Patent Publication Number: US-2023133806-A1

Title: Pylon system for coupling engine to vehicle

Description:
TECHNICAL FIELD 
     The present disclosure generally relates to systems for coupling an engine to a vehicle, and more particularly relates to a pylon system for coupling a gas turbine engine to a vehicle, such as an aircraft. 
     BACKGROUND 
     Gas turbine engines may be employed to power various devices. For example, a gas turbine engine may be employed to propel or supply power to a vehicle, such as an aircraft. Due to the size or configuration of the aircraft, in certain instances, the gas turbine engine may need to be mounted on a side of an airframe of the aircraft. In certain examples, the gas turbine engine may include a thrust reverser, which is deployable to move relative to the gas turbine engine to redirect turbine engine exhaust flow in order to generate reverse thrust to assist in stopping the aircraft. Generally, however, most side mounted gas turbine engines are unable to employ a thrust reverser that moves relative to the gas turbine engine to deploy due to mounting constraints. 
     Accordingly, it is desirable to provide a pylon structure for coupling a gas turbine engine to a vehicle, such as an aircraft, which enables a thrust reverser associated with the gas turbine engine to move relative to the gas turbine engine to deploy. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background. 
     SUMMARY 
     According to various embodiments, a pylon system for coupling an engine to a vehicle is provided. The pylon system includes a vehicle pylon configured to be coupled to the vehicle. The vehicle pylon includes a seal along a portion of the vehicle pylon. The pylon system includes an engine pylon including an inboard longeron and an outboard longeron. The inboard longeron is coupled to the outboard longeron at a first end of the engine pylon and is spaced apart from the outboard longeron at a second end of the engine pylon. The engine pylon is configured to be coupled to the engine, and the engine pylon is slidably coupled to the seal such that the engine pylon is movable relative to the vehicle pylon between at least a first position and a second position. 
     The engine includes a translating cowl thrust reverser that is movable between at least a first, stowed position and a second, deployed position. The engine pylon is configured to be coupled to the translating cowl thrust reverser of the engine and the engine pylon is configured to move with the translating cowl thrust reverser between at least the first position and the second position. The inboard longeron further comprises a forward seal at the first end. The pylon system includes a vehicle forward seal coupled to the vehicle pylon, and the forward seal is configured to contact the vehicle forward seal in the first position of the engine pylon. At least a portion of the outboard longeron overlaps the inboard longeron at the first end. The pylon system includes at least one spacer coupled to the inboard longeron proximate the outboard longeron to define a uniform exterior surface for the inboard longeron. The inboard longeron includes an inboard seal that extends along the inboard longeron from the first end to the second end. The pylon system includes an engine skin panel coupled to the inboard longeron and the outboard longeron from the first end to the second end, a vehicle skin panel coupled to the vehicle pylon, and the vehicle skin panel is substantially parallel with the engine skin panel. Each of the vehicle skin panel and the engine skin panel define at least one removable access panel. The seal of the vehicle pylon is coupled to the vehicle skin panel. The vehicle pylon includes a vehicle longeron that is coupled to the vehicle skin panel. The inboard longeron includes at least one fastening aperture configured to receive a fastener to couple the inboard longeron to the engine. The at least one fastening aperture includes at least one serrated slot configured to receive the fastener. The seal of the vehicle pylon further comprises a pair of blade seals and the engine pylon is movable relative to the vehicle pylon along the pair of blade seals. The pylon system includes a skin panel coupled to the inboard longeron and the outboard longeron such that the skin panel extends beyond the outboard longeron to define a rail, and the rail is slidably coupled to the seal. The engine is a gas turbine engine and the vehicle is an aircraft. 
     Also provided is a pylon system for coupling an engine to a vehicle. The pylon system includes a vehicle pylon configured to be coupled to the vehicle. The vehicle pylon includes a vehicle skin panel that defines an exterior surface of the vehicle pylon, and a seal coupled to the vehicle skin panel that extends along a portion of the vehicle pylon. The pylon system includes an engine pylon including an inboard longeron, an outboard longeron and a skin panel that encloses the inboard longeron and the outboard longeron. The inboard longeron is coupled to the outboard longeron at a first end of the engine pylon and spaced apart from the outboard longeron at a second end of the engine pylon. The engine pylon is configured to be coupled to the engine, and the skin panel is coupled to the outboard longeron to define a rail that is slidably coupled to the seal such that the engine pylon is movable relative to the vehicle pylon between at least a first position and a second position. 
     The engine includes a translating cowl thrust reverser that is movable between at least a first, stowed position and a second, deployed position, the engine pylon is configured to be coupled to the translating cowl thrust reverser of the engine and the engine pylon is configured to move with the translating cowl thrust reverser between at least the first position and the second position. The inboard longeron includes a forward seal at the first end and an inboard seal that extends along the inboard longeron from the first end to the second end. The vehicle pylon includes a vehicle forward seal coupled to the vehicle pylon, and the forward seal is configured to contact the vehicle forward seal in the first position of the engine pylon. At least a portion of the outboard longeron overlaps the inboard longeron at the first end, and at least one spacer is coupled to the inboard longeron proximate the outboard longeron to define a uniform exterior surface for the inboard longeron. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The exemplary embodiments will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG.  1    is a top view of an exemplary pylon system for coupling a gas turbine engine to a vehicle, such as an aircraft, in which a translating cowl or transcowl associated with a thrust reverser of the gas turbine engine is in a first, stowed position and an engine pylon of the pylon system in a first position; 
         FIG.  2    is a perspective view of the engine pylon of the pylon system coupled to the transcowl, in which the engine pylon is shown uncoupled from the vehicle pylon for clarity; 
         FIG.  3    is an exploded view of the engine pylon; 
         FIG.  4    is a perspective view of the engine pylon, which illustrates an inboard longeron of the engine pylon; 
         FIG.  5    is a detail view of a fastening aperture associated with the inboard longeron; 
         FIG.  6    is a cross-sectional view of the engine pylon, taken along line  6 - 6  of  FIG.  1   ; 
         FIG.  7    is a perspective view of a vehicle pylon of the pylon system, in which the engine pylon is removed for clarity; 
         FIG.  8    is an exploded view of the vehicle pylon; 
         FIG.  9    is a cross-sectional view of the engine pylon, taken along line  9 - 9  of  FIG.  7   ; 
         FIG.  10    is a cross-sectional view of the pylon system, taken along line  10 - 10  of  FIG.  1   , which illustrates the engine pylon in the first position when the transcowl is in the first, stowed position; 
         FIG.  11    is a cross-sectional view of the pylon system, taken along line  11 - 11  of  FIG.  1   ; 
         FIG.  12    is a cross-sectional view of the pylon system, taken from the perspective of line  10 - 10  of  FIG.  1   , which illustrates the engine pylon in a third position when the transcowl in a third, overstowed position; 
         FIG.  13    is a top view of the pylon system, in which the transcowl associated with the thrust reverser of the gas turbine engine is in a second, deployed position and the engine pylon is in a second position; and 
         FIG.  14    is a cross-sectional view of the pylon system, taken from the perspective of line  14 - 14  of  FIG.  13   , which illustrates the engine pylon in the second position when the transcowl in the second, deployed position. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary or the following detailed description. In addition, those skilled in the art will appreciate that embodiments of the present disclosure may be practiced in conjunction with any type of device that would benefit from a pylon system and the use of the pylon system for a side mounted gas turbine engine and a vehicle described herein is merely one exemplary embodiment according to the present disclosure. In addition, while the pylon system is described herein as being used with a gas turbine engine onboard a vehicle, such as a bus, motorcycle, train, automobile, marine vessel, aircraft, rotorcraft and the like, the various teachings of the present disclosure can be used with a gas turbine engine on a stationary platform. Further, it should be noted that many alternative or additional functional relationships or physical connections may be present in an embodiment of the present disclosure. In addition, while the figures shown herein depict an example with certain arrangements of elements, additional intervening elements, devices, features, or components may be present in an actual embodiment. It should also be understood that the drawings are merely illustrative and may not be drawn to scale. 
     As used herein, the term “axial” refers to a direction that is generally parallel to or coincident with an axis of rotation, axis of symmetry, or centerline of a component or components. For example, in a cylinder or disc with a centerline and generally circular ends or opposing faces, the “axial” direction may refer to the direction that generally extends in parallel to the centerline between the opposite ends or faces. In certain instances, the term “axial” may be utilized with respect to components that are not cylindrical (or otherwise radially symmetric). For example, the “axial” direction for a rectangular housing containing a rotating shaft may be viewed as a direction that is generally parallel to or coincident with the rotational axis of the shaft. Furthermore, the term “radially” as used herein may refer to a direction or a relationship of components with respect to a line extending outward from a shared centerline, axis, or similar reference, for example in a plane of a cylinder or disc that is perpendicular to the centerline or axis. In certain instances, components may be viewed as “radially” aligned even though one or both of the components may not be cylindrical (or otherwise radially symmetric). Furthermore, the terms “axial” and “radial” (and any derivatives) may encompass directional relationships that are other than precisely aligned with (e.g., oblique to) the true axial and radial dimensions, provided the relationship is predominantly in the respective nominal axial or radial direction. As used herein, the term “substantially” denotes within 5% to account for manufacturing tolerances. Also, as used herein, the term “about” denotes within 5% to account for manufacturing tolerances. 
     With reference to  FIG.  1   , a pylon system  99  is shown. In one example, the pylon system  99  couples an engine, such as a gas turbine engine  102 , to a vehicle, such as an aircraft  104 . As will be discussed, the pylon system  99  couples the gas turbine engine  102  to an airframe  106  of the aircraft  104 . Generally, the pylon system  99  enables the gas turbine engine  102  to be side or rear mounted on the aircraft  104  while enabling a thrust reverser  108  associated with the gas turbine engine  102  to move over various positions. Generally, side mounted or rear mounted gas turbine engines  102  are located aft of the wings and also above the wings of the aircraft  104 . The pylon system  99  may be configured as a left hand pylon or a right hand pylon, which may be attached to an empennage or aft section of the airframe  106 . In the example of  FIG.  1   , the pylon system  99  is configured as a left hand pylon for side mounting the gas turbine engine  102 . A right hand pylon for side mounting the gas turbine engine  102  comprises a mirror image of the pylon system  99  shown in  FIG.  1   . For ease of description, the following discussion will refer to the pylon system  99  as a left hand pylon for side mounting the gas turbine engine  102 , but it should be understood that a right hand pylon for side mounting a second gas turbine engine  102  to the aircraft  104  is a mirror image of the pylon system  99  shown and described herein. 
     Generally, the pylon system  99  enables the gas turbine engine  102  to be mounted on either the left hand side or the right hand side of the airframe  106 , aft of the wings. The pylon system  99  enables the aircraft  104  to employ the gas turbine engine  102  with the thrust reverser  108 , which improves a stopping power of the aircraft  104 , while enabling the thrust reverser  108  to move relative to the gas turbine engine  102  without interfering with the mounting of the gas turbine engine  102  on the airframe  106 . In addition, by mounting the gas turbine engine  102  on the side of the aircraft  104 , a cabin of the aircraft  104  is quieter because of the additional distance between passenger seats and the location of the gas turbine engine  102 . Further, by side mounting the gas turbine engine  102  using the pylon system  99 , the aircraft  104  has lower wing clearance, and this enables the use of shorter landing gear, which saves weight. In addition, by side mounting the gas turbine engine  102  using the pylon system  99 , less foreign object debris, such as dirt, dust and sand, is ingested by the gas turbine engine  102  during operation. 
     As the gas turbine engine  102  coupled to the pylon system  99  is any suitable engine including the thrust reverser  108  with a translating cowl or transcowl  112 , the gas turbine engine  102  and the thrust reverser  108  will not be discussed in detail herein. Briefly,  FIG.  1    is a top view of the gas turbine engine  102  with the transcowl  112  of the thrust reverser  108  in a first, stowed position. The gas turbine engine  102  typically generates thrust by means of an accelerating mass of gas. Generally, the gas turbine engine  102  is substantially encased within an aerodynamically smooth outer covering, such as a nacelle  110 . The nacelle  110  substantially surrounds the gas turbine engine  102  and forms an aerodynamically shaped cavity around a centerline C of the gas turbine engine  102 , thereby providing a flow path for engine exhaust flow when generating forward thrust. Generally, ambient air enters the gas turbine engine  102  and passes through a fan. A portion of this air is received within a core of the gas turbine engine  102  where it is pressurized by one or more compressors associated with the gas turbine engine  102 , and mixed with fuel and ignited within a combustion chamber associated with the gas turbine engine  102 . The combustion of the pressurized air and fuel generates combustion products or hot gases known as core flow. The remainder of the air from the fan bypasses the core of the gas turbine engine  102  and is known as fan flow. Together, the core flow and the fan flow mix downstream to form the engine exhaust flow that is discharged from the gas turbine engine  102 , generating forward thrust. 
     The thrust reverser  108  includes a stationary support structure and the transcowl  112 . The support structure couples the thrust reverser  108  to the gas turbine engine  102 . In this example, the transcowl  112  is axially translatable by an actuator relative to the support structure, and thus the gas turbine engine  102 , between the first, stowed position, which is the position depicted in  FIG.  1   , a second, deployed position, which is the position depicted in  FIG.  13   , and a third, overstowed position, a detailed cross-section of which depicted in  FIG.  12   . In the first, stowed position, a leading edge  112 . 1  of the transcowl  112  is adjacent to, proximate or abuts the nacelle  110 , and in the second, deployed position, the leading edge  112 . 1  of the transcowl  112  is displaced or spaced apart from the nacelle  110  to form an aperture  460  between the transcowl  112  and the nacelle  110 . In the third, overstowed position, the leading edge  112 . 1  compresses a portion of the pylon system  99  and a gap between the leading edge  112 . 1  and the nacelle  110  is less than the gap between the leading edge  112 . 1  and the nacelle  110  in the first, stowed position shown in  FIG.  1   . The actuator associated with the transcowl  112  is in communication with a controller associated with the gas turbine engine  102  or the aircraft  104  and is responsive to one or more control signals to move the transcowl  112  between the first, stowed position, the second, deployed position and the third, overstowed position. The movement of the transcowl  112  moves doors coupled to the transcowl  112  to redirect at least a portion of the engine exhaust flow through the aperture  460  to generate reverse thrust. 
     As shown in  FIG.  1   , the pylon system  99  includes an engine pylon  120  and a vehicle pylon  122 . The pylon system  99  enables the transcowl  112  to move linearly relative to the gas turbine engine  102  and the aircraft  104  between the first, stowed position, the second, deployed position and the third, overstowed position. In the first, stowed position of the transcowl  112 , the engine pylon  120  is in a first position ( FIGS.  1  and  10   ) relative to the vehicle pylon  122 . In the second, deployed position of the transcowl  112 , the engine pylon  120  is in a second position ( FIGS.  13  and  14   ) relative to the vehicle pylon  122 . In the third, overstowed position of the transcowl  112 , the engine pylon  120  is in a third position ( FIG.  12   ) relative to the vehicle pylon  122 . With reference to  FIG.  2   , the engine pylon  120  is shown. The engine pylon  120  movably couples the transcowl  112  of the gas turbine engine  102  to the vehicle pylon  122  ( FIG.  1   ). In addition, as will be discussed, the engine pylon  120  enables the transcowl  112  of the gas turbine engine  102  to be adjustably coupled to the vehicle pylon  122 . By enabling the adjustment of the gas turbine engine  102  relative to the vehicle pylon  122 , a location and orientation of the gas turbine engine  102  relative to the airframe  106  ( FIG.  1   ) is adjustable to account for manufacturing tolerances, which reduces aerodynamic drag by enabling the alignment of the engine pylon  120  with the airframe  106  ( FIG.  1   ). 
     With reference to  FIG.  3   , an exploded view of the engine pylon  120  is shown. In one example, the engine pylon  120  includes a first, inboard longeron  130 , a second, outboard longeron  132 , a forward seal  134 , at least one elongated seal  136 , at least one fastening assembly  138 , at least one spacer  140  and a skin panel  142 . The inboard longeron  130  is composed of a polymer-based material, metal, or metal alloy, and is cast, stamped, machined, additively manufactured, etc. In this example, the inboard longeron  130  has a triangular shape, with a first base  144  defined at a first end  130   a , and a first apex  146  defined at a second end  130   b . The inboard longeron  130  also has a first side  130   c  opposite a second side  130   d . The inboard longeron  130  is substantially solid at the first base  144  and the first apex  146 , but defines a plurality of cut-outs  148  between the first base  144  and the first apex  146 . In this example, the inboard longeron  130  defines three cut-outs  148   a - 148   c . The cut-outs  148   a - 148   c  reduce a mass associated with the inboard longeron  130 . The inboard longeron  130  also defines a first flange  150 , a second flange  152  opposite the first flange  150 , and at least one or a plurality of fastening apertures  154 . 
     With brief reference to  FIG.  4   , the inboard longeron  130  extends along a longitudinal axis L, which is a center line for the inboard longeron  130 , and the first flange  150  and the second flange  152  extend along an axis transverse or oblique to the longitudinal axis L. In one example, the first flange  150  extends at an angle α relative to the longitudinal axis L and the second flange  152  extends at a negative of the angle α relative to the longitudinal axis L. The angle α is about 5 degrees to about 8 degrees. The first flange  150  and the second flange  152  extend outwardly from the first base  144  at the first end  130   a  to the first apex  146  at the second end  130   b . The first flange  150  and the second flange  152  are defined along opposite outboard edges  153   a ,  153   b  of the inboard longeron  130  and extend outwardly from the first side  130   c . With reference back to  FIG.  3   , generally, the first flange  150  and the second flange  152  are spaced apart at the first apex  146  to enable the receipt of mechanical fasteners proximate the first apex  146  to couple the skin panel  142 , the spacer  140  and the elongated seal  136  to the inboard longeron  130 . In addition, the space defined between the first flange  150  and the second flange  152  at the first apex  146  enables the at least one elongated seal  136  to be positioned between the first flange  150  and the second flange  152  at the first apex  146 . The first flange  150  includes a chamfer  156  that extends for a distance D from the first end  130   a . In one example, the distance D is about 2 inches (in.) to about 4 inches (in.) and is about the same or greater than a width W of a second base  170  of the outboard longeron  132 . By defining the chamfer  156  for the distance D, when the inboard longeron  130  is coupled to the outboard longeron  132 , the second end  130   b  of the inboard longeron  130  is angled outward or away from the outboard longeron  132 . From the chamfer  156  to the first apex  146 , the first flange  150  defines a plurality of spaced apart holes  158 . Each of the holes  158  is configured to receive a fastener, such as a rivet, therethrough to couple the elongated seal  136 , the spacer  140  and the skin panel  142  to the first flange  150 . The second flange  152  defines a plurality of spaced apart second holes  159 . Each of the second holes  159  is configured to receive a fastener, such as a rivet, therethrough to couple the elongated seal  136 , the spacer  140  and the skin panel  142  to the second flange  152 . The spacing of the holes  158  and the second holes  159  is generally predetermined to provide additional stability for the elongated seal  136 . Generally, the inboard longeron  130  and the outboard longeron  132  are triangular in shape to correspond with the shape of the vehicle pylon  122 . It should be noted that the shape of the inboard longeron  130  and the outboard longeron  132  may vary to correspond with different vehicle pylon shapes. The angle α is also generally predetermined based on the vehicle pylon  122 , and may be different for different vehicle pylon shapes. 
     The fastening apertures  154  couple the inboard longeron  130  to the transcowl  112  of the gas turbine engine  102  ( FIG.  1   ). In this example, the inboard longeron  130  includes three fastening apertures  154   a - 154   c , with two of the fastening apertures  154   a ,  154   b  defined proximate the first base  144  and the fastening aperture  154   c  defined proximate the first apex  146 . Each of the fastening apertures  154   a - 154   c  are the same, and thus, a single fastening aperture  154   a  will be discussed in detail herein. With reference to  FIG.  5   , in one example, the fastening aperture  154   a  includes at least one or a pair of fastening slots  160  and a central bore  162 . The fastening slots  160  are defined so as to be spaced apart from the central bore  162  and opposite each other about the central bore  162 . Each of the fastening slots  160  are elongated along an axis that is substantially perpendicular to the longitudinal axis L. Each of the fastening slots  160  define a plurality of slot serrations  164  about a perimeter of the fastening slot  160  on the second side  130   d  of the inboard longeron  130 . The slot serrations  164  cooperate with a serrated washer  166  associated with a mechanical fastener  168  to enable a vertical position of the inboard longeron  130 , and thus, the engine pylon  120  to be adjusted relative to the vehicle pylon  122  ( FIG.  1   ). The slot serrations  164  are spaced apart in any predetermined pattern to define a plurality of defined positions for coupling the mechanical fastener  168  to the inboard longeron  130 . In this example, the mechanical fastener  168  is the bolt 147 associated with the locking positioning system  100  of commonly assigned U.S. application Ser. No. ______ (Attorney Docket No. H223712-US (002.8055US)) titled “Locking Positioning Systems” to Alstad, the relevant portion of which is incorporated herein by reference. The central bore  162  is sized to enable a portion of the locking positioning system  100  to be positioned through the inboard longeron  130  to be coupled to the transcowl  112  ( FIG.  1   ). It should be noted that the use of the locking positioning system  100  for adjustably coupling the inboard longeron  130  to the transcowl  112  is merely an example, as other mechanical fasteners may be employed and the fastening apertures  154   a - 154   c  may be modified to accommodate these mechanical fasteners. Moreover, a combination of locking positioning systems  100  and mechanical fasteners may be employed such that the inboard longeron  130  may not be coupled to the transcowl  112  via three locking positioning systems  100  as shown in  FIG.  2   . 
     With reference to  FIG.  3   , the outboard longeron  132  is coupled to the inboard longeron  130 . The outboard longeron  132  is composed of a polymer-based material, metal, or metal alloy, and is cast, stamped, machined, additively manufactured, etc. In this example, the outboard longeron  132  has a triangular shape, with the second base  170  defined at a first end  132   a , and a second apex  172  defined at a second end  132   b . The outboard longeron  132  also has a first side  132   c  opposite a second side  132   d . The second base  170  of the outboard longeron  132  is coupled to the first base  144  of the inboard longeron  130 , and the second apex  172  is spaced apart from the first apex  146  of the inboard longeron  130 . The outboard longeron  132  is substantially solid at the second base  170  and the second apex  172 , but defines a plurality of cut-outs  148  between the second base  170  and the second apex  172 . In this example, the outboard longeron  132  defines four cut-outs  174   a - 174   d . The cut-outs  174   a - 174   d  reduce a mass associated with the outboard longeron  132 . The outboard longeron  132  also defines a first outboard flange  176  and a second outboard flange  178  opposite the first outboard flange  176 . 
     With brief reference to  FIG.  2   , the outboard longeron  132  extends along a longitudinal axis L1, which is a center line for the outboard longeron  132 , and the first outboard flange  176  and the second outboard flange  178  extend along an axis transverse or oblique to the longitudinal axis L1. The longitudinal axis L of the inboard longeron  130  is oblique to the longitudinal axis L1 of the outboard longeron  132 . In one example, the first outboard flange  176  extends at an angle β relative to the longitudinal axis L1 and the second outboard flange  178  extends at a negative of the angle β relative to the longitudinal axis L1. The angle β is about 5 degrees to about 8 degrees. The first outboard flange  176  and the second outboard flange  178  extend outwardly from the second base  170  at the first end  132   a  to the second apex  172  at the second end  132   b . The first outboard flange  176  and the second outboard flange  178  are defined along opposite outboard edges  179   a ,  179   b  of the outboard longeron  132  and extend outwardly from the first side  132   c  ( FIG.  3   ). With reference back to  FIG.  3   , generally, the first outboard flange  176  and the second outboard flange  178  are spaced apart at the second apex  172  to enable the receipt of mechanical fasteners, such as rivets, proximate the second apex  172  to couple the skin panel  142  to the outboard longeron  132 . 
     The first outboard flange  176  includes a projection  180 . The projection  180  is triangular, and has a projection base  180   a  that extends outwardly from the first outboard flange  176 . An edge  180   b  of the projection  180  tapers from the projection base  180   a  to the second apex  174 . The projection  180  is sized to overlap or overlie a portion of the first flange  150  of the inboard longeron  130  at the first end  130   a . The projection  180  also includes projection holes  182  to receive mechanical fasteners to couple the outboard longeron  132  to the inboard longeron  130  at the respective first end  130   a ,  132   a . The projection  180  extends for a distance D2 from the first end  132   a . In one example, the distance D2 is about 5 inches (in.) to about 15 inches (in.). By defining the projection  180  for the distance D2, the outboard longeron  132  reinforces the inboard longeron  130  at the first end  130   a  and proximate the fastening apertures  154  when the inboard longeron  130  is coupled to the outboard longeron  132 . From the projection  180  to the second apex  172 , the first outboard flange  176  defines a plurality of spaced apart bores  184 . Each of the bores  184  is configured to receive a fastener, such as a rivet, therethrough to couple the skin panel  142  to the first outboard flange  176 . In this example, an interior surface  176   a  of the first outboard flange  176  includes a plurality of nut plates  186 . Each of the nut plates  186  is coupled to the interior surface  176   a  via rivets, for example, and is coaxial to a respective one of the bores  184 . The nut plates  186  receive the rivet inserted into the respective bore  184  to couple the skin panel  142  to the outboard longeron  132 . 
     The second outboard flange  178  includes a second projection  190 . The second projection  190  is triangular, and has a second projection base  190   a  that extends outwardly from the second outboard flange  178 . An edge  190   b  of the second projection  190  tapers from the second projection base  190   a  to the second apex  174 . The second projection  190  is sized to overlap or overlie a portion of the second flange  152  of the inboard longeron  130  at the first end  130   a . The second projection  190  also includes second projection holes  192  to receive mechanical fasteners to couple the outboard longeron  132  to the inboard longeron  130  at the respective first end  130   a ,  132   a . The second projection  190  extends for the distance D2 from the first end  132   a . By defining the second projection  190  for the distance D2, the outboard longeron  132  reinforces the inboard longeron  130  at the first end  130   a  and proximate the fastening apertures  154  when the inboard longeron  130  is coupled to the outboard longeron  132 . From the second projection  190  to the second apex  172 , the second outboard flange  178  defines a plurality of spaced apart second bores  194 . Each of the second bores  194  is configured to receive a fastener, such as a rivet, therethrough to couple the skin panel  142  to the second outboard flange  178 . In this example, an interior surface  178   a  of the second outboard flange  178  includes a plurality of second nut plates  196 . Each of the second nut plates  196  is coupled to the interior surface  172   a  via rivets, for example, and is coaxial to a respective one of the second bores  194 . The second nut plates  196  receive the rivet inserted into the respective second bore  194  to couple the skin panel  142  to the outboard longeron  132 . 
     The forward seal  134  creates a seal between the transcowl  112  and the engine pylon  120  ( FIG.  2   ). The forward seal  134  is composed of an elastomeric material, and is cast, molded, etc. The forward seal  134  has a first seal surface  200  opposite a second seal surface  202 , and a first seal end  204  opposite a second seal end  206 . In one example, the first seal surface  200  has a concave curvature to comport with the curvature of the transcowl  112  ( FIG.  2   ) and to assist in forming a seal against the surface of the transcowl  112  ( FIG.  2   ). The second seal surface  202  is substantially planar to mate against a surface of the first base  144  of the inboard longeron  130 . In one example, seal fastening bores  208  are defined through the first seal surface  200  and the second seal surface  202  to couple the forward seal  134  to the inboard longeron  130  and the outboard longeron  132 . Corresponding seal fastening bores  209  are defined in the first base  144  of the inboard longeron  130  and seal fastening bores  211  are defined in the second base  170  of the outboard longeron  132  ( FIG.  2   ). Mechanical fasteners, such as screws, are inserted through the seal fastening bores  209 ,  211  and seal fastening bores  208  to couple the forward seal  134  to the inboard longeron  130  and the outboard longeron  132 . Generally, the forward seal  134  is coupled to the inboard longeron  130  and the outboard longeron  132  such that the forward seal  134  extends beyond the first end  130   a  of the inboard longeron  130  and the first end  132   a  of the outboard longeron  132 . It should be noted that the forward seal  134  may be coupled to the inboard longeron  130  and/or the outboard longeron  132  via any technique, including, but not limited to, adhesives. With reference to  FIG.  4   , the first seal end  204  is coupled and positioned adjacent to a surface  150   a  of the first flange  150  of the inboard longeron  130 . The second seal end  206  is coupled and positioned adjacent to a surface  152   a  of the second flange  152  of the inboard longeron  130 . 
     In this example, the at least one elongated seal  136  comprises a pair of elongated seals  136   a ,  136   b . The pair of elongated seals  136   a ,  136   b  are coupled to the first flange  150  and the second flange  152 , respectively, to extend from the forward seal  134  to the first apex  146 . Each elongated seal  136   a ,  136   b  is composed of an elastomeric material, and is extruded, cast, molded, etc. Each of the elongated seals  136   a ,  136   b  is the same, and includes a first elongated end  210  opposite a second elongated end  212 , a bulb  214  and a fastening strip  216  ( FIG.  3   ). The first elongated end  210  of the elongated seal  136   a  is positioned adjacent to the first seal end  204  of the forward seal  134  and extends from the forward seal  134  to the first apex  146 . The first elongated end  210  of the elongated seal  136   b  is positioned adjacent to the second seal end  206  of the forward seal  134  and extends from the forward seal  134  to the first apex  146 . The second elongated end  212  of the elongated seals  136   a ,  136   b  is coupled to the first apex  146 . With reference back to  FIG.  3   , the bulb  214  has an oval cross-section, and extends outwardly from the elongated seal  136   a ,  136   b  to provide sealing against the transcowl  112  ( FIG.  2   ). The fastening strip  216  is defined adjacent to the bulb  214 , and extends from the first elongated end  210  to the second elongated end  212 . The fastening strip  216  is planar, and includes spaced apart seal holes  217 . The seal holes  217  are coaxially aligned with respective ones of the holes  158  and the second holes  159  to couple the elongated seals  136   a ,  136   b  to the respective one of the first flange  150  and the second flange  152 . 
     In this example, the at least one fastening assembly  138  comprises a pair of fastening assemblies  138   a ,  138   b . In one example, each of the fastening assemblies  138   a ,  138   b  is a nut plate strip, which includes a plurality of nut plates  218  fixedly coupled to an elongated body  220 . Each of the nut plates  218  and the bodies  220  are composed of a metal or metal alloy, and are stamped, cast, forged, additively manufactured, etc. The nut plates  218  are generally formed discretely from the respective body  220 , and are coupled to the respective body  220  via rivets, for example. Each nut plate  218  is coaxial with a hole  222  defined through the body  220 . Each body  220  has a first body end  224  opposite a second body end  226 . The first body end  224  is coupled adjacent to the forward seal  134 , and the second body end  226  extends to the first apex  146 . The fastening assembly  138   a  extends along the first flange  150 , and the fastening assembly  138   b  extends along the second flange  152 . As will be discussed, the fastening assemblies  138   a ,  138   b  enable the respective the elongated seal  136   a ,  136   b , the spacer  140 , and the skin panel  142  to be coupled to the respective first flange  150  and the second flange  152 . 
     In this example, the at least one spacer  140  comprises a pair of spacers  140   a ,  140   b . The spacers  140   a ,  140   b  are composed of a metal or metal alloy, and are stamped, cast, machined, additively manufactured, etc. The spacers  140   a ,  140   b  comprise elongated strips, which extend from proximate the respective projection  180  and second projection  190  along the respective first flange  150  and second flange  152  to the respective first apex  146  and second apex  172  to provide a uniform surface for the skin panel  142 . Stated another way, the spacers  140   a ,  140   b  have a thickness which is substantially equal to a thickness of the projection  180  and the second projection  190  to define a smooth coupling surface along the inboard longeron  130  for the skin panel  142 . Each of the spacers  140   a ,  140   b  defines a plurality of coupling holes  228  that are spaced apart along the spacer  140   a ,  140   b . The coupling holes  228  are coaxially aligned with respective holes  222  of the fastening assemblies  138   a ,  138   b.    
     The skin panel  142  is coupled to the inboard longeron  130  and the outboard longeron  132  to define a smooth exterior surface for the engine pylon  120 . The skin panel  142  is composed of a polymer-based material, metal, or metal alloy, and is stamped, machined, cast, additively manufactured, etc. The skin panel  142  includes a first skin panel surface  230  and a second skin panel surface  232 , which are interconnected by a fold or bend  234 . The first skin panel surface  230  is coupled along the first flange  150  of the inboard longeron  130  and the first outboard flange  176  of the outboard longeron  132  to define an exterior surface along a top of the engine pylon  120 . The second skin panel surface  232  is coupled along the second flange  152  of the inboard longeron  130  and the second outboard flange  178  of the outboard longeron  132  to define an exterior surface along a bottom of the engine pylon  120 . The bend  234  interconnects the first skin panel surface  230  with the second skin panel surface  232  and encloses the engine pylon  120  at the first apex  146  and the second apex  172 . Thus, the skin panel  142  substantially surrounds the inboard longeron  130  and the outboard longeron  132  and substantially encloses the engine pylon  120 . 
     The first skin panel surface  230  and the second skin panel surface  232  each include a plurality of skin panel bores  236 . The skin panel bores  236  are defined through the skin panel  142  for receipt of a mechanical fastener, such as a rivet  238  ( FIG.  6   ), to couple the skin panel  142  to the inboard longeron  130  and outboard longeron  132 . The skin panel bores  236  of the first skin panel surface  230  are coaxially aligned with a respective one of the holes  158  of the first flange  150 , the coupling holes  228  of the spacer  140   a , the seal holes  217  of the elongated seal  136   a , the projection holes  182  of the projection  180 , and the holes  222  of the fastening assembly  138   a ; and the bores  184  of the first outboard flange  176 . The skin panel bores  236  of the second skin panel surface  232  are coaxially aligned with a respective one of the second holes  159  of the second flange  152 , the coupling holes  228  of the spacer  140   b , the seal holes  217  of the elongated seal  136   b , the second projection holes  192  of the second projection  190 , and the holes  222  of the fastening assembly  138   b ; and the second bores  194  of the second outboard flange  178 . 
     In one example, with reference to  FIG.  6   , where the projection  180  overlies the first flange  150 , the rivets  238  are inserted through respective ones of the skin panel bores  236  of the first skin panel surface  230 , the projection holes  182  of the projection  180 , the seal holes  217  of the elongated seal  136   a , the holes  222  of the fastening assembly  138   a  and are secured to the respective one of the nut plates  218 . Where the spacer  140   a  overlies the first flange  150 , the rivets  238  are inserted through respective ones of the skin panel bores  236  of the first skin panel surface  230 , the coupling holes  228  of the spacer  140   a , the seal holes  217  of the elongated seal  136   a , the holes  222  of the fastening assembly  138   a  and are secured to the respective one of the nut plates  218 . Where the second projection  190  overlies the second flange  152 , the rivets  238  are inserted through respective ones of the skin panel bores  236  of the second skin panel surface  232 , the second projection holes  192  of the second projection  190 , the seal holes  217  of the elongated seal  136   b , the holes  222  of the fastening assembly  138   b  and are secured to the respective one of the nut plates  218 . Where the spacer  140   b  overlies the second flange  152 , the rivets  238  are inserted through respective ones of the skin panel bores  236  of the second skin panel surface  232 , the coupling holes  228  of the spacer  140   b , the seal holes  217  of the elongated seal  136   b , the holes  222  of the fastening assembly  138   b  and are secured to the respective one of the nut plates  218 . Generally, with reference to  FIG.  6   , the first skin panel surface  230  and the second skin panel surface  232  are sized such that a portion of the first skin panel surface  230  and the second skin panel surface  232  are each cantilevered over the outboard longeron  132  to define a first rail and a second rail, indicated by reference numerals  239   a ,  239   b , respectively. In one example, the first skin panel surface  230  and the second skin panel surface  232  extend a distance DR beyond the second side  132   d  of the outboard longeron  132 . The distance DR is about 0.5 inches (in.) to about 1.0 inches (in.). The first rail  239   a  and the second rail  239   b  defined by the respective portion of the first skin panel surface  230  and the second skin panel surface  232  that overhangs the outboard longeron  132  enables the engine pylon  120  to move relative to the vehicle pylon  122 , as will be discussed. 
     With reference back to  FIG.  3   , the second skin panel surface  232  defines an access opening  240 , which is enclosed with a removable access panel  242 . The access opening  240  is defined proximate the bend  234  to provide access to the fastening aperture  154   c  to enable adjustment of the coupling between the engine pylon  120  and the transcowl  112  during installation and use. The access opening  240  is generally sized to enable an operator to insert their hand and manipulate the fastening device coupled to the fastening aperture  154   c , such as the locking positioning system  100 , previously incorporated by reference herein. The access panel  242  is composed of a polymer-based material, metal, or metal alloy, and is stamped, machined, cast, additively manufactured, etc. The access panel  242  is coupled to the access opening  240  via press-fit, mechanical fasteners, etc. Generally, the access panel  242  is coupled to the access opening  240  to be removable for maintenance, but secured during operation of the aircraft  104  ( FIG.  1   ). 
     With reference to  FIG.  7   , the vehicle pylon  122  is shown in greater detail. In  FIG.  7   , the engine pylon  120  has been removed for clarity. In one example, the vehicle pylon  122  includes a vehicle or airframe longeron  300 , a forward seal assembly  302 , at least one seal fastening assembly  304 , at least one seal  306 , at least one vehicle or airframe rib  308 , at least one vehicle or airframe beam  310  and at least one vehicle skin panel or skin panel  312 . With reference to  FIG.  8   , the airframe longeron  300  is composed of polymer-based material, metal, or metal alloy, and is cast, forged, stamped, additively manufactured, etc. The airframe longeron  300  has a triangular shape, with an airframe base  320  defined at a first end  300   a , and an airframe apex  322  defined at a second end  300   b . The airframe longeron  300  also has a first side  300   c  opposite a second side  300   d . The airframe longeron  300  is substantially solid at the airframe base  320  and the airframe apex  322 , but defines a plurality of cut-outs  324  between the airframe base  320  and the airframe apex  322 . In this example, the airframe longeron  300  defines three cut-outs  324   a - 324   c . The cut-outs  324   a - 324   c  reduce a mass associated with the airframe longeron  300 . The airframe longeron  300  also defines a first airframe flange  326  and a second airframe flange  328  opposite the first airframe flange  326 . 
     With brief reference to  FIG.  7   , the airframe longeron  300  extends along a longitudinal axis L2, which is a center line for the airframe longeron  300 , and the first airframe flange  326  and the second airframe flange  328  extend along an axis transverse or oblique to the longitudinal axis L2. In one example, the first airframe flange  326  extends at an angle γ relative to the longitudinal axis L2 and the second airframe flange  328  extends at a negative of the angle γ relative to the longitudinal axis L2. The angle γ is about 5 degrees to about 8 degrees. With reference back to  FIG.  8   , the first airframe flange  326  and the second airframe flange  328  extend outwardly from the airframe base  320  at the first end  300   a  to the airframe apex  322  at the second end  300   b . The first airframe flange  326  and the second airframe flange  328  are defined along opposite edges  330   a ,  330   b  of the airframe longeron  300  and extend outwardly from the second side  300   d  ( FIG.  9   ). Generally, the first airframe flange  326  and the second airframe flange  328  are spaced apart at the airframe apex  322  to enable the receipt of mechanical fasteners proximate the airframe apex  322  to couple the seal  306  and the skin panel  312  to the airframe longeron  300 . 
     The first airframe flange  326  defines a plurality of spaced apart airframe bores  332  from the airframe base  320  to the airframe apex  322 . Each of the airframe bores  332  is configured to receive a fastener, such as a rivet  333  ( FIG.  9   ), therethrough to couple the skin panel  312  to the first airframe flange  326 . In one example, the fastener is the rivet  333 , however, any suitable fastener may be used. In this example, an interior surface  326   a  of the first airframe flange  326  includes a plurality of airframe nut plates  334  ( FIG.  9   ). Each of the airframe nut plates  334  is coupled to the interior surface  326   a  via rivets, for example, and is coaxial to a respective one of the airframe bores  332 . The airframe nut plates  334  receive the end of the rivet  333  inserted into the respective airframe bore  332  to couple the skin panel  316  to the airframe longeron  300 . The first airframe flange  326  also defines at least one rib protrusion  336 . In this example, the first airframe flange  326  defines two rib protrusions  336   a ,  336   b , which correspond with a respective one of the two airframe ribs  308   a ,  308   b . The rib protrusions  336   a ,  336   b  each extend outwardly from the first airframe flange  326  and define a rib coupling bore  338  for coupling the respective airframe rib  308   a ,  308   b  to the airframe longeron  300 . 
     With reference to  FIG.  9   , the second airframe flange  328  defines a plurality of spaced apart second airframe bores  340  from the airframe base  320  to the airframe apex  322 . Each of the second airframe bores  340  is configured to receive the rivet  333  therethrough to couple the skin panel  312  to the second airframe flange  328 . In this example, nut plates (not shown) may be used to secure the rivet  333  to the second airframe flange  328  during assembly, and thus, couple the skin panel  316  to the airframe longeron  300 . 
     With reference back to  FIG.  8   , the forward seal assembly  302  includes a vehicle or airframe forward seal  350  and a seal bracket  352 . The airframe forward seal  350  creates a seal between the engine pylon  120  and the vehicle pylon  122  ( FIG.  10   ). The airframe forward seal  350  is composed of an elastomeric material, and is cast, molded, etc. The airframe forward seal  350  has a first airframe seal surface  354  opposite a second airframe seal surface  356 , and a first airframe seal end  358  opposite a second airframe seal end  360 . The airframe forward seal  350  also includes a first seal side  362  opposite a second seal side  364 . In one example, the first airframe seal surface  354  faces aft or toward the airframe apex  322  and seals against the engine pylon  120  in the first, stowed position ( FIG.  10   ). The first airframe seal surface  354  and the second airframe seal surface  356  are generally smooth and planar. The second airframe seal surface  356  is coupled to the seal bracket  352 . The first airframe seal end  358  is positioned adjacent to the first airframe flange  326  of the airframe longeron  300 . The second airframe seal end  360  is positioned adjacent to the second airframe flange  328  of the airframe longeron  300 . The first airframe seal end  358  and the second airframe seal end  360  each define a recess  366  for coupling the at least one seal  306  to the forward seal assembly  302 . The coupling of the at least one seal  306  to the airframe forward seal  350  ensures that the at least one seal  306  remains in contact with the engine pylon  120  over an entirety of the vehicle pylon  122 . The first seal side  362  has a concave curvature to assist in forming a seal against the nacelle  110  ( FIG.  10   ). The second seal side  364  is substantially planar to mate against a surface of the airframe base  320 . 
     The seal bracket  352  couples the airframe forward seal  350  to the airframe longeron  300  ( FIG.  10   ). The seal bracket  352  is composed of polymer-based material, metal, or metal alloy, and is cast, stamped, machined, additively manufactured, etc. In one example, the seal bracket  352  is L-shaped, and includes a seal portion  370  and a coupling portion  372 . The seal portion  370  is substantially normal to the coupling portion  372 . The seal portion  370  is coupled to the airframe forward seal  350  and is planar. In one example, the airframe forward seal  350  is coupled to the seal bracket  352  via nut plates that are attached to the seal bracket  352 . The nut plates are attached to the seal bracket  352  via riveting, for example. The rivets are then used to secure the airframe forward seal  350  to the seal bracket  352 . The coupling portion  372  is coupled to the airframe base  320  and is planar. In one example, the coupling portion  372  is coupled to the airframe base  320  via welding, however, adhesives, mechanical fasteners and the like may be used. 
     In one example, with reference to  FIG.  8   , the at least one seal fastening assembly  304  includes two seal fastening assemblies  304   a ,  304   b . In one example, each of the seal fastening assemblies  304   a ,  304   b  is a nut plate strip, which includes a plurality of seal nut plates  374  fixedly coupled to an elongated body  376 . Each of the seal nut plates  374  and the bodies  376  are composed of a metal or metal alloy, and are stamped, cast, forged, additively manufactured, etc. The seal nut plates  374  are generally formed discretely from the bodies  376 , and are coupled to the bodies  376  via welding, for example. Each seal nut plates  374  is coaxial with a hole  378  defined through the body  376 . Each body  376  has a first body end  380  opposite a second body end  382 . The first body end  380  is coupled to the at least one seal  306  proximate the airframe forward seal  350 , and the second body end  382  extends to proximate the airframe apex  322 . The seal fastening assembly  304   a  extends next to, proximate or along the first side  300   c  proximate the first airframe flange  326 , and the seal fastening assembly  304   b  extends next to, proximate or along the first side  300   c  proximate the second airframe flange  328 . As will be discussed, the seal fastening assemblies  304   a ,  304   b  enable the at least one seal  306  to be coupled to the at least one skin panel  312 . 
     In this example, the at least one seal  306  comprises two seals  306   a ,  306   b . Each seal  306   a ,  306   b  is composed of an elastomeric material, and is extruded, cast, molded, etc. Each of the seals  306   a ,  306   b  is the same, and includes a blade seal  390  and a fastening strip  392  that each extend from a first seal end  394  to a second seal end  396 . The first seal end  394  of each of the seals  306   a ,  306   b  is coupled to the at least one skin panel  312  and the second seal end  396  of the airframe forward seal  350  to extend from the airframe forward seal  350  to at or beyond the airframe apex  322 . The blade seal  390  extends outwardly from the fastening strip  392  and is substantially planar. Generally, with reference to  FIG.  9   , the blade seal  390  extends a distance DB beyond the at least one skin panel  312  to contact the first skin panel surface  230  and the second skin panel surface  232 . In one example, the distance DB is about 1.5 inches (in.) to about 2.5 inches (in.). A surface  390   a  of each blade seal  390  is positioned against and in contact with the first skin panel surface  230  and the second skin panel surface  232  of the engine pylon  120 , respectively, and enables the first skin panel surface  230  and the second skin panel surface  232  to move or slide along each of the blade seals  390  as the engine pylon  120  moves relative to the vehicle pylon  122  ( FIG.  13   ), as will be discussed. The fastening strip  392  includes a plurality of spaced apart seal bores  398  that extend through the seal  306   a ,  306   b  to receive a mechanical fastener, such as a rivet  400 , to couple the seals  306   a ,  306   b  to the at least one skin panel  312 . 
     With reference to  FIG.  8   , the at least one airframe rib  308  supports the at least one skin panel  312  between the airframe longeron  300  and the at least one airframe beam  310 . In one example, the at least one airframe rib  308  includes two airframe ribs  308   a ,  308   b . In this example, the airframe rib  308   a  is larger than the airframe rib  308   b  due to the triangular shape of the vehicle pylon  122 . The airframe rib  308   a  is positioned adjacent to the airframe longeron  300  between the cut-outs  324   a ,  324   b , and the airframe rib  308   b  is positioned adjacent to the airframe longeron  300  between the cut-outs  324   b ,  324   c . The airframe ribs  308   a ,  308   b  are received between the first airframe flange  326  and the second airframe flange  328 . In one example, each of the airframe ribs  308   a ,  308   b  include a first notch  402  and a second notch  404 , which are defined on opposite sides of the airframe ribs  308   a ,  308   b  to enable the airframe ribs  308   a ,  308   b  to be received between the first airframe flange  326  and the second airframe flange  328 . The first notch  402  and the second notch  404  are each defined on a first side  406  of the airframe ribs  308   a ,  308   b , which is opposite a second side  408 . The first side  406  is coupled to the airframe longeron  300 , and the second side  408  is coupled to the at least one airframe beam  310 . The second side  408  includes L-shaped grooves  408   a ,  408   b  ( FIG.  11   ). The L-shaped grooves  408   a ,  408   b  assist in coupling the at least one airframe beam  310  to the airframe ribs  308   a ,  308   b . The airframe ribs  308   a ,  308   b  may also include a plurality of rib bores  410 , which may be defined along a top side  412  and a bottom side  414  of the airframe ribs  308   a ,  308   b . The rib bores  410  are spaced apart along each of the top side  412  and the bottom side  414 , and may be threaded to enable a mechanical fastener, such as a rivet  416  ( FIG.  7   ), to couple the at least one skin panel  312  or the at least one airframe beam  310  to the airframe ribs  308   a ,  308   b.    
     In this example, the at least one airframe beam  310  includes two airframe beams  310   a ,  310   b . The airframe beams  310   a ,  310   b  are composed of a polymer-based material, metal, or metal alloy, and are cast, forged, stamped, additively manufactured, etc. Each of the airframe beams  310   a ,  310   b  are L-shaped, and include a skin coupling portion  420  and a side portion  422 . The skin coupling portion  420  is about normal to the side portion  422 . The skin coupling portion  420  of the airframe beam  310   a  extends substantially parallel with the first airframe flange  326 , and the skin coupling portion  420  of the airframe beam  310   b  extends substantially parallel with the second airframe flange  328 . The skin coupling portion  420  includes a plurality of holes  424  for receiving a mechanical fastener, such as a rivet  426  ( FIG.  7   ), for coupling the at least one skin panel  312  to the airframe beams  310   a ,  310   b . The side portion  422  is coupled to the airframe ribs  308   a ,  308   b  and provides rigidity to the vehicle pylon  122 . Generally, the airframe beams  310   a ,  310   b  provide structural strength for attaching the at least one skin panel  312  to the vehicle pylon  122 . 
     The at least one skin panel  312  encloses a portion of the vehicle pylon  122 . In this example, the at least one skin panel  312  includes two skin panels  312   a ,  312   b . Each of the skin panels  312   a ,  312   b  is composed of a polymer-based material, metal, or metal alloy, and is stamped, machined, cast, additively manufactured, etc. The skin panels  312   a ,  312   b  cooperate to enclose the airframe longeron  300 , the airframe ribs  308   a ,  308   b  and the airframe beams  310   a ,  310   b  and to define an exterior surface of the vehicle pylon  122 . Each of the skin panels  312   a ,  312   b  include a first panel side  430  opposite a second panel side  432  and a first panel end  434  opposite a second panel end  436 . The first panel side  430  is proximate the engine pylon  120 , and includes a cut-out region  438 . The cut-out region  438  is defined to enable the engine pylon  120  to engage and move along the seals  306   a ,  306   b . The second panel side  432  is coupled to the aircraft  104  ( FIG.  1   ) and a portion of the second panel side  432  is coupled to the airframe beams  310   a ,  310   b . The first panel end  434  of each of the skin panels  312   a ,  312   b  are coupled together to enclose the first panel end  434  ( FIG.  1   ). The second panel end  436  of each of the skin panels  312   a ,  312   b  are coupled together to enclose the second panel end  436  ( FIG.  1   ). Generally, the skin panels  312   a ,  312   b  are slightly different in exterior shape to provide the predetermined optimal shape for the vehicle pylon  122  based on the aerodynamics associated with the aircraft  104 . 
     Each of the skin panels  312   a ,  312   b  also include a plurality of panel bores  440 . A portion of the panel bores  440  are defined through the skin panel  312   a  proximate the first panel side  430  to couple the skin panel  312   a  to the skin panel  312   b , the airframe longeron  300 , the seal  306   a , the seal fastening assembly  304   a  and the airframe ribs  308   a ,  308   b . A portion of the panel bores  440  are defined through the skin panel  312   b  proximate the first panel side  430  to couple the skin panel  312   b  to the skin panel  312   a , the airframe longeron  300 , the seal  306   b , the seal fastening assembly  304   b  and the airframe ribs  308   a ,  308   b . In one example, with reference to  FIG.  9   , the rivet  333  is inserted through the panel bore  440  of the skin panel  312   a , the first airframe flange  326  and is secured with the airframe nut plates  334 . The rivet  400  is inserted through the panel bore  440  of the skin panel  312   a , the seal bore  398 , the hole  378  of the seal fastening assembly  304   a  and is secured with the respective seal nut plates  374 . The rivet  333  is inserted through the panel bore  440  of the skin panel  312   b , the second airframe flange  328  and is secured with the airframe nut plates  334 . The rivet  400  is inserted through the panel bore  440  of the skin panel  312   b , the seal bore  398 , the hole  378  of the seal fastening assembly  304   b  and is secured with the respective seal nut plates  374 . A portion of the panel bores  440  are defined through the skin panel  312   a  proximate the second panel side  432  to couple the skin panel  312   a  to the airframe ribs  308   a ,  308   b  and the airframe beams  310   a ,  310   b . A portion of the panel bores  440  are defined through the skin panel  312   b  proximate the second panel side  432  to couple the skin panel  312   b  to the airframe ribs  308   a ,  308   b  and the airframe beams  310   a ,  310   b . A portion of the panel bores  440  are defined to extend between the first panel side  430  and the second panel side  432  and are coaxially aligned with a respective one of the rib bores  410  to couple the skin panel  312   a ,  312   b  to the airframe ribs  308   a ,  308   b  with a respective one of the rivets  416  ( FIG.  7   ). 
     In addition, the skin panel  312   b  defines an airframe access opening  450 , which is enclosed with a removable airframe access panel  452 . With reference to  FIG.  7   , the airframe access opening  450  is defined so as to be proximate the cut-out  324   a  of the airframe longeron  300  to provide access to the fastening aperture  154   a ,  154   b  ( FIG.  2   ) to enable adjustment of the coupling between the engine pylon  120  and the transcowl  112  during installation and use. The airframe access opening  450  is generally sized to enable an operator to insert their hand and manipulate the fastening device coupled to the fastening aperture  154   a ,  154   b , such as the locking positioning system  100 , previously incorporated by reference herein. The airframe access panel  452  is composed of a polymer-based material, metal, or metal alloy, and is stamped, machined, cast, additively manufactured, etc. The airframe access panel  452  is coupled to the airframe access opening  450  via press-fit, mechanical fasteners, etc. Generally, the airframe access panel  452  is coupled to the airframe access opening  450  to be removable for maintenance, but secured during operation of the aircraft  104  ( FIG.  1   ). It should be noted that the vehicle pylon  122  may include a number of other components, including, but not limited to, additional aircraft beams, fasteners, seals, pre-coolers, control valves, thrust links, etc. depending upon the aircraft  104 , which are outside of the scope of the present disclosure. 
     With brief reference back to  FIG.  3   , in one example, in order to assemble the engine pylon  120 , the spacers  140   a ,  140   b  are positioned on the respective one of the first flange  150  and the second flange  152 . The elongated seals  136   a ,  136   b  are positioned adjacent to the respective one of the first flange  150  and the second flange  152  to be opposite the respective one of the spacers  140   a ,  140   b . The fastening assemblies  138   a ,  138   b  are positioned on the fastening strips  216  of the respective elongated seals  136   a ,  136   b . With the nut plates  186  and the second nut plates  196  coupled to the outboard longeron  132 , the outboard longeron  132  is positioned over the inboard longeron  130  such that the projection  180  and the second projection  190  overlie the first flange  150  and the second flange  152 , respectively, and are positioned adjacent to the spacers  140   a ,  140   b . The forward seal  134  is coupled to the inboard longeron  130 . The first base  144  of the inboard longeron  130  is coupled to the second base  170  of the outboard longeron  132 . Generally, the inboard longeron  130  is coupled to the outboard longeron  132  at a first end  120   a  of the engine pylon  120  and is spaced apart from the outboard longeron  132  at a second end  120   b  of the engine pylon  120 . The skin panel  142  is positioned about the inboard longeron  130  and the outboard longeron  132 . The rivets  238  are inserted through respective ones of the skin panel bores  236  of the first skin panel surface  230 , the coupling holes  228  of the spacer  140   a , the seal holes  217  of the elongated seal  136   a , the holes  222  of the fastening assembly  138   a  and are secured to the respective one of the nut plates  218 . The rivets  238  are inserted through respective ones of the skin panel bores  236  of the second skin panel surface  232 , the coupling holes  228  of the spacer  140   b , the seal holes  217  of the elongated seal  136   b , the holes  222  of the fastening assembly  138   b  and are secured to the respective one of the nut plates  218 . 
     With reference to  FIG.  2   , with the engine pylon  120  assembled, the engine pylon  120  is coupled to the transcowl  112 . In one example, the locking positioning system  100 , previously incorporated by reference herein, is coupled to the transcowl  112  and the inboard longeron  130  to couple the engine pylon  120  to the gas turbine engine  102 . Each of the locking positioning systems  100  may be adjusted along the slot serrations  164  defined by the fastening apertures  154   a - 154   c  to adjust a position of the gas turbine engine  102  along a Z-axis, in a rectangular coordinate system in which the X-axis is parallel to a center axis C of the gas turbine engine  102 . Stated another way, the slot serrations  164  enable the locking positioning system  100  to secure the engine pylon  120  at various positions on the exterior of the transcowl  112 . Once the engine pylon  120  is coupled to the gas turbine engine  102 , the engine pylon  120  is coupled to the vehicle pylon  122 . 
     With brief reference back to  FIG.  8   , in one example, in order to assemble the vehicle pylon  122 , the airframe forward seal  350  is coupled to the seal bracket  352 . The airframe ribs  308   a ,  308   b  are coupled to the first airframe flange  326  and the second airframe flange  328 . The airframe beams  310   a ,  310   b  are coupled to the airframe ribs  308   a ,  308   b . The seals  306   a ,  306   b  are positioned on the respective one of the first airframe flange  326  and the second airframe flange  328 . The seal fastening assemblies  304   a ,  304   b  are positioned next to the respective one of the seals  306   a ,  306   b . The skin panel  312   b  is coupled to the seal  306   b , the airframe longeron  300 , the airframe ribs  308   a ,  308   b  and the airframe beam  310   b . The rivet  400  is inserted through the panel bore  440  of the skin panel  312   b , the seal bore  398 , the hole  378  of the seal fastening assembly  304   b  and is secured with the respective seal nut plate  374 . The rivets  416  are each inserted through the panel bores  440  and the respective rib bores  410  to couple the airframe ribs  308   a ,  308   b  to the skin panel  312   b . Fasteners, such as rivets, are each inserted through the panel bores  440  to couple the airframe ribs  308   a ,  308   b  to the airframe beam  310   b . The skin panel  312   a  is coupled to the seal  306   a , the airframe longeron  300 , the airframe ribs  308   a ,  308   b  and the airframe beam  310   a . The rivet  400  is inserted through the panel bore  440  of the skin panel  312   a , the seal bore  398 , the hole  378  of the seal fastening assembly  304   a  and is secured with the respective seal nut plate  374 . The rivets  416  are each inserted through the panel bores  440  and the respective rib bores  410  to couple the airframe ribs  308   a ,  308   b  to the skin panel  312   a . Fasteners, such as rivets, are each inserted through the panel bores  440  to couple the airframe ribs  308   a ,  308   b  to the airframe beam  310   a . With the vehicle pylon  122  assembled, the vehicle pylon  122  is coupled to the airframe  106  of the aircraft  104  ( FIG.  1   ). In one example, the vehicle pylon  122  is coupled to a beam of the airframe  106  to enable fuel, pneumatic, hydraulic, and electric energy to transfer from the gas turbine engine  102  to the aircraft  104 . 
     With reference to  FIG.  11   , with the vehicle pylon  122  coupled to the aircraft  104 , the engine pylon  120  is coupled to the vehicle pylon  122  to couple the gas turbine engine  102  to the aircraft  104 . It should be noted that the gas turbine engine  102  may also be coupled to the airframe  106  of the aircraft  104  at additional locations, if desired. In one example, the first rail  239   a  and the second rail  239   b  defined by the respective portion of the first skin panel surface  230  and the second skin panel surface  232  that overhangs the outboard longeron  132  is positioned over the respective blade seal  390  of the vehicle pylon  122 . Generally, a gap is defined between the first skin panel surface  230  and the skin panel  312   a , and the second skin panel surface  232  and the skin panel  312   b . The gap is about 0.800 inches (in.) plus or minus about 0.500 inches (in.). The first rail  239   a  and the second rail  239   b  are movable or slidable along the blade seal  390  until the transcowl  112  is in the first, stowed position of  FIG.  1    and the engine pylon  120  is in the first position. Generally, the engine pylon  120  is coupled to the vehicle pylon  122  such that the skin panel  312   a ,  312   b  is substantially parallel with the first skin panel surface  230  and the second skin panel surface  232 , respectively, and substantially parallel to the centerline C of the gas turbine engine  102  ( FIG.  1   ) to reduce or substantially eliminate drag. In the first, stowed position, with reference to  FIG.  10   , the forward seal  134  of the engine pylon  120  is adjacent to and in contact with the airframe forward seal  350 . The airframe access panel  452  enables an operator to adjust the coupling of the gas turbine engine  102  relative to the aircraft  104  once installed to ensure a proper alignment between the engine pylon  120  and the vehicle pylon  122  ( FIG.  7   ). In addition, the access panel  242  of the engine pylon  120  enables further adjustment of the engine pylon  120  relative to the gas turbine engine  102  to further ensure that the gas turbine engine  102  is properly aligned with the aircraft  104  ( FIG.  2   ), which also reduces drag. 
     During operation of the gas turbine engine  102 , with reference to  FIG.  12   , the transcowl  112  may be moved, via signals to the actuator received from the controller associated with the gas turbine engine  102 , to the third, overstowed position. In the third, overstowed position, the transcowl  112  is moved forward to unload locks associated with the transcowl  112  to enable the transcowl  112  to move to the second, deployed position. The advancement of the transcowl  112  relative to the gas turbine engine  102  causes the first rail  239   a  and the second rail  239   b  to move or slide along the blade seal  390  of the respective seals  306   a ,  306   b  until the engine pylon  120  is in the third position and the transcowl  112  is in the third, overstowed position. In the third position, the forward seal  134  of the engine pylon  120  compresses the airframe forward seal  350  to form a tight seal between the gas turbine engine  102  and the aircraft  104 . In addition, during operation of the gas turbine engine  102 , with reference to  FIG.  13   , the transcowl  112  may be moved, via signals to the actuator received from the controller associated with the gas turbine engine  102 , to a second, deployed position. In the second, deployed position, the transcowl  112  is moved aft relative to the gas turbine engine  102  to define the aperture  460 . With reference to  FIG.  14   , the aft movement of the transcowl  112  relative to the gas turbine engine  102  causes the first rail  239   a  and the second rail  239   b  to move or slide along the blade seal  390  of the respective seals  306   a ,  306   b  until the engine pylon  120  is in the second position and the transcowl  112  is in the second, deployed position. In the second, deployed position, the forward seal  134  of the engine pylon  120  is spaced a distance apart from the airframe forward seal  350 . 
     Thus, with reference to  FIG.  1   , the pylon system  99  enables the gas turbine engine  102  to be mounted to a side of the aircraft  104  with the thrust reverser  108 . By providing the engine pylon  120  movable relative to the vehicle pylon  122  between the first position, the second position and the third position, the transcowl  112  is also movable between the first, stowed position, the second, deployed position and the third, overstowed position, respectively, without interfering with the side or rear mounting of the gas turbine engine  102  to the aircraft  104 . The ability to employ the transcowl  112  with the gas turbine engine  102  improves the stopping performance of the aircraft  104 , which may be desirable in certain landing conditions. Moreover, by providing the inboard longeron  130  with the fastening apertures  154  ( FIG.  5   ) that may be used with the locking positioning system  100 , the position of the engine pylon  120  relative to the transcowl  112  is adjustable in multiple degrees of freedom, such as about 12 degrees of freedom, which enables the engine pylon  120  and the gas turbine engine  102  to be positioned at a position relative to the aircraft  104  that reduces or substantially eliminates drag. In addition, the elongated seals  136   a ,  136   b , the forward seal  134 , the airframe forward seal  350  and the seals  306   a ,  306   b  reduce leakage around the components of the pylon system  99 . 
     In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the exemplary embodiment or exemplary embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the disclosure as set forth in the appended claims and the legal equivalents thereof.