Pitch horn joint

A rotor assembly includes a pitch spider, rotor blade assemblies, and pitch horn joints. The pitch spider has a body and pitch spider legs extending from the body. Each blade rotor assembly includes a rotor blade, a pitch adapter joined to the rotor blade and connecting the rotor blade to the rotor hub, and a pitch horn. Each pitch horn joint joins one of the rotor blade assemblies to a corresponding pitch spider leg. Each pitch horn joint includes a pitch horn joint bolt extending from the pitch horn of the rotor blade assembly to the pitch spider leg along a pitch horn joint axis, the pitch horn joint bolt fixed to the pitch horn; a spherical bearing having an inner ring and an outer ring; and a slider sleeve coupled to the spherical bearing, the slider sleeve enabling the pitch horn to translate along the pitch horn joint axis.

TECHNICAL FIELD

This disclosure relates in general to the field of aircraft and, more particularly, though not exclusively, to a pitch horn joint for use in rotors that use a pitch spider for blade pitch articulation.

BACKGROUND

Some rotor systems used in aircraft have blades that can change pitch. One mechanism for changing the pitch of rotor blades is a pitch spider. A pitch spider connects to the blades in the rotor, and translating the pitch spider along a mast axis of the rotor changes the pitch of the blades. The pitch spider connects to each rotor blade at a joint that has multiple degrees of freedom. For example, some existing pitch spiders use a ball in socket joint, where a ball connected to the rotor blade can articulate within a socket connected to the pitch spider. Other pitch spiders use a ball in cylinder joint, where a ball connected to the rotor blade can articulate within a cylinder connected to the pitch spider, and translate along the length of the cylinder.

SUMMARY

One embodiment is a rotor assembly that includes a rotor hub, a pitch spider, a plurality of rotor blade assemblies, and a plurality of pitch horn joints. The pitch spider includes a central body and a plurality of pitch spider legs extending from the central body. Each of the plurality of rotor blade assemblies includes a rotor blade, a pitch adapter joined to the rotor blade and connecting the rotor blade to the rotor hub, and a pitch horn. Each of the plurality of pitch horn joints joins one of the plurality of rotor blade assemblies to a corresponding one of the plurality of pitch spider legs. Each pitch horn joint includes a pitch horn joint bolt extending from the pitch horn of the rotor blade assembly to the pitch spider leg along a pitch horn axis, the pitch horn joint bolt fixed to the pitch horn. Each pitch horn joint further includes a spherical bearing having an inner ring and an outer ring. Each pitch joint further includes a slider sleeve coupled to the spherical bearing, the slider sleeve enabling the pitch horn to translate relative to the pitch spider leg along the pitch horn joint axis.

In one example, the outer ring of the spherical bearing is fixed to the pitch spider leg, and the inner ring of the spherical bearing is coupled to the slider sleeve. The slider sleeve may be fixed to the pitch horn joint bolt, and the slider sleeve may be configured to slide along the inner ring of the spherical bearing to translate the pitch horn.

In another example, the inner ring of the spherical bearing is fixed to the pitch horn joint bolt, and outer ring of the spherical bearing is coupled to the slider sleeve. An outside of the slider sleeve may be fixed to the pitch spider leg, and the outer ring of the spherical bearing may be configured to slide along an inside of the slider sleeve to translate the pitch horn.

A bearing stress on the pitch horn joint maybe distributed across a width of the spherical bearing. The pitch spider may be configured to translate along a rotor hub axis, and a translation of the pitch spider along the rotor hub axis may rotate each of the plurality of rotor blade assemblies about a respective pitch change axis. The rotor assembly may further include a plurality of tension-torsion straps each attaching one of the rotor blade assemblies to the rotor hub.

Another embodiment is an aircraft that includes a tail rotor that includes a rotor hub, a pitch spider, a plurality of rotor blades, a plurality of pitch adapters, and a plurality of pitch horn joints. The pitch spider includes a central body and a plurality of pitch spider legs extending from the central body. Each of the plurality of rotor blades corresponds to one of the plurality of pitch spider legs. Each of the plurality of pitch adapters is joined to a respective one of the rotor blades and connects the rotor blade to the rotor hub. Each of the plurality of pitch adapters includes a pitch horn. Each of the plurality of pitch horn joints joins one of the plurality of pitch adapters to a corresponding one of the plurality of pitch spider legs. Each pitch horn joint includes a pitch horn joint bolt extending from the pitch horn of the pitch adapter to the pitch spider leg along a pitch horn joint axis, the pitch horn joint bolt fixed to the pitch horn of the pitch adapter; a spherical bearing having an inner ring and an outer ring; and a slider sleeve coupled to the spherical bearing, the slider sleeve enabling the pitch horn to translate relative to the pitch spider leg along the pitch horn joint axis.

In one example, the outer ring of the spherical bearing is fixed to the pitch spider leg, and the inner ring of the spherical bearing is coupled to the slider sleeve. The slider sleeve may be fixed to the pitch horn joint bolt, and the slider sleeve may be configured to slide along the inner ring of the spherical bearing to translate the pitch horn.

In another example, the inner ring of the spherical bearing is fixed to the pitch horn joint bolt, and outer ring of the spherical bearing is coupled to the slider sleeve. An outside of the slider sleeve may be fixed to the pitch spider leg, and the outer ring of the spherical bearing may be configured to slide along an inside of the slider sleeve to translate the pitch horn.

A bearing stress on the pitch horn joint maybe distributed across a width of the spherical bearing. The pitch spider may be configured to translate along a rotor hub axis, and a translation of the pitch spider along the rotor hub axis may rotate each of the plurality of rotor blades about a respective pitch change axis. The rotor assembly may further include a plurality of tension-torsion straps each attaching one of the pitch adapters to the rotor hub.

Another embodiment is a pitch horn joint between a pitch spider and a pitch adapter of a rotor blade, the pitch horn joint including a pitch horn joint bolt, a spherical bearing having an inner ring and an outer ring, and a slider sleeve coupled to the spherical bearing. The pitch horn joint bolt extends along a pitch horn joint axis from a pitch horn of the pitch adapter to a pitch spider leg of the pitch spider, the pitch horn joint bolt fixed to the pitch horn of the pitch adapter. The slider sleeve enables the pitch horn of the pitch adapter to translate along the pitch horn joint axis.

In one example, the outer ring of the spherical bearing is fixed to the pitch spider leg, and the inner ring of the spherical bearing is coupled to the slider sleeve. The slider sleeve may be fixed to the pitch horn joint bolt, and the slider sleeve may be configured to slide along the inner ring of the spherical bearing to translate the pitch horn. A bearing stress on the pitch horn joint maybe distributed across a width of the spherical bearing.

DETAILED DESCRIPTION

Additionally, as referred to herein in this Specification, the terms “forward”, “aft”, “inboard”, and “outboard” may be used to describe relative relationship(s) between components and/or spatial orientation of aspect(s) of a component or components. The term “forward” may refer to a spatial direction that is closer to a front of an aircraft relative to another component or component aspect(s). The term “aft” may refer to a spatial direction that is closer to a rear of an aircraft relative to another component or component aspect(s). The term “inboard” may refer to a location of a component that is within the fuselage of an aircraft and/or a spatial direction that is closer to or along a centerline of the aircraft (wherein the centerline runs between the front and the rear of the aircraft) or other point of reference relative to another component or component aspect. The term “outboard” may refer to a location of a component that is outside the fuselage of an aircraft and/or a spatial direction that farther from the centerline of the aircraft or other point of reference relative to another component or component aspect.

Further, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Example embodiments that may be used to implement the features and functionality of this disclosure will now be described with more particular reference to the accompanying FIGURES.

Embodiments described herein provide a pitch horn joint that connects a leg of a pitch spider to a blade assembly that includes a pitch horn. Moving the pitch spider changes the pitch of the blade assembly. The pitch horn joint includes a spherical bearing that slides along a slider sleeve. The slider sleeve allows for translation of the blade assembly relative to the pitch spider. The spherical bearing allows angular articulation of the joint.

Rotors that use pitch spiders typically use the pitch spider to control the pitch of the rotor blades, and tension-torsion straps to anchor the rotor blades to the rotor hub. The tension-torsion straps resist centrifugal force while allowing the rotor blades to change pitch. Pitch horn joints connect the pitch spider to the rotor blades, and the pitch horn joints withstand the stresses on the rotor assembly of maintaining the blades in a pitched position as the rotor is rotated about its axis. The load on the pitch horn joint increases non-linearly as the size of the rotor increases. In some previous pitched rotors, a ball-in-cylinder joint was used at the pitch horn joint. The contact between the ball portion of the joint and the cylinder is a circular line contact. The ball-in-cylinder joint is simple to construct and adequately manages stresses on the joint for relatively small scales and loads, e.g., for rotors under 4 feet in diameter. However, for larger rotor (e.g., rotors greater than 4 feet or greater than 4.5 feet in diameter), the stress on the pitch horn joint may be too great for the circular line contact of the ball-in-cylinder joint to withstand.

The pitch horn joints described herein include a spherical bearing, which provides a larger contact area within the joint than previous ball-in-cylinder joints. The larger contact area allows the pitch horn joint to withstand greater forces at larger rotor sizes. The pitch horn joint further has a translational degree of freedom provided by a slider sleeve. As the pitch spider translates along the hub axis to pitch the blade, the distance between the pitch spider leg and the pitch horn of the blade assembly changes, and the slider sleeve accommodates the translation of the pitch spider relative to the pitch horn.

Referring toFIGS. 1 and 2, illustrated therein are different views (i.e., a side view and a front view, respectively) of an example embodiment of an aircraft, which in the illustrated example is a rotorcraft100. As shown inFIGS. 1 and 2, rotorcraft100includes a fuselage102, a primary rotor system104, and an empennage106. The fuselage102is the main body of the rotorcraft100, which may include a cabin (e.g., for crew, passengers, and/or cargo) and/or may house certain mechanical components, electrical components, etc. (e.g., engine(s), transmission, flight controls, etc.).

The rotor system104is used to generate lift for rotorcraft100. For example, the rotor system104(also generally referred to as the “rotor”) may include a rotor hub112(also referred to as a “rotor hub assembly” or more generally as a “hub”) coupled to a plurality of rotor blades114(also referred to generally as “blades”) that extend radially from the rotor hub112via blade extensions115. Torque generated by the engine(s) of the rotorcraft causes the rotor blades114to rotate, which generates lift. In accordance with features of embodiments disclosed herein, the rotor hub112is completely shrouded by a rotor hub fairing116.

Rotorcraft100relies on rotor system104for flight capabilities, such as controlling (e.g., managing and/or adjusting) flight direction, thrust, and lift of the rotorcraft. For example, the pitch of each rotor blade114can be controlled using collective control or cyclic control to selectively control direction, thrust, and lift of the rotorcraft100. During collective control, all of the rotor blades114are collectively pitched together (e.g., the pitch angle is the same for all blades), which affects overall thrust and lift. During cyclic control, the pitch angle of each of the rotor blades114varies depending on where each blade is within a cycle of rotation (e.g., at some points in the rotation the pitch angle is not the same for all blades), which can affect direction of travel of the rotorcraft100.

Aircraft such as rotorcraft100can be subjected to various aerodynamic and operational forces during operation, such as lift, drag, centrifugal force, aerodynamic shears, and so forth. Lift and centrifugal force, for example, are forces produced by the rotation of a rotor system. Lift is an upward force that allows a rotorcraft to elevate, while centrifugal force is a lateral force that tends to pull the rotor blades outward from the rotor hub. These forces can subject the rotor hub, rotor yoke, and/or the rotor blades (referred to herein using the terms “hub/blades”, “yoke/blades”, “hub/yoke/blades”, and variations thereof) to flapping, leading and lagging, and/or bending. For example, flapping is a result of the dissymmetry of lift produced by rotor blades at different positions (typically referred to as “pitch” or “pitch angles”) during a single rotation. During rotation, for example, a rotor blade may generate more lift while advancing in the direction of travel of the rotorcraft than while retreating in the opposite direction. A rotor blade may be flapped up (also sometimes referred to as being pitched “nose-up”) while advancing in the direction of travel, and may flap down (e.g., pitched “nose-down”) while retreating in the opposite direction. When a blade is pitched more nose-up, more lift is created on that blade, which will drag the side of the rotor/hub upward, which makes the hub/yoke flap. For example, for rotorcraft100, the most aft blade (e.g., nearest to tail rotor or anti-torque system122) of the rotor system104may be pitched more nose-up and the most forward blade may be pitched more nose-down; to provide a forward direction of travel (as generally indicated by arrow128) for rotorcraft100.

The empennage106of the rotorcraft100includes a horizontal stabilizer118, a vertical stabilizer120, and a tail rotor or anti-torque system122. Although not shown in the view illustrated inFIG. 1, a corresponding horizontal stabilizer is disposed on the other side of the rotorcraft100opposite the horizontal stabilizer118. The horizontal stabilizer118and vertical stabilizer120respectively provide horizontal and vertical stability for the rotorcraft100. The tail rotor or anti-torque system122is used to provide anti-torque and/or direction control for the rotorcraft100. The tail rotor in the example shown inFIG. 1is a ducted tail rotor that includes a hub124and blades126surrounded by a duct. The set of rotor blades126extend radially from the rotor hub124, and the rotor hub124rotates about a mast axis through the center of the rotor hub124. In a neutral position, the rotor blades126are along a neutral blade plane that is perpendicular to the mast axis of the rotor hub124. The rotor hub124controls the pitch angle of the rotor blades126, e.g., using a pitch spider described further below. The rotor system122has a pitch envelope bounded by a minimum blade angle and a maximum blade angle, and the rotor hub124can pitch the rotor blades126to different positions within this pitch envelope.

FIG. 3illustrates a top isometric cutaway view of a rotor assembly300. The rotor assembly300may be an example of the tail rotor122shown inFIG. 1, or the main rotor104shown inFIG. 1. In other examples, the rotor assembly300may be a rotor assembly used another application, e.g., a propeller of a fixed wing aircraft or a tiltrotor aircraft. The rotor assembly300includes a rotor hub310and a set of blade assemblies320connected to the rotor hub310. Each of the blade assemblies320includes a pitch adapter322that extends into the rotor hub310and a blade324that extends outward from the rotor hub310. The pitch adapter322joins to the blade324and connects the blade324to the rotor hub310.

The rotor hub310has a rotor hub axis312that extends through the center of the rotor hub310. The rotor hub310includes a pitch spider314that is centered on the rotor hub axis312. The pitch spider314connects to each of the blade assemblies320at a pitch horn joint330. The pitch spider314translates up and down along the rotor hub axis312to change the pitch of the blades324, i.e., to rotate the blades324about a pitch change axis, shown inFIGS. 5 and 6. In the example shown inFIG. 3, if the pitch spider314translates upwards along the rotor hub axis312, this pitches the leading edge of the blade324upwards; if the pitch spider314translates downwards along the rotor hub axis312, this pitches the leading edge of the blade324downward. The pitch horn joint330connecting the pitch spider314to one of the rotor blade assemblies320is shown in greater detail inFIGS. 4-6.

The view shown inFIG. 3shows certain components of the rotor assembly300while other components are not depicted or are hidden from view. For example, the rotor hub310includes a hub housing, a portion of which is shown inFIG. 3, and a drive hub located underneath the pitch spider314. A mast attaches to the drive hub along the rotor hub axis312and rotates the rotor assembly300about the rotor hub axis312. The pitch adapters322may be fastened to tension-torsion straps that are also fastened to the drive hub underneath the pitch spider. Example cross-sections showing the tension-torsion straps are shown inFIGS. 5 and 6.

FIG. 4illustrates a close-up view showing one of the pitch horn joints330shown inFIG. 3.FIG. 4further shows the connections between the pitch adapter322, the pitch horn joint330, and the pitch spider314. The pitch adapter322has a pitch horn420extending from one side. As shown inFIG. 3, the pitch horn420is an integral piece of the pitch adapter322that extends off the side of the pitch adapter322corresponding to the leading edge of the blade324. In other embodiments, the pitch horn420may extend from the side of the pitch adapter322corresponding to the trailing edge of the blade324.

The pitch spider314includes a pitch spider body410that makes up the central portion of the pitch spider314around the rotor hub axis312. The pitch spider314also includes a set of pitch spider legs415extending from the pitch spider body410. Each of the pitch spider legs415corresponds to one of the rotor blade assemblies320and connects the pitch spider314to a corresponding pitch horn joint330.

The pitch horn joint330joins a pitch spider leg415to a pitch horn420. The pitch horn joint330includes a slider sleeve430, a spherical bearing440, and a pitch horn joint bolt450. The slider sleeve430allows the pitch horn420to translate away from the pitch spider leg415and towards the pitch spider leg415as the pitch spider314changes the pitch of the blade assembly320. In the example shown inFIG. 4, the slider sleeve430, pitch horn joint bolt450, and pitch horn420are fixed to each other. The slider sleeve430is coupled to the spherical bearing440, and the pitch horn joint bolt450and the slider sleeve430slide into and out of an inner ring of the spherical bearing440. The spherical bearing440is fixed to the pitch spider leg415. The spherical bearing440enables angular rotation of the pitch horn joint bolt450and the slider sleeve430about the spherical bearing440.

FIG. 5illustrates a cross-section of the pitch horn joint330and pitch adapter322. A joint axis510is shown extending through the pitch horn joint330. The pitch horn joint bolt450extends from the pitch horn420to the pitch spider leg415along the joint axis510. As noted above, in this embodiment, the slider sleeve430is fixed to the pitch horn joint bolt450. The pitch horn joint bolt450and slider sleeve430are fixed to the pitch horn420by a nut512; the end of the pitch horn joint bolt450extending out of the pitch horn420in the direction of the blade assembly320is threaded and fastened to the nut512, which is separated from the pitch horn420by a spacer514(e.g., a washer).

The spherical bearing440includes an inner ring520, which may also be referred to as a ball, and an outer ring525, which may also be referred to as a race. The outer ring525is fixed to the pitch spider leg415. The inner ring520can rotate within the outer ring525, allowing the slider sleeve430and pitch horn joint bolt450to change angle relative to the outer ring525and pitch spider leg415. The slider sleeve430is coupled to the inner ring520and enables the pitch horn420to translate relative to the pitch spider leg415along the joint axis510, moving the pitch horn420away from or towards the pitch spider leg415as the pitch of the blade assembly320changes. A slide zone530drawn inFIG. 5indicates the length along the slider sleeve430that the inner ring520can translate.

As described above, the rotation of the rotor system, especially when the blade assembly320is pitched away from a neutral position, puts stress on the pitch horn joint330. A bearing stress on the pitch horn joint330is distributed across a width W of the spherical bearing440. Distributing the stress across a greater portion of the joint than in prior pitch horn joints allows the pitch horn joint330to be used in larger, more highly loaded rotors.

As noted above, the pitch spider314controls the pitch angle of the blade assembly320. More particularly, motion of the pitch spider314causes each blade assembly320to rotate about a respective pitch change axis550to change the pitch angle. The pitch change axis550extends through the center of the pitch adapter322towards the rotor hub axis312shown inFIG. 3. The blade assembly320is held to the drive hub, which fits underneath the pitch spider314in the view shown inFIG. 3, by a tension-torsion strap. An example tension-torsion strap540is shown extending radially from the drive hub and through an inside of the pitch adapter322and attaching to the pitch adapter322. The tension-torsion strap540attaches to a mounting point on the drive hub, not shown inFIG. 5.

FIG. 6illustrates a cross section of an alternate embodiment of a pitch horn joint600. The example shown inFIG. 6flips the positions of the slider sleeve and the spherical bearing relative toFIG. 5. In particular, the inner ring620of the spherical bearing is fixed to the pitch horn joint bolt610, and the outer ring625of the spherical bearing is coupled to the slider sleeve630. The pitch horn joint bolt610and inner ring620of the spherical bearing are fixed to the pitch horn605by a nut612; the end of the pitch horn joint bolt610extending out of the pitch horn605in the direction of the blade assembly is threaded and fastened to the nut612, which is separated from the pitch horn605by a spacer614(e.g., a washer). In addition, a bearing spacer616separates the pitch horn605and the inner ring620of the spherical bearing and holds the spherical bearing in a fixed position along a pitch horn joint axis618relative to the pitch horn605.

The outside of the slider sleeve630is fixed to the pitch spider leg615. The outer ring625of the spherical bearing is configured to slide along the inside of the slider sleeve630to translate the pitch horn605relative to the pitch spider leg615. A slide zone635drawn inFIG. 6indicates the length along the slider sleeve630that the outer ring625can translate. The inner ring620of the spherical bearing can rotate freely within the outer ring625, allowing the pitch horn joint bolt610to change angle relative to the outer ring625, slider sleeve630, and pitch spider leg615.

The environment around the pitch horn joint600(e.g., the pitch adapter, the tension-torsion strap, the rotor hub, the pitch spider, etc.) are similar to the environment shown around the pitch horn joint330shown and described with respect toFIGS. 3-5. For example, the pitch spider controls the pitch angle of the blade assembly by causing the blade assembly to rotate about a pitch change axis650in the same manner described above. The blade assembly is held to the drive hub by a tension-torsion strap640, which attaches to a mounting point on the drive hub, as described above.

It should be appreciated that the pitch horn joint described herein can be used in various applications of rotors that use pitch spiders to pitch rotor blades. Indeed, the various embodiments of the pitch horn joint, and rotors that include the pitch horn joints, described herein may be used on any aircraft that utilizes rotors, such as helicopters, tiltrotor aircraft, hybrid aircraft, dual tiltrotor aircraft, unmanned aircraft, gyrocopters, airplanes, commuter aircraft, electric aircraft, hybrid-electric aircraft, ducted fan aircraft having any number of ducted fans, tiltwing aircraft, including tiltwing aircraft having one or more interwing linkages, more or fewer ducted fans or non-ducted rotors and the like. While the rotor assembly300is shown with nine rotor blade assemblies320, it should be understood that the pitch horn joint described herein may be used in rotor assemblies having as few as two rotor blades or more than nine rotor blades, with each rotor blade having a respective pitch horn joint connecting the rotor blade assembly to the rotor hub.

The components of the rotor assemblies and pitch horn joints described herein may comprise any materials suitable for use with an aircraft rotor. For example, the pitch spider314and pitch horn420may comprise aluminum. The spherical bearing440may be made of a stainless steel alloy, with a PTFE (Polytetrafluoroethylene) liner between the outer and inner rings. In some embodiments, the inner bore diameter of the inner ring is also lined, e.g., with a PTFE liner. The slider sleeve430may comprise stainless steel.

Example 1 is a rotor assembly including a rotor hub, a plurality of rotor blade assemblies, and a plurality of pitch horn joints. The rotor hub includes a pitch spider that has a central body and a plurality of pitch spider legs extending from the central body. Each rotor blade assembly includes a rotor blade, a pitch adapter joined to the rotor blade and connecting the rotor blade to the rotor hub, and a pitch horn. Each of the pitch horn joints joins one of the plurality of rotor blade assemblies to a corresponding one of the plurality of pitch spider legs. Each pitch horn joint includes a pitch horn joint bolt extending from the pitch horn of the rotor blade assembly to the pitch spider leg along a pitch horn joint axis, the pitch horn joint bolt fixed to the pitch horn; a spherical bearing having an inner ring and an outer ring; and a slider sleeve coupled to the spherical bearing, the slider sleeve enabling the pitch horn to translate relative to the pitch spider leg along the pitch horn joint axis.

Example 2 provides the rotor assembly according to example 1, where the outer ring of the spherical bearing is fixed to the pitch spider leg, and the inner ring of the spherical bearing is coupled to the slider sleeve.

Example 3 provides the rotor assembly according to either of the previous examples, where the slider sleeve is fixed to the pitch horn joint bolt, and the slider sleeve is configured to slide along the inner ring of the spherical bearing to translate the pitch horn.

Example 4 provides the rotor assembly according to example 1, where the inner ring of the spherical bearing is fixed to the pitch horn joint bolt, and the outer ring of the spherical bearing is coupled to the slider sleeve.

Example 5 provides the rotor assembly according to example 1 or example 4, where an outside of the slider sleeve is fixed to the pitch spider leg, and the outer ring of the spherical bearing is configured to slide along an inside of the slider sleeve to translate the pitch horn.

Example 6 provides the rotor assembly according to any of the previous examples, where a bearing stress on the pitch horn joint is distributed across a width of the spherical bearing.

Example 7 provides the rotor assembly according to any of the previous examples, where the pitch spider is configured to translate along a rotor hub axis, and a translation of the pitch spider along the rotor hub axis rotates each of the plurality of rotor blade assemblies about a respective pitch change axis.

Example 8 provides the rotor assembly according to any of the previous examples, further including a plurality of tension-torsion straps, each tension-torsion strap attaching one of the plurality of rotor blade assemblies to the rotor hub.

Example 9 an aircraft having a tail rotor, the tail rotor including a rotor hub, a plurality of rotor blades, a plurality of pitch adapters, and a plurality of pitch horn joints. The rotor hub includes a pitch spider that has a central body and a plurality of pitch spider legs extending from the central body. Each rotor blade corresponds to one of the pitch spider legs. Each pitch adapter is joined to a respective one of the plurality of rotor blades, and each pitch adapter includes a pitch horn. Each of the pitch horn joints joins one of the plurality of pitch adapters to a corresponding one of the plurality of pitch spider legs. Each pitch horn joint includes a pitch horn joint bolt extending from the pitch horn of the pitch adapter to the pitch spider leg along a pitch horn joint axis, the pitch horn joint bolt fixed to the pitch horn of the pitch adapter; a spherical bearing having an inner ring and an outer ring; and a slider sleeve coupled to the spherical bearing, the slider sleeve enabling the pitch horn to translate relative to the pitch spider leg along the pitch horn joint axis.

Example 10 provides the aircraft according to example 9, where the outer ring of the spherical bearing is fixed to the pitch spider leg, and the inner ring of the spherical bearing is coupled to the slider sleeve.

Example 11 provides the aircraft according to example 9 or example 10, where the slider sleeve is fixed to the pitch horn joint bolt, and the slider sleeve is configured to slide along the inner ring of the spherical bearing to translate the pitch horn.

Example 12 provides the aircraft according to example 9, where the inner ring of the spherical bearing is fixed to the pitch horn joint bolt, and the outer ring of the spherical bearing is coupled to the slider sleeve.

Example 13 provides the aircraft according to either of example 9 or example 12, where an outside of the slider sleeve is fixed to the pitch spider leg, and the outer ring of the spherical bearing is configured to slide along an inside of the slider sleeve to translate the pitch horn.

Example 14 provides the aircraft according to any of examples 9 through 13, where a bearing stress on the pitch horn joint is distributed across a width of the spherical bearing.

Example 15 provides the aircraft according to any of examples 9 through 14, where the pitch spider is configured to translate along a rotor hub axis, and a translation of the pitch spider along the rotor hub axis rotates each of the plurality of rotor blades about a respective pitch change axis.

Example 16 provides the aircraft according to any of examples 9 through 15, further including a plurality of tension-torsion straps, each tension-torsion strap attaching one of the plurality of pitch adapters to the rotor hub.

Example 17 provides a pitch horn joint between a pitch spider and a pitch adapter of a rotor blade, the pitch horn joint including a pitch horn joint bolt, a spherical bearing having an inner ring and an outer ring, and a slider sleeve coupled to the spherical bearing. The pitch horn joint bolt extends along a pitch horn joint axis from a pitch horn of the pitch adapter to a pitch spider leg of the pitch spider, the pitch horn joint bolt fixed to the pitch horn of the pitch adapter. The slider sleeve enables the pitch horn of the pitch adapter to translate relative to the pitch spider leg along the pitch horn joint axis.

Example 18 provides the pitch horn joint according to example 17, where the outer ring of the spherical bearing is fixed to the pitch spider leg, and the inner ring of the spherical bearing is coupled to the slider sleeve.

Example 19 provides the pitch horn joint according to either of examples 17 or 18, where the slider sleeve is fixed to the pitch horn joint bolt, and the slider sleeve is configured to slide along the inner ring of the spherical bearing to translate the pitch horn.

Example 20 provides the pitch horn joint according to any of examples 17 through 19, where a bearing stress on the pitch horn joint is distributed across a width of the spherical bearing.

The diagrams in the FIGURES illustrate the architecture, functionality, and/or operation of possible implementations of various embodiments of the present disclosure. Although several embodiments have been illustrated and described in detail, numerous other changes, substitutions, variations, alterations, and/or modifications are possible without departing from the spirit and scope of the present disclosure, as defined by the appended claims. The particular embodiments described herein are illustrative only and may be modified and practiced in different but equivalent manners, as would be apparent to those of ordinary skill in the art having the benefit of the teachings herein. Those of ordinary skill in the art would appreciate that the present disclosure may be readily used as a basis for designing or modifying other embodiments for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. For example, certain embodiments may be implemented using more, less, and/or other components than those described herein. Moreover, in certain embodiments, some components may be implemented separately, consolidated into one or more integrated components, and/or omitted. Similarly, methods associated with certain embodiments may be implemented using more, less, and/or other steps than those described herein, and their steps may be performed in any suitable order.

Numerous other changes, substitutions, variations, alterations, and modifications may be ascertained to one of ordinary skill in the art and it is intended that the present disclosure encompass all such changes, substitutions, variations, alterations, and modifications as falling within the scope of the appended claims.

One or more advantages mentioned herein do not in any way suggest that any one of the embodiments described herein necessarily provides all the described advantages or that all the embodiments of the present disclosure necessarily provide any one of the described advantages. Note that in this Specification, references to various features included in “one embodiment”, “example embodiment”, “an embodiment”, “another embodiment”, “certain embodiments”, “some embodiments”, “various embodiments”, “other embodiments”, “alternative embodiment”, and the like are intended to mean that any such features are included in one or more embodiments of the present disclosure, but may or may not necessarily be combined in the same embodiments.

As used herein, unless expressly stated to the contrary, use of the phrase “at least one of”, “one or more of” and “and/or” are open ended expressions that are both conjunctive and disjunctive in operation for any combination of named elements, conditions, or activities. For example, each of the expressions “at least one of X, Y and Z”, “at least one of X, Y or Z”, “one or more of X, Y and Z”, “one or more of X, Y or Z” and “A, B and/or C” can mean any of the following: 1) X, but not Y and not Z; 2) Y, but not X and not Z; 3) Z, but not X and not Y; 4) X and Y, but not Z; 5) X and Z, but not Y; 6) Y and Z, but not X; or 7) X, Y, and Z. Additionally, unless expressly stated to the contrary, the terms “first”, “second”, “third”, etc., are intended to distinguish the particular nouns (e.g., blade, rotor, element, device, condition, module, activity, operation, etc.) they modify. Unless expressly stated to the contrary, the use of these terms is not intended to indicate any type of order, rank, importance, temporal sequence, or hierarchy of the modified noun. For example, “first X” and “second X” are intended to designate two X elements that are not necessarily limited by any order, rank, importance, temporal sequence, or hierarchy of the two elements. As referred to herein, “at least one of”, “one or more of”, and the like can be represented using the “(s)” nomenclature (e.g., one or more element(s)).

In order to assist the United States Patent and Trademark Office (USPTO) and, additionally, any readers of any patent issued on this application in interpreting the claims appended hereto, Applicant wishes to note that the Applicant: (a) does not intend any of the appended claims to invoke paragraph (f) of 35 U.S.C. Section 112 as it exists on the date of the filing hereof unless the words “means for” or “step for” are specifically used in the particular claims; and (b) does not intend, by any statement in the Specification, to limit this disclosure in any way that is not otherwise reflected in the appended claims.