Abstract: A tilting rotor of a convertible aircraft comprises, between the mast and the hub, a constant velocity drive mechanism and pivoting arrangement comprising two gimbals, each of which is driven by the mast and pivots about one respectively of two diametral axes by two diametrically opposite bearings. Each gimbal is also hinged to the hub by ball joint connections diametrically opposite and centred respectively in a radial plane passing through the axis of the mast and through the diametral axis about which the other gimbal pivots. The two resulting trains transmitting torque between the mast and the hub have substantially the same torsional rigidity, and one at least of the components of each torque transmission train exhibits a flexibility in deformation about the axis of rotation of the hub.

Abstract: A drag damper for use on a rotary wing aircraft rotor comprises a body defining two variable volume chambers linked by a piston. The chambers are filled with fluid and are connected by a restriction port (35) and by a channel (32) of larger cross-section than the restriction port. A secondary piston slidable and pressure-tight piston is fitted in the channel and loaded by an elastic bias (34). The equivalent mass of this secondary piston (33) and of the fluid which it displaces, and the stiffness of the elastic bias (34) are such that the secondary piston is resonant in the channel (32) at the rotation frequency of the rotor, to filter the dynamic component at this frequency of stresses applied to the damper (20).

Abstract: An active mount is provided for use in a rotary wing aircraft between each of the gearbox and airframe mounting locations for mechanically suspending the airframe from the gearbox. The active mount comprises first and second linear hydraulic actuators each having a principal axis. The length of the actuators is variable along the principal axis for providing relative movement between the airframe and the gearbox. The principal axes of the actuators are adapted to lie in the directional planes of the primary forces necessary for supporting the airframe and acting on the transmission gearbox mounting locations for providing movement of the gearbox relative to the airframe in the planes at a frequency for reducing the transfer of vibration through the active mount to the airframe. A system for reducing vibration in the rotary wing aircraft further comprises a hydraulic system for supplying a controlled flow of pressurized hydraulic fluid to the actuators.

Abstract: A telescopic vertical take-off aircraft is disclosed. The aircraft comprises a main rotor assembly 2 at the top of the aircraft which consists of an assembly of blades 3a, 3b and a rotor 4. Rotation of the main rotor assembly 2 is achieved by means of a main engine assembly 5. The main engine assembly 5 is connected to the main body 6 of the aircraft by a tilt enabling joint 7. The tilt enabling joint 7 enables tilting of the main engine assembly 5 relative to the main body 6 of the aircraft to occur in a controlled manner during flight. A universal joint 8 is used to allow tilting to occur. The tilt enabling joint 7 is fitted with hydraulic actuators 9, 10 and 11, that allow the tilting of the tilt enabling joint 7 to be controlled. When the main engine assembly 5 is tilted, the main rotor assembly 2 is tilted with it. Tilting of the main engine assembly 5 thus initiates changes in the direction of travel of the aircraft without the need to change the pitch angles of the rotor blades 3a and 3b.

Abstract: Determining adjustments for rotating blades includes measuring a plurality of vibration values corresponding to vibrations caused by the blades, providing coefficient of vibration data that corresponds to effects on vibration caused by adjustments to the blades, applying the coefficient of vibration data to the vibration values, and solving for possible values for the adjustments that may be applied to the blades, wherein the possible values for the adjustments are constrained to be greater than a first predetermined value or zero. The adjustments may include at least one of hub weights, blade tabs, PCR adjustments, and blade tip weight adjustments. Measuring vibrations may include obtaining signals from a plurality of accelerometers. Determining adjustments may also include performing an FFT on the vibration data, where the data indicating effects on vibration is provided in the frequency domain. Applying the data to the vibration values may be performed in the frequency domain.

Abstract: A composition for reducing vibrations, including both damping structure borne vibrations and reducing radiated airborne noise. The composition is either a mixture of at least two different granular materials, or is a granular material having a bulk sound speed of less than 90 m/s. The damping properties of a mixture can be calculated from the bulk densities and stiffnesses of its individual components.

Abstract: An energy-absorbing connecting strut comprises a substantially straight rigid body with means of connection to two components which it links, and undergoing tensile/compressive stresses. The body comprising a buckling portion with a calibrated buckling load corresponding to a compressive load threshold, a hollowed portion housing a component absorbing energy by plastic deformation in compression, and a piston moving integrally with a rigid axial end part of the body. The body is configured so that under a compressive load greater than the compressive load threshold, the buckling portion deforms causing axial shortening of the connecting strut and movement of the piston with the rigid part, so that the piston crushes and plastically deforms the energy-absorbing component, limiting the load amplitude. The energy-absorbing strut may be used as a suspension strut of a main gearbox on the structure of a rotary wing aircraft.

Abstract: A main rotor support structure assembly includes a support housing which transmits loads developed by the main rotor assembly into the airframe. Integral main rotor servo attachment lugs extend from the cylindrical body member to provide lower attachment points for the rotor servo actuators which are operable to articulate a rotor swash plate or the like. The servo attachment lugs are integrally formed as part of the cylindrical body member and spaced thereabout. A substantially L-shaped metallic insert is sandwiched and bonded within each servo attachment lug to resist axial and transverse tension of the rather high forces exerted by the rotor servo actuators.

Abstract: An adaptive controller is used to adaptively generate vibration cancellation signals driving a controlled device which effects an associated vibration and noise-producing plant. The adaptive controller has multiple control paths to generate the control signal. In a vibration attenuation control path(s), an adaptive control signal is generated by plant compensation and adaptive filtering techniques to cancel vibrations. In a position control, saturation prevention path, the available operational extents of the controlled device are monitored and compensation signals are generated which direct the movement of the controlled device in such a manner as to prevent the controlled device from reaching the extents of control. The control signals from the multiple paths are then combined and transmitted to the controlled device which alters in some fashion the noise and vibration being generated or transmitted by the associated vibrating plant.

Abstract: An aircraft has a fuselage that defines an interior cabin and an exterior; a first housing located along one side of the fuselage exterior; a second housing located along the second side of the fuselage exterior; and an active vibration control system for limiting fuselage vibration, the vibration control system comprising a plurality of sensors located in the cabin; a controller in signal receiving relation with the sensor means; first actuator means located in the first housing and second actuator means located in the second housing and wherein the actuator means are in signal receiving relation with the controller.

Abstract: A damping apparatus for damping vibrations in a vibrating system including a piston which is reciprocally movable in a fluid filled chamber, piston movement in either direction of movement being resisted by fluid pressure in the chamber behind the piston, which resistance provides damping forces which act to oppose piston movement, the piston being connected to one component of the vibrating system and the chamber being connected to a second component of the vibrating system, characterised in that structure is provided to relieve the fluid pressure behind the piston to allow substantially unopposed piston movement in the chamber without damping forces being provided, during piston movements which occur in response to vibrations in the vibrating system at frequencies other than a fundamental frequency which the damping apparatus primarily is intended to damp.

Abstract: The present invention relates to an improved vibration cancellation device designed to overcome many of the shortcomings inherent in prior devices. In many embodiments, the vibration cancellation device is smaller in scale than prior designs, facilitating more versatility with respect to design options. The device of the present invention achieves a smaller size partly due to the use of suspension springs having an offset, rather than a parallel arrangement.

Abstract: An actuator is disclosed for an active vibration and noise control system in an aircraft. The actuator is configured to attach a vibrating component, such as a gearbox mounting foot, to an aircraft support structure. The actuator is actuated by the control system to control the transmission of vibratory loads from the gearbox foot. The actuator includes a housing and a mounting member. The housing mounts to the aircraft. The mounting member attaches to the vibrating component within the aircraft. A piston arrangement is attached to the housing and includes a sleeve located within the housing, and a piston slidably disposed within the sleeve. A bearing assembly engages the mounting member with the piston. The bearing assembly includes a first bearing located between the mounting member and an inner bearing member. The first bearing is adapted to transmit axial motions between the mounting member and the piston.

Abstract: A method for determining a minimal set of adjustments for the blades of a rotor supported by a supporting structure for reducing rotation-induced vibration in the supporting structure at at least one harmonic rotation order and/or for reducing track deviation while maintaining structure vibration over at least one harmonic order within an acceptable limit. In one embodiment, a relationship is established by which vibration of the supporting structure may be calculated at harmonic orders of rotor rotation from Fourier coefficients of adjustment, Fourier coefficients of unit vibration influence and Fourier coefficients of vibration measurements. Thereafter, a value is determined for each selected Fourier coefficient of adjustment that provides a desired virtual reduction of vibration of the supporting structure at the harmonic order of the selected Fourier coefficient of adjustment using the vibration relationship.

Abstract: An adaptive controller is used to adaptively generate vibration cancellation signals driving a controlled device which effects an associated vibration and noise-producing plant. The adaptive controller has multiple control paths to generate the control signal. In a vibration attenuation control path(s), an adaptive control signal is generated by plant compensation and adaptive filtering techniques to cancel vibrations. In a position control, saturation prevention path, the available operational extents of the controlled device are monitored and compensation signals are generated which direct the movement of the controlled device in such a manner as to prevent the controlled device from reaching the extents of control. The control signals from the multiple paths are then combined and transmitted to the controlled device which alters in some fashion the noise and vibration being generated or transmitted by the associated vibrating plant.

Abstract: An actuator is disclosed for an active vibration and noise control system in an aircraft. The actuator is configured to attach a vibrating component, such as a gearbox mounting foot, to an aircraft support structure. The actuator is actuated by the control system to control the transmission of vibratory loads from the gearbox foot. The actuator includes a housing and a mounting member. The housing mounts to the aircraft. The mounting member attaches to the vibrating component within the aircraft. A piston arrangement is attached to the housing and includes a sleeve located within the housing, and a piston slidably disposed within the sleeve. A bearing assembly engages the mounting member with the piston. The bearing assembly includes a first bearing located between the mounting member and an inner bearing member. The first bearing is adapted to transmit axial motions between the mounting member and the piston.

Abstract: A rotor shaft support and drive arrangement comprises a bearing damper including a number of interconnected oil cylinders circumferentially distributed about a rotor to dampen the vibration thereof. A flexible diaphragm coupling is provided for transmitting a driving torque. The flexible diaphragm coupling provides improved misalignment capability.

Abstract: A safety system is provided on a helicopter by mounting a parachute within a cylinder located in a hollow drive shaft of the propeller or in an external container. Four auxiliary parachutes are located in front and behind, and to the left and right of the propeller. The propeller may be locked in a predetermined angular position by a braking system of the drive shaft when the helicopter is disabled in an air accident such that the auxiliary parachutes are located in the spaces between the propeller blades for their safe deployment for suspending the helicopter in air. Speed reducing jets are provided for reducing the falling speed of the helicopter and for landing it safely on the ground. Inflatable bags are provided for maintaining the helicopter afloat when it falls on to a body of water or to cushion its landing impact on the ground.

Abstract: A power plant and transmission arrangement for a helicopter wherein the helicopter engine is integrated to the helicopter transmission to form therewith a single unit rigidly mounted to the helicopter frame. By so integrating the engine to the helicopter transmission the center of gravity of the engine can be placed closer to the rotor mast of the helicopter, thereby enhancing the stability and the handling characteristics of the helicopter.

Abstract: The anti-vibration suspension device comprises at least three oblique bars pivotably mounted each on the gearbox and on the structure, by means of a rigid lever supporting a vibrating weight and in turn pivotably mounted on this structure, and each lever is also linked to the structure by at least one torsion spring biased about a torsion axis substantially perpendicular to the radial plane defined by the axes of the rotor and the corresponding oblique bar.

Abstract: Apparatus for damping vibrations of a structure such as the air frame of a helicopter wherein a spring system (1), which has an elastic wall structure forming a tube-shaped hollow body supports a weighted vibrating object (23). At least one region of the wall structure is constructed to be elastically deformable in its plane, with a spring stiffness, tuned to the frequency of the vibration to be damped. The wall structure is formed by several planar spring elements (11a, 11b, 11c, 11d), each of which can be elastically deformed in its plane by an arrangement of longitudinal strips (110a, 110b, 111a, 111b) and connecting cross pieces (120a, 120b, 121a, 121b). A battery of the helicopter can be used as the vibrating weight (23). The vibration damper containing the battery is installed at a location on the helicopter where clear structural vibrations occur in two directions perpendicular to each other and wherein the vibration damper is tuned to the vibrations frequencies in both directions.

Abstract: The anti-vibration suspension device comprises at least three oblique bars, each articulated on the gearbox and on the structure by means of a rigid lever supporting an oscillating weight and in turn pivotally mounted by means of at least one pivot on this structure, and each lever is also joined to the gearbox by means of at least one torsion spring biassed about a torsion axis substantially perpendicular to the radial plane defined by the axes of the rotor and the corresponding oblique bar.

Abstract: A damping apparatus for damping vibrations in a vibrating system including a piston which is reciprocally movable in a fluid filled chamber, piston movement in either direction of movement being resisted by fluid pressure in the chamber behind the piston, which resistance provides damping forces which act to oppose piston movement, the piston being connected to one component of the vibrating system and the chamber being connected to a second component of the vibrating system, characterized in that means are provided to relieve the fluid pressure behind the piston to allow substantially unopposed piston movement in the chamber without damping forces being provided, during piston movements which occur in response to vibrations in the vibrating system at frequencies other than a fundamental frequency which the damping apparatus primarily is intended to damp.

Abstract: The present invention relates to an antivibration device intended to reduce the transmission of vibration between two bodies (2, 3). According to the invention, the antivibration device comprises an elastic annular element (4) which is connected to two bodies (2, 3) so as to serve as a connection between them and which is capable of being deformed under the action of vibration generated in at least one of the bodies, and a resonator (5) connected, via at least two leaves (6, 7) which are flexible in terms of bending and rigid in terms of tension and in terms of compression, to the internal face (8) of the annular element (4) so as to be set in oscillating rotation when the annular element (4) is deformed, by the action of vibration so that, by this oscillating rotation, the resonator (5) generates an antivibration inertia force which opposes the vibration and thus reduces its transmission from one body to the other.

Abstract: The device for the individual control of the blades includes at least two sets of rotating swashplates centered on the rotor axis and non-rotating swashplates at least inclinable in all directions under the action of at least two actuators inserted between the first set and a non-rotating structure, and under the action of at least one other actuator inserted between this structure and the second set. Each non-rotating plate is held by a connecting piece to the non-rotating structure, and each rotating plate is rotated with the rotor and connected to at least one blade respectively of the rotor via a respective pitch rod. The device also includes at least as many actuators as the rotor has blades, and all the actuators are non-rotating.