[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.

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.

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.

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 bond fixture includes a support structure and a first assembly coupled to the support structure. The first assembly includes a frame defining a chamber and a first pressure pad and second pressure pad coupled to the frame opposite one another and positioned within the chamber. The second pressure pad is movable to control a pressure applied by the first pressure pad and the second pressure pad.

A bond fixture includes a support structure and a first assembly coupled to the support structure. The first assembly includes a frame defining a chamber and a first pressure pad and second pressure pad coupled to the frame opposite one another and positioned within the chamber. The second pressure pad is movable to control a pressure applied by the first pressure pad and the second pressure pad.

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 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.