Patent Abstract:
A method of loading a landing gear in an aircraft comprises accessing an ideal path specifying movement of the landing gear from a starting location to an expected mounting location on the aircraft; determining a difference between the expected mounting location and an actual mounting location on the aircraft; modifying the ideal path to move the expected mounting location to the actual mounting location; and moving the landing gear along the modified path.

Full Description:
BACKGROUND 
     Main landing gears may be installed in an aircraft during or after final body join. Each main landing gear may be mounted to spars or other primary structural members of a wing. 
     Consider the example of a large commercial jetliner in which each main landing gear weighs tens of thousands of pounds and, when upright, exceeds aircraft working height. Clearances for moving the main landing gear through an opening in the wing&#39;s skin, and positioning the main landing gear at a mounting location at a spar, are very tight. If the main landing gear bumps into the skin or spar, it can damage the skin or spar. The damage can be expensive in terms of money and time, especially if production is delayed. 
     Some aircraft factories have pits for installing main landing gears. An upright landing gear is loaded into the pit, the aircraft is moved over the pit, and the upright landing gear is raised until its load bearing interfaces arrive at their mounting locations. 
     If a pit is not available, a landing gear loader may be used to position a main landing gear underneath a wing, and translate and tilt the landing gear until its load bearing interfaces arrive at their mounting locations. However, this process involves a series of discrete movements. After each discrete movement, a visual inspection is performed to determine whether there is sufficient clearance. Installation time is prohibitive. 
     SUMMARY 
     According to an embodiment herein, a method of loading a landing gear in an aircraft comprises accessing an ideal path specifying movement of the landing gear from a starting location to an expected mounting location on the aircraft; determining a difference between the expected mounting location and an actual mounting location on the aircraft; modifying the ideal path to move the expected mounting location to the actual mounting location; and moving the landing gear along the modified path. 
     According to another embodiment herein, a system for loading a landing gear in an aircraft comprises a multi-axis loader for rotating and translating the landing gear; and a controller programmed to access an ideal path for commanding the loader to move the landing gear from a starting location and orientation to an ending orientation at an expected mounting location. The controller is further programmed to receive information about an actual mounting location in the aircraft, and modify the ideal path so the loader moves the landing gear from the starting orientation and location to the ending orientation at the actual mounting location instead of the expected mounting location. 
     These features and functions may be achieved independently in various embodiments or may be combined in other embodiments. Further details of the embodiments can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an illustration of an aircraft. 
         FIG. 2  is an illustration of a main landing gear of an advanced commercial aircraft. 
         FIG. 3  is an illustration of a method of loading a main landing gear in an aircraft. 
         FIGS. 4A-4C  are illustrations of a loading system for loading a landing gear in an aircraft. 
         FIG. 5  is an illustration of a method of loading a landing gear in an aircraft in a factory. 
     
    
    
     DETAILED DESCRIPTION 
     Reference is made to  FIG. 1 , which illustrates an aircraft  100  including a fuselage  110 , wings  120 , and an empennage  130 . The aircraft  100  further includes landing gear, which supports the entire weight of the aircraft  100  during landing and ground operations. The landing gear includes main landing gears  140  attached to spars and and/or other primary structural members of the wings  120 . The landing gear may also include a front landing gear attached to a keel of the fuselage  110 . 
     Additional reference is made to  FIG. 2  where the aircraft  100  is on a surface  150  that may be a factory floor, runway or other flat surface as discussed below. In an advanced commercial jetliner, each main landing gear  140  may weigh tens of thousands of pounds. When upright, each main landing gear  140  may exceed aircraft working height. 
     Each main landing gear  140  typically includes struts, fairings, gear actuators, support units, steering systems, and wheel and brake assemblies. Each main landing gear  140  may further include primary load bearing interfaces such as a forward trunion H-block fitting  160  and a rear trunion fitting  162  ( FIGS. 4A-4C ). 
     During installation of a main landing gear  140  to a wing  120  the main landing gear  140  is “loaded.” The process of loading the main landing gear  140  is to index and affix its load bearing interfaces (e.g., the forward trunion H-block fitting  160  and the rear trunion  162 ) to mounting locations on primary structural members of the wing  120 . For instance, the forward trunion H-block fitting  160  is attached to a rear spar  460  of the wing  120 , and the rear trunion  162  is pinned to a landing gear beam  462  ( FIGS. 4A-4C ). Additional structural and articulation features may be attached after the landing gear  140  is loaded but before it is ready to bear weight. 
     The main landing gear  140  may be loaded by a multi-axis loader. The multi-axis loader may translate the main landing gear  140  along a primarily forward axis while translating and rotating the main landing gear  140  about other axes. 
     Reference is now made to  FIG. 3 , which illustrates a general method of using the multi-axis loader to load the main landing gear  140  in the aircraft  100 . At block  300 , the main landing gear  140  is placed in the multi-axis loader. At block  310 , the multi-axis loader moves the main landing gear  140  to a starting location and orientation, alongside the aircraft  100 . If the method is performed in a factory, the multi-axis loader moves the main landing gear  140  along the floor  150  of the factory. 
     At block  320 , prior to loading, an ideal path is accessed. The ideal path specifies location and orientation of the main landing gear  140  as the multi-axis loader moves it from the starting orientation and location to an expected mounting orientation and location. If the actual mounting location is at its expected location, and if the main landing gear  140  follows the ideal path during loading, then the load bearing surfaces  160 ,  162  of the main landing gear  140  will arrive at the actual mounting locations on the primary structural members  460 ,  462  of the aircraft  100 . Moreover, if the main landing gear  140  follows the ideal path, and if the actual mounting location is where it is expected, then the main landing gear  140  will arrive without bumping into any portion of the aircraft  100  or any other constraints during loading. 
     The ideal path may be computer-generated from a simulation based upon computer-aided design (CAD) models of the landing gear  140 , and the aircraft  100 , and any other constraints (e.g., factory surfaces, surrounding access platforms and other equipment, expected locations of people during loading). The simulation may also produce machine commands that cause the multi-axis loader to move the main landing gear  140  from the starting orientation and location and follow the ideal path to the expected mounting orientation and location. Thus, the ideal path may be represented as coordinates of a local coordinate system, or as machine commands. The coordinate system may be defined by the multi-axis loader. 
     However, the actual mounting location might not be where it is expected. For instance, there might be positioning errors of the aircraft  100 , the landing gear  140  and the multi-axis loader. The factory floor  150  might be uneven or not level. 
     At block  330 , a difference between the actual mounting location and the expected mounting location on the aircraft  100  is determined. After the difference has been determined, the aircraft  100  is not allowed to move until the landing gear  140  has been loaded. Although  FIG. 3  shows block  320  occurring before block  330 , a method herein is not so limited. The difference may be determined before, during or after the ideal path is accessed. 
     At block  340 , the ideal path is modified to move the expected mounting location to the actual mounting location. As a first example, any position errors are treated as an offset of the expected mounting location, and the ideal path is modified to correct the offset. As a second example, mathematical methods are used to compensate from axes of the ideal path to the loader&#39;s functional axes. If the loader is parked with its forward axis 0.5 degrees off from a forward axis of the ideal path, the x and y components of the ideal path are modified to be in the correct relation to the aircraft  100 . 
     At block  350 , the multi-axis loader moves the landing gear  140  along the modified path. The landing gear  140  is moved from its starting orientation and location to the actual orientation and location. As the landing gear  140  is moved, its load bearing interfaces  160 ,  162  fit through an opening in lower skin of the aircraft  100  and are positioned at the actual mounting location on a primary structural member  460 ,  462 , all without bumping into any portion of the aircraft  100  or any other constraints. 
     As the landing gear  140  is being loaded, its actual location and orientation may be tracked. For instance, a scanning system may track discrete points on the landing gear during loading. Knowledge of the actual location and orientation may be used to improve the accuracy of loading the landing gear  140 . For instance, the tracked points may be compared to the modified path, and loader commands may be adjusted to reduce error between the modified path and the actual orientation and location of the landing gear  140 . 
     At block  360 , load bearing interfaces  160 ,  162  of the main landing gear  140  are affixed to primary structural members  460 ,  462  of the aircraft  100 . As the main landing gear  140  is being affixed, the loader continues to support the main landing gear  140 . The load bearing interfaces  160 ,  162  are typically large bore, tight tolerance interfaces. The multi-axis loader may also have a functionality to allow a mechanic to “bump” the main landing gear  140  relative to the primary structural members  460 ,  462 . The bumping creates very small movement to allow tight bore pins to fit. 
     In the method of  FIG. 3 , the expected mounting orientation is not necessarily upright. For instance, the main landing gear  140  may be loaded in a stowed or partially stowed orientation. 
     The method of  FIG. 3  may be used to install the main landing gear  140  in a factory during or after final body join. However, the method is not so limited. The method of  FIG. 3  may be performed on an aircraft outside of a factory. As but one example, main landing gear  140  of an aircraft  100  may be replaced while the aircraft  100  is on a runway or other flat surface  150  of an airport. In this example, the aircraft  100  is supported while the main landing gear 140  is removed from the aircraft  100 . The multi-axis loader may be used to “walk” the main landing gear  140  out of position. The ideal path would be the same, but performed backwards, to avoid collisions upon exit. After the main landing gear  140  has been removed, the multi-axis loader moves replacement main landing gear  140  to a starting location and orientation, and loads the replacement main landing gear  140  according to blocks  320  to  360 . 
     Reference is made to  FIGS. 4A-4C , which illustrate an example of a loading system  410  for loading the landing gear  140  according to the method of  FIG. 3 . The loading system  410  includes a multi-axis loader  420 . The multi-axis loader  420  includes first and second linear rails  430  that are straight and parallel to each other. The linear rails  430  define forward functional x-axes. The linear rails  430  are intended to provide a straight path alongside the aircraft  100 . 
     The linear rails  430  may be configured for mobility. For example, wheels, air bearings or castors may be mounted underneath the linear rails  430 . 
     The multi-axis loader  420  further includes a first pair of first and second loading towers  440  and  445  for the first linear rail  430 , and a second pair of first and second loading towers  440  and  445  for the second linear rail  430 . Each loading tower  440  and  445  of each pair is independently movable along its linear rail  430 . Linear motion along the linear rails  430  may be achieved with machine screw components (e.g., roller screw, ball screw, or acme screw), a rack and pinion type system (e.g., roller rack, belt system, or traditional sliding friction point), an electromagnetic linear motor, a pressured cylinder system (hydraulic or pneumatic), or other linear drive system. 
     The multi-axis loader  420  further includes a first beam  450  mounted to the first pair of loading towers  440  and  445 , and a second beam  450  mounted to the second pair of loading towers  440  and  445  (one of the beams  450  is shown most clearly in  FIG. 4C ). Each loading tower of each pair is mounted to its corresponding beam  450  at a mounting point. Each mounting point is linearly and independently movable along its corresponding loading tower  440  or  445  in a vertical y-axis. Linear motion may be achieved with machine screw components, a rack and pinion type system, an electromagnetic linear motor, a pressured cylinder system, or other linear drive system. 
     When the main landing gear  140  is placed in the multi-axis loader  420 , there is a beam  450  on each side of the main landing gear  140 . The main landing gear  140  is mounted to the beams  450 , for example, by pinching tires of the main landing gear  140  from above and below with wheel chalks  460 . 
     Through independent movement of the loading towers  440  and  445  along the linear rails  430 , and through independent movement of the mounting points along the loading towers  440  and  445 , the main landing gear  140  may be translated and tilted with respect to multiple axes. 
     The ideal path may be determined with respect to a local coordinate system of the multi-axis loader. The linear rails  430  define x-axes of the coordinate system, and the loading towers  440  and  445  define y-axes of the coordinate system. 
       FIG. 4A  shows the multi-axis loader  420  with the main landing gear  140  in the starting location and orientation. The main landing gear  140  is retracted and tilted. 
       FIG. 4B  shows the main landing gear  140  being walked under a wing  120  (the spar  460  and landing gear beam  462  of the wing  20  are shown in phantom). Each pair of loading towers  440  and  445  is slid together along the linear rails  430  in a forward direction. 
       FIG. 4C  shows the landing gear  140  at the end of the modified path, after having been walked under the aircraft  100 . The first loading towers  440  are moved ahead of the second loading towers  445 , causing the main landing gear  140  to tilt into an upright position. The forward trunion H-block fitting  160  of the main landing gear  140  is now in position to be attached to the rear wing spar  460 , and the rear trunion  162  is now in position to be pinned to the landing gear beam  462 . 
     At all times, the front wheels of the landing gear  140  are on the floor  150  so as to support some of the weight of the landing gear  140 . After the main landing gear  140  has been tilted to the upright position, all of its wheels are on the floor  150 . 
     Operation of the multi-axis loader  420  may be controlled by a controller (not shown). The controller accesses commands for the linear drive systems of the multi-axis loader  420 , modifies the commands to account for a difference between the expected and actual mounting locations, and sends the modified commands to the linear drive systems to move the main landing gear  140  along the modified path. The controller may be mounted to the multi-axis loader  420  to form a cohesive whole. Alternatively the controller may be implemented as part of a higher level cell-controller. 
     The loading system  410  may further include a metrology system  470  (shown in  FIG. 4B ), such as radar, laser tracker or vision-based motion capture. The metrology system  470  can measure the distance to specific points (e.g., features) on the actual mounting locations on the rear spar  460  and landing beam  462 . Examples of these specific points may include landing gear mounting points, tooling balls on the loader, side of body fittings, assembly pin locations, retroreflective monuments, and surface-mounted photogrammetric targets. The metrology system  470  can also measure the distance to specific points on the linear rails  430  of the multi-axis loader  420 . The metrology system  470  may also measure the distance to specific points on the main landing gear  140  as the main landing gear  140  is being loaded. Given this information, the controller can determine the difference between the expected and actual mounting locations. 
     Reference is now made to  FIG. 5 , which illustrates a method of using the loading system  410  in a factory to load main landing gear  140  in an aircraft  100 . The factory has a floor  150  that is relatively flat. The factory floor  150  may have indexing marks for positioning the aircraft  100 . For example, the indexing marks may include paint stripes for indicating the position of the aircraft  100  on the factory floor  150 . 
     The factory floor  150  may also have having indexing  480  for positioning the multi-axis loader  420  relative to the aircraft  100 . As a first example, indexing pins (not shown) may protrude from the factory floor  150 . As a second example, paint stripes  480  ( FIGS. 4A-4C ) on the factory floor  150  indicate the position of the multi-axis loader  420 . 
     At block  500 , the main landing gear  140  is placed in the multi-axis loader  420 . For instance, the landing gear  140  may be placed in the multi-axis loader  420  by an overhead crane or forklift. 
     At block  510 , the multi-axis loader  420  retracts and tilts the main landing gear  140  to its starting location and orientation. 
     At block  520 , the aircraft  100  and the multi-axis loader  420  are moved along the factory floor  150  to their respective designated positions and parked. The multi-axis loader  420  may be moved across the factory floor  150  by means such as an omni-directional crawler or a tug. If the factory floor  150  has indexing pins, the linear rails  430  of the multi-axis loader  420  may engage the indexing pins to establish a precise location on the factory floor  150 . The multi-axis loader  420  is now dimensionally stable, and its linear rails  430  will not be moved until the method has been completed. The aircraft  100  may be parked prior to parking the multi-axis loader  420 , or the multi-axis loader  420  may be parked prior to parking the aircraft  100 . 
     At block  530 , scaffolding, stands, and other temporary movable equipment (TME) are moved across the factory floor  150  and positioned relative to the aircraft  100  and the multi-axis loader  420 . TME such as scaffolding and stands may be used to fasten the landing gear  140  to the aircraft  100  and attach additional structural and articulation features after the landing gear  140  has been loaded but before it is ready to bear weight. The TME may also be used to perform or complete a wing-to-fuselage join. 
     At block  540 , the metrology system  470  is used to determine the difference between actual mounting locations and expected mounting locations on the aircraft  100 . The difference is supplied to the controller. If the actual mounting locations are obscured by aircraft skin, tooling may be indexed to the actual mounting locations. The tooling may serve as a proxy to give points with lines of sight. 
     At block  550 , the controller modifies the ideal path to move the expected mounting locations to the actual mounting locations. At block  560 , the controller commands the multi-axis loader  420  to move the landing gear  140  to follow the modified path. 
     At block  570 , load bearing interfaces  160 ,  162  of the main landing gear  140  are affixed to primary structural members  460 ,  462  of the aircraft  100 . The multi-axis loader may hold the main landing gear  140  in place while the load bearing interfaces  160 ,  162  are being affixed. 
     At block  580 , the multi-axis loader  420  is detached from the main landing gear  140 . For instance, the wheel chalks  460  may be removed. The multi-axis loader  420  is then retracted. 
     Thus, the main landing gear  140  is loaded above grade at current aircraft working height without having to raise the aircraft  100 . A series of discrete movements of the main landing gear  140  is eliminated during loading. As a result, loading time is reduced significantly. 
     The method of  FIG. 5  eliminates the need for pits and other fixed structures on a factory floor  150 . This, in turn, minimizes impact to the rest of the factory. It also enables floor space to be reconfigurable. This flexibility allows for a production line to be adjusted and optimized. Work can be balanced across multiple cells, and the location of each work cell may be shifted, by a couple feet or by a full airplane length. 
     The floor area for installing the landing gear may be shared with several labor intensive activities, including side of body join, fuselage joins, and aircraft equipment fitting. Having the loading accurately staged ahead of time allows the landing gear to be loaded without a risk of collision and with increased ergonomic access. 
     The method of  FIG. 5  is not limited to main landing gear  140 . For instance, the method of  FIG. 5  may be applied to front landing gear. 
     The methods and system above are not even limited to landing gear. For instance, the multi-axis loader may be used to install objects such as boat propellers, motors, and munitions.

Technology Classification (CPC): 1