Abstract:
Methods for servicing shock struts are provided. In various embodiments, a method for servicing a shock strut may comprise deflating the shock strut; compressing the shock strut until the shock strut is in a fully compressed position; and charging the shock strut with a liquid until a pressure of the liquid decreases a volume of a residual air located inside of the shock strut. In various embodiments, charging the shock strut with liquid under pressure may reduce the volume of trapped air inside of the shock strut to a negligible volume, eliminating the servicing variations.

Description:
FIELD 
       [0001]    The present disclosure relates to landing gear, and more particularly, to systems and methods for increasing the serviceability of shock struts within landing gear. 
       BACKGROUND 
       [0002]    Functionality and performance of a landing gear shock strut depends on its gas pressure and oil volume. Often, a shock strut assembly features a piston that compresses a fluid within a sealed chamber. The fluid typically includes a gas segment and a liquid segment. To this end, shock struts may be serviced with gas and hydraulic fluid on a regular basis to compensate for normal gas and oil leakage during operation. With typical single stage shock struts, the aircraft is lifted above the ground so that the shock strut can be cycled multiple times in attempt to fully remove any trapped gas internal to the shock strut during servicing. This can be time consuming, cumbersome, and/or costly. 
       SUMMARY 
       [0003]    Methods for servicing a shock strut are provided. A method for servicing a shock strut may comprise: deflating the shock strut; compressing the shock strut until the shock strut is in a fully compressed position; and charging the shock strut with a liquid until a pressure of the liquid decreases a volume of a residual air located inside of the shock strut. 
         [0004]    In various embodiments, the method may further comprise increasing the pressure of the liquid until a shock strut piston reaches a pre-determined extension. The method may further comprise charging the shock strut with a gas. The method may further comprise discharging a pre-determined volume of liquid from the shock strut. The shock strut may include a first valve and a second valve. The compressing may be performed via at least one of a jack or a weight of a vehicle, the vehicle supported at least in part by the shock strut. The method may further comprise lowering the jack until a shock strut piston is in a fully extended position. 
         [0005]    A method for weight on wheel shock strut servicing may comprise: deflating the shock strut until the shock strut is in a fully compressed position; charging the shock strut with an oil until a pressure of the oil decreases a volume of a residual air located inside of the shock strut; and charging the shock strut with a gas until the gas comprises a pre-determined pressure. 
         [0006]    In various embodiments, the charging the shock strut with the oil may comprise pumping the oil into a second valve and closing a first valve in response to the oil exiting the shock strut via the first valve. The deflating may comprise releasing the gas from the shock strut, wherein a weight of a vehicle, supported at least in part by the shock strut, compresses the shock strut. The pre-determined pressure may be determined, at least in part, based upon a servicing temperature. The method may further comprise increasing the pressure of the oil until a shock strut piston reaches a pre-determined extension. The pre-determined extension may be determined, at least in part, based upon a servicing temperature. The method may further comprise discharging a pre-determined volume of oil from the shock strut. The pre-determined volume of oil may be determined, at least in part, based upon a servicing temperature. 
         [0007]    A method for weight off wheel shock strut servicing may comprise: deflating the shock strut; compressing the shock strut via a jack until the shock strut is in a fully compressed position; charging the shock strut with an oil until a pressure of the oil reduces a volume of a residual air located inside of the shock strut; lowering the jack until a shock strut piston reaches a pre-determined extension; and charging the shock strut with a gas until the gas comprises a pre-determined pressure. 
         [0008]    In various embodiments the charging the shock strut with the oil may comprise pumping the oil into a second valve and closing a first valve in response to the oil exiting the shock strut via the first valve. The deflating may comprise releasing the gas from the shock strut. The pre-determined pressure may be determined, at least in part, based upon a servicing temperature. The pre-determined extension may be determined, at least in part, based upon a servicing temperature. 
         [0009]    The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures, wherein like numerals denote like elements. 
           [0011]      FIG. 1  illustrates, in accordance with various embodiments, a single stage shock strut for use in landing gear of an aircraft; 
           [0012]      FIG. 2A  illustrates, in accordance with various embodiments, a schematic view of a shock strut in a fully compressed position during a weight on wheel oil servicing procedure including filling a strut with oil; 
           [0013]      FIG. 2B  illustrates, in accordance with various embodiments, a schematic view of a shock strut in a fully compressed position during a weight on wheel oil servicing procedure including charging a strut with pressurized oil; 
           [0014]      FIG. 2C  illustrates, in accordance with various embodiments, a schematic view of a shock strut in a fully compressed position during a weight on wheel servicing procedure according to procedure #2 of the servicing chart in  FIG. 3 ; 
           [0015]      FIG. 2D  illustrates, in accordance with various embodiments, a schematic view of a shock strut extended to a pre-determined position during a weight on wheel gas servicing procedure including charging a strut with gas; 
           [0016]      FIG. 2E  illustrates, in accordance with various embodiments, a schematic view of a shock strut extended to a pre-determined position during a weight on wheel servicing procedure according to procedure #1 of the servicing chart in  FIG. 3 ; 
           [0017]      FIG. 3  illustrates, in accordance with various embodiments, a shock strut oil servicing chart; 
           [0018]      FIG. 4  illustrates, in accordance with various embodiments, a shock strut gas servicing chart; 
           [0019]      FIG. 5A  illustrates, in accordance with various embodiments, a schematic view of a shock strut in a fully compressed position during a weight off wheel servicing procedure according to procedure #2 of the servicing chart in  FIG. 3 ; 
           [0020]      FIG. 5B  illustrates, in accordance with various embodiments, a schematic view of a shock strut in a fully extend position during a weight off wheel gas servicing procedure; 
           [0021]      FIG. 5C  illustrates, in accordance with various embodiments, a schematic view of a shock strut extended to a pre-determined position during a weight off wheel servicing procedure according to procedure #1 of the servicing chart in  FIG. 3 ; 
           [0022]      FIG. 6  illustrates, in accordance with various embodiments, a method for weight on wheel servicing of a shock strut; and 
           [0023]      FIG. 7  illustrates, in accordance with various embodiments, a method for weight off wheel servicing of a shock strut. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]    The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical and mechanical changes may be made without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected or the like may include permanent, removable, temporary, partial, full and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact. 
         [0025]    Aircraft landing gear systems in accordance with the present disclosure may comprise a shock strut. A shock strut may comprise various fluids such as oil and gas. Performance of the shock strut may be evaluated by monitoring aspects of the shock strut, including gas temperature, gas pressure, oil pressure, and stroke of the shock strut at various points during operation of the aircraft. Stroke may refer to a shock strut piston position. Servicing of a shock strut may be performed weight on wheel or weight off wheel or also a combination of weight on wheel and weight off wheel. Weight on wheel service refers to the servicing of a shock strut when the weight of a vehicle, such as an aircraft, is supported by the vehicles wheel assembly via at least one shock strut on the ground. Weight off wheel service refers to the servicing of a shock strut when the weight of a vehicle, such as an aircraft, is not supported by the vehicles wheel assembly via at least one shock strut on the ground. In the case of weight off wheel, the vehicles weight may be supported by the frame of the vehicle, such as an aircraft wing, for example. 
         [0026]    Accordingly, with reference to  FIG. 1 , a landing gear assembly  100  is illustrated. In various embodiments, landing gear assembly  100  comprises a shock strut  104 . Shock strut  104  may be mechanically coupled to a wheel assembly  106 . In various embodiments, shock strut  104  may be configured to absorb and dampen forces transmitted by wheel assembly  106  to an aircraft. 
         [0027]    Shock strut  104  may comprise, for example, a piston  102  and a cylinder  108 . Cylinder  108  may be configured to receive piston  102  in a manner that allows the two components to telescope together and absorb and dampen forces transmitted by wheel assembly  106 . 
         [0028]    In various embodiments, a liquid, such as hydraulic fluid or an oil, is located within cylinder  108 . Cylinder  108  and piston  102  may, for example, be configured to seal such that liquid contained within cylinder  108  is prevented from leaking as piston  102  translates relative to cylinder  108 . Further, cylinder  108  may be configured to contain a gas or air. Shock strut  104  may comprise a proximal end and a distal end, wherein the distal end is opposite the proximal end, the distal end being the end of the shock strut closest to a wheel or wheel assembly of a vehicle, such as wheel assembly  106 , for example. The air may be positioned above the oil (referred to as an “air-over-oil” arrangement) or vice versa, where the term “above” in this context means in the direction of the proximal end of the shock strut. Similarly, cylinder  108  and piston  102  may be sealed such that gas and oil is prevented from leaking as piston  102  moves relative to cylinder  108 . As such, shock strut  104  may comprise a pressurized environment within cylinder  108 . 
         [0029]    Shock strut  104  may further comprise, for example, a gas pressure sensor  110 . In various embodiments, gas pressure sensor  110  may be capable of measuring the pressure of the gas within shock strut  104  at a desired time. For example, gas pressure sensor  110  may measure the gas pressure within shock strut  104  before, during, or after take-off, or at any point during the duty cycle of shock strut  104 . 
         [0030]    In various embodiments, shock strut  104  may further comprise, for example, a gas temperature sensor  112 . Gas temperature sensor  112  may be capable of measuring the temperature of the gas within shock strut  104  at any point during the duty cycle of shock strut  104 . 
         [0031]    Similarly, shock strut  104  may comprise an oil pressure sensor  114 . In various embodiments, oil pressure sensor  114  may be capable of measuring the pressure of the oil within shock strut  104  at a desired time. For example, oil pressure sensor  114  may measure the oil pressure within shock strut  104  at any point during the duty cycle of shock strut  104 . 
         [0032]    In various embodiments, shock strut  104  may include various other sensors. Shock strut  104  may include a temperature sensor. A temperature sensor may be used to measure the temperature of oil inside of shock strut  104 . 
         [0033]    Shock strut  104  may also comprise a position sensor  116 . In various embodiments, position sensor  116  may be capable of measuring the position of piston  102  relative to cylinder  108 , which is conventionally referred to as the stroke or stroke, of shock strut  104  at a desired time. Position sensor  116  may be configured to measure the position indirectly, for example, by measuring the orientation of one or more shock strut torque links  118  (or other components). For example, position sensor  116  may measure the stroke of shock strut  104  at any point during the duty cycle of shock strut  104 . 
         [0034]    With respect to  FIG. 2B  through  FIG. 2E , elements with like element numbering, as depicted in  FIG. 2A , are intended to be the same and will not necessarily be repeated for the sake of clarity. 
         [0035]    With reference to  FIG. 2A , a schematic view of a shock strut (also referred to herein as a single stage shock strut)  200  is illustrated in a fully compressed position. In various embodiments, shock strut  210  may be similar to shock strut  104  (see  FIG. 1 ). In various embodiments, shock strut  210  may include piston  202  and cylinder  204 . In various embodiments, cylinder  204  may be configured to receive piston  202  in a manner that allows the two components to telescope together and absorb and/or dampen forces transmitted by wheel assembly  206 . 
         [0036]    In various embodiments, shock strut  210  may include a gas charge/dis-charge valve (also referred to herein as a first valve)  212 . In various embodiments, gas charge/discharge valve  212  may be used to discharge gas from inside of shock strut  210 . In various embodiments, gas charge/discharge valve  212  may be used to charge gas into shock strut  210 . In various embodiments, gas charge/discharge valve  212  may be used to charge and/or discharge oil into shock strut  210 . In various embodiments, shock strut  210  may include an oil charge/discharge valve (also referred to herein as a second valve)  214 . In various embodiments, oil charge/discharge valve  214  may be used to charge oil into shock strut  210 . In various embodiments, oil charge/discharge valve  214  may be used to discharge oil from shock strut  210 . Although shock strut  210  is described herein as a shock strut comprising two charge/discharge valves  212 ,  214 , the methods as described herein may be performed on a shock strut having a single valve. For example, an adaptor with two ports may be connected to a single valve of shock strut  210 , wherein one of the ports is connected to an oil pump and the other port is connected to a charged gas cylinder. 
         [0037]    With momentary reference to  FIG. 6  a method for weight on wheel servicing of a shock strut is provided, in accordance with various embodiments. 
         [0038]    In various embodiments, a weight on wheel shock strut servicing procedure  200  may be performed. Weight on wheel shock strut servicing procedure  200  may include an oil servicing procedure followed by a gas servicing procedure. In various embodiments, weight on wheel shock strut servicing procedure  200  may begin by deflating the shock strut  210  (Step  602 ) such that it is in a fully compressed position as illustrated in  FIG. 2A . Shock strut  210  may be deflated by removing gas from inside of shock strut  210  via gas charge/discharge valve  212 . Stated another way, shock strut  210  may be deflated by opening gas charge/discharge valve  212 . However, shock strut  210  may be deflated via any suitable method. The weight of a vehicle, such as an aircraft for example, may compress shock strut  210  into a fully compressed position when servicing is performed weight on wheel. A first hose  216  may be coupled to gas charge/discharge valve  212 . In various embodiments, first hose  216  may be a transparent hose. In various embodiments, any air pockets located in oil flowing through first hose  216  may be visible through first hose  216 . A second hose  218  may be coupled to the oil charge/discharge valve  214 . The second hose  218  may be coupled to an oil pump  220  (see  FIG. 2B ). Hydraulic fluid (also referred to herein as oil) may be pumped into the shock strut  210 . Oil may be pumped into shock strut  210  until oil starts to flow out of the shock strut through first hose  216  as shown at arrow  224 . Thus, oil may be cycled through shock strut  210 , wherein oil enters shock strut  210  via the oil charge/discharge valve  214  and exits shock strut  210  via gas charge/discharge valve  212 . Oil flowing out of first hose  216  may be captured in a container  222  as shown at arrow  224 . Gas charge/discharge valve  212  may be closed in response to oil beginning to flow out first hose  216 . Accordingly, shock strut  210  may be filled with oil. 
         [0039]    With reference to  FIG. 2B , weight on wheel shock strut servicing procedure  200  of shock strut  210  may be continued by monitoring shock strut  210  internal pressure. As illustrated in  FIG. 2B , pressure is monitored by attaching a pressure gauge  230  to charge/discharge valve  212 . However, it is contemplated that shock strut  210  internal pressure may be measured using any suitable method. For example, shock strut  210  may be equipped with a gas pressure transducer which may monitor shock strut pressure. Thus, pressure gauge  230  may not be used in some instances. In various embodiments, pressure gauge  230  may be located at charge discharge valve  214  or at oil pump  220 . 
         [0040]    In various embodiments, a servicing temperature may be measured. The servicing temperature may be the ambient temperature. An operator or technician may determine an oil servicing procedure based upon the measured servicing temperature. In various embodiments, a first or second oil servicing procedure may be performed wherein the first oil servicing procedure involves the shock strut extending during the oil servicing procedure and the second oil servicing procedure involves the shock strut remain fully compressed or retracted during the oil servicing procedure. What follows is a description of a second oil servicing procedure followed by the gas servicing procedure which concludes a weight on wheel shock strut servicing procedure, in accordance with various embodiments. Then, a first oil servicing procedure is described with reference to  FIG. 2E , in accordance with various embodiments. 
         [0041]    With momentary reference to  FIG. 3 , a service chart  300  may be provided. Service chart  300  may indicate to a technician the type of oil servicing procedure to use depending on the servicing temperature. For example, as illustrated in  FIG. 2B , if the servicing temperature were negative twenty degrees Celsius (−20° C.) (−4° F.), then service chart  300  may indicate to a technician to use procedure #2 (also referred to herein as a second oil procedure). 
         [0042]    In various embodiments, with gas charge/discharge valve  212  closed, oil may be pumped into shock strut  210  via oil charge/discharge valve  214  at pressure (see step  603 ). In various embodiments, oil may be pumped into shock strut  210  via gas charge/discharge valve  212 . Oil may be pumped into shock strut  210  until the internal pressure of the oil inside of shock strut  210  is large enough to crush any pockets of air (also referred to herein as residual air) located inside of shock strut  210  but not large enough to extend shock strut  210 . Accordingly, the volume of any residual air inside of shock strut  210  may be reduced to a negligible volume. In various embodiments, a negligible volume may be defined as having reduced the volume of residual air inside of the shock strut  210  by at least ten times. Thus, the pressure of the oil inside of the shock strut may be increased. Stated another way, shock strut  210  may be filled with pressurized oil. For example, oil may be pumped into shock strut  210  until the internal pressure of shock strut  210  reaches between 100 and 150 psig (689.48-1034.21 kPa). Next, oil charge/discharge valve  214  may be closed and second hose  218  removed. The internal pressure of shock strut  210  may be recorded and, if applicable, pressure gauge  230  may be removed. This may complete the oil servicing procedure. 
         [0043]    With reference to  FIG. 2C , a gas servicing procedure may be performed according to procedure #2 of servicing chart (see  FIG. 3 ) following the oil servicing procedure. A compressed gas tank  236  may be coupled to gas charge/discharge valve  212 . In various embodiments, compressed gas tank  236  may contain a gas such as nitrogen. However, it is contemplated that any suitable gas may be contained by compressed gas tank  236 . In various embodiments, compressed gas tank  236  may be coupled to gas charge/discharge valve  212  via a hose (also referred to herein as a gas charging hose)  238  or any other suitable method. In various embodiments, gas charging hose  238  may be pressurized to a pressure which is greater than the internal pressure of the shock strut before opening gas charge/discharge valve  212  in order to avoid back flow of oil when gas charge/discharge valve  212  is opened. In various embodiments, the gas charge/discharge valve  212  may be opened to maintain pressure inside of shock strut  210 . 
         [0044]    In various embodiments, with shock strut  210  in a fully compressed position, a variable valve  232  may be coupled to oil charge/discharge valve  214 . In various embodiments, variable valve  232  may comprise ground support equipment (GSE). In various embodiments, variable valve  232  may comprise a valve with a variable restriction flow path such that a flow rate of a fluid flowing through variable valve  232  may be varied in a controlled manner. In various embodiments, a measuring element  234  may be used during the gas servicing procedure. In various embodiments, measuring element  234  may comprise a graduated container or the like for measuring the volume of a fluid. The technician may use the variable valve  232  to drain or discharge a pre-determined volume of oil from shock strut  210  (see step  604 ) into measuring element  234  according to service chart  300  (see  FIG. 3 ). Continuing with the example of a servicing temperature of −20° C., the technician may drain sixteen cubic inches (16 in 3 ) (262.19 cm 3 ) from shock strut  210  into measuring element  234 . Thus, shock strut  210  may be filled with a desired amount of oil. The variable valve  232  may then be removed and oil charge/discharge valve  214  closed and capped. 
         [0045]    With reference to  FIG. 2D , a continuation of the gas servicing procedure is illustrated. With the desired amount of oil inside of shock strut  210 , the gas servicing procedure may continue by charging or inputting gas from compressed gas tank  236  into shock strut  210  via gas charge/discharge valve  212 . Accordingly, gas may be charged into shock strut  210  until the internal pressure of shock strut  210  counteracts the weight of a vehicle supported by shock strut  210  and the shock strut  210  extends. With further reference to  FIG. 4 , gas may be charged into shock strut  210  (see step  606 ) until the internal pressure “P 2 ” of shock strut  210  and the extension dimension “X2” of shock strut  210  match the reference curves  402  at the servicing temperature as initially used in service chart  300  (see  FIG. 3 ). Thus,  FIG. 4  illustrates internal pressure “P 2 ” and extension dimension “X2” matching the reference curves  402  at the servicing temperature of −20° C. In various embodiments, this may determine that weight on wheel shock strut servicing procedure  200  is appropriate. 
         [0046]    With reference to  FIG. 2E , during weight on wheel shock strut servicing procedure  200  the servicing temperature may be such that service chart  300  (see  FIG. 3 ) indicates to a technician to use Procedure #1 (also referred to herein as a first oil procedure). For example, if the servicing temperature is 50° C., service chart  300  may indicate to use procedure #1. In various embodiments, procedure #1 may include pumping oil into shock strut  210  until the internal pressure counter acts the weight of a vehicle supported by shock strut  210  and piston  202  extends to extension “X1” (also referred to herein as a pre-determined extension) as illustrated in  FIG. 2E  (see step  605 ). For example, if the servicing temperature is 50° C., then according to service chart  300  of  FIG. 3 , oil may be pumped into shock strut  210  until piston  202  extends to an extension “X1” of 0.5″. Thus, a greater volume of oil may be pumped into shock strut  210  in procedure #1 than in procedure #2 as described herein. This may compensate for thermal expansion of the oil at higher temperatures. Accordingly, shock strut  210  may be filled with a desired volume of oil. Next, as previously mentioned oil charge/discharge valve  214  may be closed and second hose  218  removed. The internal pressure of shock strut  210  may be recorded and, if applicable, pressure gauge  230  may be removed. This may complete the oil servicing procedure. The gas servicing procedure may then continue as previously described in  FIG. 2D  in regards to weight on wheel shock strut servicing procedure  200 . 
         [0047]    With respect to  FIG. 5A  through  FIG. 5C , elements with like element numbering, as depicted in  FIG. 2A  through  FIG. 2E , are intended to be the same and will not be repeated for the sake of clarity. 
         [0048]    A second oil servicing procedure is described followed by a gas servicing procedure which concludes a weight off wheel shock strut servicing procedure, in accordance with various embodiments. Then, a first oil servicing procedure is described in  FIG. 5C , in accordance with various embodiments. 
         [0049]    With reference to  FIG. 5A , a weight off wheel shock strut servicing procedure  500  may be performed, in accordance with various embodiments. Weight off wheel shock strut servicing procedure  500  may include an oil servicing procedure followed by a gas servicing procedure. In various embodiments, weight off wheel shock strut servicing procedure  500  may be similar to weight on wheel shock strut servicing procedure  200 . 
         [0050]    With momentary reference to  FIG. 7  a method  700  for weight off wheel servicing of a shock strut is provided, in accordance with various embodiments. 
         [0051]    In various embodiments, weight off wheel shock strut servicing procedure  500  may begin by deflating the shock strut  210  (see step  702 ) in a similar manner as described in weight on wheel shock strut servicing procedure  200 . However, the weight of a vehicle, such as an aircraft for example, may be supported by means other than the wheel assembly  206 . Thus, a jack  552  may be used to compress shock strut  210  into a fully compressed position as illustrated in  FIG. 5A  (see step  703 ). 
         [0052]    As described herein, with momentary reference to  FIG. 3 , a service chart  300  may be used to determine if a first or second oil servicing procedure should be used to service shock strut  210  according to the servicing temperature. In the event that it is determined that procedure #2 should be used, oil may be pumped into shock strut  210  in a similar manner as described in weight on wheel shock strut servicing procedure  200  until the internal pressure of the oil inside of shock strut  210  is large enough to crush any pockets of air (also referred to herein as residual air) located inside of shock strut  210  but not large enough to extend shock strut  210  (see step  704 ). For example, oil may be pumped into shock strut  210  until the internal pressure of shock strut  210  reaches between 100 and 150 psig (689.48-1034.21 kPa). Next, oil charge/discharge valve  214  may be closed and second hose  218  removed. The internal pressure of shock strut  210  may be recorded and, if applicable, pressure gauge  230  may be removed. This may complete the oil servicing procedure. Similar to weight on wheel procedure, following the oil servicing procedure, a compressed gas tank  236  may be coupled to gas charge/discharge valve  212  and a variable valve  232  (see  FIG. 2C ) may be used to drain or discharge a pre-determined volume of oil from shock strut  210  (see step  705 ) into measuring element  234  (see FIG.  2 C) according to service chart  300  (see  FIG. 3 ) while oil remains pressurized by the gas tank  236  (see  FIG. 5B ). 
         [0053]    With reference to  FIG. 5B , a gas servicing procedure is illustrated, in accordance with various embodiments, for a weight off wheel shock strut servicing procedure  500 . In various embodiments, gas may then be charged into shock strut  210  via compressed gas tank  236 . Jack  552  may then be slowly lowered while gas is charged into shock strut  210  until shock strut  210  is in a fully extended position as illustrated in  FIG. 5B  (see step  707 ). Shock strut  210  may comprise an extension dimension “X max ” (also referred to herein as a pre-determined extension) when shock strut  210  is in a fully extended position. Gas may continue to be charged into shock strut  210  until the internal pressure of shock strut  210  reaches a value that corresponds to the reference curves  402  given in servicing chart  400  (see  FIG. 4 ) corresponding to the servicing temperature and an extension of “X max ” (see step  708 ). When the desired pressure is reached, gas charge/discharge valve may be closed and the compressed gas tank removed from shock strut  210 . 
         [0054]    With reference to  FIG. 5C , procedure #1 (see  FIG. 3 ) for weight off wheel shock strut servicing procedure  500  is described, in accordance with various embodiments. Oil may be pumped into shock strut  210  via oil charge/discharge valve  214  until the internal pressure of shock strut  210  is large enough to crush any pockets of residual air located inside of shock strut  210  but not large enough to extend shock strut  210 . Next, while oil pressure is maintained by pumping oil into shock strut  210 , jack  552  may be slowly lowered until piston  202  has extended to a pre-determined extension “X1” according to service chart  300  (see  FIG. 3 ) (see step  706 ). Next, oil charge/discharge valve  214  may be closed and second hose  218  removed. The internal pressure of shock strut  210  may be recorded and, if applicable, pressure gauge  230  may be removed. This may complete the oil servicing procedure. The gas servicing procedure may then continue as previously described in  FIG. 5B  in regards to weight off wheel shock strut servicing procedure  500 . 
         [0055]    Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials. 
         [0056]    Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments. 
         [0057]    Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.