Abstract: A friction damper (50) provides friction damping for gas turbine engine airfoils to reduce vibrations thereto. The friction damper (50) includes a plate (52) underlying radially outer shrouds (30) of two adjacent airfoils (20). Friction generated between an outer surface (53) of the plate (52) and undersides (42) of the adjacent shrouds (30) reduces undesirable vibrations in the airfoils (20).

Abstract: A seal for sealing the gaps between adjacent turbine blade structures is disclosed in which the seal is disposed in a compartment formed between adjacent turbine blade structures having first and second sealing surfaces adjacent to a generally axially extending gap and a generally radially extending gap, respectively. The seal also has a thrust surface extending obliquely to a radius from the axis of rotation of the rotor disk to which the turbine blade structures are attached which is engaged with a reaction surface formed on a reaction member located in the compartment. During rotation of the rotor disk, centrifugal force acting in a radially outward direction is transmitted both radially and axially to a seal by contact between the reaction surface and the oblique thrust surface to cause the first sealing surface to seal the generally axially extending gap and the second sealing surface to seal the generally radially extending gap.

Abstract: A ram air turbine power system is provided with a deployable ram air turbine mounted in-line with a power supply unit such as an electrical generator and/or an hydraulic pump. The ram air turbine includes a turbine shaft supported for rotation by bearings within a generator housing, wherein a rear end of the turbine shaft and a generator shaft are supported by a common bearing, and further wherein the forwards ends of the turbine and generator shafts are supported by a pair of bearings separated by a resilient bearing mount. In addition, the in-line ram air turbine and related power supply unit are supported from a hollow strut with hydraulic and electrical lines and related mechanical linkages extending therethrough.

Abstract: A rotor blade for a rotor assembly is provided comprising a root, an airfoil, and a damper. The airfoil includes a base, a tip, a first cavity, a second cavity, and a passage. The passage includes a pair of walls converging from the first cavity to the second cavity, thereby connecting the first and second cavities. The damper is received within the passage. According to one aspect of the present invention, a difference in gas pressure across the damper biases the damper against the converging walls of the passage. According to another aspect of the present invention, centrifugal force biases the damper against the converging walls of the passage.

Abstract: A friction damper (50) provides friction damping for gas turbine engine airfoils to reduce vibrations therein. The friction damper (50) includes a plate (52) underlying radially outer shrouds (30) of two adjacent airfoils (20). Friction generated between an outer surface (53) of the plate (52) and undersides (42) of the adjacent shrouds (30) reduces undesirable vibrations in the airfoils (20).

Abstract: A rotor blade for a turbine engine rotor assembly is provided comprising a root, an airfoil, a platform, and apparatus for damping vibrations in the airfoil. The airfoil includes a pocket formed in a chordwise surface. The apparatus for damping vibrations in the blade includes a damper and a pocket lid. The damper is received within the pocket between an inner surface of the pocket and the pocket lid. The pocket lid is attached to the airfoil by conventional attachment apparatus and contoured to match the curvature of the airfoil.

Abstract: An improved, highly stable blade-to-blade vibration damper configuration which provides substantially continuous blade vibration damping and sealing of an interplatform gap due to positional stability thereof. Disposed in a subplatform cavity, the damper is comprised of a generally triangular shaped body having a vertex thereof aligned with the interplatform gap. A primary damper load face abuts a first inclined platform load face and a secondary damper load face abuts a second inclined platform load face. Maintenance of sliding planar contact between primary and first load faces and sliding linear contact between secondary and second load faces is afforded by orienting inclined platform faces to have an included angle greater than that of the damper vertex and offsetting a damper center of gravity toward the primary load face. The damper may include one or more legs to orient the damper in the cavity and one or more extending tabs to discourage hot gas flow thereby.

Abstract: Damping and sealing of the quill shaft (30) that transmits torque from one rotating component to another as for example in a pitch change actuator system for aeronautical propellers is provided by an O-ring (40) mounted in the space between the end of ball screw (20) and the flange (41) radially extending from quill shaft (30) and the preload of the O-ring (40) provided by the shims (46) bearing against flange (41) and O-ring (40) which serves to enhance the wearability of splines (26, 28 and 50).

Abstract: A flexible seal (26) is located beneath blade platform (14) with end seals (28) in contact with adjacent platforms. A friction damper (34) formed of a flat slug of metal is supported only by the flexible seal (26) and in particular by the center section (32) of the seal.

Abstract: An "adaptive synchrophaser" is disclosed for modifying the phase angle relationship between aircraft propellers to reduce cabin noise and/or vibration. Rather than use a constant pre-selected angle for a specific passenger cabin configuration during a particular flight mode (e.g., during liftoff or cruise), the synchrophaser periodically monitors actual operating conditions and modifies the phase angle accordingly. In the preferred embodiment, a plurality of transducers (microphones) are installed at several cabin locations to sample noise periodically. The signals are then transmitted via a signal conditioner, a multiplexer and an analog-to-digital converter to a signal processor. The processor calculates the maximum acoustic noise at each microphone location for all possible phase angles. It then identifies the optimum phase angle that resulted in the lowest maximum noise anywhere in the cabin, and signals a synchrophaser to set that angle.

Abstract: A rotor assembly 10 having a rotor disk 12 and a plurality of outwardly extending rotor blades 16 is disclosed. Various construction details are developed to provide effective cooling to the platform sections 20 of such rotor blades. In one particular embodiment, a damper 58 engages the underside of the rotor blades 16 and a seal member 42 inwardly of the damper engages the damper to provide damping of vibrations in the rotor blades. Both the damper and the seal member are provided with cooling air holes 42, 74 to positively distribute cooling air collected inwardly of the damper and seal member and to direct the cooling air preferentially between the adjacent platform sections 20 of the rotor blades to effectively cool the rotor blades.

Abstract: Damping for the airfoils of stator vanes is provided by a spring damper formed from an elongated spring element bent into a "U" or "V" shape in cross section and oriented in the hollow of the airfoil so that the legs of the "U" or "V" frictionally engage the inner surfaces of the opposing pressure side and suction side walls of the airfoil to dissipate the vibratory energy. The elongated spring element is inserted through a hole formed on one end of the airfoil to extend just short of one of the ends of the airfoil to form a cantilevered mounted spring. The edge of the legs may be scalloped to allow the passage of air from one inner surface to the other of the airfoil.

Abstract: The present invention is a viscoelastic damper assembly for a front frame for a gas turbine engine that is removable, reusable, and retrofitable. The viscoelastic damper is disposed within a strut for damping vibration of the strut caused by airstream pressure pulses from first stage fan blades operating at transonic speeds. The viscoelastic damper can be installed in struts on gas turbine engines already in service or during manufacture. Also, the viscoelastic damper can be easily removed and reused when repairs to the front frame are required.

Abstract: Higher harmonic control (hereinafter HHC) of helicopter rotor blade vibrations is provided by an actively controlled, rotatable, slotted cylinder which is mounted at an outboard section of each blade. Continuous rotation of each cylinder about its longitudinal axis produces a periodic aerodynamic force on the blade at a frequency of twice the rotational frequency of the cylinder. The amplitude of force is controlled by the size of a slot opening in the cylinder while the rotational speed of the cylinder is synchronized to run at a multiple of the speed of a rotor blade drive shaft. The amplitude and phase of the HHC force is regulated, either manually or by active feedback control, to minimize any vibratory load transmitted to the airframe through the rotor blade drive shaft. A significant advantage offered by this concept relative to other HHC methods, such as high-frequency blade pitch motions actuated either by the swash plate or by moveable tabs at the blade trailing edge, is its low power requirement.

Abstract: An integrated damper and windage cover 52 has a windage cover portion 56 cantilevered at the upstream end, free of contact with the blade platform 24, 32. The contact portion 54 is rigid and bears against the underside of the blade platform 24, spanning blade platform clearance 50.

Abstract: A medallion-style blade iron assembly for use on a ceiling fan includes a vibration isolation system for eliminating transmission of vibration from the fan motor to the blades. The assembly includes an arm securable to the fan motor and medallion securable to the arm, with the distal end of a blade being secured therebetween. A plurality of mounting holes are provided in the blade for allowing screws to be inserted through the arm into the medallion, with each hole have a resilient elastomeric grommet disposed therein. Each grommet has a pair of annular shoulders resting on the top and bottom surfaces of the blade, and a central tapered opening for receiving the frusto-conical bosses formed on the arm and medallion. The grommets prevent contact between the blade, the arm, and the medallion.

Abstract: A blade of a built-up marine propeller is balanced by forming an open cavity of a predetermined size at a predetermined location proximate to the blade tip, conducting a spin-balancing test in which the blade being balanced and a calibration blade are assembled diametrically opposite each other on a dummy hub to form a simulated two-blade propeller, determining from the test the weight that must be added to the blade to balance the simulated propeller, and affixing a balance member of a predetermined weight in the blade cavity. A cover plate is secured in the cavity opening of the blade in sealed relation, and the external surface of the cover plate is ground to make it fair to the profile of the portion of the blade face adjacent the cavity opening.

Abstract: A generally wedge-shaped vibration damper for rotor blades of a gas turbine engine has a pair of scrubbing surfaces and is loosely retained in a pocket incorporated in the rotor blade platform. The pocket is partly defined by a plurality of surfaces which orient the damper so that it is slidably displaceable and rotatable only in a predetermined plane. During rotation of the rotor disk, the damper of one rotor blade is displaced in a plane transverse to the rotor axis of rotation by centrifugal forces to a position at which one scrubbing surface of the damper abuts a side surface of the platform of the adjacent rotor blade and the other scrubbing surface abuts an inner surface of the platform of the rotor blade in which the damper is inserted. The scrubbing action of the damper serves to damp vibratory motion in the platforms of both blades.

Abstract: Freestanding rotor blades are mixed tuned by varying the dimensions of the blades at two locations. First, a profiled tip includes a machined-out strip, having a height which can be varied to achieve the desired tuning effect. The longer or deeper the profile, the higher the frequency will become. This tuning technique is used in conjunction with a broadened base section. Blades having a shorter profile tip are machined beginning at the base section, so as to remove enough mass from between the base section and a next upper section to provide the desired tuning effect. The lower frequency blade has a thinner base section and a shorter profile tip.

Abstract: A rotor blade having axially spaced gussets disposed between a root portion and a platform is disclosed. Various construction details are developed which provide a gusset providing both platform support and damper positioning means. In one particular embodiment, a rotor blade assembly includes a plurality of circumferentially spaced rotor blades having dampers disposed between adjacent blades, wherein each blade includes an axially spaced pair of gussets extending laterally from the rotor blade. The gussets extend from a root portion of the rotor blade to a platform and provide radial support of the platform during rotation of the rotor assembly. The gussets include a curved lateral edge which, during rotation of the rotor assembly, urges the damper away from the root portion of the blade.

Abstract: Sheet Metal thermal control dampers are disposed in the cavities between turbine blades to bear against the undersides of opposed blade platforms portions of angularly adjacent blades under centrifugal loading to dampen blade vibrations and to seal the gaps between platforms against the radial flow of working fluid into the interblade cavities. The dampers are configured to cooperate with forward and aft seals to also block the axial flow of working fluid through the interblade cavities. Holes are provided in the dampers through which cooling air introduced into the interblade cavities can flow into contact with the platform undersides and cool the platforms, thereby controlling temperature rise in the blade attachment structure.

Abstract: A fan blade and rotor disk assembly for a gas turbine engine has a projection attached to a shank region of a fan blade. The projection makes contact with a surface region of a disk post when the fan blade is assembled to the rotor disk. In one form, a spring urges the fan blade to a position to maintain the projection in contact with the disk post surface so as to maintain the radial position of the fan blade. The projection member absorbs impact loading, shears off, allowing the blade to rotate and reduces the moment experienced by the root region of the fan blade when the fan blade is impacted by a foreign object.

Abstract: A rotor blade balance weight assembly comprises a weight retention housing (10) having a hollow core (22) and being closed on one end (12). The housing is disposed in an aperture which extends from the upper (52) to the lower (53) airfoil surfaces of the rotor blade (50). The closure end of the housing is contoured to match the airfoil upper surface contour. A stud (70) extends along the central axis of the housing, and washer-like balance weights (72) are received over the stud and secured by a locking nut (75). The open end of the housing is closed by a cover plate (25) that is contoured to match the airfoil lower surface contour, the cover plate being secured to the housing by a nut (78) in locking engagement with the stud. A pair of clips (37) are received within the housing, each clip having a tab surface (40) which extends through slots (42) in the housing, the clips being secured by the locking nut and stud.

Abstract: A composite axial flow rotary machine blade (50) and method of blade construction is disclosed. A partial-length, spanwisely-disposed hollow spar (20) partially captures a shaped foam core (30) which extends from within the spar's cavity (26) along a substantial length of the blade (50) in a spanwise fashion. A resin-impregnated high strength, high modulus cloth (34) and graphite (32) composition overlays the spar-core assembly (36) and forms the casing (50) with airfoil regions (52, 54) of the propeller blade (10). This construction results in a rotor blade (50) with enhanced natural frequencies thereby providing for an enhanced operational speed range.

Abstract: A generally wedge-shaped vibration damper for rotor blades of a gas turbine engine has a pair of scrubbing surfaces and is loosely retained in a pocket incorporated in the root cavity. The pocket is partly defined by a plurality of surfaces which orient the damper so that it is slidably displaceable and rotatable only in a predetermined plane. The retaining device is a hook-shaped sheet metal clip which is attached to the damping member. The clip has a resilient curved portion which is compressed to pass through a throat by which the pocket communicates with the remainder of the root cavity. When the curved portion of the clip clears the throat, it springs back to its uncompressed state in which the height of the curved portion is greater than the height of the throat, whereby the damping member is retained in the pocket.

Abstract: A method of repairing a turbine blade comprising the steps of ascertaining a normal vibration characteristic of the blade, separating an outer end part of the blade from a residual inner part of the blade and subsequently securing a new end part to the residual part so that a joint between the new end part and the residual part is positioned in a predetermined relationship to said vibration characteristic.

Abstract: A platform motion restraint for freestanding blades having Christmas tree shaped roots comprising a plurality of L shaped members which fit in circumferential notches machined in the outer portion of rotor steeples, one leg of the L shaped member being forced into the groove under platform portions of the blade to move the blades radially outward and the other leg filling the gap between adjacent blades.

Abstract: Method and device for the reduction of the oscillations of a divergent nature induced in the fuselage (2) of a helicopter (1) by its rotary wings (3) when they are turning. According to the invention, the oscillations are detected (at 17, 18) and they are converted (at 19, 20) into electrical signals, which are used (at 13) in order to produce pitch variations of the blades (4) of the rotary wings (3), in such a way that a rotating torque vector opposing said oscillations results.

Abstract: In a rotor blade fastening arrangement in the drum rotor of an axial flow turbomachine, the blades are fastened by means of their roots in rows in peripheral blade grooves with support indentations at the side. The blade groove provided for the first blade row is an L groove with two vertical support surfaces and one horizontal support indentation. The blade root engaging in it consists of a vertical protrusion and only one horizontal protrusion to the side.

Abstract: A twisted compressor or fan hollow blade is damped by an internal loose slug. The slug contacts the skin of the blade at two transversely spaced locations. This slug is located with its center of gravity eccentric of a radial line through the contact location.

Abstract: An underplatform damper contact portion 54 is rigid, and provides a loose seal between the underplatform cooling air 46 and the gas stream 40. At the aft end of the blade platform the pressure difference increases and a more effective seal is provided by the snap-in flexible seal 71.

Abstract: The present invention provides a phase independent damper and damper assembly capable of damping rotor blade vibrations in the axial, circumferential, and radial directions. One embodiment, particularly useful in an aircraft gas turbine engine compressor rotor, provides a damper and damper assembly including a generally axially extending blade damper operable to fictionally engage a generally axially extending circumferentially facing surface of a disk and axially extending angled surface under the platform of the blade. The invention provides an additional advantage of allowing simple and easy modification of existing engines to incorporate the damper of the present invention.

Abstract: The hydraulic damper according to the invention has at least one restricted communication passage (47) between its two working chambers (8, 9) whose cross section is controlled by a viscous restriction valve (51) positioned via a control pressure of a fluid of a control damper with at least one secondary chamber (41, 42) delimited in a secondary cylinder (39) by a control piston (40), which cylinder and control piston are integrally attached, one to the main body (1), the other to the damping piston (4) of the damper, such that the damping law of the control fluid positioning said valve (51) is linked to the relative displacements of the main body (1) and damping piston (4).Application to the equipping of elastic-return struts with integral damping, in particular for helicopter rotors and blades. FIG. 2.

Abstract: A vibration damper for rotor blades of a gas turbine engine has a shaft and a contact head connected thereto. The shaft is slidably inserted in a cylindrical recess incorporated in the rotor blade platform. During rotation of the rotor disk, the shaft of the damping member slides along the shaft axis, whereby the damping member is moved at least in the radial and circumferential directions by centrifugal forces. The contact head of the damping member of one rotor blade finally bears against the platform portion of an adjacent rotor blade, serving to damp vibratory motion of both blades.

Abstract: The vane platform 14 of each vane 12 has an inwardly extending foot 14. A resilient spring damper 24 extends from the base end 28 of the foot and is biased against the platform 14 at a remote contact location 32.

Abstract: A shrouded aerofoil assembly such as a turbine rotor for a gas turbine engine has a multiplicity of blades with tip shrouds circumferentially distributed around a rotor disk. Inevitably, in use, the assembly vibrates and must be designed so the potentially most dangerous vibratory modes occur outside the engine speed range. The proposed arrangement has a number of neighbouring blades sharing a common shroud segment. Adjacent shroud segments are interlocked by Z-notch abutments. Blade assemblies have sufficient pre-twist load to maintain frictional contact in the interlocks over the speed range to maintain damping constraints.

Abstract: An assembly or coupling arrangement for an impeller associated with a drive shaft. The impeller is supported by the drive shaft by a radial bearing having a small radial clearance. The bearing allows relative rotary motion between the impeller and shaft. In addition, an elastic or resilient element is mounted between the shaft and the impeller to transmit the torque from the shaft to the impeller while preventing or reducing transmission of torque pulsations.

Abstract: A fan blade damper system includes a fan disk integrally connected to a disk post. A retainer is fastened to the disk post and is molded to retain a damper block. The top portion of the damper block is shaped to make frictional contact with the underside of the platform of a fan blade, the underside of the platform being the region of the fan blade which experiences the highest platform vibratory amplitude when the fan blade is rotated. The damper block is thus mounted in a statically determinant fashion. The rotation of the fan blade produces centrifugal forces which produce reactionary forces in the damper block and retainer such that a maximum damping force amplitude is reacted to the fan disk.

Abstract: Disclosed is apparatus to prevent vibration of a pinned root fan blade during low speed revolution of the blade comprising a damping device which extends between the airfoil of the blade and the engine structure.

Abstract: A tapered twisted rotating blade for the fourth rotating blade row of a BB71 and BB471 turbine has a shroud segment integrally formed on the tip of the airfoil portion such that the shroud is dimensionalized according to materials used so that the tuned frequencies remain the same regardless of materials used, based on changes in Young's modulus due to use of different materials. The blade also has a pitch to chord ratio that increases linearly with length of the blade.

Abstract: A rotor includes a disc having a plurality of blades extending therefrom. The blades include tip shrouds, each having first and second axial ends, and first and second circumferential faces. The first and second faces of adjacent tip shrouds are spaced from each other to define gaps therebetween. The first and second ends each include U-shaped slots, each having an arcuate damper wire disposed therein. The slots are aligned generally parallel to an axial centerline axis of the rotor for allowing ease of manufacture and assembly while providing effective frictional damping by the damper wires urged by centrifugal force against the slots.

Abstract: The suspension device is interposed between the rotor and the fuselage of the helicopter for filtering the vibration exciting forces and moments coming from the rotor. In this helicopter, a speed reducer (1) is provided in a housing mounted on the fuselage (22) by rigid oblique bars (28). According to the invention, there are disposed around the housing of the speed reducer, in a number equal to the number of rigid oblique bars (28), monodirectional antiresonant means (20,21,23,23a,23b,25) connecting the upper ends of the rigid oblique bars (28) to the speed reducer (1).

Abstract: The present invention provides a rotor blade capable of being axially loaded in slots on a gas turbine engine rotor and particularly suited for use on turbine disks. The blade has a generally axially extending dovetail root which is effective for being loaded into a rotor disk slot between adjacent disk posts. Anti-rock tangs are disposed radially outward of the root and tangentially extend from the shank and are generally linear in the axial direction. The anti-rock tangs are effective to engage the radially outwardmost facing surfaces of the adjacent dovetail posts between which is disposed the associated dovetail slot.

Abstract: The internal blade damper is an elongated member with a damping surface of discrete width in contact with the interior blade surfaces. Contact is continuous throughout a substantial length. The damper extends between 2.degree. and 30.degree. from the radial direction, producing a direction of contact having some radial component. Centrifugal force loads the damping surface.

Abstract: A main helicopter rotor has a number of blades and drive shaft that supports, at its top end, a hub defined by a rocking toroidal body, the inner and outer edges of which are connected to the drive shaft via respective spherical elastomeric joints having a common center on the axis of the drive shaft. The toroidal body is fitted with and supports a rigid tubular body substantially coaxial with the drive shaft. Each blade is connected to the hub by a connecting element extending through both the tubular body and the toroidal body and connected respectively to the same by a first and second elastomeric bearing.

Abstract: An aircraft propeller system of the unducted fan type includes a plurality of propeller blades which are respectively fastened to a rotor, rotate about an axis of rotation and also rotate about a pitch axis. Each blade is fastened to the rotor by a hinge which has a pivot axis to reduce the effective stiffness of each blade, the pivot axis being non-parallel to the axis of rotation.

Abstract: A rotor blade (1) is disclosed which recenters itself in relation to the retention member (10) in which it is installed. Imposition of an external force (A) upon the rotor blade (1) creates a moment (M) which acts about the rotor blade's root (3). Recentering is accomplished by centrifugal forces acting through an offset distance (C") resulting from an off-center rotation of the blade and its captivated shaped retaining pin (6) within a plurality of retention member tenons (12), achieving an enhanced opposing restorative moment (M'.sub.R) on the rotor blade (1). The retention member tenons (12) contain arcuate bearing surfaces (8) which bear against a corresponding arcuate surface (9) with a smaller radius of curvature lengthwise disposed on the shaped retaining pin (6).

Abstract: A fan or compressor stage rotor comprises a disc, radial blades mounted in axial sockets formed in the periphery of the disc, and spacer blocks interposed between the blades to constitute the inner boundary of the air flow path through the rotor. The spacer blocks each comprise an outer wall which is spaced from the periphery of the disc, and front and rear walls extending radially inwardly to overlap at least partially the front and rear faces of the disc. The front and rear walls each comprise at least one hook which co-operates with a corresponding groove provided in the respective face of the disc to fix the spacer block to the disc. The spacer block also comprises a median partition projecting inwards from its outer wall and having a slot through which passes a leaf spring of a vibration damper.

Abstract: A metallic reinforced shim is attached to the dovetail of turbine or compressor blades. The shim reduces frictionally induced wear damage to the rotor. In one form, a single ply shim reinforced with a metallic doubler has an anti-fretting layer deposited on the shim face contacting the dovetail slot pressure face, and a doubler layer fastened to the anti-fretting layer in the non-contacting regions to prevent slippage of the shim on the blade. In another form, a multi-layer shim has two layers interposed between the blade dovetail and the disk dovetail slot, with the layers treated so that they do not readily slip relative to the titanium pieces, but do slip relative to each other. The shim is also reinforced with a metallic doubler. Fretting is confined to the consumable shim, and therefore the disk dovetail slot and the mating blade dovetails are not subject to surface degradation with corresponding reduction in fatigue capability.

Abstract: A freestanding mixed tuned taper-twisted steam turbine blade having an X-X axis parallel to a rotor axis, includes a root portion having a root center line defined by a root center line radius, a platform portion connected to the root portion; and an airfoil portion connected to the platform portion and having a leading edge, a trailing edge, a convex section-side surface, a concave pressure-side surface and a profiled tip, the platform portion having a concave edge, a convex edge, a first end in vertical proximity to the leading edge of the airfoil portion and a second end in vertical proximity to the trailing edge of the airfoil portion, the concave edge being sloped towards the root center line radius at a predetermined angle of slope to define an arcuate sloped surface, and having a sloped flat cut-out surface formed at the second end of the platform portion, the flat cut-out surface having the same predetermined angle of slope as the concave edge and sloping towards the X-X axis.