Assembly for a tilt rotor aircraft

Abstract

An assembly includes a plurality of blades for generating force to propel the tilt rotor aircraft. The assembly includes a nacelle connected to the blades, the nacelle having a first rotation axis about which the nacelle rotates and a roller. The assembly further includes a pitch rod configured to adjust a pitch of the plurality of the blades, and a shaft connected to the pitch rod by a drive link. The assembly also includes a cam connected to the shaft, and a tilt track that is connected to the roller of the nacelle such that motion of the roller along the tilt track causes the cam to adjust the tilt of the nacelle about the first rotation axis. The cam further includes a second rotation axis that is different from the first rotation axis, about which the cam rotates.

Description

Attorney Docket No.: 00379-0048-00304ASSEMBLY FOR A TILT ROTOR AIRCRAFT CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 685,867, filed August 22, 2024, which is incorporated by reference herein in its entirety.TECHNICAL FIELD

[0002] Embodiments of this disclosure are directed to a rotor assembly, and in particular, to systems and methods for an assembly for a tiltrotor aircraft.BACKGROUND OF THE INVENTION

[0003] Tilt rotor aircraft are typically capable of operating in a vertical hover mode and in a horizontal flight mode. In the vertical hover mode, rotor assemblies of the aircraft are generally vertically oriented, such that the rotors provide thrust in a vertical direction. In the horizontal flight mode, the rotor assemblies are generally horizontally oriented, such that the rotors provide thrust in a horizontal direction. Nacelles of the rotor assemblies tilt from a generally vertical position to a generally horizontal position to switch between the vertical hover mode and the horizontal flight mode.

[0004] During the process of tilting the nacelles, it may be desirable to change the pitch of the blades. Previous designs coupling the tilt of the rotor assemblies to the blade pitch control involve high variations in control thrust, which may generate high vibratory loads and present other structural design challenges. Also, existing designs linearly couple the tilt angle to the blade pitch angle, use geared teeth, and / or employ a single shared axis of rotation for the components of the assembly.

[0005] Chinese Patent Publication CN112265635A (the ‘635 publication) describes a rotor wing tilting mechanism for an unmanned aerial vehicle. The tilt mechanism includes a first driving device arranged on a connecting seat that is rotatably sleeved on a connecting shaft. The first driving device drives the connecting seat and a rotor to rotate around an axis of the connecting shaft using gears that are attached to the driving device and the connecting shaft. One end of the connecting shaft is provided with an arc plate portion with a first guide groove that interacts with a guide rod connected to a transmission rod for controlling the pitch of the blades. When the connecting seat rotates, the guide rod slides in the first guideAttorney Docket No.: 00379-0048-00304groove, and gradually approaches or moves away from the shaft, so that the transmission rod slides an axial direction, thereby driving the blades to rotate and change the angle of attack of the blade. The tilting mechanism of the ‘635 publication, describes a rotor assembly that rotates about a fixed shaft having a plate for controlling blade pitch and a separate geared mechanism for controlling rotor tilt. Also, the tilting mechanism of the ’635 publication is not able to control the pitch of the blades during either a hover configuration or a cruise configuration of the vehicle.

[0006] There is a need for a tilt assembly for a tilt rotor aircraft in which the rotation of a cam causes the nacelle to tilt and the blades to pitch.

[0007] The background description provided herein is for the purpose of generally presenting the context of the disclosure. Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art, or suggestions of the prior art, by inclusion in this section.SUMMARY OF THE DISCLOSURE

[0008] In one aspect, the disclosure relates to a rotor assembly for a tilt rotor aircraft. The rotor assembly may include a plurality of blades for generating force to propel the tilt rotor aircraft, and a nacelle connected to the blades. The nacelle may have a first rotation axis about which the nacelle rotates, and a roller. The rotor assembly may further include a pitch rod configured to adjust a pitch of the plurality of blades, a shaft connected to the pitch rod by a drive link, and a cam connected to the shaft. The cam may include a tilt track that is connected to the roller of the nacelle such that motion of the roller along the tilt track causes the cam to adjust the tilt of the nacelle about the first rotation axis. The cam may also include a second rotation axis that is different from the first rotation axis, about which the cam rotates.

[0009] In another aspect, the disclosure relates to an assembly for a tilt rotor aircraft. The assembly may include a nacelle having a tilt roller and a nacelle rotation axis, a shaft connected to a first arm and to a second arm, a pitch rod connected to the second arm of the shaft by a drive link, and a cam. The cam may be rotatable about a cam rotation axis and include a first side, a second side, a tilt track on the first side having a first section and a second section, and a pitch track on the second side having a first section and a second section. The rotation of the cam about the cam rotation axis may cause the tilt roller to traverse through the tilt track and the first arm to traverse through the pitch track.Attorney Docket No.: 00379-0048-00304

[0010] In another aspect, the techniques described herein relate to a method of rotating a rotor assembly of a tilt rotor aircraft. The method may include the steps of rotating a cam about a first rotation axis, the cam having a first track including a first section and a second section. The method may further include the steps of rotating a nacelle about a second rotation axis as a roller connected to the nacelle moves through the first section of the first track. The method may further include the steps of moving a pitch rod relative to the second rotation axis as the nacelle rotates. The method may further include the steps of holding the nacelle in an angular position relative to the second rotation axis as the tilt roller moves through the second section of the first track, and rotating a shaft connected to the cam and the pitch rod while the nacelle is held in an angular position relative to the second rotation axis, such that the pitch rod moves radially relative to the second rotation axis.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various examples and, together with the description, serve to explain the principles of the disclosed examples and embodiments.

[0012] Aspects of the disclosure may be implemented in connection with embodiments illustrated in the attached drawings. These drawings show different aspects of the present disclosure and, where appropriate, reference numerals illustrating like structures, components, materials, and / or elements in different figures are labeled similarly. It is understood that various combinations of the structures, components, and / or elements, other than those specifically shown, are contemplated and are within the scope of the present disclosure.

[0013] Moreover, there are many embodiments described and illustrated herein. The present disclosure is neither limited to any single aspect or embodiment thereof, nor is it limited to any combinations and / or permutations of such aspects and / or embodiments. Moreover, each of the aspects of the present disclosure, and / or embodiments thereof, may be employed alone or in combination with one or more of the other aspects of the present disclosure and / or embodiments thereof. For the sake of brevity, certain permutations and combinations are not discussed and / or illustrated separately herein. Notably, an embodiment or implementation described herein as “exemplary” is not to be construed as preferred or advantageous, for example, over other embodiments or implementations; rather, it is intended to reflect or indicate the embodiment s) is / are “example” embodiment(s).

[0014] FIG. 1 illustrates a front perspective view of vertical takeoff and landing vehicle having rotor assemblies, according to aspects of the present disclosure.Attorney Docket No.: 00379-0048-00304

[0015] FIG. 2 illustrates a front perspective view of a portion of a rotor assembly of the vertical takeoff and landing vehicle of FIG. 1.

[0016] FIG. 3 illustrates a side cross-sectional view of a portion of a rotor assembly of the vertical takeoff and landing vehicle of FIG. 1.

[0017] FIG. 4 A illustrates a side cross-sectional view of a portion of the rotor assembly of the vertical takeoff and landing vehicle of FIG. 1 in a first configuration. FIG. 4B illustrates a side cutaway view of a portion of the rotor assembly of the vertical takeoff and landing vehicle of FIG. 1 in a second configuration. FIG. 4C illustrates a side cutaway view of a portion of the rotor assembly of the vertical takeoff and landing vehicle of FIG. 1 in a third configuration. FIG. 4D illustrates a side cutaway view of a portion of the rotor assembly of the vertical takeoff and landing vehicle of FIG. 1 in a fourth configuration.

[0018] FIG. 5 illustrates a close up, front perspective view of a portion of a rotor assembly, according to a further embodiment of the present disclosure.

[0019] FIG. 6 illustrates a side cutaway view of the rotor assembly of FIG. 5.

[0020] FIG. 7 illustrates a plot of nacelle tilt and pitch horn angles as a cam rotates.

[0021] FIG. 8 illustrates a flowchart describing a method of rotating a rotor assembly of a tilt rotor aircraft, according to aspects of the present disclosure.

[0022] As used herein, the terms “comprises,” “comprising,” “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. The term “exemplary” is used in the sense of “example,” rather than “ideal.” In addition, the terms “first,” “second,” and the like, herein do not denote any order, quantity, or importance, but rather are used to distinguish an element or a structure from another. Moreover, the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of one or more of the referenced items.

[0023] Notably, for simplicity and clarity of illustration, certain aspects of the figures depict the general structure and / or manner of construction of the various embodiments. Descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring other features. Elements in the figures are not necessarily drawn to scale; the dimensions of some features may be exaggerated relative to other elements to improve understanding of the example embodiments. For example, one of ordinary skill in the art appreciates that the side views are not drawn to scale and should not be viewed as representing proportional relationships between different components. The side views areAttorney Docket No.: 00379-0048-00304provided to help illustrate the various components of the depicted assembly, and to show their relative positioning to one another.DETAILED DESCRIPTION

[0024] Reference will now be made in detail to examples of the present disclosure, which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. In the discussion that follows, relative terms such as “about,” “substantially,” “approximately,” etc. are used to indicate a possible variation of a numerical range in a stated numeric value, as will be designated below.

[0025] The present disclosure generally provides for systems, methods, and devices of a vertical takeoff and landing (VTOL) aircraft at various speeds, modes, and phases of flights to control position, orientation, direction, and / or speed of the VTOL aircraft. Although the present disclosure makes reference to a VTOL aircraft, those of ordinary skill in the art will readily recognize that reference to an aircraft is exemplary, and that the concepts of the present disclosure may be used in conjunction with any suitable or comparable aircraft, e.g., airplanes, helicopters, aerostats, flight simulators, space crafts, commercial airplanes, electrical vertical takeoff and landing aircraft (eVTOL aircraft), or any other type of rotor-propelled aircraft. Still further, aspects of the present disclosure may be used in conjunction with any vehicle or rotor assembly, including, but not limited to, vehicles designed for operation on land, on water, in the air, in space, or any combination thereof, as well as turbines, such as wind turbines. The above list is not, in any matter, supposed to signify a limited list of what the term “aircraft” defines in terms of structure.

[0026] FIG. 1 is a front perspective view of a vehicle takeoff and landing vehicle (hereinafter vehicle 100) having at least one rotor assembly 107. Vehicle 100 includes a fuselage 101 and wings 103. The fuselage may further be connected to a tail 105. At least one rotor assembly 107 may be connected to each of the wings 103. Each rotor assembly 107 may include one or more blades 111 for generating force to propel the vehicle 100, and each rotor assembly 107 may be associated with an actuator 109 within, or adjacent to the rotor assembly 107, actuator 109 being configured to control both rotor tilt and blade pitch. The rotor assemblies 107 may transition from a vertical orientation or position (FIGS. 1-3, 4A) to a horizontal orientation or position (FIGS. 4C-4D). In the vertical orientation, the rotor assemblies 107 allow the vehicle 100 to hover and translate vertically for takeoff and landing.Attorney Docket No.: 00379-0048-00304In the horizontal orientation, the rotor assemblies 107 allow the vehicle 100 to propel itself forward with increased efficiency.

[0027] In the example shown in FIG. 1 , some of the rotor assemblies 107 are in a tractor configuration in which the blades 111 are in front of the motor (not shown) relative to the airflow, and other rotor assemblies 107 are in a pusher configuration in which the blades 111 are behind the motor relative to the airflow. In the tractor configuration, the rotor assemblies 107 pull the vehicle 100 through the air, while in the pusher configuration, the rotor assemblies 107 push the vehicle 100 through the air. In the illustrated example, half of the rotor assemblies 107 are configured to be placed in a tractor configuration while the other half of the rotor assemblies 107 are configured to be placed in a pusher configuration. However, other configurations are possible. In some examples, a greater number, or all, of the rotor assemblies 107 may be in the tractor configuration. In other examples, a greater number, or all of the rotor assemblies 107 may be in the pusher configuration.

[0028] In the example shown in FIG. 1, the vehicle 100 shows each of the rotor assemblies 107 in the vertical orientation for takeoff or landing. In other stages of flight, the rotor assemblies 107 may all be in the horizontal orientation. In some examples, the rotor assemblies 107 may be in different positions, such that at least some of the rotor assemblies 107 may be in the vertical orientation, some of the rotor assemblies 107 may be in the horizontal orientation, and some of the rotor assemblies 107 may be between the vertical and horizontal orientation. In some examples, some of the rotor assemblies 107 may transition between the vertical and horizontal orientations, while other rotor assemblies 107 may be fixed in either the vertical or horizontal orientation (fixed rotor assemblies 107 not shown in FIG. 1).

[0029] In the example shown in FIG. 1, the vehicle 100 has eight rotor assemblies 107. In other examples, the vehicle 100 may have more or less rotor assemblies 107. For example, the vehicle 100 may have one, two, four, six, ten, or twelve rotor assemblies 107. In the example shown in FIG. 1, the vehicle 100 has rotor assemblies 107 mounted to the wings 103. In other examples, the rotor assemblies 107 may additionally or alternatively be mounted to the tail 105. In further examples, the vehicle 100 may have rotor assemblies 107 that are additionally or alternatively attached to the fuselage 101, or another part of the vehicle 100.

[0030] FIG. 2 illustrates a close up, front perspective view of a portion of a rotor assembly 107 of the vertical takeoff and landing vehicle 100. FIG. 3 illustrates a close up, side cutaway view of a portion of a rotor assembly 107 of the vertical takeoff and landing vehicle 100.Attorney Docket No.: 00379-0048-00304

[0031] Referring now generally to FIGS. 2-3, the rotor assembly 107 may include a nacelle 131, and a pair of cams 121 attached to a rotatable shaft 113 within the nacelle 131. The shaft 113 may be connected to a link end 139 of pitch rod 117 via one or more drive links 115. The pitch rod 117 may be partially internal to, and partially external to, the nacelle 131. The end of the pitch rod 117 opposite the link end 139 (not shown) may be connected to a blade control system (e.g., including one or more pitch arms; not shown) of the one or more blades 111 (FIG. 1) such that a movement of the pitch rod 117 adjusts the pitch of the blades 111 of a respective rotor assembly 107.

[0032] The cams 121 may be generally elliptical plates, with a narrow end 137 and a broad end 135 (FIG. 3). A rotation axis 141, described below and also referred to as a first axis, may extend through the cam 121. The narrow end 137 may be at a greater radial distance away from the rotation axis 141 than the broad end 135. Each of the cams 121 may have a first side, outside face 120, and a second side, inside face 122 opposite the outside face 120. The inside face 122 of each cam 121 may face and connect to the shaft 113, as well as to the inside face 122 of the other cam 121. The outside face 120 may face the interior nacelle wall 129. The outside face 120 of each of the cams 121 may include one or more outside track walls 123 extending perpendicularly away from the outside face 120. The one or more outside track walls 123 may form a tilt track 155 (FIG. 3). The inside face 122 may include one or more inside track walls 125 extending perpendicularly away from the inside face 122. The one or more inside track walls 125 may form a pitch track 165 (FIG. 3).

[0033] The inside face 122 may further include an actuator connection opening 127 centered about the cam rotation axis 141 for connecting the cams 121 to an actuator 109 (FIG.1). In other examples, the opening 127 may be on the outside face 120 of the cams 121, or may extend through the cams 121. The actuator 109 may be a rotary actuator or a linear actuator, and may be electrically powered, pneumatically powered, or hydraulically powered, or powered by another means. The actuator 109 may be controlled by a controller within the vehicle 100. The actuator 109 may be connected to the actuator connection opening 127 via one or more rods or shafts. In other embodiments, the actuator 109 may be connected to another part of the cam 121, for example, the perimeter 161. The actuator 109 may be connected to, for example, both cams 121 within each rotor assembly 107. In other examples, multiple actuators 109 may be associated with each rotor assembly 107, such that a separate actuator controls each cam 121 and / or provides redundancy. In some examples, a single actuator may control cams within multiple rotor assemblies 107.Attorney Docket No.: 00379-0048-00304

[0034] In the example shown in FIG. 2, the rotor assembly 107 includes two generally elliptical cams 121, as described above. In other examples, the rotor assembly 107 may include exactly one cam 121, or more than two cams 121. In other examples, the cams 121 may have a shape other than an elliptical shape. For example, the cams 121 may be circular, irregularly-shaped, rectangular, or another shape.

[0035] In the example shown in FIGS. 2-3, the tilt track 155 and the pitch track 165 are formed by the outside track walls 123 and the inside track walls 125, respectively. In other examples, the tilt track 155 or the pitch track 165 may be formed by slots or recesses within the cams 121. In some examples, the tilt track 155 and the pitch track 165 may be formed on a side of the cams 121 between the outside face 120 and the inside face 122 of the cams 121 (e.g., the edge of the cam 121). In some examples, the tilt track 155 and / or the pitch track 165 may be formed by a single outside track wall 123 and / or a single inside track wall 125, respectively.

[0036] In the examples shown in FIGS. 2-3, the tilt track 155 and the pitch track 165 are shown as being formed by smooth surfaces of the one or more outside track walls 123 and the one or more inside track walls 125, respectively, such that the tilt rollers 133 and the cam arm 153 may roll or slide along the tilt track 155 and the pitch track 165 as explained further below.

[0037] In the example shown in FIGS. 2-3, the tilt track 155 is formed on the outside face 120 of the cam 121, and the pitch track 165 is formed on the inside face 122 the cam 121. In other examples, the tilt track 155 may be formed on the inside face 122 of the cam 121, and the pitch track 165 may be formed on the outside face 120 of the cam 121. In some examples, both the tilt track 155 and the pitch track 165 may be formed on the outside face 120 or on the inside face 122 of the cam 121.

[0038] Referring again to FIGS. 2-3, the tilt track 155 may include a first, variable or radially-changing section 157 and a second, radially-constant section 159 in succession. The radially-changing section 157 may extend along the perimeter 161 of the cams 121, from the narrow end 137 towards the broad end 135 until reaching a predefined radial distance from the cam rotation axis 141, the radial distance represented in FIG. 3 by a circle 145 for illustrative purposes. The radially-changing section 157 may have a changing radius of curvature relative to the cam rotation axis 141, with the radial distance increasing towards the narrow end 137. The radially-constant section 159 may extend from the broad end 135 until reaching the radially-changing section 157 at a point 185. The radially-constant section 159 may be at aAttorney Docket No.: 00379-0048-00304constant radial distance from the cam rotation axis 141, such that it follows the circle 145 between the point 185 and the broad end 135.

[0039] In the examples shown in FIGS. 2-3, the tilt track 155 includes a single, radially-constant section 159 in succession with a single, radially-changing section 157. The radially the radially-changing sections 157 interact with the tilt rollers 133 (as explained further below) to tilt the nacelle 131 when the cams 121 rotate, while the radially-constant sections 159 allow the cams 121 to rotate without tilting the nacelle 131. In other examples, the tilt track 155 may include more than one radially-changing section 157 or more than one radially-constant section 159. Additionally or alternatively, the order of the radially-changing section 157 and radially-constant section 159 may be swapped. In examples having more than one radially-changing section 157 or radially-constant section 159, the multiple radially-changing sections 157 and radially-constant sections 159 may be interspersed with one another such that, for example, a radially-constant section 159 may be between two radially-changing sections 157, or a radially-changing section 157 may be between two radially-constant sections 159. In some examples including multiple radially-constant sections 159, the radially-constant sections 159 may have different radii of curvature relative to the cam rotation axis 141.

[0040] The pitch track 165 may include a first, radially-constant section 169 and a second, variable or radially-changing section 167. The radially the radially-changing sections 167 interact with the cam arms 153 (as explained further below) to rotate the shaft 113 when the cams 121 rotate, while the radially-constant sections 169 allow the cams 121 to rotate without rotating the shaft 113. The radially-constant section 169 may be at a constant radial distance from the cam rotation axis 141 that is slightly greater than the radius of the circle 145, and may extend from the perimeter 161 (FIG. 3) into the interior 163 of the cam 121. The radially-changing section 167 may extend from a point 187 at an end of the radially-constant section 169 towards the narrow end 137 within the interior 163 of the cam 121. As with the tilt track 155, the number, order, and / or positions of the radially-changing section 167 and radially-constant section 169 may be varied, as well as the curvature. Further, the pitch track 165 may be a single radially-changing section 167.

[0041] Still referring to FIGS. 2-3, the shaft 113 may extend between the cams 121 in a longitudinal direction. The shaft 113 may be cylindrical, with a longitudinal axis aligned with the nacelle rotation axis 143. The shaft 113 may connect to the cams 121 via cam arms 153 that extend radially away from longitudinal ends of the shaft 113. The cam arms 153 may slidably engage the inside track walls 125 of the cams 121, via a roller, such as a pin, that protrudes from the cam arm 153 in a direction that is generally parallel to the nacelle rotationAttorney Docket No.: 00379-0048-00304axis 143. In some examples, the roller of the cam arms 153 (and / or the tilt rollers 133) may be sliders that slide along the track walls 125 (or 123), or may be another suitable means of retaining the cam arms 153 (or the tilt rollers 133) within the track walls 125 (or 123). A link arm 151 may extend from the axial center of the shaft 113. The link arm 151 may rotatably connect to one or more drive links 115. The cam arms 153 may be angularly offset from the link arm 151 by a fixed angle a (FIG. 3). In the example shown in FIGS. 2-3, the angle a may be 90 degrees. In other examples, the angle a may be greater than or less than 90 degrees.

[0042] The drive links 115 may be elongate in shape, with a first end rotatably connected to the link arm 151, and a second end rotatably connected to the link end 139 of the pitch rod 117. In other examples, the drive links 115 may have a different shape (as described further below). The pitch rod 117 may extend between the one or more one or more drive links 115 and the blade control system for the blades 111. In some examples, pitch rod 117 may extend and connect to a spider plate or a control plate (not shown) of the blade control system. In other examples, the pitch rod 117, may extend and connect to a swashplate. In further examples, the pitch rod 117 may extend and connect to another part of the blade control system.

[0043] FIGS. 4A-4D illustrate a series of close up, side cutaway views of a rotor assembly 107 of the vertical takeoff and landing vehicle 100 in a first, second, third, and forth configuration, respectively, during which the vehicle 100 transitions from a vertical hover mode to a horizontal flight mode. In the first configuration (FIG. 4A), the vehicle 100 is in a vertical hover mode, with the nacelle 131 in a vertical position and the blades 111 at a first pitch angle. In the second configuration (FIG. 4B), the vehicle 100 is transitioning between the vertical hover mode and the horizontal flight mode. In the second configuration, the nacelle 131 is at a first angle xl from the vertical axis 171, and the blades 111 are at a second pitch angle. In the third configuration (FIG. 4C), the vehicle 100 is in the horizontal flight mode. In the third configuration, the nacelle 131 forms an angle X2 with the vertical axis 171, and the blades 111 are at a third pitch angle. In the fourth configuration (FIG. 4D), the vehicle 100 remains in the horizontal flight mode, such that the nacelle 131 remains at angle X2 relative to the vertical axis 171, while the blades 111 are adjusted to a fourth pitch angle.

[0044] As described further below, in use, actuator 109 (FIG. 1) may rotate the one or more cams 121 about the cam rotation axis 141, which may in turn cause the nacelle 131 to rotate or tilt about the nacelle rotation axis 143 as the rotor assembly 107 moves between one or more of the first, second, third, and fourth configuration. When the tilt roller 133 is within the radially-changing section 157 of the tilt track 155, the rotation of the cam 121 may cause rotation of the nacelle 131, transitioning the rotor assembly 107 from the vertical hover modeAttorney Docket No.: 00379-0048-00304to the horizontal flight mode. When the tilt roller 133 is within the radially-constant section 159 of the tilt track 155, the rotation of the cams 121 may cause no rotation of the nacelle 131.

[0045] The rotation of the cams 121 may cause the pitch rod 117 to reciprocate in a radial direction (e.g., towards and away from the nacelle rotation axis 143 along the rod axis 119). When the cam arm 153 is within the radially-changing section 167, the rotation of the cam 121 may cause the shaft 113 to rotate, which may in turn cause the pitch rod 117 to move radially towards or away from the nacelle rotation axis 143 due to forces applied to, or exerted on, the pitch rod 117 by the one or more drive links 115 attached to the link arm 151 of the shaft 113. When the cam arm 153 is within the radially-constant section 169 of the pitch track 165, the rotation of the cam 121 does not cause the shaft 113 to rotate, in at least some embodiments. However, the rotation of the nacelle 131 about the nacelle rotation axis 143 may cause the rotation of the pitch rod 117 about the nacelle rotation axis 143 while the shaft 113 remains stationary relative to the nacelle rotation axis 143. The relative motion of the pitch rod 117 about the stationary the shaft 113 may cause the pitch rod 117 to move radially towards or away from the nacelle rotation axis 143 due to forces applied to the pitch rod 117 by the one or more drive links 115.

[0046] Although the rotor assemblies 107 may contain multiple cams 121, tilt rollers 133, cam arms 153, link arms 151, and drive links 115, the following description will be directed to a single cam 121, tilt roller 133, cam arm 153, link arm 151, and link 115. Further, although the following describes a sequence of configurations in a particular order, it will be understood that the sequence could be reversed or changed.

[0047] As shown in FIG. 4 A, the rotor assembly 107 may initially be in a first position, where the nacelle 131 and the rod axis 119 are in a vertical position and aligned with a vertical axis 171 that is perpendicular to the nacelle rotation axis 143 and aligned with a gravity vector. In the first position, the tilt roller 133 may be at the end of the radially-changing section 157 of the tilt track 155 nearest the narrow end 137 of the cam 121, and the pin of the cam arm 153 may be at the end of the radially-constant section 169 of the pitch track 165 nearest the broad end 135 of the cam 121. Further, the link end 139 of the pitch rod 117 may be at a first distance n away from the nacelle rotation axis 143 and at an angle yi relative to the vertical axis 171.

[0048] As the actuator 109 rotates the cam 121 about the cam rotation axis 141, the rotor assembly 107 may move from the first configuration (FIG. 4 A) to the second configuration (FIG. 4B). As shown in FIG. 4B, as the cam 121 rotates, the tilt roller 133 may traverse the radially-changing section 157 of the tilt track 155 towards the broad end 135 of the cam 121, causing the nacelle 131 to rotate or tilt about the nacelle rotation axis 143 such thatAttorney Docket No.: 00379-0048-00304the nacelle 131 reaches an angle xi, for example, relative to the vertical axis 171. Additionally, the cam arm 153 traverses through the radially-constant section 169 of the pitch track 165 towards the narrow end 137 of the cam 121 while the shaft 113 remains stationary with respect to the nacelle rotation axis 143 such that the link arm 151 remains at the angle yi relative to the vertical axis 171.

[0049] As the nacelle 131 rotates, the pitch rod 117 (as well as the rod axis 119) rotates about the nacelle rotation axis 143. The rotation of the pitch rod 117 about the nacelle rotation axis 143 may cause the drive link 115 to pivot about the link arm 151, which may cause the pitch rod 117 to translate along the rod axis 119. As shown in FIG. 4B, in the second configuration, the link end 139 may reach a distance r2 away from the nacelle rotation axis 143. In the example of FIG. 4B, the distance r2 may be greater than the distance rl, such that the pitch rod 117 moves radially away from the nacelle rotation axis 143 due to a force applied to the pitch rod 117 by the drive link 115. The radial motion of the pitch rod 117 may change the pitch of the blades due to the interaction of the pitch rod 117 with the control system of the blades. In other examples, and in other portions of the radially-changing section 157, the pitch rod 117 may move further or closer to the nacelle rotation axis 143 depending on the curvature of the radially-changing section 157 and the rotation of the shaft 113.

[0050] As the cam 121 continues to rotate about the cam rotation axis 141, the rotor assembly 107 may move from the second configuration (FIG. 4B) to the third configuration (FIG. 4C), where the tilt roller 133 is within the radially-constant section 159 of the tilt track 155, and the cam arm 153 is within the radially-constant section 169 of the pitch track 165. Before reaching the third configuration (FIG. 4C) after moving from the second configuration (FIG. 4B), the nacelle 131 may continue to rotate about the nacelle rotation axis 143 until reaching angle X2 relative to the vertical axis 171, at which point the tilt roller 133 exits the radially-changing section 157 and enters the radially-constant section 159. When the tilt roller 133 is within the radially-constant section 159, the cam 121 may continue to rotate about the cam rotation axis 141 such that the tilt roller 133 traverses the tilt track 155 towards the narrow end 137 of the cam 121 while the nacelle 131 remains fixed at angle X2 relative to the vertical axis 171. In the example shown in FIG. 4C, the angle X2 may be 90 degrees, such that the nacelle 131 is in a horizontal position. In other examples, the angle X2 may be greater than or less than 90 degrees. As the cam arm 153 is still within the radially-constant section 169 of the pitch track 165, the shaft 113 remains stationary with respect to the nacelle rotation axis 143, and link arm 151 remains at the angle y i relative to the vertical axis 171. As there is no rotation of the nacelle 131 or the shaft 113, the rod axis 119 of the pitch rod 117 may remain at aAttorney Docket No.: 00379-0048-00304distance n away from the nacelle rotation axis 143. In the example shown in FIG. 4C, the distance n may be less than the distance rc. In other examples, the distance n may be greater than, less than, or equal to the distance rc.

[0051] In some examples, the cam arm 153 may transition from the radially-constant section 169 to the radially-changing section 167 of the pitch track 165 as the tilt roller 133 transitions from the radially-changing section 157 to the radially-constant section 159 of the tilt track 155, such that the shaft 113 begins to rotate as soon as the nacelle 131 reaches angle X2. In further examples, the cam arm 153 may transition from the radially-constant section 169 to the radially-changing section 167 of the pitch track 165 before the tilt roller 133 transitions from the radially-changing section 157 to the radially-constant section 159 of the tilt track 155, such that the shaft 113 begins to rotate before the nacelle 131 reaches angle X2.

[0052] Referring again to FIGS. 4A-4D, the cam 121 continues to rotate about the cam rotation axis 141, the rotor assembly 107 may transition from the third configuration (FIG. 4C) to the fourth configuration (FIG. 4D). During this transition, the tilt roller 133 remains within the radially-constant section 159 of the tilt track 155, and the cam arm 153 is within the radially-changing section 167 of the pitch track 165. When the tilt roller 133 is within the radially-constant section 159, the cam 121 may continue to rotate about the cam rotation axis 141 such that the tilt roller 133 traverses through the tilt track 155 towards the narrow end 137 of the cam 121, but the nacelle 131 may remain fixed at an angle X2 relative to the vertical axis 171. When the cam arm 153 is within the radially-changing section 167 of the pitch track 165, the cam arm 153 traverses through the pitch track 165 towards the narrow end 137 of the cam 121. The movement of the cam arm 153 through the radially-changing section 167 may cause the shaft 113 to rotate about the nacelle rotation axis 143, rotating the link arm 151 from angle yl to, for example, an angle yz relative to the vertical axis 171, as shown in FIG. 4D. The rotation of the shaft 113 may cause the pitch rod 117 to move radially to a distance n away from the nacelle rotation axis 143. In the example shown in FIG. 4D, the distance n may be greater than the distance n. In other examples, the distance r4 may be greater than, less than, or equal to the distance n.

[0053] As can be seen in FIGS. 4A-4D, the tilt track 155 and the pitch track 165 may produce a non-linear relationship between the tilt of the nacelle 131 and the pitch of the blades 111. This non-linear relationship result from the motion of the pitch rod 117. In particular, as the tilt roller 133 moves through the radially-changing section 157 of the tilt track 155 and the link arm 151 is traversing through the radially-constant section 169 of the pitch track 165, the rate of change of the rotation or tilt of the nacelle 131 may be less than or greater than the rateAttorney Docket No.: 00379-0048-00304of change in the pitch of the blades 111. Similarly, as the link arm 151 traverses through the radially-changing section 167 of the pitch track 165 and the tilt roller 133 is within the radially-constant section 169 of the tilt track 155, the rate of change of the pitch of the blades 111 may be greater than or less than the rate of change of the rotation or tilt of the nacelle 131.

[0054] The tilt track 155 and pitch track 165 may be shaped so as to produce a desired relationship between the tilt of the nacelle 131 and the pitch angle of the blades 111. In the example shown in FIGS. 4A-4D, when the nacelle tilts from a vertical to horizontal position, the tilt roller 133 first traverses through a radially-changing section 157 of the tilt track 155 before reaching a radially-constant section 159 of the tilt track 155. As previously explained, in other examples, the tilt roller 133 may first encounter a radially-constant section 159, and may then encounter one or more radially-changing sections 157 and / or additional radially-constant sections 159. Similarly, the cam arm 153 may first encounter a radially-changing section 167, and may additionally or alternatively encounter additional radially-changing sections 167 and / or radially-constant sections 169. Therefore, depending on the arrangement of radially-changing sections 157, radially-constant sections 159, radially-changing sections 167, and radially-constant sections 169, the nacelle 131 may rotate simultaneously with the rotation of the shaft 113, or only one of the nacelle 131 and the shaft 113 may be rotating when actuator 109 is activated for a certain period of time. Moreover, the nacelle 131 and the shaft 113 may alternate between simultaneous and independent rotation depending on the inclusion and ordering of the radially-changing sections 157, radially-constant sections 159, radially-changing sections 167, and radially-constant sections 169.

[0055] In the example shown in FIGS. 4A-4D, the tilt roller 133 may roll or slide through the tilt track 155, and the interaction of the tilt roller 133 with the one or more outside track walls 123 of the tilt track 155 may cause a rotation of the nacelle 131. In other examples, movement of the tilt roller 133 may cause the nacelle 131 to tilt through another mechanism. For example, the tilt roller 133 may rotate due to its interaction with the tilt track 155. The rotation of the tilt roller 133 may induce a rotation in a gear set between the tilt roller 133 and the nacelle 131. The rotation of the gear set may cause the nacelle 131 to rotate. The tilt roller 133 may additionally or alternatively be connected to one or more pulleys or linkages that connect to the nacelle 131, such that the motion of the tilt roller 133 causes a rotation or tilt of the nacelle 131 due to the motion of the pulleys or linkages. In examples where the tilt track 155 and / or the pitch track 165 are formed on the outside edge of the cams 121, the edge of the cam 121 may push or rotate rollers, or other connection means as the cams 121 rotate to cause the nacelle 131 to tilt and / or the blades 111 to pitch due to the motion of the pitch rod 117.Attorney Docket No.: 00379-0048-00304

[0056] FIG. 5 is a close up, front perspective view of a rotor assembly 107A, according to a further embodiment of the present disclosure, and FIG. 6 is a close up, side cutaway view of the rotor assembly 107A of FIG. 5. Referring now generally to FIGS. 5-6, the rotor assembly 107A of FIGS. 5-6, may include one or more cams 121 that are connected to a the shaft 113 within the nacelle 131. The shaft the shaft 113 may be connected to a “J” shaped drive link, J link 175, via a link arm 151. The J link 175 may also be connected to the pitch rod 117.

[0057] In the example rotor assembly 107A of FIGS. 5-6, the cams 121 may be generally semi -elliptical, with a narrow end 137 and a broad end 135. The narrow end 137 may be at a greater radial distance away from the rotation axis 141 than the broad end 135. The cams 121 have a curved perimeter 161 along one edge of the cams 121, and a generally straight perimeter 173 along another edge of the cams 121 opposite the curved perimeter 161. The cams 121 may have a first side, outside face 120, and a second side, inside face 122 opposite the outside face 120. The inside face 122 of each of the cams 121 may face and connect to the shaft 113, as well as the inside face 122 of the other cam 121. The outside face 120 may face the nacelle 131. The outside face 120 of each of the cams 121 may include one or more outside track walls 123 extending perpendicularly away from the outside face 120. The one or more outside track walls 123 may form a tilt track 155 (FIG. 6). The inside face 122 of the cams 121 of FIGS. 5-6 may be connected to the shaft 113. The link arm 151 of the shaft 113 may extend radially away from the center of the shaft 113.

[0058] The tilt track 155 may include a first, radially-changing section 157 and a second, radially-constant section 159. The radially-changing section 157 may extend along the perimeter 161 of the cams 121, from the narrow end 137 towards the broad end 135 until reaching a predefined radial distance from the cam rotation axis 141, the radial distance represented in FIG. 6 by a circle 145 for illustrative purposes. The radially-changing section 157 may have a changing radius of curvature relative to the cam rotation axis 141, with the radial distance increasing towards the narrow end 137. The radially-constant section 159 may extend along the perimeter 161 of the cams 121 from the broad end 135 until reaching the radially-changing section 157. The radially-constant section 159 may be at a constant radial distance from the cam rotation axis 141, such that the radially-constant section 159 follows the circle 145.

[0059] In the example show in FIGS. 5-6, the cams 121 are generally elliptical and the tilt track 155 is depicted as formed by one or more outside track walls 123 on the outside face 120 of the cams 121. In other examples, the cams 121 have a different shape, and the tilt track 155 may be formed on the inside face 122 of the cams 121. In some examples, the tilt trackAttorney Docket No.: 00379-0048-00304155 may be formed as a groove within the cams 121, as an edge surface of the cam 121 between the outside face 120 and the inside face 122, or by or on another portion of the cams 121.

[0060] The J link 175 may include a first, short end 177 and a second, long end 179 separated by a curved section 181. The short end 177 may be angularly disposed relative to the long end 179 due to the curve section 181. The curved section 181 may from a pocket 183. In the Example shown in FIGS. 5-6, the curved section 181 may be curved approximately 90 degrees, such that the short end 177 and the long end 179 are approximately perpendicular to one another. The short end 177 may be rotatably connected to the link arm 151 of the shaft 113, and the long end 179 may be connected rotatably connected to the pitch rod 117.

[0061] In the example rotor assembly 107A shown in FIGS. 5-6, the cam rotation axis 141 may be aligned the shaft 113. The nacelle rotation axis 143 may be parallel to, and radially spaced from, the cam rotation axis 141 such that the nacelle rotation axis 143 is not aligned with the cam 121 or the shaft 113 when the rotor assembly is the position shown in FIGS. 5-6.

[0062] In use, the actuator 109 may cause the shaft 113 to rotate, causing the cams 121 to rotate about the cam rotation axis 141. As the cam 121 rotates, the tilt roller 133 traverse through the radially-changing section 157 and radially-constant section 159 of the tilt track 155. As explained above with respect to FIGS. 4A-D, while in the tilt roller 133 is in the radially-changing section 157, the nacelle 131 rotates about the nacelle rotation axis 143 from, for example, a vertical position shown in FIGS. 5-6 to a horizontal position. When the tilt roller 133 is within the radially-constant section 159, the nacelle 131 may remain in a given position, for example, a horizontal position.

[0063] In the example rotor assemblies 107A shown in FIGS. 5-6, the rotation of the cams 121 may cause a continuous rotation of the shaft 113. The rotation of the shaft 113 may cause the rotation of the J link 175 about the link arm 151. As the J link 175 rotates, the long end 179 may pull or push the pitch rod 117, such that the pitch rod 117 moves radially away or towards the nacelle rotation axis 143, depending on the direction of rotation of the cams 121. For example, a counterclockwise rotation of the cam 121 of FIG. 6 may pull the pitch rod 117 towards the nacelle rotation axis 143. When the cam 121 is in the fully rotated position, such that the tilt roller 133 at the end of the tilt track 155 nearest the broad end 135, the J link 175 may be positioned such that the shaft 113 is received within the pocket 183 of the pitch rod 117.

[0064] In the example show in FIGS. 5-6, the pitch of the blades 111 due to the rotation of the J link 175 and the motion of the pitch rod 117 may be non-linearly coupled to the tilt angle of the nacelle 131 due to the interaction of the tilt rollers 133 with the tilt track 155, suchAttorney Docket No.: 00379-0048-00304that the tilt angle of the nacelle 131 may change faster or slower than the pitch angle of the blades 111. In other examples, the J link 175 may have a different shape that maintains a nonlinear coupled movement of the pitch angle of the blades 111 to the tilt angle of the nacelle 133. For example, the curved section 181 may instead be replaced by a number of straight sections, with each straight sections angled relative to one another. In other examples, the long end 179 and the short end 177 may be directly connected to one another at an angle which may be greater than, less than, or equal to 90 degrees. In other examples, the J link 175 may be generally straight, such that there is no curved section 181.

[0065] FIG. 7 illustrates a plot 700 of nacelle tilt angle 750 for a nacelle 131 and a pitch horn angle 740 for a pitch horn (not shown) attached to a blade 111 about a rotation axis relative to a horizontal plane as the cam 121 rotates for an example rotor assembly 107, 107 A. The rotation of a pitch horn may increase or decrease the pitch of the blade 111, but the angle of the blade is not necessarily the same as the pitch horn angle 740. Although FIG. 7 depicts the kinematics for an example rotor assembly 107, 107 A, the depicted example does not necessarily show the kinematics of the example rotor assemblies 107, 107A in FIGS. 2-6. The plot 700 includes a horizontal axis 710 measuring the rotation angle of the cam 121, a first vertical axis 720 measuring tilt angle 750 of the nacelle 131, and a second vertical axis 730 measuring the pitch horn angle 740 of the pitch horn attached to a blade 111. The tilt angle 750 of the nacelle 131 in plot 700 may be measured from a vertical axis, such as vertical axis 171, such that the nacelle pitch angle 750 increases as the nacelle 131 tilts or rotates from a vertical position to a horizontal position. As the cam 121 (which is not necessarily the same as the cam 121 of FIGS. 2-6) begins to rotate, the nacelle 131 may maintain a constant tilt angle 750, until the cam 121 reaches a first cam rotation angle 711. Before the cam 121 reaches the first cam rotation angle 711, the pitch horn angle 740 may initially increase positively until reaching a local maximum 741 after witch the pitch horn angle 740 beings to decrease. After the cam 121 reaches a first cam rotation angle 711, the nacelle tilt angle 750 increases until reaching a maximum nacelle rotation angle 721 at a second cam rotation angle 713. Between the first cam rotation angle 711 and the second cam rotation angle 713, the pitch horn angle 740 may decrease through a neutral or zero pitch angle 731 such that the pitch horn angle 740 becomes negative until reaching a first local minimum 743, at which point the pitch horn angle 740 begins to increase. After the second cam rotation angle 713, the nacelle tilt angle 750 may remain constant. The pitch horn angle 740 may increase until reaching a slightly positive second local maximum 745 before beginning to decrease, returning to a negative pitch horn angle 740.Attorney Docket No.: 00379-0048-00304

[0066] FIG. 8 is a flowchart describing a method of rotating a rotor assembly 107, 107A of a tilt rotor aircraft, according to aspects of the present disclosure. In a step 810, the cam 121 is rotated by an actuator 109 about the cam rotation axis 141. The cam 121 includes a radially-changing section 157 and a radially-constant section 159. In a step 820, the nacelle 131 rotates about a nacelle rotation axis 143 as the tilt roller 133 traverses through the radially-changing section 157 of the cam 121. In a step 830, the pitch rod 117 moves radially relative to the nacelle rotation axis 143 as the nacelle 131 rotates, due to a force applied by one or more drive links 115 connected via the shaft 113 to the cam 121. In a step 840, the nacelle 131 is held in an angular position relative to the nacelle rotation axis 143 as the one or more drive links 115 moves through the radially-constant section 159 of the tilt track 155. In a step 850, the shaft 113 connected to the cam 121 and the pitch rod 117 rotates while the nacelle 131 is held in an angular position relative to the nacelle rotation axis 143. The rotation of the shaft 113 causes the pitch rod 117 to move radially relative to the nacelle rotation axis 143, which in turn causes the blades 111 to pitch.

[0067] In some examples, the method further includes the steps of moving an end of the cam arm 153 of the shaft 113 connected to the cam 121through a pitch track 165 on the cam 121, the pitch track 165 having a radially -changing section 167 and a radially-constant section 169. The cam 121 rotates as the cam arm 153 moves through the radially -changing section 167. In further examples, the method further includes moving the pitch rod 117 radially relative to the nacelle rotation axis 143 as the nacelle 131 rotates, and moving the pitch rod 117 radially relative to the nacelle rotation axis 143 as the cam arm 153 of the shaft 113 connected to the cam 121 traverses through radially-constant section 169 of the pitch track 165.

[0068] From the foregoing detailed description, it will be evident that there are a number of changes, adaptations and modifications of the present disclosure which come within the province of those persons having ordinary skill in the art to which the aforementioned disclosure pertains. However, it is intended that all such variations not departing from the spirit of the disclosure be considered as within the scope thereof as limited by the appended claims.

Claims

Attorney Docket No.: 00379-0048-00304CLAIMS1. A rotor assembly for a tilt rotor aircraft, the rotor assembly comprising:a plurality of blades for generating force to propel the tilt rotor aircraft;a nacelle connected to the blades, the nacelle having:a first rotation axis about which the nacelle rotates; anda roller;a pitch rod configured to adjust a pitch of the plurality of the blades;a shaft connected to the pitch rod by a drive link; anda cam connected to the shaft, the cam including:a tilt track that is connected to the roller of the nacelle such that motion of the roller along the tilt track causes the cam to adjust the tilt of the nacelle about the first rotation axis, anda second rotation axis that is different from the first rotation axis, about which the cam rotates.

2. The rotor assembly of claim 1, wherein the cam further includes a pitch track, the pitch track having a first section and a second section, and the shaft includes an arm connected to the pitch track, such that the rotation of the cam causes the pitch rod to adjust the pitch of the plurality of blades.

3. The rotor assembly of claim 1, wherein the tilt track includes a first section and a second section, the second section having a constant radius of curvature, the first section having a changing radius of curvature.

4. The rotor assembly of claim 1, wherein a rotation of the cam causes the roller of the nacelle to traverse through the tilt track.

5. The rotor assembly of claim 1, wherein a rotation of the cam causes the drive link to exert a force on the pitch rod.

6. The rotor assembly of claim 1, wherein the shaft is connected to a pitch track by an arm, and the arm of the shaft traverses through the pitch track as the cam rotates.Attorney Docket No.: 00379-0048-003047. The rotor assembly of claim 1, wherein the tilt track has a first section and a second section, and wherein the nacelle rotates about the first rotation axis as the roller traverses through the first section of the tilt track.

8. The rotor assembly of claim 1, wherein the tilt track has a first section and a second section, and the nacelle remains in an angular position relative to the first rotation axis as the roller traverses through second section of the tilt track.

9. The rotor assembly of claim 1, wherein rotation of the shaft about the first rotation axis cause the pitch rod to move relative to a longitudinal axis aligned with the pitch rod.

10. The rotor assembly of claim 1, wherein a rotation of the shaft about the first rotation axis causes the pitch rod to move relative to a longitudinal axis aligned with the pitch rod.

11. The rotor assembly of claim 1, wherein the drive link includes a first end and a second end, the first end separated from the second end by a curved section.

12. The rotor assembly of claim 1, wherein the drive link includes a first end and a second end, the first end separated from the second end by a curved section forming a pocket.

13. An assembly for a tilt rotor aircraft, the assembly comprising:a nacelle having a tilt roller and a nacelle rotation axis;a shaft connected to a first arm and to a second arm;a pitch rod connected to the second arm of the shaft by a drive link; anda cam, the cam being rotatable about a cam rotation axis and including:a first side,a second side,a tilt track on the first side, the tilt track having a first section and a second section, anda pitch track on the second side, the pitch track having a first section and a second section,wherein the rotation of the cam about the cam rotation axis causes the tilt roller to traverse through the tilt track and the first arm to traverse through the pitch track.Attorney Docket No.: 00379-0048-0030414. The assembly of claim 13, wherein the nacelle rotates as the tilt roller traverses through the first section of the tilt track, the shaft rotates as the first arm traverses through the second section of the pitch track, the rotation of the nacelle causes the pitch rod to move radially relative to the nacelle rotation axis, and the rotation of the shaft causes the pitch rod to move radially relative to the nacelle rotation axis.

15. The assembly of claim 13, wherein the first section of the tilt track has a variable radius of curvature, and the second section of the tilt track has a constant radius of curvature centered at the cam rotation axis.

16. The assembly of claim 13, wherein the first section of the pitch track has a constant radius of curvature centered at the cam rotation axis, and the second section of the pitch track has a variable radius of curvature.

17. The assembly of claim 13, wherein the cam has an elliptical shape, and a first end of the cam is radially further from the cam rotation axis than a second end of the cam.

18. A method of rotating a rotor assembly of a tilt rotor aircraft, the method comprising the steps of:rotating a cam about a first rotation axis, the cam having a first track including a first section and a second section;rotating a nacelle about a second rotation axis as a roller connected to the nacelle moves through the first section of the first track;moving a pitch rod relative to the second rotation axis as the nacelle rotates; holding the nacelle in an angular position relative to the second rotation axis as the tilt roller moves through the second section of the first track; androtating a shaft connected to the cam and the pitch rod while the nacelle is held in an angular position relative to the second rotation axis, such that the pitch rod moves radially relative to the second rotation axis.

19. The method of claim 18, further including the steps of moving an end of an arm on a shaft connected to the cam through a second track on the cam, the second track having a firstAttorney Docket No.: 00379-0048-00304section and a second section, wherein the cam rotates as the arm moves through the second section.

20. The method of claim 18, further including the steps of moving a pitch rod radially relative to the second rotation axis as the nacelle rotates, and moving the pitch rod radially relative to the second rotation axis as an arm of a shaft connected to the cam traverses through a section of a second track on the cam.

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