Abstract:
An aircraft assembly ( 10 ) having an indicator ( 20 ) configured to provide an indication of when an element of the aircraft assembly has received a predetermined load or traveled to a predetermined position.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Aircraft assemblies may require a visual indicator to determine if a load or position has been exceeded. For example, load and position indicators which are frangible have been used in a landing gear assembly which break in a plurality of pieces when the load or position exceeds the pre-determined value. When the frangible indicators break, the parts will become foreign objects and may cause Foreign Object Damage (FOD) to the aircraft. Also, once broken the frangible indicator may not be reset, instead the part must be replaced causing increased costs of maintenance. Another alternate example is an electronic system for measuring inertial or physical loads. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0002]    An embodiment of the invention relates to an aircraft assembly having a movable element which moves in response to an applied load. The movable element is further coupled to a rehomeable indicator which mechanically moves between a non-home and home position in response to the moveable element moving to a predetermined position within a range of motion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0003]    In the drawings: 
           [0004]      FIG. 1  is a schematic front view of a landing gear assembly of an aircraft having a rehomeable indicator. 
           [0005]      FIG. 2  is an enlarged partial perspective view of  FIG. 1  of the indicator in a home position on the landing gear assembly. 
           [0006]      FIG. 3  is an enlarged partial view of the indicator in a non-home position on the landing gear assembly. 
           [0007]      FIG. 4  is a second embodiment of the indicator in the home position. 
           [0008]      FIG. 5  is a second embodiment of the indicator in the non-home position. 
           [0009]      FIG. 6  is a third embodiment of the indicator in the home position. 
           [0010]      FIG. 7  is a third embodiment of the indicator in the non-home position. 
           [0011]      FIG. 8  is a fourth embodiment of the indicator in the home position. 
           [0012]      FIG. 9  is a fourth embodiment of the indicator in the non-home position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]      FIG. 1  illustrates a first embodiment of an aircraft assembly  10 , one example of which is a landing gear assembly. The aircraft assembly  10  comprises a moveable element  12 , a stationary element  14 , and a rehomeable load and position indicator  20 . The moveable element  12  comprises a portion of the landing gear for an aircraft, one example of which is an actuator. The moveable element  12  is moveable through a range of motion in response to an applied load such as the actuator extending or retracting due to an internal pneumatic device or in reaction to a force of a landing. 
         [0014]    The rehomeable indicator  20  is operably coupled to the moveable element  12  such that the rehomeable indicator  20  moves from a home position  22  to a non-home position  24  in response to the moveable element  12  moving to a predetermined position within a range of motion. For example, the indicator  20  will start in the home position  22  when the actuator is retracted. When the actuator is in a predetermined normal range of extension, the indicator  20  will remain in the home position  22 . When the actuator is extended beyond the predetermined range of extension, the indicator  20  is snapped into the non-home position  24 . Once the actuator is retracted once again, the indicator  20  remains in the non-home position  24 . 
         [0015]    The predetermined position may correspond to an operational range limit in response to a predetermined load within the operational load limit. The operational load limit may be any predetermined limit wherein an inspection is necessitated if said load is exceeded. The load limit need not be the maximum limit load for the part. 
         [0016]    While the aircraft assembly  10  is illustrated as a landing gear assembly, the environment for the rehomeable indicator  20  is not limited to a particular aircraft assembly. Other aircraft assemblies are contemplated such as transmission beams, engine mounts, struts, wings, empennage, primary fittings, or other principle structural elements. The aircraft assembly  10  is not limited to the aforementioned examples. 
         [0017]    Shown in  FIGS. 2 and 3 , the load and position indicator  20  can mechanically move between a home  22  and non-home position  24 . In  FIGS. 1 and 2 , it is illustrated in the home position  22  where it is protruding perpendicularly to both the moveable element  12  and stationary element  14 . The first end  42  of the indicator  20  is a free end while the second end  44  is coupled to the moveable element  12 , in a cantilevered in position. The home position  22  corresponds to a position which visually signals that the aircraft assembly  10  to which the indicator  20  is coupled has not experienced any excessive force or displacement. The non-home position  24 , shown in  FIG. 3 , visually signals that the aircraft assembly  10  has experienced an excessive force or displacement. The non-home position  24  is illustrated as curled or coiled, but may be of other positions as long as the non-home position  24  is obviously visually different than the home position  22 . The rehomeable indicator  20  is non-frangible when moving between the home  22  and non-home position  24  and vice versa. 
         [0018]    The term “non-frangible” as described herein is defined as not breaking, splitting, or coming apart. The part will remain intact throughout changes in position regardless of the number of times the position is changed. 
         [0019]    The term “rehomeable” as described herein is defined as having the ability to be repositioned into another semi-permanent position. If no force is applied to the item, the item will stay in the current position. 
         [0020]    The indicator  20  comprises a concave side  26  and a convex side  28 . The indicator  20  comprises a bistable spring band  40  having a first stable condition  34  corresponding to the non-home position  24  and a second stable condition  32  corresponding to a home position  22 . The bistable spring band  40  is configured to change between the first  34  and second  32  conditions in response to the application of a predetermined force  50 , not shown. The predetermined force  50  corresponds to a predetermined load acting on the moveable element  12 . The bistable spring band  40  has one portion  46  located within the path of movement of the moveable element  12  such that the bistable spring band  40  moves between the second  32  and first  34  conditions when the moveable element  12  contacts the one portion  46 . A second end  44  is operably coupled to the moveable element  12 . The bistable spring band  40  comprises opposing first  42  and second  44  ends, and the one portion  46  lies between the second  44  and first  42  ends. 
         [0021]    The indicator  20  is made of a thin rectangular material that is slightly curved, forming the concave side  26  and opposing convex side  28 . If the force or displacement is applied to the convex side  28 , the indicator  20  will not move to the non-home position  24 . If the force or displacement is applied to the concave side  26 , the indicator will move to the non-home position  24 . 
         [0022]    The indicator  20  in the first embodiment is made of metal and may have a fabric or plastic covering but it may be any material which can repeatably move from one stable position to another, visually different, stable position. The indicator  20  may comprise layers of different materials or be of a uniform material. 
         [0023]      FIG. 3  illustrates an enlarged view of the indicator  20  in the non-home position  24 . The first end  42  is curled and visually indicates that a load or position has been exceeded. The indicator  20  is rehomeable and thus can be reset to the home position by the user. The indicator  20  is manually moveable from the non-home  24  to the home position  22  and is repeatable, resettable between the non-home  24  and home positons  22  without failing. The indicator  20  can be moved from the home position  22  to the non-home position  24  by a force or displacement acting on the indicator  20  directly or indirectly through the aircraft assembly  10  to which the indicator  20  is coupled. Only a user can manually move the indicator  20  back to the home position  22  once the indicator  20  is in the non-home position  24 . 
         [0024]      FIG. 4  illustrates a second embodiment of an indicator  120  in the home position  122 . The second embodiment is similar to the first embodiment, with the primary difference being the second embodiment comprises a mass  130  at the first end  142 . The mass can be tuned to the desired inertial load range due to acceleration or deceleration by adjusting the weight and having a heavier tip at end  142 . An alternate embodiment may have increased thickness at the first end  142  instead of a separately added mass  130 . For the most part, like parts between the two embodiments will be identified with like numerals, with the numerals of the second embodiment being increased by  100 . 
         [0025]      FIG. 5  illustrates the second embodiment of the indicator  120  in a non-home position  124  which acts in the same manner as aforementioned in  FIG. 3 . The first end  142  is in the curled position after an inertial load exceeds the pre-determined range. The added thickness or mass  130  will not prevent the indicator  120  from moving to the non-home position  124  and curling but facilitate the changing of position via an inertial load instead of necessitating a physical, applied force. 
         [0026]      FIG. 6  illustrates a third embodiment of an indicator  220  in the home position  222 . The indicator  220  is a long strip of material, of any applicable cross section e.g. flat, round, square, held at each end  242  and  244  in a configuration where it is bowed upwards. The indicator  220  is illustrated as being surrounded by a support element  216  on three sides with the indicator  220  spanning the distance between two sides of the support element  216 . A force  250  may be applied to the indicator  220  by direct contact, inertial force, or indirectly through the aircraft assembly  210  to which the indicator  220  is coupled. The material and shape can be any which will allow the indicator  220  to move from the home position  222  to the non-home position  224  and remain in the non-home position  224  until the user manually changes the position back to the home position  222 .  FIG. 7  illustrates the third embodiment of an indicator  220  in the non-home position  224  in a bowed downwards position after the force  250  has been applied. 
         [0027]      FIG. 8  illustrates a fourth embodiment of an indicator  320  in the home position. The fourth embodiment is similar to the third embodiment, with the primary difference being the fourth embodiment comprises a mass  330  at the center. The mass can be tuned to the desired inertial load range due to acceleration by having a heavier section. An alternate embodiment may have increased thickness at the center instead of an added mass  330 . For the most part, like parts between the two embodiments will be identified with like numerals, with the numerals of the fourth embodiment being increased by  100 . 
         [0028]      FIG. 9  illustrates the indicator  320  in the non-home position, similar to the aforementioned in  FIG. 7  in a bowed down position, after an inertial force has been applied. 
         [0029]    Regarding  FIGS. 1-5 , the first and second embodiments of the indicator  20 , 120  respectively, protrude horizontally from the moveable element  12 ,  112 . In alternate embodiments, the indicator  20 ,  120  may be vertically oriented or disposed inside a moveable element  12 ,  112 . When a physical load, inertial load, or position is exceeded, the indicator  20 ,  120  is snapped into the non-home position  24 ,  124 . The force applied on the concave side  26 ,  126  cause the indicator  20 ,  120  to curl under the convex side  28  so the concave side  26  become the outer side due to the shape and designed thickness. The thickness of material can be made to correspond to the operational load range so as to not snap to the non-home positon  24  when too light of a force is applied. The force which snaps the indicator  20  to the non-home position will differ based on the implementation of the invention. 
         [0030]    When the indicator  20 ,  120  is in the non-home position  24 ,  124 , this alerts a user to inspect the area for damage caused by the exceeded load or displacement e.g. a hard landing. A hard landing causes a high deceleration which can be detrimental to a landing gear assembly. If an indicator  20 ,  120  is on each landing gear assembly, the indicators  20 ,  120  work independently thus allowing a user to quickly see if there was an asymmetric hard landing. When the inspection of the area is complete a user may uncurl the indicator  20 ,  120  in order to reset to the home position  22 ,  122 . In this manner the indicator  20 ,  120  may be triggered and reset as many times as needed. 
         [0031]    There are at least three methods to activate the indicator  20 ,  120  to snap from the home position  22 ,  122  to the non-home positon  24 ,  124 . One, is if a physical force  50 ,  150  is applied directly or indirectly against any part of the concave side  26 ,  126  of the indicator  20 ,  120 . The second is if an inertial load is applied either directly or indirectly to the indicator  20 , 120  on the concave side  26 ,  126 . The mass  130  or thickened section will react the inertial load which will result in the snapping of the indicator  120  into the non-home position. The inertial force is typically indirectly applied to the indicator  120  when the entire aircraft assembly  100  or individual part of the aircraft assembly  100  like the moveable element  112  experiences an application of a high force, e.g. the jarring force of a hard landing. The third is if a position of a part is exceeded. For example, if the actuator is over extended. This will push the indicator  20 ,  120  from the home position  22 ,  122  into the non-home position  24 ,  124 . 
         [0032]    Regarding  FIGS. 6-9 , the third and fourth embodiments of the indicator  220 ,  320  respectively also react to any of the at least three methods aforementioned. Both ends  242 ,  342  and  244 ,  344  are fixed and the center moves between the home position  222 ,  322  and the non-home position  224 ,  324  instead of curling as illustrated in the first and second embodiments. 
         [0033]    This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.