Abstract:
An aircraft is equipped with a spinnion coupling an inboard wing to a tilting nacelle. The spinnion is advantageously configured to extend across the nacelle from an inboard junction to an outboard junction, and terminates inside the inboard wing. This provides an efficient lightweight structure to support a nacelle and facilitate tilting of the nacelle. The spinnion, which can be configured to be at least partially disposed within the inboard wing, is advantageously concentric with the tilting axis in order to facilitate tilting of a nacelle. A cross-wing driveshaft can be included, disposed at least partly within the inboard wing, and can advantageously be configured to terminate inside the spinnion at a junction with a miter gearbox. The miter gearbox can be disposed at least partly within the spinnion but more preferably lies entirely within the spinnion, and functions to transfer power from an input shaft to the cross-wing driveshaft.

Description:
[0001]    This application claims priority to U.S. Provisional Application Ser. No. 61/047853 filed Apr. 25, 2008 which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The field of the invention is rotorcraft 
       BACKGROUND 
       [0003]    Tiltrotor aircraft are known in the prior art, including the Bell™ XV-3, XV-15, V-22, and BA609. Tiltrotor and tiltwing aircraft convert between a forward flight cruise mode and a hover mode by changing the orientation of their propellers or rotors and nacelles. Tilting of the nacelle or wing typically occurs about a pivot point commonly called the conversion spindle. The spindle is usually a circular pivot attached to the rotating structure (i.e. wing or nacelle) and inserted into the non-rotating fuselage or wing of the aircraft. For increased redundancy and reliability, the engine driving a rotor on one side of the aircraft is usually configured to have the capability of driving the rotor on the other side of the aircraft by linking the two propulsion systems with what is commonly termed a cross-wing driveshaft. This shaft runs from one propulsion and gearbox system across the wing and into another rotor gearbox and propulsion system. As this driveshaft leaves the wing and enters the nacelle and gearbox of a tilting nacelle it passes through the center of the tilting pivot so that it is not interrupted by the tilting motion. As used herein, a component that rotates can complete an entire revolution about an axis, while a component that tilts can only rotate through a portion of a complete revolution. 
         [0004]      FIG. 1  shows a typical prior art tiltrotor aircraft  100  comprising a wing  102  and fuselage  104  with a first tilting rotor system  110  comprising a first rotor blade  112  and first nacelle  118  in aircraft cruise mode corresponding with a generally horizontal position of the nacelle  118 . The aircraft is also equipped with a second tilting rotor system  120  on the opposite end of the wing  102 . The second rotor system  120  is depicted in conversion from a horizontal position consistent with aircraft cruise mode to a vertical position consistent with helicopter mode. In practice, nacelles  118 ,  128  on either side of the aircraft in prior art tiltrotors have a substantially identical tilt angle. The tilt angle  136  of a nacelle  128  is the angle  136  between the tilting nacelle axis  138  and the aircraft axis  134 . In a typical tilt rotor aircraft  100 , the nacelle  104  is also capable of operation in a generally vertical position used in helicopter mode flight. The nacelle  128  tilt angle  136  is usually affected using a tilt actuator and mechanism to convert from helicopter mode flight to aircraft cruise mode. A cross-shaft  106  is disposed within the wing  102  and runs between left and right nacelles  118 ,  128 . 
         [0005]    The article “Fail safety aspects of the V-22 pylon conversion actuator” by Duane Hicks published in 1992 summarizes the state of prior art tiltrotor conversion mechanisms. Prior art  FIG. 2  is a top view schematic of the Bell™ V-22 tilting system  200  including conversion mechanism, nacelle  218 , and wing  202 . An engine and gearbox  238  drive a rotor hub  230  coupled to a mast  236  by means of a gimbal  232 . A pitchable blade  234  is coupled to the hub  230 . 
         [0006]    The nacelle  218  and rotor hub  230  pivot as a system about the conversion axis  256 . The conversion spindle  250  is aligned and centered on the conversion axis  256 . The conversion spindle  250  is supported at two locations, a first inboard bearing  252  carried by the wing  202  and a second outboard bearing  254  also carried by the wing, in order to cantilever the nacelle from the wing. An actuator  240  connected to an actuator spindle  242  aligned with an actuator spindle axis  244  provides motive force to tilt to tilt the nacelle  218  and rotor about the conversion axis  256 . The input to the cross-wing driveshaft  260  enters a miter gearbox  262  that converts motion on the miter gearbox axis  264  to the conversion axis  256 . The tilting split line  208  is shown as a dashed line. 
         [0007]    In the V-22 and other known tiltrotors, the conversion spindle  250  acts as a tunnel between the wing  202  and nacelle  218 , through which the cross-wing driveshaft  266  passes. In prior art configurations, the conversion spindle  250  is attached to the nacelle  218  through nacelle structure and a support  254  on the inboard side wall (where inboard is defined as the fuselage side at a parting plane at the rotor rotation axis). This leaves the cross-wing shaft  266  exposed inside the nacelle but outside of the conversion spindle  250 . This configuration cantilevers the nacelle  218  on the spindle  250 , transferring any bending in the spindle  250  into the nacelle frame at the inboard support  254 . A bending load in the spindle  250  can be produced in either forward flight mode or helicopter mode. In forward flight mode, the torque reaction to the rotor and rotor hub  230  induces a bending load on the conversion spindle  250 . Lift and drag forces on the nacelle  218  also contribute to this load. In hover, bending is induced in the conversion spindle  250  through the vertical lift generated by the rotor and rotor hub  230  and any lateral thrust vectoring of the rotor thrust. 
         [0008]    Prior art tiltrotor aircraft mentioned herein operate with what is termed “gimbaled” or “hinged” rotor systems. That is, their rotors are allowed to tilt about an axis at the hub to nacelle or blade to hub interface, but their masts remain stationary with respect to the non-rotating structure. This hinging means that although the rotors transmit a substantial thrust load, they transmit only small moments from the rotor to the aircraft structure. 
         [0009]    A tiltrotor with a hingeless rotor would be able to produce large rotor moments that create operational advantages over traditional tiltrotors. These large moments could easily exceed the moment capability of a traditional conversion spindle. For example, a stiff hingeless rotor such as an Optimum Speed Tilt Rotor (OSTR) as described in U.S. Pat. No. 6,641,365 would provide the increased rotor moment capability of the hingeless rotor and the increased torque output of a large and lightweight rotor. Additionally, it is now appreciated that a wing section outboard of the nacelle (see Tilt Outboard Wing For Tilt Rotor Aircraft, U.S. patent application Ser. No. 11/505,025) can increase the aircraft cruise efficiency but will substantially increase the bending loads through the spindle. These combined loads dramatically increase the applied bending transmitted to the conversion spindle both in hover and airplane flight modes. 
         [0010]    The &#39;365 patent and the &#39;025 application, and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. 
         [0011]    In airborne vehicles, weight is usually critical to the viability of the vehicle. Thus, in designing the attachment structure between the nacelle and wing, designers of the prior art have typically opted for the lowest loading configuration. To this end, the concept of outboard wings on tilt rotor aircraft has been largely ignored due to the high bending moments that applied to the conversion spindle. Conversion spindles in the prior art are short, ending at the first inboard wall of the nacelle and not continuing through to a second interface. In a lightly loaded case, the increased cantilevered load that this configuration transmits to the nacelle is minimal. The implementation of a hingeless rotor vehicle configuration presents benefits and challenges in this area. 
         [0012]    Thus, there is still a need for a system that provides (a) a conversion spindle capable of high moment loading in a tiltrotor aircraft, and (b) an integral structural support for an outboard wing, while minimizing weight of the support. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention provides apparatus, systems and methods in which an aircraft is equipped with a spinnion coupling an inboard wing to a tilting nacelle. The spinnion is advantageously configured to extend across the nacelle from an inboard junction to an outboard junction, and terminates inside the inboard wing. This provides an efficient lightweight structure to support a nacelle and facilitate tilting of the nacelle. 
         [0014]    The tilting of the nacelle relative to the inboard wing defines a tilting axis. The spinnion, which can be configured to be at least partially disposed within the inboard wing, is advantageously concentric with the tilting axis in order to facilitate tilting of a nacelle. In applications where an aircraft has more than one nacelle, a cross-wing driveshaft may transfer power from one nacelle to another. The cross-wing driveshaft can be disposed at least partly within the inboard wing, and can advantageously be configured to terminate inside the spinnion at a junction with a miter gearbox. The miter gearbox can be disposed at least partly within the spinnion but more preferably lies entirely within the spinnion, and functions to transfer power from an input shaft to the cross-wing driveshaft. 
         [0015]    A rotorcraft such as a tiltrotor can be equipped with a hingeless rotor carried by a nacelle, the rotor having a rotation axis, wherein the tilting axis may or may not be orthogonal to the rotor rotation axis. In more preferred aircraft, an outboard wing can advantageously be coupled to the nacelle by means of the spinnion. In especially preferred embodiments, the spinnion can serve as the primary structural support for the outboard wing, and can extend from the inboard wing through the nacelle to the outboard wing. When the spinnion serves as a support for the outboard wing, the spinnion can be constructed with a kink so that it is be entirely linear; this allows it to pass through the thickest portion of the outboard wing. 
         [0016]    Viewed from another perspective, an aircraft having an inboard wing and a rotor carried by a tilting nacelle is subject to loads produced by both the rotor and the nacelle. Such an aircraft can advantageously be configured with a spinnion that extends from the inboard wing, across an inboard load-carrying junction of the nacelle to an outboard load-carrying junction of the nacelle, such that a subset of the loads is introduced into the spinnion at the inboard junction. 
         [0017]    In more preferred embodiments, a second portion of the loads can be introduced into the spinnion at the outboard junction. In especially preferred embodiments, the aircraft can be configured with an outboard wing that is cantilevered off the nacelle, and wherein the spinnion provides a primary structural support for the outboard wing. The outboard wing can advantageously be configured to tilt with the tilting nacelle. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0018]      FIG. 1  shows a typical prior art tiltrotor aircraft. 
           [0019]      FIG. 2  is a top view schematic of a prior art tilting system. 
           [0020]      FIG. 3  is a schematic top view illustration of a preferred tiltrotor aircraft. 
           [0021]      FIG. 4  is a perspective illustration of a portion of a preferred tiltrotor aircraft including a spinnion. 
           [0022]      FIG. 5  is perspective illustration of an alternate preferred spinnion and aircraft structure. 
           [0023]      FIG. 6  is an illustration showing the details of an interface between a spinnion and a miter gearbox. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The present invention provides apparatus, systems and methods in which a conversion spindle disposed at least partially within an inboard wing extends across a nacelle to an outboard junction. As used herein, the resulting integrated structure is termed a “spinnion”. 
         [0025]      FIG. 3  is a schematic top view illustration of a preferred tiltrotor aircraft  300 . The aircraft comprises a fuselage  302 , inboard wing  304 , first rotor system  310 , and second rotor system  320 . The second rotor system  320  is shown in a vertical orientation, consistent with helicopter-mode flight. The first rotor system  310  is shown in a horizontal orientation, consistent with airplane-mode cruise flight. In practice, the first rotor system  310  and second rotor system  320  are likely to have a substantially similar orientation at any given time in flight. An outboard wing  306  tilts with the nacelle  312 . 
         [0026]    A first rotor system  310  comprises a hub  314  coupled to a tilting nacelle  312 , which tilts with respect to the wing  304 . A rotor blade  316  is coupled to the rotor hub  314 . An engine  350  is preferably disposed within the tilting nacelle  312  and is coupled to a shifting gearbox  370 . The shifting gearbox is coupled to a numerical reduction ratio reduction gearbox  380 . The reduction gearbox  380  is coupled to and drives the rotor hub  314 . A miter gearbox  360  is also coupled to the shifting gearbox  370  as well as a cross-wing driveshaft  362 . The cross-wing driveshaft  362  is preferably disposed within the wing  304  and distal ends of the cross-wing driveshaft  362  are preferably coupled by a mid-wing gearbox  364 . The cross-wing driveshaft  362  serves to transmit power from an engine  350  in a tilting nacelle  312  to a second rotor system  320  on the opposite side of the aircraft  300 . 
         [0027]    In preferred configurations, the miter gearbox  360  is disposed within a spinnion  390 , which also serves as a spar and support for both the outboard wing  306  and tilting nacelle  312 . The cross-wing driveshaft  362  terminates inside the spinnion  390  at an interface with the miter gearbox  360 . 
         [0028]      FIG. 4  is a perspective illustration of a portion of a preferred tiltrotor aircraft that comprises an inboard wing  402  (inboard of the rotor rotation axis  472 ) that carries a tilting nacelle  412  that defines a tilting axis  474  relative to the inboard wing  402 . A spinnion  490  is at least partially disposed within the inboard wing  402 , and a cross-shaft  462  having a gearbox  460  is at least partially disposed within the spinnion  490 . The aircraft has a tilting axis  474  that can be orthogonal to the rotor rotation axis  472 . 
         [0029]    In more preferred embodiments, the gearbox  460  is completely disposed within the spinnion, the aircraft further comprises an outboard wing  406 , and the spinnion  490  extends into the outboard wing  406 . In that manner a first portion of the loads is introduced into the spinnion  490  at an inboard junction, and a second portion of the loads are introduced into the spinnion at an outboard junction. It can further be seen that the inboard junction is on the inboard side of the rotor rotation axis while the outboard junction is on the outboard side of the rotor rotation axis. 
         [0030]    The specific angle between the tilting axis and the rotor rotation axis is regarded as a design choice. Accordingly,  FIG. 4  should be interpreted generically as including both alternatives (a) where the tilting axis is orthogonal to the rotor rotation axis and (b) where the tilting axis is not orthogonal to the rotor rotation axis. 
         [0031]      FIG. 5  is another perspective illustration of an alternate preferred spinnion and aircraft structure. An inboard wing  502  is coupled to a tilting nacelle  512  and an outboard wing  506  that tilts with the nacelle  512 . The nacelle  512  carries a rotor comprising a spinner  514  and rotor blade  516 . The rotor rotates about a rotor rotation axis  572  in the manner indicated by arrow  576 . The rotor and nacelle  512  tilts about a tilting axis  574  relative to the inboard wing  502 . In some preferred embodiments, and as shown in  FIG. 5 , the tilting axis  574  is orthogonal to the rotor rotational axis  572 . In other embodiments (as in  FIG. 3 ), the tilting axis might not be orthogonal to the rotor rotational axis. 
         [0032]    A spinnion  590  runs between the inboard wing  502  and extends into the outboard wing  506  through the nacelle  512 . The spinnion is at least partly disposed within the inboard wing. A miter gearbox  560  is at least partially and more preferably completely disposed within the spinnion  590 . In some preferred embodiments, and as shown in  FIG. 5 , the spinnion  590  is not entirely linear from the inboard wing  502  to the outboard wing  506 , and may have a kink or bend in it. 
         [0033]    From examination of  FIG. 5 , it may be seen that the spinnion  590  extends across the nacelle  512 . The nacelle  512  has an inboard load-carrying junction  530  with the spinnion  590 , which may comprise a bearing. The nacelle also has an outboard load-carrying junction  532  with the spinnion  590 . The spinnion  590  can advantageously have a cutout to allow a cross-wing input shaft  564  to interface with a miter gearbox  560  disposed within the spinnion  590 , the miter gearbox  560  also interfacing with a cross-wing driveshaft. Some embodiments may have a support bearing  524  inboard of the inboard load-carrying junction  530  which can also carry some loads. The support bearing  524  can be carried by a wing rib  522 . 
         [0034]    Both the rotor, comprising a rotor blade  516 , and the outboard wing  506  produce loads. It is contemplated that for a tiltrotor aircraft with a hingeless rotor, the rotor might produce mast moments of 100000, 300000, or even 600000 pounds that can be transferred to the nacelle  512  and spinnion. Likewise, the outboard wing  506  might produce lift of 5000, 10000, or even 15000 pounds which are transferred to the spinnion. One skilled in the art will appreciate that a first subset of the total loads carried by the spinnion  590  is introduced at the inboard junction  530 , while a second subset of the total loads is introduced at the outboard junction  532 . 
         [0035]    Unless a contrary intent is apparent from the context, all ranges recited herein are inclusive of their endpoints, and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary. 
         [0036]    The outboard wing  506  is seen to be cantilevered off the nacelle  512 , and the primary support spar of the outboard wing  506  can advantageously be configured to be the spinnion  590 . In preferred embodiments, the outboard wing structural spar which is the spinnion  590  runs through the thickest portion of the outboard wing  506 , which is intended to maximize the effectiveness of the spar material. Those skilled in the art will appreciate that the spinnion need not be entirely linear from the inboard wing to the outboard wing. 
         [0037]    Those skilled in the art will also appreciate that there is a discontinuity between the position of the cross-wing driveshaft and the desired position of the outboard wing spar. In order to integrate the conversion spindle with the outboard wing spar structure, the outboard wing is staggered slightly behind the inboard wing, allowing the two structures to coincide, and thus be integrated into a spinnion. 
         [0038]    In preferred embodiments, the spinnion extends not only from the inboard wing, and across to a cantilevered outboard load-carrying junction of the nacelle, but also into an outboard wing. In the outboard wing, the spinnion acts as a primary structural support. 
         [0039]      FIG. 6  is an illustration showing the details of an interface  600  between a spinnion  610  and a miter gearbox  620 . Because the spinnion continues across the nacelle  602 , the miter gearbox  620  can be advantageously encased within the spinnion  610 . In such a configuration, the shaft exit of the gearbox interrupts the spinnion structure. The miter gearbox  620  must convert motion and input torque from a miter gearbox input shaft  624  to a cross-wing driveshaft  622 . Such conversion can require an angle change of 70, 80, 90, 110, or even 110°, and can advantageously be achieved using a bevel gear  626 . 
         [0040]    In preferred embodiments, the spinnion  610  is constructed of carbon composite. An interface for the cross-wing driveshaft  622  and the miter gearbox input shaft  624  is accommodated by creating a cutout  612  in the spinnion  610 . In especially preferred embodiments, this interface occurs on the side web of the spinnion structure, leaving the high strength composite caps at the top and bottom of the spinnion  610  intact. The web laminate (which consists primarily of biased plies) is cut out, and a titanium bolted fitting and bulkhead  630  are installed. The resulting titanium bulkhead  630  acts as both the mounting face for the miter gearbox  620  and the shear carrying web of the spinnion  610  in the area of the cutout  612 . The titanium fittings attaching the nacelle to the spinnion are also shown. 
         [0041]    The nacelle  602  is also equipped with an inboard load-carrying junction  616  with the spinnion  610  as well as an outboard load-carrying junction  614 . The total loads carried by the spinnion  610  are transferred through these junctions  614 ,  616 . In some preferred embodiments, these junctions  614 ,  616  may be constructed of a different material than the spinnion. For example, the junctions can be constructed of titanium and the spinnion can be of carbon composite construction. 
         [0042]    Methods are also contemplated herein for using moment loads to directionally control an aircraft having a hingeless rotor supported by a nacelle. Preferred methods comprise providing a spinnion that extends between an inboard wing and the nacelle, and using the spinnion to transfer moment loads produced by the rotor to the inboard wing. Especially preferred methods comprise extending the spinnion to an outboard junction of the nacelle, providing an outboard wing that tilts with the nacelle, and extending the spinnion into the outboard wing. In such methods the spinnion would be used to transfer moment loads produced by the outboard wing to the inboard wing. 
         [0043]    Thus, specific embodiments and applications of a tilt conversion spindle and integral spar have been disclosed. It should be apparent, however, to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.