Patent Publication Number: US-7708325-B2

Title: Systems and methods for rotation of objects

Description:
This invention was made with United States, Government support under Contract No. N00019-03-C-0063. The Government has certain rights in this invention. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates generally to rotation of objects, and more particularly to rotation of an object having a suspended center of gravity that lies within the rotation axis area of the object. 
   2. Description of the Related Art 
   Often times it is desirable to lift and rotate large pieces of equipment to gain access to all sides of the equipment In this regard, handling systems have been developed that lift and rotate objects such as rail cars, trailer frames, engine blocks, etc. Such handling systems include powered sling material handling systems such as a FLIP-RITE™ handling system available from ITNAC Corporation of Birdsboro, Pa. A powered sling material handling system employs continuous powered slings that are suspended from an overhead device that may be hung from a bridge crane or trolley hoist. Each of the continuous powered slings are passed over a rotating drum of the overhead device and around the object to be handled so as to enclose the suspended center of gravity of the object. The object is lifted by raising the overhead device and the attached slings that surround the device. The lifted object is then rotated by turning the rotating drums and slings of the overhead device using electric gear motors. 
   In the past, powered sling material handling systems have been used to suspend and rotate P3 Orion aircraft wing boxes to provide access to the lower wing surface for maintenance and repair. During such an operation, engines, leading edge, and trailing edge assembly are removed from the wing assembly prior to lifting and rotating the wing box. In this regard,  FIG. 1  illustrates a wing box portion  100  of a disassembled wing assembly suspended above a horizontal floor surface  103  and rotated into vertical position using a conventional powered sling material handling system. As shown in  FIG. 1 , leading and trailing edge assemblies have been removed from wing box  102 , and an end cap fitting is attached to the root edge  106  of wing box  100  that includes two lifting horns  108   a  and  108   b  that create two support points  109   a  and  109   b . The distance between lifting horns  108   a  and  108   b  may be adjustable. Removal of leading and trailing edge assemblies, and installation of the end cap fitting are performed while wing box  100  rests in an upright horizontal position upon a wing support tool (not shown). 
   Prior to lifting wing box  100  from its horizontal position on the wing support tool, a first continuous sling  120  is passed around the body  102  of wing box  100  and around spacers or standoff devices  114   a  and  114   b  at an outboard position toward the wing tip edge  110  of the wing box  100  so that it is in position to contact the leading edge of the wing box  100  at support point  112   a  and to contact the trailing edge of wing box  100  at support point  112   b . A second continuous sling  122  is passed around lifting horns  108   a  and  108   b  of the end cap fitting. As illustrated by the dashed hash lines in  FIG. 1 , support points  112   a  and  112   b  and support points  109   a  and  109   b  together define a rotation axis area  107  that encloses the suspended center of gravity  130  of wing box  100 , i.e., so that the suspended center of gravity  130  stays between continuous slings  120  and  122  at all positions during rotation operations. Furthermore, the position of the suspended center of gravity is at or near the axis of rotation  190  of wing box  100 . The distance between support points  109   a  and  109   b  is equal to the distance between support points  112   a  and  112   b , support point  109   a  is horizontally aligned with support point  112   a , and support point  109   b  is horizontally aligned with support point  112   b . This equidistant and horizontally aligned support point configuration allows continuous slings  120  and  122  to rotate wing box  100  in an even manner or 1:1 relationship (i.e., rotation speed of continuous sling  120  is the same as the rotation speed of continuous sling  122 ) without inducing excess torque on the wing box. 
   As shown in  FIG. 1 , continuous slings  120  and  122  are passed around rotating drums  140  and  142  of lifting device  150  that is supported at pick point  170 , e.g., by hoist. Lifting device  150  is then raised at pick point  170  in the direction of arrow  172  to lift wing box  100 , still in horizontal position, from the wing support tool. Once clear of the wing box  100 , now supported by continuous slings  120  and  122 , is rotated by simultaneously turning rotating drums  140  and  142  of lifting device  150 , e.g., as illustrated by arrows  174  and  176  to rotate leading edge of wing box  100  downward while maintaining wing box  100  in a position parallel to horizontal floor surface  103 . In this manner wing box  100  may be rotated in the direction of arrow  160  through a vertical position (shown in  FIG. 1 ) to a horizontal upside down position, i.e., so that its lower surface faces upward. Pick point  170  may be variably positioned relative to horizontal beam  151  of lifting device  150  as shown by arrows  171 , i.e., so that pick point  170  may be vertically aligned with suspended center of gravity  130  as shown. This is necessary where center of gravity of beam  151  is not horizontally aligned with suspended center of gravity  130 , and may be accomplished by lifting wing box  100  by a distance of about 1″ above the wing support tool and then rebalancing the suspended load by repositioning pick point  170 . 
   Although the above-described wing rotation method using powered sling material handling systems has simplified the process of lifting and rotation of aircraft wing box portions of disassembled wing assemblies, both the moving and stationary components of the trailing edge assembly of a P3 Orion aircraft wing assembly (including stationary flap and aileron sections) are removed from the wing box prior to lifting and rotation to ensure that the suspended center of gravity of the wing box is enclosed within an area defined between the support points and lifting horns and is near the axis of rotation of the wing assembly. Otherwise, the wing box may become unstable during the lifting and/or rotation process, and/or excessive torque may be required to rotate the wing box. Removal of the entire trailing edge assembly (i.e., moving and stationary components) is a time consuming and labor intensive operation (e.g., requiring 680 man-hours of time). 
   SUMMARY OF THE INVENTION 
   Disclosed herein are systems and methods for rotating objects, such as wing assemblies. The disclosed systems and methods may be used to rotate objects, for example, using a material handling system that employs rotatable slings. The disclosed systems and methods may be advantageously implemented to rotate an object having a suspended center of gravity that lies outside the rotation axis area of conventional powered sling material handling systems by shifting the suspended center of gravity of the object to fall within the rotation axis area. 
   In one embodiment, the disclosed systems and methods may be advantageously implemented to rotate objects having a suspended center of gravity that lies outside the rotation axis area of a material handling system (i.e., the suspended center of gravity of the object has a position that falls outside the attached slings of the material handling system in at least one position of rotation) by shifting the suspended center of gravity of the object to fall within the rotation axis area of the material handling system (i.e., so that the suspended center of gravity stays in a position that is between the slings of the material handling system at all positions of rotation). For example, the suspended center of gravity of an object may be shifted using at least one ballast component (or other suitable force-applying device) that is attached or otherwise coupled to exert a force on the object in a direction and magnitude that is sufficient to shift the suspended center of gravity of the object from a point outside the rotation axis area to a point within the rotation axis area of a material handling system that is being employed to rotate the object. 
   In one exemplary embodiment, a ballast pendant may be provided that attaches to the end cap fitting of a powered sling material handling system that is employed to rotate an aircraft wing assembly (e.g., such as a P3 Orion wing assembly) with one or more trailing edge wing components of the trailing edge assembly left intact and unremoved. In such an exemplary embodiment, the ballast pendant shifts the suspended center of gravity of the wing assembly (with trailing edge components) from a point that lies outside the rotation axis area to a point that lies within the rotation axis area so that the wing assembly may be rotated in a stable manner with the trailing edge components attached. 
   In one respect, disclosed herein is a method of rotating an object having a center of gravity located at a first position within the object. The method may include: suspending a first end of the object from a first set of spaced support points; suspending a second end of the object from a second set of spaced support points; and rotating the object simultaneously about the first and second sets of spaced support points, wherein a rotation axis area is defined between the first set of spaced support points and the second set of spaced support points; and applying at least one force to the object that is sufficient to shift the suspended center of gravity of the object from a position outside the rotation axis area to a position within the rotation axis area. 
   In another respect, disclosed herein is a method of rotating an aircraft wing assembly having a center of gravity located at a first position within the wing assembly. The method may include: suspending a first end of the wing assembly from a first set of spaced support points provided at a root edge of the wing assembly; suspending a second end of the wing assembly from a second set of spaced support points provided at a position between the root edge and the wing tip edge of the wing assembly; rotating the wing assembly simultaneously about the first and second sets of spaced support points, wherein a rotation axis area is defined between the first set of spaced support points and the second set of spaced support points; and applying at least one force to the wing assembly that is sufficient to shift the suspended center of gravity of the wing assembly from a position outside the rotation axis area to a position within the rotation axis area. 
   In another respect, disclosed herein is a system for rotating objects. The system may include: a first set of spaced support points configured to suspend and rotate a first end of the object; a second set of spaced support points configured to suspend and rotate a second end of the object, a rotation axis area being defined between the first set of spaced support points and the second set of spaced support points; and a force application device configured to apply at least one force to the object that is sufficient to shift the suspended center of gravity of the object from a position outside the rotation axis area to a position within the rotation axis area. 
   In another respect, disclosed herein is an apparatus configured for attachment to a root edge of a wing assembly. The apparatus may include an end fitting having first and second lifting horns; and a force application device configured for attachment to the end fitting. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  illustrates a side view of a disassembled wing assembly suspended and rotated into vertical position using a conventional powered sling material handling system. 
       FIG. 2  illustrates a side view of a wing assembly suspended and rotated into vertical position according to one embodiment of the disclosed systems and methods. 
       FIG. 3  illustrates a root edge end view of a wing assembly suspended in upright horizontal position according to one exemplary embodiment of the disclosed systems and methods. 
       FIG. 4A  illustrates a leading edge end view of a wing assembly suspended in upright horizontal position according to one exemplary embodiment of the disclosed systems and methods. 
       FIG. 4B  illustrates an overhead view of a wing assembly suspended in upright horizontal position according to one exemplary embodiment of the disclosed systems and methods. 
       FIG. 5  illustrates a side view of a wing assembly suspended and rotated into vertical position according to one embodiment of the disclosed systems and methods. 
       FIG. 6  illustrates a root edge end view of a wing assembly suspended and rotated into vertical position according to one embodiment of the disclosed systems and methods. 
       FIG. 7  illustrates an root edge end view of a wing assembly suspended and rotated into a horizontal inverted position according to one embodiment of the disclosed systems and methods. 
   

   DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     FIG. 2  illustrates a wing assembly  200  suspended above a horizontal floor surface  203  and rotated into vertical position according to one exemplary embodiment of the disclosed systems and methods. As shown in  FIG. 2 , stationary trailing edge components  201  (e.g., flap section, aileron section, etc.) of the trailing edge assembly are attached to wing box  202  (i.e., stationary flap and aileron sections remain intact and have not been removed from the wing assembly). An end fitting in the form of an end cap is attached to the root edge  206  of wing assembly  200 , and includes two lifting horns  208   a  and  208   b  that create two support points  209   a  and  209   b . Installation of the end fitting is performed while wing assembly  200  rests in an upright horizontal position upon a wing support tool (not shown). In the illustrated embodiment of  FIG. 2 , the leading edge  298  of wing box  202  is positioned parallel to floor surface  203 . 
   As shown in  FIG. 2 , a segment of the trailing edge assembly (e.g., a 51.5″ upper skin panel between flap and aileron sections at a position about 136″ from the wing tip of P3 wing assembly) have been removed, leaving a gap  211  in the trailing edge assembly for accommodating a continuous sling  220  passed around a structural part of the wing assembly at a position between the wing root edge and wing tip edge of the wing assembly. Gap  211  may also be present to accommodate an optional trailing edge spacer or standoff device  214   b  at an outboard position toward the wing tip edge  210  of the wing assembly  200 , and in a position that is opposite an optional leading edge spacer or standoff device  214   a . In this embodiment, spacer or standoff devices  214   a  and  214   b  are used to protect the upper and lower spar caps. It may also be desirable to remove the piano hinge locally in this area to prevent damage. 
   In the practice of the disclosed systems and methods, removal of one or more trailing edge components to leave one or more gaps is optional, and may be practiced as desired or needed to fit the requirements of a particular wing assembly. For example, in some embodiments no trailing edge components may be removed, and in other embodiments trailing edge components may be removed to form more than one gap in a trailing edge assembly, e.g., to accommodate two or more continuous slings that are passed around a structural part of a wing assembly (e.g., wing box) at positions between the wing root edge and wing tip edge of the wing assembly. 
   Optional spacer/standoff devices  214  may be employed as necessary or desired to provide parallel leading and trailing edge contact surfaces for slings  220  and  222  as described further below, to provide protection for leading and trailing edge surfaces of wing box  202  (to prevent damage to front and rear spars), etc. In this regard, spacer/standoff devices  214  may be of any suitable configuration, and may be provided with a contoured or shaped contacting surface that is shaped complimentary to leading and trailing edge surfaces of wing box  202 , i.e., for contacting and mating with leading and trailing edge surfaces of wing box  202 . In one embodiment, spacer/standoff devices  214  may be manufactured from machinable “red block” material, and may be provided with carpeted or other soft surface/s for contacting leading and trailing edge surfaces of wing box  202 . In one embodiment, clearance holes may be provided in spacer/standoff devices to provide clearance in all areas in contact with fasteners, e.g., such as Hiloc fasteners. Further, spacer/standoff devices may have slots cut in them that mate with protruding angle stiffeners in front and rear spars. Proper placement may be determined by snug mating between these two surfaces. 
   One or more suitably sized openings or contours may be optionally provided in the contacting surface of spacer/standoff devices  214  to allow clearance for one or more wing components (e.g., stiffeners, collars, other wing structural components, etc.) that may be present at and/or extend from leading and/or trailing edge surfaces of wing box  202 . Such openings may be provided so that such wing components do not have to be removed when spacer/standoff devices  214  are installed to wing box  202 . The interior of spacer/standoff devices  214  may also be at least partially hollow (e.g., on the ends of a spacer/standoff device) or open in order to reduce weight, e.g., to allow for easy manual handling. It may be desirable that areas which take the load of the wing (e.g., middle section of a spacer/standoff device) be left solid. 
   Prior to lifting wing assembly  200  from its horizontal position on the wing support tool, a first continuous sling  220  is passed around the body of the wing box  202  and around spacers or standoff devices  214   a  and  214   b  so that it is in position to contact the leading edge of the wing assembly  200  at support point  212   a  and to contact the trailing edge of wing assembly  100  at support point  212   b . A second continuous sling  222  is passed around lifting horns  208   a  and  208   b  of the end fitting. As illustrated, the distance between support points  209   a  and  209   b  is substantially equal to the distance between support points  212   a  and  212   b , support point  209   a  is substantially horizontally aligned with support point  212   a , and support point  209   b  is substantially horizontally aligned with support point  212   b . This substantially equidistant and substantially horizontally aligned support point configuration allows continuous slings  220  and  222  to rotate wing assembly  200  in an even manner or 1:1 relationship (i.e., rotation speed of continuous sling  220  is the same as the rotation speed of continuous sling  222 ) without inducing excess torque on the wing assembly. In one embodiment, during rotation the leading edge is kept directed downward first and parallel with ground at all times. 
   The lateral positioning of trailing edge gap  211  relative to the longitudinal axis of wing assembly  200  (i.e., how far toward the tip edge  210  of wing assembly  200  that gap  211  is located from the root edge of wing assembly  200 ) may be any position suitable for providing support points  212  for first continuous sling  220  that together with support points  209  provided for a second continuous sling  222  may be cooperatively employed to lift and rotate wing assembly  200  in a substantially stable manner as described further herein. 
   Referring to  FIG. 2 , horizontal beam  251  may be leveled and continuous slings  220  and  222  may be passed around rotating drums  240  and  242  of lifting device  250  (e.g., powered sling material handling systems such as a FLIP-RITE™ handling system available from ITNAC Corporation of Birdsboro, Pa.) that is supported at pick point  270 , e.g., by hoist. Lifting device  250  may then be raised at pick point  270  in the direction of arrow  272  to lift wing assembly  200 , still in horizontal position, from the wing support tool. Wing assembly  200  may be lifted a few inches above the wing support tool, and horizontal beam  251  re-leveled by adjusting the pick point prior to further lifting and moving of wing assembly  200  clear of the wing support tool. Once clear of the wing support tool, wing assembly  200 , now supported by continuous slings  220  and  222 , may be rotated by simultaneously turning rotating drums  240  and  242  of lifting device  250 , e.g., as illustrated by arrows  274  and  276 . In this manner wing assembly  200  may be rotated in the direction of arrow  260  through a vertical position (shown in  FIG. 2 ) to a horizontal upside down position, i.e., so that its lower surface faces upward. 
   In one embodiment, the lateral position of trailing edge gap  211  may be any lateral position selected so that first and second continuous slings  220  and  222  straddle the suspended center of gravity of wing assembly  200 , and so that pick point  270  is positioned (or may be variably positioned in one exemplary embodiment) to substantially balance root edge moment of inertia  291  with wing tip moment of inertia  292 , i.e., so that the lateral position of pick point  270  substantially coincides with the lateral position of the suspended center of gravity of wing assembly  200  and so that the weight supported by rotating drum  240  is substantially equal to the weight supported by rotating drum  242  of lifting device  250  during lifting and/or rotation operations. In one exemplary embodiment, pick point  270  may be variably positioned in relative to horizontal beam  251  of lifting device  250  as indicated by arrow  271  and dashed outline of an alternate pick point location to vertically coincide with the lateral position of the suspended center of gravity of wing assembly  200  during lifting and/or rotation operations. In the context of this exemplary embodiment, it will be understood that the “suspended center of gravity” refers to the effective center of gravity of suspended wing assembly  200  when supported by lifting device  250 , i.e., including root edge end fitting and spacer/stand-offs  214 . 
   Although a lifting device  250  having a variable pick point  270  is described and illustrated herein, it will be understood that this is not necessary and that the disclosed systems and methods may be practiced using a lifting device that employs a non-variably positionable pick point as well. Furthermore, benefit of the disclosed systems and methods may be realized with lifting devices that are supported and/or raised using more than one pick point (e.g. two or more pick points). 
   As illustrated by the dashed hash lines in  FIG. 2 , support points  212   a  and  212   b  and support points  209   a  and  209   b  together define a rotation axis area  207 . As further illustrated in  FIG. 2 , distance between support points  209   a  and  209   b  is less than the length of root edge  206  of wing assembly  200 , i.e., so that the entire wing assembly  200  is not captured within the rotation axis area  207 . It will be understood that the disclosed systems and methods may be employed to suspend and rotate other objects having at least one end that has a length greater than the distance between the individual support points of a support point pair, and/or in which the entire object is not captured within the rotation axis area (i.e., at least a portion of the object lies outside the rotation axis area). Examples of such objects include, but are not limited to, irregular objects, triangular or other angular-shaped objects, non-square shaped objects, non-rectangular shaped objects, etc. 
     FIG. 2  illustrates non-adjusted suspended center of gravity  230  of wing assembly  200  that exists in the absence of any external applied force. As shown, presence of stationary trailing edge components  201  cause non-adjusted center of gravity  230  to be positioned closer to the trailing and root edges of wing box  202  than is center of gravity  130  of wing box  100  of  FIG. 1  that has its trailing edge assembly removed. As a result, non-adjusted suspended center of gravity  230  falls outside rotation axis area  207 , e.g., so that the center of gravity  230  does not fall between continuous slings  220  and  222  in a horizontal position. Thus, without adjustment, non-adjusted suspended center of gravity  230  will cause wing assembly  200  to be unbalanced (or trailing edge heavy) when suspended in a horizontal position by continuous slings  220  and  222  of lifting device  250 , and will be unstable and require greater torque to rotate wing assembly  200  to a vertical position. Furthermore, non-adjusted center of gravity  230  will cause wing assembly  200  to “swing” in an unstable manner as it is rotated about rotation axis  290  (i.e., to swing in a trailing edge direction as it is rotated from horizontal to vertical position, and to swing in a leading edge direction as it is rotated back from vertical to horizontal position). 
   In the practice of the disclosed systems and methods, one or more external forces may be applied that have location, magnitude and direction that are effective to shift the suspended center of gravity of a suspended wing assembly to a selected position, e.g., to a selected position that is within the rotation axis area of the suspended wing assembly from a position that is outside the rotation axis area of the suspended wing assembly. For example, still referring to the exemplary embodiment of  FIG. 2 , an external force  280  may be downwardly applied to shift the suspended center of gravity of wing assembly  200  to a selected position that is within rotation axis area  207 , e.g., as represented by adjusted suspended center of gravity  232  in  FIG. 2 . In the illustrated embodiment, adjusted suspended center of gravity  232  is also shown positioned at or near axis of rotation  290  of wing assembly  200 , i.e., so that the adjusted suspended center of gravity  232  of said wing assembly  200  is substantially intersected by said axis of rotation  290 . In the embodiment shown, adjusted suspended center of gravity  232  is located at a position relative to wing assembly  200  that is forward and inboard of non-adjusted suspended center of gravity  230 . As further illustrated, pick point  270  is moved in the direction of arrow  271  to a position that is vertically aligned with adjusted center of gravity  232  so that moments  291  and  292  are balanced about the pick point. 
   Using the disclosed systems and methods one or more external forces may be applied to a wing assembly in any manner or manners suitable for shifting the suspended center of gravity of a suspended wing assembly to a selected position. For example, a single external force of substantially uniform magnitude (such as external force  280  of  FIG. 2 ), may be applied at a given location of a suspended wing assembly (such as suspended wing assembly  200  of  FIG. 2 ) in a substantially uniform direction, regardless of position of rotation (horizontal upright position, vertical position, horizontal inverted position, etc.) of wing assembly  200  as will be further described below in relation to the exemplary embodiment of  FIGS. 3-7 . However, it will be understood that more than one force may be applied to a suspended wing assembly at one or more locations and/or in one or more directions, and/or that the force/s may vary in direction, location and/or magnitude (e.g. in a non-uniform manner) as a suspended wing assembly is rotated about a rotation axis of the suspended wing assembly. 
     FIGS. 3-7  illustrate one exemplary embodiment as it may be employed to apply an external force  280  to a suspended wing assembly  200  to shift the suspended center of gravity of the wing assembly to fall within the rotation axis area of the suspended wing assembly. In  FIGS. 3-7 , direction of rotation is indicated by arrows for rotating suspended wing assembly  200  from horizontal upright position to horizontal inverted position (e.g., about 180 degrees of rotation), it being understood that rotation in the opposite direction may be employed to rotate suspended wing assembly  200  from horizontal inverted position back to horizontal upright position (e.g., prior to re-assembly of wing assembly  200  to an aircraft fuselage). 
     FIG. 3  illustrates a root edge end view of a wing assembly  200  that is suspended above a horizontal floor surface  203  in upright horizontal position by continuous slings  222  and  220  (continuous sling  220  being directly behind continuous sling  222  and therefore not visible) and lifting device  250 , e.g., after being removed from an aircraft and lifted from a wing support tool. As illustrated in  FIG. 3 , suspended wing assembly  200  includes stationary trailing edge components  201  attached to wing box  202 . In  FIG. 3 , dashed line  228  represents a vertical projection of non-adjusted suspended center of gravity of suspended wing assembly  200 . As may be seen, the position of the non-adjusted suspended center of gravity does not lie between continuous slings  222  and  220 , but instead is located aft and outside of the rotation axis area of the suspended wing assembly, i.e., at a position between support points  209  and trailing edge components  201 . As previously described and illustrated in relation to  FIG. 2 , the presence of attached trailing edge components  201  acts to shift the suspended center of gravity of a suspended wing assembly in direction aft toward the trailing edge of the wing assembly, as compared to the suspended center of gravity of the same wing assembly without attached trailing edge components  201 . 
   Still referring to the exemplary embodiment of  FIG. 3 , a force application device in the form of a pendant weight assembly  300  is provided for applying external force  280  in a manner that shifts the suspended center of gravity forward toward the leading edge of the suspended wing assembly to a position represented by the vertical projection of dashed line  226 . As shown the position of the adjusted suspended center of gravity represented by dashed line  226  lies between continuous slings  222  and  220 , and is located inside the rotation axis area of the suspended wing assembly. In the exemplary embodiment of  FIG. 3 , pendant weight assembly  300  is coupled to a root edge end fitting that itself is coupled to root edge  206  of suspended wing assembly  200 . In a manner as previously described, the root edge end fitting of this exemplary embodiment includes an end cap  215  that is attached to the root edge  206  of wing assembly  200 , and that includes two lifting horns  208   a  and  208   b  that create two support points  209   a  and  209   b  for continuous sling  222 . 
   In one embodiment, end cap  215  may be configured to include a steel plate that is fastened to the root edge  206  of wing assembly  200  with one or more suitably sized openings  350  optionally provided in the steel plate to allow clearance for one or more wing components  352  (e.g., projecting control lines, hoses, nozzles, wing structural components, etc.) that may be present at and/or extend from root edge  206 . Such openings may be provided so that such wing components  352  do not have to be removed when end cap  215  is attached to wing box  202 . In another embodiment, end cap  215  may be configured so that the distance between lifting horns  208   a  and  208   b  is adjustable. 
   As illustrated, pendant weight assembly  300  includes pendant ballast in the form of multiple ballast weights  302  that each are removably attachable to pendant tension rod  304 , which is in turn coupled to root edge end cap  215  by eyelet  306  in a manner so that tension rod  304  is capable of pivoting relative to root edge end cap  215  as wing assembly  200  is rotated in the direction of arrow  390  (and so that force  280  is exerted in a substantially uniform downward direction as wing assembly  200  is so rotated), i.e., so that ballast weights  302  and tension rod  304  remain substantially in place while wing assembly  200  is rotated around them. In the illustrated embodiment, ballast weights  302  and tension rod  304  are configured so that the amount of weight of pendant weight may be changed in order to vary the magnitude of external force  280  by changing the number and/or weight of individual ballast weights  302  that are hung from pendant tension rod  304  (e.g., to shift the suspended center of gravity of the wing assembly by the desired or selected amount). 
   Ballast weights  302  may be removably attachable to pendant tension rod  304  using any suitable configuration, e.g., each of ballast weights  302  may be configured with an opening for receiving tension rod  304  (which may be threaded as illustrated by darker portion of rod  304 ) through the center thereof, and with a threaded fastener  305  threaded onto rod  304  from the underside to secure ballast weights  302  to tension rod  304 . In one embodiment, a ballast weight  302  may be configured with an elongated opening extending to the edge of the weight  302 , e.g., so that the weights  302  may be slid onto rod  304  of pendant assembly  300  from the side without removing threaded fastener  305 . As illustrated in  FIG. 3 , an optional lifting bracket  308  may be provided on torsion rod  304  for handling pendant weight assembly  300 . 
   With regard to  FIG. 3 , it will be understood that the illustrated embodiment of pendant weight assembly  300  is exemplary only, and that a pendant weight assembly may employ and other suitable type and configuration of ballast weight and/or ballast weight securing mechanism/s capable of exerting an external force  280 . For example, multiple ballast weights  302  may be replaced with a single ballast weight of desired density. Alternatively, a ballast container may be pivotably attached to a root edge end cap  215  (e.g., by eyelet and tension rod or other suitable mechanism) that is configured to contain solid and/or liquid ballast material (e.g., so that solid and/or liquid ballast material may be added or subtracted from the container so that that may be incrementally added or subtracted to achieve a desired external force  280 . It is also possible that force application device may be provided that is configured to applying external force  280  using alternative types of force application mechanisms, e.g., mechanical, electromechanical, electromagnetic, etc. For example a cable or rod may be pivotably attached to root edge end cap  215  (e.g., by eyelet) and used to apply external force  280  by mechanical or electromechanical force, rather than by using a pendant weight assembly. 
   It will also be understood that the point of application of external force  280  may vary, i.e., the point of attachment of eyelet  306  to root edge end cap  215  shown in  FIG. 3  is exemplary only. In this regard, any other alternative force application point or multiple force application points may be used that are suitable for applying an external force/s of any magnitude/s and/or direction/s to a suspended wing assembly in any manner or manners suitable for shifting the suspended center of gravity of a suspended wing assembly to a selected position. For example, a pendant weight assembly may be provided that pivotably attaches in another position to root edge end cap  215 , e.g., using a tension rod with eyelet or bearing that rotatably attaches to a pivot pin  380  shown in dashed outline adjacent to lifting horn  208   a  and, extending in a direction outward from the page in  FIG. 3 . Furthermore, it is not necessary that a force application device be provided that attaches to a root edge end fitting, and/or that applies an external force/s to a suspended wing assembly at a point/s on a root edge end fitting. In this regard, one or more external forces may be applied indirectly or directly to a component/s of a wing assembly itself (e.g., wing box, leading edge, trailing edge, etc.) at any position/s (e.g., from inboard to outboard position, and/or from leading to trailing edge position) that is suitable for shifting the suspended center of gravity of a suspended wing assembly to a selected position. 
     FIG. 4A  illustrates a leading edge end view of wing assembly  200  of  FIG. 3  that is suspended above a horizontal floor surface  203  in upright horizontal position by continuous slings  222  and  220 , and lifting device  250 , e.g., after being removed from an aircraft and lifted from a wing support tool.  FIG. 4A  shows pick point  270  positioned over the adjusted suspended center of gravity represented by dashed line  226 . 
     FIG. 4B  illustrates an overhead view of wing assembly  200  of  FIG. 3  that is suspended above a horizontal floor surface  203  in upright horizontal position by continuous slings  222  and  220 , and lifting device  250 , e.g., after being removed from an aircraft and lifted from a wing support tool. In  FIG. 4B , pick point  270  is positioned over the adjusted suspended center of gravity of suspended wing assembly  200 . 
     FIG. 5  illustrates a side view of wing assembly  200  of  FIG. 3  that is rotated into vertical position and suspended above a horizontal floor surface  203  by continuous slings  222  and  220 , and lifting device  250 .  FIG. 5  shows pick point  270  positioned over the adjusted suspended center of gravity represented by dashed line  226 . 
     FIG. 6  illustrates a root edge end view of wing assembly  200  of  FIG. 3  that is rotated into vertical position and suspended above a horizontal floor surface  203  by continuous slings  222  and  220 , and lifting device  250 .  FIG. 6  shows pick point  270  positioned over the adjusted suspended center of gravity represented by dashed line  226 . 
     FIG. 7  illustrates a root edge end view of wing assembly  200  that has been rotated by 180 degrees from a horizontal upright position into a horizontal inverted position and suspended above a horizontal floor surface  203  by continuous slings  222  and  220 , and lifting device  250 .  FIG. 7  shows pick point  270  positioned over the adjusted suspended center of gravity represented by dashed line  226 . 
   Although particular examples of an overhead lifting device  250  in the form of a powered sling material handling system that employs two continuous slings  220  and  222  has been described and illustrated herein, it will be understood that benefits of the disclosed systems and methods may be realized using any type of system and/or method that may be employed to suspend and rotate a wing assembly including, but not limited to, overhead lifting devices employing more than two continuous slings, overhead lifting devices that do not employ slings (e.g., that employ belts, chains or other suitable rotation mechanism), etc. In addition, the disclosed systems and methods may be practiced to suspend and rotate objects other than aircraft wing assemblies. Examples of other such objects include, but are not limited to, aircraft tail assemblies (vertical stabilizer or horizontal stabilizer component), etc. 
   Furthermore, it will be understood that in the practice of the disclosed systems and methods one or more external forces may be applied to an object having location, magnitude and direction that are effective to shift the suspended center of gravity of an object to a selected position, regardless of whether the non-adjusted suspended center of gravity is without or within the rotation axis area of the suspended object, and/or regardless of whether the non-adjusted suspended center of gravity is without or within the rotation axis area of the suspended object, e.g., the disclosed systems and methods may be employed to shift the suspended center of gravity from any given point to any other give point as may be needed or desired to fit the requirements of a given application. For example it may be desirable to shift the suspended center of gravity from a first position relatively farther from the rotational axis of an object to a second position that is relatively closer to the rotational axis of the object, regardless of whether the first and/or second positions are within or without the rotation axis area of the suspended object. 
   In addition, although an end fitting in the form of an end cap  215  is described and illustrated herein, it will be understood that an end fitting may be of any other suitable form for creating one or more support points for suspending and rotating an object. Furthermore, it will be understood that use of an end fitting is not necessary in all embodiments. For example, two or more continuous slings may encircle an object such as a wing box at points between the ends of the object, e.g., at points between the wing root edge and wing tip edge of a wing assembly. 
   While the invention may be adaptable to various modifications and alternative forms, specific embodiments have been shown by way of example and described herein. However, it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. Moreover, the different aspects of the disclosed systems and methods may be utilized in various combinations and/or independently. Thus the invention is not limited to only those combinations shown herein, but rather may include other combinations.