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.

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.

A turbomachine includes a rotor and a stator, the stator having a plurality of profiled structures, each profiled structure being elongated in a direction of elongation in which the profiled structure has a length exposed to an airflow, and having a leading edge and/or a trailing edge, at least one of which is profiled and has, in said direction of elongation, serrations defined by a succession of peaks and troughs and having a geometric pattern transformed, over at least a part of said length exposed to the airflow, by successive scaling, via multiplicative factors, in the direction of elongation and/or transverse to the direction of elongation. The geometric pattern, as defined with reference to a radial distribution of the integral scale of the turbulence, evolves in a non-periodic manner.

A turbomachine includes a rotor and a stator, the stator having a plurality of profiled structures, each profiled structure being elongated in a direction of elongation in which the profiled structure has a length exposed to an airflow, and having a leading edge and/or a trailing edge, at least one of which is profiled and has, in said direction of elongation, serrations defined by a succession of peaks and troughs and having a geometric pattern transformed, over at least a part of said length exposed to the airflow, by successive scaling, via multiplicative factors, in the direction of elongation and/or transverse to the direction of elongation. The geometric pattern, as defined with reference to a radial distribution of the integral scale of the turbulence, evolves in a non-periodic manner.

A propeller includes a plurality of blades that extends outward in a radial direction of a rotation central axis relative to the rotation central axis, and includes an end that is located on an opposite side of the rotation central axis. Each of the plurality of blades has a maximum angle of elevation in a position ranging from 30% to 60% with the rotation central axis as a starting point of a radius of a circle that passes through the end of each of the plurality of blades with the rotation central axis as a center, the maximum angle of elevation being a maximum of an angle of elevation in each of the plurality of blades. A change in the angle of elevation in a longitudinal direction of each of the plurality of blades is within 10 degrees per 5% of the radius. A change in the longitudinal direction of a cross-sectional maximum blade thickness is within 20% of a maximum blade thickness of each of the plurality of blades per 5% of the radius, the cross-sectional maximum blade thickness being a maximum blade thickness in a cross section of each of the plurality of blades, the cross section being orthogonal to the longitudinal direction. A change in a chord length of each of the plurality of blades in the longitudinal direction is within 20% of a maximum of the chord length in each of the plurality of blades per 5% of the radius.

A propeller having a plurality of blades extending radially outward from a hub, the blades forming a loop. Each loop having an intake portion, an exhaust portion and a tip portion extending radially outward from the hub and a gap between the intake root and the exhaust root. The tip portion of each of the blades is 30%-75% of the blade, the tip portion beginning at a first deviation from zero of the roll value and extending to 90 degrees, wherein roll value is zero in a plane parallel to the hub axis, and wherein the blades have a vertical angle between −45 degrees and 45 degrees throughout.

A propeller having a plurality of blades extending radially outward from a hub, the blades forming a loop. Each loop having an intake portion, an exhaust portion and a tip portion extending radially outward from the hub and a gap between the intake root and the exhaust root. The tip portion of each of the blades is 30%-75% of the blade, the tip portion beginning at a first deviation from zero of the roll value and extending to 90 degrees, wherein roll value is zero in a plane parallel to the hub axis, and wherein the blades have a vertical angle between −45 degrees and 45 degrees throughout.

A propeller having a plurality of blades extending radially outward from a hub, the blades forming a loop. Each loop having an intake portion, an exhaust portion and a tip portion extending radially outward from the hub and a gap between the intake root and the exhaust root. The tip portion of each of the blades is 30%-75% of the blade, the tip portion beginning at a first deviation from zero of the roll value and extending to 90 degrees, wherein roll value is zero in a plane parallel to the hub axis, and wherein the blades have a vertical angle between −45 degrees and 45 degrees throughout.

A propeller having a plurality of blades extending radially outward from a hub, the blades forming a loop. Each loop having an intake portion, an exhaust portion and a tip portion extending radially outward from the hub and a gap between the intake root and the exhaust root. The tip portion of each of the blades is 30%-75% of the blade, the tip portion beginning at a first deviation from zero of the roll value and extending to 90 degrees, wherein roll value is zero in a plane parallel to the hub axis, and wherein the blades have a vertical angle between −45 degrees and 45 degrees throughout.

Embodiments are directed to systems and methods for deploying an outboard rotor blade of proprotor pylon to act as an extended lifting surface. Blade control actuators may provide primary rotor flight control as well as providing fold linkage actuation when fold locks are disengaged. During cruise flight, the blade control actuator may provide feathering inputs to the extended rotor blade, wherein the amplitude and frequency of feathering inputs are tuned to mitigate undesirable wing and fuselage dynamic modes thereby enhancing aircraft stability. The deployed rotor blades also improve the total lifting area of the aircraft, which may increase aircraft range and efficiency.