Patent Publication Number: US-2007110552-A1

Title: Aircraft landing gear loader

Description:
TECHNICAL FIELD  
      This invention pertains to mechanisms for lifting and manipulating heavy loads in general, and more particularly, to a loader for the main landing gear of a large aircraft.  
     BACKGROUND  
      Modern large aircraft, such as the Boeing 777, are typically assembled on a moving assembly line, sometimes referred to simply as a “Boeing Production System. (BPS)” Moving line assembly requires that the aircraft&#39;s main landing gear (MLG), each of which may weigh more 14,000 lbs., be installed while the weight of the aircraft is supported on jacks, with the belly of its fuselage disposed 106 inches or more above the floor. Moreover, repairs or maintenance of large aircraft in the field often must be effected in an actual “flight line” environment, necessitating the removal and installation of large MLG at heights of up to 154 inches above the tarmac, and additionally, in a potentially more hazardous environment, e.g., an Underwriters Laboratories (“UL”) “Class 1, Division 1” (fueled aircraft) environment.  
      The prior art methods for installing large MLG are typically accomplished on the flight line or in a customer&#39;s hangar. Several examples of specialized apparatus adapted for effecting such heavy equipment lifts and manipulations can be found in the patent art, e.g., in U.S. Pat. No. 5,460,474 to L. E. Iles; U.S. Pat. No. 6,390,762 to W J. Peery et al.; and, U.S. Pat. No. 6,485,247 to O. J. Groves et al.  
      One such prior art method and associated apparatus are those developed for loading the MLG of the Boeing 747 aircraft. However, it should be noted that the 747 MLG loader is not capable of supporting the increased weight of more recent, larger aircraft, e.g., the Boeing 777, and is therefore incapable of installing the 777 MLG in either a moving line or a flight line environment. This prior art MLG loader comprises three separate towers having associated floor plates that are installed concentrically to the MLG. The equipment necessitates that all six MLG wheels be removed from their respective axels, and that at least three protective sleeves be installed on the bare axels, two on the outboard side and one at the opposite inboard side on the center axle. The protective sleeves are in turn attached to three, six-ton lever hoists located on respective ones of the three towers. The lever chain hoists are attached to the plates and respective hoist chains are attached between the tower and the MLG, each of which are then independently tensioned or relaxed in the desired direction to align the upper end of the strut of the MLG into position inside the wheel well of the aircraft.  
      The foregoing sequence must be accomplished prior to either the installation or the removal of a MLG from an aircraft, and either case, the aircraft must first be fully supported on jacks or other supports. The disadvantage of the prior art method and apparatus is that they take substantial setup time and manual labor, including disassembly of the MLG wheels and the manual manipulation of the MLG with multiple, independent lever chain hoists, and with the subsequent need to reassemble three of the six wheels on the gear and disassemble the equipment after the MLG has been installed.  
      Accordingly, there is a long-felt but as yet unsatisfied need in the industry for a loader that can install a large MLG into or remove it from an aircraft in either a moving line or a flight line environment in a controllable, safe, accurate, reliable manner, and in a substantially reduced amount of time.  
     BRIEF SUMMARY  
      In accordance with the exemplary embodiments thereof described herein, the present invention provides a method and apparatus for loading the MLG of a large aircraft into or from the wheel wells of the aircraft in either a moving assembly line or a flight line environment in a safer, more reliable and accurate manner, and in a substantially reduced amount of time than those of the prior art.  
      In one advantageous exemplary embodiment, the MLG loader comprises a U-shaped support frame having opposing symmetrical portions disposed on opposite sides of a sagittal plane extending through the MLG, and a fixture supported on the support frame and coupled to the MLG such that both axial forces and turning moments applied to the fixture by the loader are coupled through the fixture to the MLG. The fixture may comprise, for example, an MLG shipping fixture that is coupled to the tires of the wheels on the MLG truck. Means are provided for both controllably translating and rotating the fixture in both a horizontal plane and the sagittal plane of the MLG.  
      The means for controllably translating the fixture in the sagittal plane include a pair of opposing slide mechanisms respectively coupled to an opposite side of the fixture and supported on a corresponding one of the opposing support frame side portions for simultaneous, coextensive sliding movement relative to the support frame and parallel to the sagittal plane, and means are provided, e.g., a ball-screw or hydraulic linear actuator, for urging the slide mechanisms in such movement.  
      The means for controllably rotating the fixture in the sagittal plane include first and second pairs of opposing vertical jacks, each pair having a jack supported on a corresponding one of the opposing support frame side portions, the first pair being fixed relative to the support frame and the second pair being axially moveable on the support frame relative to the first pair. Means are provided for rotatably coupling opposite ends of each of the slide mechanisms to an output end of a corresponding one of the jacks of each of the first and second pairs of jacks, and means are provided for controllably raising and lowering the output ends of the jacks of each opposing pair of jacks simultaneously, coextensively and independently of those of the other pair, such that the slide mechanisms, and hence, the fixture and MLG, are caused to rotate in the sagittal plane as a result thereof. The raising and lowering means of the jacks can also comprise a ball-screw or a hydraulic linear actuator.  
      In a preferred embodiment of the loader, means are also provided for controllably rotating and translating the fixture in a horizontal plane. These means can comprise a drive mechanism coupled to the support frame, in which the drive mechanism includes a plurality of synchronized, steerable wheels, each equipped with an independently controllable servo drive mechanism. In the preferred embodiment, all operations of the loader, including movement of the MLG in both the horizontal and sagittal planes, can be controlled by an operator remotely from the MLG using, e.g., a control pendant.  
      Optionally, the loader can include an electromechanical or a hydraulic linear actuator coupled between the strut and truck of the MLG which is operative to rotate the strut about a central axis of the strut and relative to the truck, for fine adjustments of the upper end of the strut relative to associated structure located in the wheel well of the aircraft.  
      In one advantageous embodiment, the loader can include a portable power supply, e.g., one or more battery or generator carts coupled to the loader, for powering the loader independently of fixed power sources.  
      A method for loading a MLG of an aircraft using the novel loader comprises coupling the fixture to the MLG and positioning the opposing side portions of the support frame on opposite sides of the fixture. The side portions of the support frame are then brought together and locked to each other such that the slide mechanisms of the loader respectively engage opposite sides of the MLG coupling fixture. When the MLG has thus been captured by the loader, the MLG can be easily translated and rotated in the horizontal plane using the loader drive mechanism so as to align it appropriately with the wheel well of the aircraft, then controllably translated and rotated in the sagittal plane of the MLG using the jacks and slider mechanisms until the upper end of the strut of the MLG enters the wheel well and is correctly aligned with associated engaging structure located in the wheel well.  
      A better understanding of the above and many other features and advantages of the methods and apparatus of the present invention may be obtained from a consideration of the detailed description of the exemplary embodiments thereof below, particularly if such consideration is made in conjunction with the appended drawings, wherein like reference numerals are used to identify like elements illustrated in one or more of the figures therein. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a partial left side elevation view of a large aircraft situated on a horizontal surface, such as a hangar floor or tarmac and supported by a nose gear and a left main landing gear (“MLG”);  
       FIG. 2  is a partial schematic elevation view of the aircraft and MLG of  FIG. 1 , showing a strut of the MLG disposed in a generally horizontal orientation and aligned with a wheel well of the aircraft, preparatory to being loaded into the wheel well;  
       FIG. 3  is a view similar to  FIG. 2 , showing the MLG rotated through an angle Θ y  in a sagittal plane of the MLG;  
       FIG. 4  is a view similar to  FIGS. 2 and 3 , showing the MLG in a generally upright, loaded position, with an upper end of the strut of the MLG disposed in the wheel well of the aircraft;  
       FIG. 5  is a perspective view of an MLG coupling fixture used by an exemplary embodiment of a loader in accordance with the present invention to apply both axial and turning forces to the MLG;  
       FIG. 6  is a perspective view of an exemplary embodiment of a MLG loader in accordance with the present invention, showing symmetrical right- and left-hand portions thereof coupled to each other across the sagittal plane of the MLG, with the fixture of  FIG. 5  coupled between a pair of slide mechanisms of the loader for translational and rotational movement of the MLG in the sagittal plane, and wherein the MLG and surrounding work platforms have been omitted for clarity;  
       FIG. 7  is a perspective view of a left side half-portion of the exemplary loader of  FIG. 6 ;  
       FIG. 8  is a top plan view of the exemplary loader of  FIG. 6 , showing the MLG disposed between the slide mechanisms of the loader, and wherein the coupling fixture and surrounding work platforms have been omitted for clarity;  
       FIG. 9  is a front-and-side perspective view of the exemplary loader, showing the MLG rotated in the sagittal plane to a nearly upright position by the loader, and with an elevated work platform of the loader surrounding the MLG;  
       FIG. 10  is a right side elevation of the loader, showing the MLG rotated in the sagittal plane to an angle of about a 45 degrees relative to the horizontal by the loader; and,  
       FIG. 11  is a partial front perspective view of the MLG, showing an optional MLG strut rotating mechanism of the loader. 
    
    
     DETAILED DESCRIPTION  
       FIG. 1  is a left side partial elevation view of a large aircraft  10  situated on a generally horizontal surface, such as a hangar floor or tarmac  12  and supported thereon by a nose gear  14  and a left main landing gear (“MLG”)  16  of the aircraft. In the particular embodiment of aircraft and MLG illustrated, the MLG comprises an elongated strut  18  having an upper end  20  extending into a wheel well  22  of the aircraft, where it is coupled to associated structure adapted to support the aircraft on the MLG and to extend the MLG from and retract it completely into the wheel well during takeoff, flight and landing operations. The MLG typically further includes a truck  24  having a plurality of wheels  26  rotatably mounted thereon. In a typical embodiment, the MLG may include six wheels, can weigh more than 7 tons, and measure more than 154 inches in length.  
       FIGS. 2-4  schematically illustrate the sequential steps involved in one method of loading, i.e., installing, the MLG  16  into the aircraft  10 , and particularly, insertion of the upper end  20  of the elongated strut  18  thereof into the wheel well  22  of the aircraft, wherein it should be understood that during the entire procedure, the weight of aircraft is supported on a plurality of jacks or other supporting mechanisms (not illustrated), and that the procedure for unloading, or uninstalling the MLG involves a reversal of the procedural steps illustrated. As shown in  FIG. 2 , the loading procedure begins with the strut disposed generally horizontally and the truck disposed generally vertically, with the strut aligned with the wheel well both longitudinally, i.e., along the x axis shown, and transversely, i.e., along the y-axis, such that a sagittal plane extends commonly through both the MLG and the wheel well.  
      In  FIG. 3 , the MLG  16  is shown having been rotated in the sagittal plane through an angular displacement Θ y , such that the upper end  20  of the MLG strut  18  is partially disposed in the wheel well  22  of the aircraft  10 , and in  FIG. 4 , the MLG is shown fully rotated to a substantially upright orientation, in which the upper end of the strut can be coupled to associated MLG structure (not illustrated) within the wheel well. Thus, it will be understood that, to effect the foregoing procedures effectively in connection with a relatively large, heavy MLG, a MLG loader must be capable of first grasping and holding the MLG, and then manipulating it controllably, safely, and accurately in at least four degrees of movement, i.e., along three orthogonal axes of translation, two horizontal (i.e., “x,” or fore-and-aft, and “y,” or transverse) and one vertical (i.e., “z”), and in at least one degree of rotational movement within the sagittal plane of the MLG (i.e., “Θ y ”).  
      An advantageous tool  50  for grasping and holding the MLG  16  for such manipulation by a loader is illustrated in the perspective view of  FIG. 5 , and comprises a shipping fixture that couples to the tires on the wheels  26  of the truck  24  of the MLG. The fixture comprises a pair of longitudinal beams  52  having ends coupled to corresponding ends of a pair of transverse beams  54 . Each of four vertical rods  56  is slidably moveable on the transverse beams and mounts a pair of spaced-apart, adjustable spatulate fingers  58  adapted to resiliently clamp onto the aft end of the front, or leading pair of tires, both the leading and aft ends of the middle pair of tires, and the leading ends of the aft or rearmost pair of tires of the truck, in a strong, clamping attachment. Because the center of gravity of the MLG is located closely to the truck, such a fixture provides a convenient means for lifting and transporting the MLG, e.g., by means of a forklift, over moderate distances, and since it is capable of coupling both translational forces and turning moments to the MLG, is also well suited for use by a loader in effecting the above-described types of translations and rotations of the MLG.  
      An exemplary embodiment of a MLG loader  60  in accordance with the present invention is illustrated in the perspective view of  FIG. 6 , and comprises two generally symmetrical L-shaped “half-units,” viz., a left-hand half-unit  62 L and a right-hand half-unit  62 R, which are respectively disposed on opposite sides of the sagittal plane of the MLG (omitted for clarity). The half-units are coupled to each other and the coupling fixture  50  across the sagittal plane of the MLG via two sets of alignment pins  64  (see  FIG. 7 ) located at their respective centers to form a single, generally U shaped apparatus that engages the MLG through the agency of the coupling fixture  50  for the lifting and manipulation of the MLG in the above four degrees of movement.  
      As illustrated in  FIG. 7  (showing the left-hand L-shaped half-unit  62 L), the bilateral half-units  62 L and  62 R of the loader  60  each comprises a rigid, L-shaped support frame  66 L or  66 R, one of a laterally opposing pair of vertical jacks  68 L or  68 R that is fixedly attached to a corresponding one of the opposing support frame portions, and one of a second pair of laterally opposing vertical jacks  70 L or  70 R that is mounted on a rail system on the corresponding support frame side portion such that the second pair of jacks is movable on the support frame in the x, or fore-and-aft direction, toward and away from the fixed first pair of jacks. Each of the jacks has a base end supported on the support frame and an opposite, vertically extendible output end  72 L,  72 R and  74 L,  74 R. A pair of slide mechanisms  76 L and  76 R are respectively attached to each of the L-shaped loader half-units, and in turn, engage the coupling fixture  50  on opposite sides thereof, as illustrated in  FIG. 6 . The horizontal slides cooperate with each other and the coupling fixture to define a single, translatable and rotatable platform that enables the loader to manipulate the MLG both in translation and rotation in the sagittal plane of the MLG, as indicated by the dashed line of  FIG. 8 , and relative to the support frame, i.e., in the x, z and Θ y  directions, respectively, in the following manner.  
      As illustrated in, e.g., the top plan view of  FIG. 8 , respective, opposite end portions of each of the slide mechanisms  76 L and  76 R of each L-shaped half-unit  62  is rotatably coupled to a corresponding one of the output ends  72 ,  74  of the jacks  68 ,  70  by means of a foot-block assembly  78  so as to be rotatable relative to the respective jack assemblies, and is also slidably mounted on rollers on the respective slide mechanisms for translational movement in the sagittal plane and relative to the respective jacks, as may be required, for example, to clear the lip of the aircraft wheel well  22  or other structures when the MLG  16  is rotated. Each of the two foot-block assemblies of each slide mechanism is thus capable of rotation, and has a respective axial position relative to the other foot-block mechanism that is adjustable in the following manner.  
      Each foot-block assembly  78  is positionable on a horizontal rail of a respective one of the slide mechanisms  76  by means of a 10-ton ball-screw linear actuator  80  driven by a one-horsepower electric motor equipped with a C-face braking mechanism. The electric motor is connected to an inline gear box having a 5:1 gear ratio mounted to a bracket and coupled to the ball-screw actuator. The actuator ball screw nut is attached to the foot-block assembly by means of a bracket. A first, or forward one, of the two foot-block assemblies of each bilateral slide mechanism is adjusted by positioning it manually on the rails of the slide mechanism to align with the MLG coupling fixture  50  described above when the loader  60  is initially coupled to the MLG  16 , whereas, the aft one of the foot-blocks of each slide mechanism is allowed to float freely on the rail of the slide mechanism. The forward foot/block assembly is then positioned and controlled by the electric drive motor of the linear actuator. Thus, when the motor drives the primary foot-block of a respective slide mechanism, it simultaneously controls translational movement of both of the aft foot-blocks and the fixture, and hence, the translational movement of the MLG in the sagittal plane. The respective slide mechanisms  78  of the two L-shaped half-units  62 L and  62 R thus translate simultaneously and coextensively with each other to translate the MLG  16  in the sagittal plane relative to the U-shaped support frame  66 , regardless of the rotational position of Θ y  of the MLG in the sagittal plane, which is controlled by the loader in the following manner.  
      In the exemplary embodiment of the loader  60  illustrated, each of the two pairs of opposing vertical jacks  68 ,  70  comprises a one-horsepower electric motor with a C-face brake that attaches to an in-line helical box having a 5:1 gear ratio. The gear box attaches to a miter gear box having a 1:1 gear ratio, which in turn, attaches to a 20 ton ball-screw mechanism  82 . The screw nut of the ball-screw mechanism is restrained from rotating by fixing it, e.g., by means of a weldment on a respective slide mechanism  76 , and is attached to a respective one of the two block feet  78  of a respective slide mechanism. In one exemplary embodiment, the maximum stroke or extension of the jack ball screw mechanisms, and hence, the output ends  72 ,  74  of the jacks, is adjusted to be about 65 inches. However, the stroke can be extended for use of the loader in, e.g., a flight line environment in which a greater stroke may be required.  
      The vertical position of the MLG  16 , as well as its rotational position Θ y  in the sagittal plane and relative to the support frame  66 , is thus controlled by the vertical stroke of the four jacks  68 ,  70  acting in concert, in the case of the vertical position of the MLG  16 , or in concerted, opposing pairs, i.e., the front, or forward opposing pair  70 L and  70 R moving in concert with each other, and/or the aft, or rearward pair  68 L and  68 R moving in concert with each other and independently of the front pair. Thus, if the MLG is loaded onto the loader  60  with the strut end  20  extending forward relative to the loader, as illustrated in the front-and-left side perspective view of  FIG. 9 , wherein the MLG is shown surrounded on all sides by a plurality of elevated scaffolds, or work platforms  84  of the loader, the strut end can be rotated in a rearward direction by simultaneously and coextensively raising the output ends  74 L and  74 R of the front opposing pair of jacks  70 L and  70 R relative to the output ends  72 L and  72 R of the aft pair of jacks  68 L and  68 R, and/or by lowering the output ends of the aft pair relative to the front pair, and if the strut end of the MLG is initially oriented in a rearward direction relative to the loader, as illustrated in the right-side elevation view of  FIG. 10 , the strut end can be rotated in a forward direction by raising the rearward pair of jacks in concert and/or by retracting the forward pair in concert. As the MLG rotates, the moveable pair of opposing jacks slide axially on the support frame relative to the fixed pair to accommodate the changing horizontal distance between the respective fore and aft foot-block assemblies  78  of the slide mechanisms  76  as they are rotated by the jacks. The initial MLG orientation selected will depend on whether it is desirable to approach the wheel well  22  of the aircraft  10  with the MLG strut  18  from the front or the aft end of the aircraft. The exemplary loader illustrated and described herein is capable of rotating the MLG at an inclination of at least 60 degrees relative to the horizon, with the strut of the MLG strut initially oriented in the aft direction, or an inclination of 52 degrees, with the MLG strut initially oriented in the forward direction. In the preferred embodiment, the latter procedure is typically followed because there fewer operations involved in the installation of the MLG into the aircraft.  
      In a preferred embodiment, the loader  60  is driven over the ground by a drive mechanism comprising six, synchronized, steerable, nine-inch dual-wheel assemblies  86 , each equipped with an electric servo drive. The drive mechanism enables an operator of the loader to precisely control the x and y positions of the loader, and hence, the MLG, relative to the wheel well  22  of the aircraft  10  from outside of the aircraft using, e.g., a control console located on the loader, or a control “pendant,” i.e., a control pad attached to the loader by an electric cord (preferably, one which is UL rated for Class 1, Division 2, i.e., a flight line environment), or alternatively, by a wireless RF connection. As those of skill in the art will appreciate, the drive mechanism also provides the loader with an additional degree of rotational control, namely, the ability to rotate in the horizontal plane (“Θ z ”), i.e., about the vertical z axis. The total weight of the MLG Loader is distributed over the wheels of the drive mechanism such that the bearing weight of the fully burdened loader does not exceed a rated floor load of 450 PSI. In the exemplary embodiment of the loader  60  illustrated in the figures, the total weight of the loader is about 26,000 lbs., and its overall dimensions are 190 inches long×194 inches wide×120 inches high.  
      In one advantageous embodiment, the MLG loader  60  is provided with a pair of battery carts  88  (see  FIGS. 8 and 10 ) that respectively attach to the back end of each of the right- and left-hand L-shaped half-units  62 L and  62 R of the loader. The battery packs power the electric motors of the jacks  68  and  70  and the slide mechanisms  76  as well as the variable frequency drive wheels  86  of the loader. Each of the battery carts can be replaced with a backup battery cart when recharging is necessary. The battery carts, like the control pendant described above, are designed to meet UL requirements for Class 1, Division 1 and 2, while operating in the vicinity of a fueled aircraft, and enable the loader to move freely along the assembly line for up to eight hours without recharging. However, if desired, a secondary power source, such as an electric extension cord or a generator cart, can be used for redundancy.  
       FIG. 11  illustrates an optional mechanism  90  that can be used advantageously in conjunction with the exemplary loader  60  of the present invention. The tool, a strut/truck MLG drive assembly, comprises a ball-screw linear actuator  92  having an electric motor and-C face brake attached. A ball-screw worm drive mounting plate  94  is connected to a fitting on the MLG truck  24 , and an attachment fitting  96  is located at the opposite end of the actuator and connects to the strut  18  by means of a bushing that enables the strut to rotate freely about the long axis of the strut in either direction relative to the truck without binding when the drive assembly is actuated. This angular adjustment of the strut relative to the truck can be accomplished using the same control pendant that controls the movements of the loader and its features. In use, the tool enables the strut of the MLG, and in particular, fittings at the upper end  20  thereof, to be rotated relative to the truck of the MLG and thereby enable a fine positioning of the fittings with respect to associated structures in the wheel well  22  during the marriage of the MLG to the aircraft  10 .  
      The method used for attaching the exemplary loader  60  of the present invention to the MLG  16 , and thence, the MLG to the aircraft  10 , is as follows. The MLG is initially provided at the location of the loader, e.g., with a forklift, with the shipping fixture  50  already coupled to the wheels  26  of the MLG truck  24 . The two L-shaped half-units  62 L and  62 R of the loader are then moved toward each other across the sagittal plane of the MLG until opposing fingers on respective ones of the slider assemblies  76 L and  76 R engage in respective openings on opposite sides of the fixture. The two L-shaped units are then locked together such that the slider mechanisms, together with the fixture, define a single platform coupled to the MLG that can be raised, lowered, horizontally traversed, and rotated about two axes of rotation, through control of the loader.  
      The operator of the loader  60 , while positioned, for example aboard the loader on one of the work platforms  84  thereof, or remotely from the loader, can then steer the loader and MLG into position under the wing of the aircraft  10  at the position of the desired well  22 , and using the control pendant, manipulate the MLG up into the wheel well without causing any interference between the MLG and the airplane wing or any auxiliary working or support stands that provide access and/or support of the airplane on the moving assembly line.  
      By now, those of skill in this art will appreciate that many modifications, substitutions and variations can be made in and to the materials, apparatus, configurations and methods of MLG loader of the present invention without departing from its spirit and scope. For example, in an appropriate situation, hydraulic linear actuators can be substituted for one or more of the electrical ball-screw linear actuators illustrated and described herein. Accordingly, the scope of the present invention should not be limited to that of the particular embodiments illustrated and described herein, as they are only exemplary in nature, but rather, should be fully commensurate with that of the claims appended hereafter and their functional equivalents.