propeller blade includes stepped changes in local blade stiffness at calculated intervals that can reduce resonant blade vibrations and their resultant noise. This ultra-quiet propeller design can also be used for quieting hovercraft, drones, surveillance aircraft, indoor fans, wind tunnels and other applications.

The present disclosure provides methods and systems for propeller balancing of an aircraft comprising a propeller. Acceleration data is obtained from an acceleration sensor coupled to the aircraft. The acceleration data is filtered using a filter to obtain propeller-specific vibration data, the filter defining a range of acceptable frequencies associated with a frequency of rotation of the propeller. The propeller-specific vibration data is compared to trend data associated with the propeller. When the propeller-specific vibration data differs from the trend data beyond a predetermined threshold, an alert indicative of a balancing need for the propeller is issued.

A general mounting method for ducted fan propulsors is disclosed. This mounting method uses extremely slender stators that connect the duct ring to the propulsor which is mounted in the middle and drives the rotor, fan or propeller. The slender stators take the form of spokes and as such are so slender that the midspan stresses within the spokes are dominated by axial tension loads rather than the shear loads experienced by conventional stators. The spokes may have an aerodynamic shape and damping methods may be used to retard spoke vibrations and transmission of engine vibrations to the duct and force. The duct itself is also stiffened by the spoke arrangement, thereby reducing low frequency vibration modes.

A method of increasing a stability speed of a tiltrotor aircraft includes pivoting a rotor assembly having at least three rotor blades from a first position for operating the tiltrotor aircraft in a helicopter mode to a second position for operating the tiltrotor aircraft in an airplane mode, and increasing a stiffness of the rotor assembly when the rotor assembly is in the second position.

Systems and methods for protecting an aerodynamic structure, e.g., a wind turbine blade, rotor blade, aerodynamic aerostructure, etc., are provided. Long fiber reinforced composites having a helicoidal architecture with material aligned with a graded hardness and stiffness are used to develop an efficient and highly tailorable leading edge protection (LEP) solution with longer durability than conventional solutions while yielding lighter, and optionally, more environmentally sustainable solutions. At least a portion of the plurality of plies are helicoidally arranged relative to one another to tailor stress wave propagation speed of the aerodynamic blade and to provide load carrying strength for the aerodynamic blade.

A propeller provided with interchangeable blades, and to a method of mounting such interchangeable blades on the propeller. The propeller comprises a hub, fastening fittings, rotation guide devices for guiding the fastening fittings in rotation relative to the hub, locking parts, and blades. The fastening fittings are configured to be assembled into the hub from the inside of the hub, and the locking parts lock respective ones of the fastening fittings onto the hub. The blades are fastened to respective ones of the fastening fittings outside the hub and can thus easily be replaced with other blades without removing the 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.

In some examples, an aircraft comprises an airframe, a rotor system coupled to the airframe, and a vibration attenuation system. The rotor system is operable to exert a vibratory force on the airframe. The vibration attenuation system comprises two or more batteries and elastic devices. The two or more batteries are operable to supply power to the rotor system. The elastic devices coupled to the two or more batteries and the airframe. The elastic devices are configured to attenuate the vibratory force based on facilitating oscillation of the two or more batteries. In other examples, a method comprises coupling elastic devices to two or more batteries and an airframe of an aircraft. The elastic devices receiving a vibratory force via the airframe and attenuate the vibratory force based on facilitating oscillation of the two or more batteries.

A device for self-balancing a rotating part, such as a propeller, along a given axis is disclosed. The propeller 102 coupled to, a drive shaft with freedom for linear movement along longitudinal axis L-L; at least one pair of levers 614/616, comprising a first lever 614-1/616-1 and a second lever 614-2/616-2, that are pivotally mounted on mounting plate 606 at two diametrically opposite points 618; and at least one pair of weights 622 fixed at external ends of the levers 614/616. inner ends of levers 614/616 are operatively coupled to the propeller 102 such that when propeller 102 undergoes a linear movement in any direction along the longitudinal, axis L-L due to unbalance, inner ends of levers are, moved to cause the weights 622 to move to provide a balancing force to neutralize the unbalance in the propeller. An embodiment with only one pair of levers is also disclosed.