Variable Pitch Fan Assembly with Remote Counterweight

Abstract

The variable pitch fan assembly includes a plurality of rotating trunnion assemblies, a plurality of counterweight assemblies, a first coordinated ring gear engaged with the trunnion assemblies, and a second coordinated ring member that limits the asynchronous movement of the counterweights relative to each other.

Description

Technical Field

[0001] The present subject matter generally relates to variable pitch fan assemblies for turbines, and more particularly to remote counterweight systems for such variable pitch fan assemblies. Background Art

[0002] The operating principle of turbine engines for turbofans and turboprops is that a central gas turbine core drives airfoil elements, such as propeller or fan blades, that generate thrust. In some turbofan engines, variable pitch fan assemblies allow the angle of incidence, or pitch angle, of the airfoil elements to be changed relative to a rotating hub that carries the airfoil elements. Since engine designs for turbines require efficient and reliable operation, it is desirable to improve the efficiency and reliability of these engines and their components, including variable pitch fan assemblies. Summary of the Invention

[0003] Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned by practice of the techniques disclosed in the description.

[0004] Various turbine engines and variable pitch fan assemblies are described herein. In some embodiments, a variable pitch fan assembly includes a plurality of trunnions and a plurality of counterweight assemblies. The counterweight assemblies can include a counterweight, a counterweight shaft, and one or more counterweight gears. One or more coordinating annular members can engage with one or more of the counterweight gears.

[0005] These and other features, aspects, and advantages of the present disclosure will be better understood with reference to the following description and the appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosed technology and, together with the description, serve to explain the principles of the disclosure. Brief Description of the Drawings

[0006] This specification sets forth a complete and enabling disclosure of the invention for the person of ordinary skill in the art, with reference to the accompanying drawings, in which:

[0007] Figure 1 is a cross-sectional schematic view of an exemplary embodiment of a gas turbine engine of an aircraft;

[0008] Figure 2 is a cross-sectional schematic view of an exemplary fan section that includes a pitch changing mechanism and a remote counterweight phase control mechanism;

[0009] Figure 3 is Figure 2 a front view of a portion of the pitch changing mechanism and the remote counterweight phase control mechanism shown in

[0010] Figure 4 is Figure 2Stereogram of a part of the pitch change mechanism and the remote counterweight phase control mechanism shown in

[0011] Figure 5 is Figure 2 Another stereogram of a part of the pitch change mechanism and the remote counterweight phase control mechanism shown in

[0012] Figure 6 is a schematic diagram of an exemplary remote counterweight phase control mechanism;

[0013] Figure 7 is another schematic diagram of an exemplary remote counterweight phase control mechanism;

[0014] Figure 8 is another schematic diagram of an exemplary remote counterweight phase control mechanism;

[0015] Figure 9 is another schematic diagram of an exemplary remote counterweight phase control mechanism; and

[0016] Figure 10 is another schematic diagram of an exemplary remote counterweight phase control mechanism. Detailed Description

[0017] Reference will now be made in detail to embodiments of the present invention, one or more examples of which are illustrated in the accompanying drawings. Each example is provided by way of explanation of the present invention, and not as a limitation thereof. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the scope or spirit thereof. For example, features illustrated or described as part of one embodiment can be used with another embodiment to yield a further embodiment. Accordingly, it is an object of the present invention to cover such modifications and variations within the scope of the appended claims and their equivalents.

[0018] The term "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as more preferred or advantageous than other embodiments.

[0019] As used herein, the terms "first", "second", and "third" can be used interchangeably to distinguish one component from another, rather than to denote the position or importance of the respective components.

[0020] The terms "front" and "rear" refer to relative positions within a gas turbine engine or a vehicle, and refer to the normal operating attitude of the gas turbine engine or the vehicle. For example, with respect to a gas turbine engine, the front refers to a position closer to the engine inlet, and the rear refers to a position closer to the engine nozzle or exhaust port.

[0021] The terms "upstream" and "downstream" refer to the relative directions with respect to the fluid flow in a fluid path. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction towards which the fluid flows.

[0022] The terms "coupled", "fixed", "attached to", etc. refer to both direct coupling, fixing or attachment and indirect coupling, fixing or attachment through one or more intermediate components or features, unless otherwise specified herein.

[0023] The approximating language used throughout this specification and the claims is applied to modify any quantitative representation that can permit variation without resulting in a change in the basic function associated therewith. Thus, values modified by one or more terms (such as "about", "approximately" and "substantially") are not limited to the specified exact values. In at least some instances, the approximating language can correspond to the precision of the instrument used to measure the value, or the precision of the method or machine used to construct or manufacture the component and / or system. For example, the approximating language can refer to within a margin of 1%, 2%, 4%, 10%, 15% or 20%.

[0024] Herein and throughout the specification and the claims, range limitations are combined and interchanged, and such ranges are recognized and include all subranges subsumed therein, unless the context or language indicates otherwise. For example, all ranges disclosed herein include the endpoints, and the endpoints can be combined independently of each other.

[0025] Figure 1 A cross-sectional view of an exemplary turbofan aircraft engine 100 according to an embodiment suitable for use in the variable pitch fan system disclosed herein is depicted. Figure 1 A high bypass turbofan jet engine 100 is shown; however, it should be understood that the systems disclosed herein can be used in other turbine engines, such as turboprop engines and ducted fan engines.

[0026] As Figure 1 shown, the turbofan engine 100 defines an axial direction parallel to the longitudinal centerline 102 and a radial direction extending perpendicular to the axial direction. Generally, the turbofan 100 includes a fan section 104 and a core engine 106 disposed downstream of the fan section 104. The engine 100 also includes a gear assembly or power gearbox 136 having a plurality of gears for coupling a gas turbine shaft to a fan shaft. The position of the power gearbox 136 is not limited to the position shown in the exemplary embodiment of the turbofan 100. For example, the position of the power gearbox 136 can vary along the axial direction.

[0027] The exemplary core engine 106 described generally includes a generally tubular outer casing 108 that defines an annular inlet 110. The outer casing 108 surrounds, in serial flow relationship, a compressor section that includes a booster or low pressure (LP) compressor 112 and a high pressure (HP) compressor 114; a combustor section 116; a turbine section that includes a high pressure (HP) turbine 118 and a low pressure (LP) turbine 120; and an exhaust nozzle section 122. A high pressure (HP) shaft or spool 124 drivingly connects the HP turbine 118 to the HP compressor 114. A low pressure (LP) shaft or spool 126 drivingly connects the LP turbine 120 to the LP compressor 112. Additionally, the compressor section, the combustor section 116, and the turbine section together at least partially define a core air flow path extending therethrough.

[0028] Still referring to Figure 1 the exemplary embodiment of, the disk 132 is covered by a rotatable front nacelle 138 that has an aerodynamic profile to facilitate air flow through the plurality of fan blades 130. Additionally, the exemplary fan section 104 includes an annular fan housing or outer nacelle 140 that circumferentially surrounds the fan blades 130 and / or at least a portion of the core engine 106. In the described embodiment, the nacelle 140 is supported relative to the core engine 106 by a plurality of circumferentially spaced outlet guide vanes 142. Additionally, a downstream section of the nacelle 140 extends over an outer portion of the core engine 106 so as to define a bypass air flow passage 146 therebetween.

[0029] During operation of the turbofan engine 100, a volume of air 148 enters the turbofan 100 through the nacelle 140 and / or a related inlet of the fan section 104. When the volume of air 148 passes through the fan blades 130, a first portion 152 of the air is directed or routed to the bypass air flow passage 146, while a second portion 154 of the air is directed or routed to the LP compressor 112. The ratio between the first portion 152 of the air and the second portion 154 of the air is generally referred to as the bypass ratio. The pressure of the second portion 154 of the air is then increased as it is routed through the high pressure (HP) compressor 114 and into the combustor section 116, where it is mixed with fuel and burned to provide combustion gases 156.

[0030] The combustion gas 156 is routed through the HP turbine 118, where a portion of the thermal energy and / or kinetic energy is extracted from the combustion gas 156 via sequential stages of HP turbine stator vanes coupled to the outer casing 108 and HP turbine rotor blades coupled to the HP shaft or spool, thereby rotating the HP shaft or spool and supporting the operation of the HP compressor 114. The combustion gas 156 is then routed through the LP turbine 120, where a second portion of the thermal energy and kinetic energy is extracted from the combustion gas 156 via sequential stages of LP turbine stator vanes coupled to the outer casing and LP turbine rotor blades coupled to the LP shaft or spool, thereby rotating the LP shaft or spool and supporting the operation of the LP compressor 112 and / or the rotation of the fan blades 130.

[0031] The combustion gas 156 is then routed through the jet exhaust nozzle section 122 of the core engine 106 to provide propulsion thrust. At the same time, when a first portion 152 of the air is routed through the bypass air flow passage 146 before being discharged from the fan nozzle exhaust section 166 of the turbofan 100, the pressure of the first portion 152 of the air is greatly increased, also providing propulsion thrust. The HP turbine 118, the LP turbine 120, and the jet exhaust nozzle section 122 at least partially define a hot gas path for routing the combustion gas 156 through the core engine 106.

[0032] As Figure 1 shown, the fan section 104 includes a variable pitch fan having a plurality of fan blades coupled to the disk 132 in a spaced-apart manner. As shown, the fan blades 130 generally extend radially outward from the disk 132. Each fan blade 130 is rotatable relative to the disk 132 about a pitch axis P because the fan blade 130 is operatively coupled to a suitable actuating member 134 configured to collectively change the pitch of the fan blades 130. The fan blades 130, the disk 132, and the actuating member 134 can rotate together about the longitudinal axis 102 either directly through the LP shaft 126 or through a gear assembly (such as the gear assembly 136), which provides a speed change between a first shaft (such as the LP shaft 126) and a second shaft (such as the LP compressor shaft and / or the fan shaft).

[0033] Figure 2 Illustrated is a portion of the fan section that includes a pitch change mechanism and a remote balance phase control mechanism. As described above, pitch change includes an actuating member 134 that engages a plurality of trunnions 172, each trunnion being configured to hold a corresponding fan blade. Movement of the trunnions 172 changes the pitch of the associated fan blade.

[0034] The actuating member 134 can be any suitable type of actuator, including any electrical, mechanical, and / or hydraulic device. The actuating member 134 can operate to directly provide rotational motion, or a linear actuator can be used in conjunction with a suitable mechanism to convert its motion into a rotational output. For example, Figure 2 the actuating member 134 shown in Figure 2 can be a linear actuator that changes the pitch of the fan blades 130 by sliding forward and backward in the axial direction A, causing the fan blades to rotate together about the pitch axis P. The actuating member 134 can have a stationary portion 168 and a moving portion 170, and the moving portion 170 can move relative to the stationary portion 168 when a force (e.g., via hydraulic fluid) is applied to the moving portion 170.

[0035] As Figure 2-5 shown, a plurality of counterweights 174 can be axially spaced from the trunnions 172 to counteract the centrifugal torsional moment of the fan blades. The counterweights 174 can be any high-density mass that can rotate about the counterweight (CW) centerline 176. The counterweights 174 can have an offset mass that is movable relative to the CW centerline 176. In other words, the center of mass (CM) of each counterweight 174 is not coaxial with the CW centerline. It should be understood that the offset mass can take any suitable shape. For example, in some embodiments, the offset mass can be formed by a mass positioned at the end of a rod, such as a spherical or other suitable shaped mass.

[0036] Figure 3 FIG. illustrates a front view of a portion of an exemplary remote counterweight phase control system. As Figure 3 shown, corresponding counterweights 174 are associated with respective trunnions 172.

[0037] Referring again to Figure 2 , each counterweight 174 can include a counterweight (CW) gear 178 that engages the respective trunnion 172 via a first coordinating ring gear 180. When the trunnion 172 rotates, a first gear engagement 182 between the surface of the trunnion 172 and the first coordinating ring gear 180 causes the first coordinating ring gear 180 to engage and rotate the CW gear 178 via a second gear engagement 184 therebetween. As the CW gear 178 rotates, the counterweight 174 associated with the CW gear 178 also rotates, thereby changing the position of the counterweight relative to the CW centerline 176.

[0038] In Figure 2 , for increased safety and reliability, a second coordinating ring gear 186 is provided radially outward from the CW gear 178. For example, as Figure 3 and Figure 4As shown, the second coordinated ring gear 186 is an external ring gear that extends around all of the CW gears 178 and engages the CW gears 178 to provide a redundant feature to ensure that the phases of the counterweights remain in sync.

[0039] In some embodiments, the second coordinated ring gear 186 is not driven or loaded. Thus, during normal operation, it will simply move with the assembly. However, if a gear failure occurs or one of the counterweights otherwise loses connection to the designed load path, the second coordinated ring gear 186 can react to the load from that counterweight and prevent it from getting out of phase with the other counterweights.

[0040] Figure 3 A front view of multiple counterweights 174 is shown, with the trunnions and associated structures removed for clarity. As Figure 3 shown, both the first coordinated ring gear 180 and the second coordinated ring gear 186 engage the CW gears 178 of the respective counterweights 174. The first coordinated ring gear 180 is an internal ring gear whose outer gear surface engages the outer gear surface of the CW gears 178, while the second coordinated ring gear 186 is an external ring gear whose inner gear surface also engages the outer gear surface of the CW gears 178.

[0041] Figure 4 and Figure 5 are front perspective views of parts of an exemplary remote counterweight phase control system. As Figure 4 shown, the counterweight mounting fixture 188 engages the counterweight shaft 190 to maintain the axial orientation of the counterweight 172 as the counterweight 172 rotates about the CW centerline 176. Figure 5 is the same view as Figure 4 but with the counterweight mounting fixture 188 removed for clarity. As Figure 5 shown, in this embodiment, the counterweight shaft 190 can be hollow so that the corresponding pins of the counterweight mounting fixture 188 can extend into the shaft 190.

[0042] Figure 6 is a schematic view of the remote counterweight phase control system 100, as described above with respect to Figure 2-5 As Figure 6As shown and discussed above, each trunnion 172 engages a first coordinated ring gear 180, which in turn engages a CW gear 178 to rotate the counterweight shaft 190 and its corresponding counterweight 174 about the CW centerline 176. Thus, during normal operation, the actuating member rotates the trunnion (and associated fan blade) about the pitch axis P. At the same time, movement of the trunnion causes the first coordinated ring gear 180 to rotate the corresponding counterweight 174 to the desired position. In the event of a failure of the actuating member, the counterweight can provide a reaction force to drive the blade to the desired safe pitch angle.

[0043] Figure 7 is a schematic view of an alternative embodiment of the remote counterweight phasing control system 200. In Figure 7 this embodiment, each trunnion 272 engages a first coordinated ring gear 280, which in turn engages a CW gear 278 to rotate the counterweight shaft 290 and its corresponding counterweight 274 about the CW centerline 276. A second coordinated ring gear 286 is provided in front of the first coordinated ring gear 280. Thus, instead of being at least partially concentric with the first coordinated ring gear 280, the second coordinated ring gear 286 does not overlap the first coordinated ring gear 280 and is axially spaced from the first coordinated ring gear 280. To facilitate this arrangement, a second redundant CW gear 278 is provided at the front end of the counterweight shaft 290. As in the Figure 6 embodiment shown, the second coordinated ring gear provides additional safety protection in the event of a gear failure by ensuring that the counterweight 274 remains in phase.

[0044] Figure 8 is a schematic view of an alternative embodiment of the remote counterweight phasing control system 300. In Figure 8 this embodiment, each trunnion 372 engages a first coordinated ring gear 380, which in turn engages a CW gear 378 to rotate the counterweight shaft 390 and its corresponding counterweight 374 about the CW centerline 376. However, in addition to this, the second coordinated ring gear 386 is concentric with the first coordinated ring gear 380. The second coordinated ring gear 386, like the first coordinated ring gear 380, has a gear engagement with the trunnion 372. Thus, both the first coordinated ring gear 380 and the second coordinated ring gear 386 are driven by the trunnion, providing a redundant gear system to provide additional safety protection in the event of a gear failure.

[0045] Figure 9 is a schematic view of an alternative embodiment of the remote counterweight phasing control system 400. In Figure 9In [the situation], the CW gear 478 directly engages with each corresponding trunnion 472, causing the counterweight shaft 490 and its corresponding counterweight 474 to rotate about the CW centerline 476. One or more coordinating ring gears 486 can be provided and engage with the CW gear 478 or a second CW gear 478 positioned forward. In this embodiment, by ensuring that the counterweights 474 remain in phase, one (or two) coordinating ring gears 486 can be used to provide additional safety protection in the event of a failure.

[0046] Figure 10 is a schematic view of an alternative embodiment of the remote counterweight phase control system 500. In Figure 10 [the situation], each trunnion 572 engages with a first coordinating ring gear 580, which in turn engages with the CW gear 578, causing the counterweight shaft 590 and its corresponding counterweight 574 to rotate about the CW centerline 576. However, in addition to this, each second coordinating ring member 586 can be provided to engage with a pin 591 axially extending from the corresponding CW gear 578. Thus, instead of gear meshing, the second coordinating ring member 586 can facilitate maintaining the phase synchronization of each counterweight through a mechanical connection of the pin 591 with a corresponding slot in the second coordinating ring member 586.

[0047] Although certain embodiments described herein may refer to forward or rearward directions, it should be understood that these directions can be reversed. For example, the second coordinating ring member in the embodiments described herein can be behind or in front of the first coordinating ring member, and the associated figures should be interpreted as disclosing either arrangement.

[0048] This written description uses examples to disclose the invention, including the best mode, and also enables any person skilled in the art to practice the invention, including making and using any device or system and performing any incorporated method. The patentable scope of the invention is defined by the claims and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that are identical to the literal language of the claims or if they include equivalent structural elements that are not materially different from the literal language of the claims.

[0049] A further aspect of the invention is provided by the subject matter of the following clauses:

[0050] 1. A variable pitch fan assembly includes a plurality of trunnions, each trunnion having a first trunnion gear surface; a plurality of counterweight assemblies, each counterweight assembly including a counterweight, a counterweight shaft, and a first counterweight gear having a first counterweight gear surface; a first coordinating ring gear having a first gear surface engaging the first trunnion gear surface and a second gear surface engaging the first counterweight gear surface; and a second coordinating ring gear having a third gear surface engaging the first counterweight gear surface.

[0051] 2. The variable pitch fan assembly according to any of the preceding clauses, wherein each of the counterweight assemblies includes a counterweight centerline about which the counterweight rotates, and the mass of each counterweight is offset relative to the counterweight centerline.

[0052] 3. The variable pitch fan assembly according to any of the preceding clauses, further comprising an actuating member configured to rotate each of the plurality of trunnions about a pitch axis associated with each of the plurality of trunnions.

[0053] 4. The variable pitch fan assembly according to any of the preceding clauses, wherein at least a portion of the second coordinating ring gear axially overlaps the first coordinating ring gear.

[0054] 5. The variable pitch fan assembly according to any of the preceding clauses, wherein the second coordinating ring gear does not axially overlap the first coordinating ring gear.

[0055] 6. The variable pitch fan assembly according to any of the preceding clauses, wherein each of the plurality of counterweight assemblies further includes a second counterweight gear having a second counterweight gear surface.

[0056] 7. The variable pitch fan assembly according to any of the preceding clauses, wherein the counterweight and the first counterweight gear of the respective counterweight assembly of the plurality of counterweight assemblies are fixedly coupled to the respective counterweight shaft such that rotation of the first counterweight gear causes the counterweight to rotate about its respective counterweight centerline.

[0057] 8. The variable pitch fan assembly according to any of the preceding clauses, wherein the first counterweight gear and the second counterweight gear of the plurality of counterweight assemblies are fixedly coupled to the respective counterweight shafts.

[0058] 9. The variable pitch fan assembly according to any of the preceding clauses, each trunnion having a second trunnion gear surface, wherein the third gear surface of the second coordinating ring gear engages the second trunnion gear surface.

[0059] 10. A variable pitch fan assembly, comprising: a plurality of trunnions, each trunnion having a first trunnion gear surface; a plurality of counterweight assemblies, each counterweight assembly including a counterweight, a counterweight shaft, and a first counterweight gear having a first counterweight gear surface; and a first coordinating ring gear having a first gear surface engaging the first counterweight gear surface; wherein the first trunnion gear surface engages the first counterweight gear surface.

[0060] 11. The variable pitch fan assembly according to any of the preceding clauses, further comprising a second coordinating ring gear having a second gear surface, and a second counterweight gear associated with each counterweight assembly, each said second counterweight gear having a second counterweight gear surface, wherein the second coordinating ring gear engages the second counterweight gear surface of the second counterweight gear.

[0061] 12. The variable pitch fan assembly according to any of the preceding clauses, further comprising an actuating member configured to rotate each of the plurality of trunnions about a pitch axis associated with each of the plurality of trunnions, wherein each counterweight assembly includes a counterweight centerline about which the counterweight rotates, and the mass of the counterweight is offset relative to the counterweight centerline.

[0062] 13. A variable pitch fan assembly, comprising: a plurality of trunnion assemblies, each trunnion having a first trunnion gear surface; an actuating member configured to rotate each of the plurality of trunnions about a pitch axis associated with each of the plurality of trunnions; a plurality of counterweight assemblies, each counterweight assembly including a counterweight that is an offset mass rotatable about a counterweight centerline and coupled to a first counterweight gear having a first counterweight gear surface, the plurality of counterweight assemblies being configured to move synchronously with respect to their respective counterweight centerlines; a first coordinating ring gear having a first gear surface engaging the first trunnion gear surface and a second gear surface engaging the first counterweight gear surface; and a second coordinating ring member that limits asynchronous movement of the counterweights relative to each other, the second coordinating ring member extending radially outward from the first coordinating ring gear.

[0063] 14. The variable pitch fan assembly according to any of the preceding clauses, wherein the second coordinating ring member includes a ring gear that at least partially axially overlaps the first coordinating ring gear.

[0064] 15. The variable pitch fan assembly according to any of the preceding clauses, wherein the second coordinating ring member is axially non-overlapping with the first coordinating ring gear.

[0065] 16. A variable pitch fan assembly according to any of the preceding clauses, wherein each counterweight gear includes an axially extending portion, and the second coordinated annular member includes a plurality of guide slots that receive at least a portion of the axially extending portion of the counterweight gear.

[0066] 17. A variable pitch fan assembly according to any of the preceding clauses, wherein each counterweight assembly of the plurality of counterweight assemblies further includes a second counterweight gear having a second counterweight gear surface.

[0067] 18. A variable pitch fan assembly according to any of the preceding clauses, wherein the counterweight and the first counterweight gear are fixedly coupled to a respective counterweight shaft such that rotation of the first counterweight gear causes the counterweight to rotate about its respective counterweight centerline.

[0068] 19. A variable pitch fan assembly according to any of the preceding clauses, further including a second counterweight gear coupled to each counterweight shaft, wherein the second coordinated annular member engages the second counterweight gear to maintain the phase relationship of the counterweight relative to its respective counterweight centerline.

[0069] 20. A variable pitch fan assembly according to any of the preceding clauses, wherein each trunnion has a second trunnion gear surface, and a third gear surface of the second coordinated annular member engages the second trunnion gear surface.

Claims

1. A variable pitch fan assembly, characterized in that, comprising: a plurality of trunnions, each trunnion having a first trunnion gear surface; a plurality of counterweight assemblies, each counterweight assembly including a counterweight, a counterweight shaft, and a first counterweight gear having a first counterweight gear surface; a first coordinating ring gear having a first gear surface engaging the first trunnion gear surface and a second gear surface engaging the first counterweight gear surface; and a second coordinating ring gear having a third gear surface engaging the first counterweight gear surface.

2. The variable pitch fan assembly according to claim 1, characterized in that, wherein each of the counterweight assemblies includes a counterweight centerline about which the counterweight rotates, and the mass of each counterweight is offset relative to the counterweight centerline.

3. The variable pitch fan assembly according to claim 1, characterized in that, further comprising an actuating member configured to rotate each of the plurality of trunnions about a pitch axis associated with each of the plurality of trunnions.

4. The variable pitch fan assembly according to claim 1, characterized in that, wherein at least a portion of the second coordinating ring gear axially overlaps the first coordinating ring gear.

5. The variable pitch fan assembly according to claim 1, characterized in that, wherein the second coordinating ring gear does not axially overlap the first coordinating ring gear.

6. The variable pitch fan assembly according to claim 5, characterized in that, wherein each of the plurality of counterweight assemblies further includes a second counterweight gear having a second counterweight gear surface.

7. The variable pitch fan assembly according to claim 2, characterized in that, wherein the counterweight and the first counterweight gear of the respective counterweight assembly of the plurality of counterweight assemblies are fixedly coupled to the respective counterweight shaft such that rotation of the first counterweight gear causes the counterweight to rotate about its respective counterweight centerline.

8. The variable pitch fan assembly according to claim 6, characterized in that, wherein the first counterweight gear and the second counterweight gear of the plurality of counterweight assemblies are fixedly coupled to the respective counterweight shafts.

9. The variable pitch fan assembly according to claim 1, characterized in that, each trunnion has a second trunnion gear surface, wherein the third gear surface of the second coordinating ring gear engages the second trunnion gear surface.

10. A variable pitch fan assembly, characterized in that, comprising: a plurality of trunnions, each trunnion having a first trunnion gear surface: a plurality of counterweight assemblies, each counterweight assembly including a counterweight, a counterweight shaft, and a first counterweight gear having a first counterweight gear surface; and a first coordinating ring gear having a first gear surface engaging the first counterweight gear surface; wherein, the first trunnion gear surface engages the first counterweight gear surface.

11. The variable pitch fan assembly according to claim 10, characterized in that, Further comprising a second coordinated ring gear having a second gear surface, and a second counterweight gear associated with each counterweight assembly, each said second counterweight gear having a second counterweight gear surface, wherein the second coordinated ring gear engages the second counterweight gear surface of the second counterweight gear.

12. The variable pitch fan assembly according to claim 10, wherein, further comprising an actuating member configured to rotate each of the plurality of trunnions about a pitch axis associated with each of the plurality of trunnions, wherein each counterweight assembly includes a counterweight centerline about which the counterweight rotates, and the mass of the counterweight is offset relative to the counterweight centerline.

13. A variable pitch fan assembly, wherein, comprising: a plurality of trunnion assemblies, each trunnion having a first trunnion gear surface; an actuating member configured to rotate each of the plurality of trunnions about a pitch axis associated with each of the plurality of trunnions; a plurality of counterweight assemblies, each counterweight assembly including a counterweight that is an offset mass rotatable about a counterweight centerline and coupled to a first counterweight gear having a first counterweight gear surface, the plurality of counterweight assemblies being configured to move synchronously with respect to their respective counterweight centerlines; a first coordinated ring gear having a first gear surface that engages the first trunnion gear surface and a second gear surface that engages the first counterweight gear surface; and a second coordinated ring member that limits asynchronous movement of the counterweights relative to each other, the second coordinated ring member extending radially outward from the first coordinated ring gear.

14. The variable pitch fan assembly according to claim 13, wherein, wherein the second coordinated ring member includes a ring gear that at least partially axially overlaps the first coordinated ring gear.

15. The variable pitch fan assembly according to claim 13, wherein, wherein the second coordinated ring member is axially non-overlapping with the first coordinated ring gear.

16. The variable pitch fan assembly according to claim 13, wherein, wherein each counterweight gear includes an axially extending portion, and the second coordinated ring member includes a plurality of guide slots that receive at least a portion of the axially extending portion of the counterweight gear.

17. The variable pitch fan assembly according to claim 13, wherein, wherein each of the plurality of counterweight assemblies further includes a second counterweight gear having a second counterweight gear surface.

18. The variable pitch fan assembly according to claim 13, wherein, wherein the counterweight and the first counterweight gear are fixedly coupled to a respective counterweight shaft such that rotation of the first counterweight gear causes the counterweight to rotate about its respective counterweight centerline.

19. The variable pitch fan assembly according to claim 18, wherein, Further includes a second counterweight gear coupled to each counterweight shaft, wherein the second coordinated annular member engages the second counterweight gear to maintain the phase relationship of the counterweight relative to its respective counterweight centerline.

20. The variable pitch fan assembly according to claim 13, wherein, each trunnion has a second trunnion gear surface, and a third gear surface of the second coordinated annular member engages the second trunnion gear surface.

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