An aerial vehicle is provided including rotor units connected to the aerial vehicle, and a control system configured to operate at least one of the rotor units. The rotor unit includes rotor blades, wherein each rotor blade includes a surface area, and wherein an asymmetric parameter is defined, at least in part, by the relationship between the surface areas of the rotor blades. The value of the asymmetric parameter is selected such that the operation of the rotor unit: (i) moves the rotor blades such that each rotor blade produces a respective vortex and (ii) the respective vortices cause the rotor unit to produce a sound output having an energy distribution defined, at least in part, by a set of frequencies, wherein the set of frequencies includes a fundamental frequency, one or more harmonic frequencies, and one or more non-harmonic frequencies having a respective strength greater than a threshold strength.

A rotor for a hover-capable aircraft includes a hub rotatable about a first axis and at least two blades hinged to the hub. Each blade has a main portion hinged to the hub and a tip portion, which is arranged radially outermost with respect to first axis with respect to the corresponding main portion. The tip portion of each blade is movable with respect to the corresponding main portion of that blade. The tip portion of each blade is selectively movable with respect to the corresponding main portion of that blade between a first position, in which it defines a dihedral or anhedral angle with respect to the corresponding main portion; and a second position, in which it defines a positive or negative sweep angle with respect to the corresponding main portion.

[Object] To provide a main rotor blade for a helicopter such as a main blade type helicopter, which may reduce a drag coefficient during high-velocity forward flight and which provides easy control. It is an object of the present invention to provide a helicopter including such a main rotor blade.

[Solving Means] A main rotor blade 1, which is the main rotor blade 1 for a high-velocity helicopter, includes: a blade root part 10 having a length of 30% or more of a rotor radius R; and a blade main body 20 continuous with the blade root part 10. Preferably, a cross-sectional shape of the blade root part 10 satisfies (x/a).sup.m+(y/b).sup.m=1 and a>b, where m: arbitrary number, x: chord length direction, and y: blade thickness direction.

A method of fabricating a filler body for a blade of a rotor. In addition, such a method comprises a succession of steps of adding material layer by layer, each step consisting in making a new layer of material on a preceding layer of material made in the preceding step, at least one of the steps consisting in making an openwork layer of material presenting a plurality of openings, the succession of steps of adding material layer by layer generating openwork layers of material, each having a closed outline, the respective closed outlines of the openwork layers of material touching mutually in pairs and forming a closed envelope of the filler body for the blade.

A duct for a ducted-rotor aircraft may include an internal structure and an aerodynamic exterior skin that is adhesively bonded to the internal structure. The skin may include a leading-edge portion disposed at an inlet of the duct and an inner portion disposed along an interior of the duct. The inner portion of the skin may be bonded to the internal structure with a first bondline of adhesive and the leading-edge portion of the skin may be bonded to the inner portion of the skin with a second bondline of adhesive. One or both of the first and second bondlines of adhesive may be of non-uniform thickness to take up tolerance stackups between the inner portion of the skin, the leading-edge portion of the skin, and the internal structure.

A tip structure may be arranged for example on a rotor blade (12) of a HAWT (10). The tip structure comprises a pressure side structure (50) arranged on a pressure side (43) of the blade, and a suction side structure (60) arranged on a suction side (44) of the blade (12). The pressure side and suction side structures (50, 60) have different pitch angles (P, S) so that the chord (CP2) of the pressure side structure (50) extends forwardly in the direction of motion (D) and relatively more radially outwardly away from the blade root, or less radially inwardly towards the blade root, than the chord (CS2) of the suction side structure (60), defining a relative twist angle (T) between the two structures (50, 60).

A propeller assembly includes a first and a second propellers. The first propeller includes a first propeller blade including a first propeller root, a first propeller tip opposite to the first propeller root, a first propeller pressure surface, and a first propeller suction surface opposite to the first propeller pressure surface. The second propeller includes a second propeller blade including a second propeller root, a second propeller tip opposite to the second propeller root, a second propeller pressure surface, and a second propeller suction surface opposite to the second propeller pressure surface. The first propeller tip is configured to extend obliquely along a span direction of the first propeller blade toward a side where the first propeller suction surface is located. The second propeller tip is configured to extend obliquely along a span direction of the second propeller blade toward a side where the second propeller pressure surface is located.

A sensor simultaneously determines a maximum rub depth and running clearance of a plurality of blade tips in a jet engine. The sensor includes an inductive component (e.g. inductor) and a resistive component comprising resistor portions each indicative of a depth into a layer of abradable material near the blade tips. When the blade tips move in proximity to the inductor, eddy currents in the blades generates a magnetic field that interact with the magnetic field generated by the inductor, which appears as an AC component in the current. When the blade tips abrade the abradable material, the resistor portions are severed and the DC current changes due to a change in resistance at the resistive component. An amplitude of the AC component indicates a running clearance as the blades move in proximity to the inductor. The frequency of the AC component indicates the rotational speed of the blades.

According to one embodiment, a noise reduction device includes speakers, microphones, and a processing circuit. The speakers are arranged around a rotor and emit control sound based on control signals. The microphones are arranged around the rotor and convert the control sound and noise emitted by the rotor into microphone signals. The processing circuit generates the control signals for reducing acoustic power in positions of the microphones, based on the microphone signals, rotation speed of the rotor, and a phase of noise that reaches the microphones from the rotor.

An aerial vehicle is provided including rotor units connected to the aerial vehicle, and a control system configured to operate at least one of the rotor units. The rotor unit includes rotor blades, wherein each rotor blade includes a surface area, and wherein an asymmetric parameter is defined, at least in part, by the relationship between the surface areas of the rotor blades. The value of the asymmetric parameter is selected such that the operation of the rotor unit: (i) moves the rotor blades such that each rotor blade produces a respective vortex and (ii) the respective vortices cause the rotor unit to produce a sound output having an energy distribution defined, at least in part, by a set of frequencies, wherein the set of frequencies includes a fundamental frequency, one or more harmonic frequencies, and one or more non-harmonic frequencies having a respective strength greater than a threshold strength.