Abstract: This invention relates to a rotorcraft rotor head which includes an even number of blades arranged in groups of two blades (2) which are diametrically opposed to each other, and linked to each other by a connection system without any link with the rotor hub. Each blade (2) is articulated in flapping and in pitch on the hub body (1) by a sleeve (3) which is arranged between the root of the blade (2) and the hub body (1). The sleeve (3) bears against the periphery of the hub body (1) by a laminated spherical stop (5) and includes an introduction member for controlling the pitch of the blade (2). Each system for connecting two diametrically opposed blades (2) is comprised of two tie rods (4) which link the two diametrically opposed sleeves (3) of the blades (2). The two tie rods (4) are arranged parallel to the plane of the rotor on either side of the longitudinal axis which is common to the two diametrically opposed blades ( 2).

Abstract: The invention relates to a drag elastic-return and damping device (28) for a blade, and a rotor head including it.The device (28) comprises a connecting rod (30) connected to the blade and transmitting its drag movements to a rotary member (29) for elastic return with incorporated damping whose outer armature (32) it causes to rotate about a coaxial inner armature (31) in order to shear at least one thin collar (33) of a viscoelastic elastomer about its axis (B). The connecting rod (30) is coupled by way of rotational joints (43, 44) to a sleeve (15) for attaching the blade to the hub (1), and to a lever (34) of the outer armature (32). The member (29) is supported at the periphery of the hub (1), between two adjacent blades, or in the sleeve for attaching an adjacent blade such that the corresponding connecting rod is mounted as an inter-blade tie. On the rotor head, each blade is articulated with the hub (1) by a spherical laminated thrust block (5).

Abstract: The invention relates to a flapping restrainer device for the blades of a rotorcraft main rotor, and a rotor head comprising the same. The lower restrainers comprise a reciprocal star-shaped plate (32), having as many radial branches (33) as blades, and each one of the branches being engaged into a radial opening (6) of the hub (3). Outside the latter, the star-shaped plate (32) cooperates with supporting runners (47) integral with the blades. The upper restrainers comprise, for each blade, a stop which is retractable by the effect of the centrifugal force and which is composed of a lever (52), pivoting on a pivot (53) carried by the hub (3), and a first arm (55) of which constitutes a stop finger directed towards an upper supporting component (60) integral with the blade, while a second arm (56) carries a governor weight (57) and a nose (58) for support against a shoulder (59) integral with the hub (3).

Abstract: The invention relates to a device incorporating retractable stops for limiting the flappings of the blades of the main rotor of a rotorcraft. Each lower stop comprises a convex roller presenting a convex stop surface and bearing a weight at the end of an arm. By its convex roller, the lower stop is mounted to pivot about the pin for retaining the blade on the hub. On the ground, the bearing member is in contact with a lower bearing surface fast with the blade at the level of the pitch control lever, in order to limit the downward flappings of the blade. The lower stop pivots about the pin above the lower plate. The upward flappings of the blade may be limited by upper stops disposed substantially symmetrically below the upper plate. A second lower weight, returned by a spring, and engaging by a nose-shaped element in a notch in the rear of the bearing surface, acts as upper stop. The invention is more particularly applicable to equipping helicopters.

Abstract: Apparatus for controlling both collective and cyclic pitch of blades of a helicopter rotor comprises a non-rotating plate which is connected via a fixed caliper and servo controls to a fixed housing and to which is attached the internal ring of a ball race bearing. The external ring of the bearing carries a rotating plate, which is connected by means of rotating caliper or links to each of the rotors and by means of pitch rods to control levers for adjusting the pitch of the blades. The non-rotating plate is fixed to external armatures of laminated joint pieces which are mounted slidingly up and down a guide base. The collective pitch is controlled by sliding the assembly of non-rotating plate and joint pieces up or down the guide base while the cyclic pitch is controlled by inclining the assembly relative to the main rotor shaft. This inclination involves deformations in the laminated joints.

Abstract: The invention relates to a device for damping the vibrations of a rotary-wing aircraft rotor. An annular weight is disposed concentrically of the rotor axis. This weight is supported by at least three resiliently deformable elements such as helical springs, radially biased in directions distributed regularly around the rotor axis. The inner ends of the springs directly bear on a part extending the rotor shaft axially. Their outer ends directly bear on the annular weight so that the spring apply statically balanced centrifugal thrusts to the annular weight. The springs are so still that they support the annular weight without substantially bending.

Abstract: The invention relates to a device for damping the vibrations of the rotor of a rotary-wing aircraft. This device comprises a flapping weight concentrated near the rotor axis and at least three resiliently deformable elements, such as helical springs. The deformable elements are radially biassed in directions regularly distributed around the rotor axis. The inner ends of the deformable elements directly bear on the flapping weight. Their outer ends directly bear on rigid structure elements, rigidly secured to the rotor hub, so that the biassed deformable elements apply statically balanced centripetal thrusts to the flapping weight.