Patent Publication Number: US-2022227471-A1

Title: Pressure bulkhead assembly and method and system for making the same

Description:
PRIORITY 
     This application claims priority from U.S. Ser. No. 63/139,406 filed on Jan. 20, 2021. 
    
    
     FIELD 
     The present disclosure relates generally to methods and systems for joining structural components and, more particularly, to methods and systems for indexing structural components associated with a pressure bulkhead assembly of an aircraft. 
     BACKGROUND 
     Pressure bulkheads are often used in aircraft to separate a pressurized section of a fuselage from an unpressurized section. In some applications, the pressure bulkhead may be mounted within the fuselage and attached to the outer skin of one or more sections of the fuselage. In some instances, the pressure bulkhead is mounted to the aircraft using a plurality of angled members, referred to as splice angles. 
     The splice angles and the pressure bulkhead are typically assembled on a drill jig using complex and expensive assembly jig tooling. For example, the pressure bulkhead is initially joined with the splice angles. Subsequently, holes are drilled through the pressure bulkhead and the splice angles while both are temporarily joined to each other. However, the use of drill jigs to drill such primary structural joints may result in oversized holes, can require multiple measurement and alignment steps, and/or require the pressure bulkhead and the splice angles to be repeatedly placed and removed from the jig, with any or all leading to production lags. The use of drill jigs can also lead to the pressure bulkhead having nonconforming joining surfaces and/or design of shims that is larger than desired. Also, the flexibility of carbon fiber materials that make up some of the pressure bulkhead components can make it harder to machine the surface of the pressure bulkhead and holes when the pressure bulkhead is attached to the jig. 
     Thus, there is a need for an assembly method for pressure bulkheads that reduces installation time, increases the accuracy of the size and locations of the hole, increases the accuracy of the position of the splice angles, reduces labor, is readily automated, and minimizes wastage of parts. Accordingly, those skilled in the art continue with research and development efforts in the field of pressure bulkhead assembly. 
     SUMMARY 
     Disclosed are examples of a method of making a pressure bulkhead assembly, a system for making a pressure bulkhead assembly, and a pressure bulkhead assembly for an aircraft. The following is a non-exhaustive list of examples, which may or may not be claimed, of the subject matter according to the present disclosure. 
     In an example, the disclosed method includes steps of: (1) determining an optimized position of a plurality of splice angles such that a plurality of splice surfaces of the plurality of splice angles will form a circumferential splice surface of the pressure bulkhead assembly with an optimized shape; (2) performing a virtual fit between the plurality of splice angles, at the optimized position, and an aft pressure bulkhead; (3) determining splice-angle-hole positions of splice-angle holes to be drilled in each one of the plurality of splice angles such that the splice-angle holes will correspond to aft-pressure-bulkhead holes, pre-drilled in the aft pressure bulkhead; (4) drilling the splice-angle holes in each one of the plurality of splice angles at the splice-angle-hole positions; and (5) joining each one of the plurality of splice angles with the aft pressure bulkhead such that the plurality of splice surfaces forms the circumferential splice surface with the optimized shape. 
     In an example, the disclosed system includes a measurement machine configured to take measurements of an aft pressure bulkhead and a plurality of splice angles. The system includes a computer system having memory storing a program and a processor. The processor is configured to execute the program to: (1) determine an optimized position of the plurality of splice angles such that a plurality of splice surfaces of the plurality of splice angles will form a circumferential splice surface with an optimized shape; (2) perform a virtual fit between the plurality of splice angles, at the optimized position, and an aft pressure bulkhead; and (3) with the plurality of splice angles at the optimized position, determine splice-angle-hole positions of splice-angle holes to be drilled in each one of the plurality of splice angles such that the splice-angle holes will correspond to aft-pressure-bulkhead holes, pre-drilled in the aft pressure bulkhead. The system includes a Computer Numerically Controlled machine configured to drill the splice-angle holes in each one of the plurality of splice angles at the splice-angle-hole positions. When the plurality of splice angles is joined with the aft pressure bulkhead at the optimized position, the plurality of splice surfaces forms the circumferential splice surface with the optimized shape. 
     In an example, the disclosed pressure bulkhead assembly includes an aft pressure bulkhead, including a bulkhead interface surface and aft-pressure-bulkhead holes, pre-drilled through the bulkhead interface surface, and a plurality of splice angles, configured to be coupled to the aft pressure bulkhead. Each one of the plurality of splice angles includes a flange surface, configured to mate with the bulkhead interface surface, splice-angle holes, drilled through the flange surface, and a splice surface, extending from the flange surface. With the splice-angle holes aligned with the aft-pressure-bulkhead holes, a plurality of splice surfaces forms a circumferential splice surface with an optimized shape. 
     Other examples of the disclosed method, system and structural assembly will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, perspective view of an example of a pressure bulkhead assembly; 
         FIG. 2  is a schematic illustration of an example of an aircraft that includes the pressure bulkhead assembly; 
         FIG. 3  is a schematic, cut away, perspective view of an example of a portion of the pressure bulkhead assembly coupled to a fuselage of the aircraft; 
         FIG. 4  is a flowchart of an example of a method of making the pressure bulkhead assembly; 
         FIG. 5  is a schematic block diagram of an example of a system for making the pressure bulkhead assembly; 
         FIG. 6  is a schematic, cut away, perspective view of an example of a portion of a first bulkhead surface of an aft pressure bulkhead of the pressure bulkhead assembly; 
         FIG. 7  is a schematic, cut away, perspective view of an example of a portion of a second bulkhead surface of the aft pressure bulkhead of the pressure bulkhead assembly; 
         FIG. 8  is a schematic, perspective view of an example of a splice angle configured to be installed on the aft pressure bulkhead to form the pressure bulkhead assembly; 
         FIG. 9  is a schematic, perspective view of an example of the splice angle configured to be installed on the aft pressure bulkhead to form the pressure bulkhead assembly; 
         FIG. 10  is a schematic illustration of a plurality of splice-angle scans, representing a plurality of splice angles, at an initial position in which a circumferential splice surface of the pressure bulkhead assembly has an initial shape; 
         FIG. 11  is a schematic, perspective view of a portion of the splice-angle scans shown in  FIG. 10 ; 
         FIG. 12  is a schematic, perspective view of a portion of the splice-angle scans shown in  FIG. 10  being adjusted from the initial position to an optimized position; 
         FIG. 13  is a schematic illustration of the plurality of splice-angle scans, representing the plurality of splice angles, at the optimized position in which the circumferential splice surface of the pressure bulkhead assembly has an optimized shape; 
         FIG. 14  is a schematic, perspective view of a portion of the splice-angle scans shown in  FIG. 13 ; 
         FIG. 15  is a schematic illustration of an example of a three-dimensional virtual overlay of an aft-pressure-bulkhead scan and one of the plurality of splice-angle scans; 
         FIG. 16  is a schematic, perspective view of an example of the splice angle shown in  FIGS. 8 and 9  with a plurality of splice-angle holes drilled therein; 
         FIG. 17  is a schematic, sectional view of an example of the pressure bulkhead assembly; 
         FIG. 18  is a schematic, plan view of an example of a shim of the pressure bulkhead assembly with shim holes drilled therein; and 
         FIG. 19  is a flow diagram of an aircraft manufacturing and service methodology. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description refers to the accompanying drawings, which illustrate specific examples described by the present disclosure. Other examples having different structures and operations do not depart from the scope of the present disclosure. Like reference numerals may refer to the same feature, element, or component in the different drawings. Throughout the present disclosure, any one of a plurality of items may be referred to individually as the item and a plurality of items may be referred to collectively as the items and may be referred to with like reference numerals. Moreover, as used herein, a feature, element, component or step preceded with the word “a” or “an” should be understood as not excluding a plurality of features, elements, components or steps, unless such exclusion is explicitly recited. 
     Illustrative, non-exhaustive examples, which may be, but are not necessarily, claimed, of the subject matter according the present disclosure are provided below. Reference herein to “example” means that one or more feature, structure, element, component, characteristic, and/or operational step described in connection with the example is included in at least one aspect, embodiment, and/or implementation of the subject matter according to the present disclosure. Thus, the phrases “an example,” “another example,” “one or more examples,” and similar language throughout the present disclosure may, but do not necessarily, refer to the same example. Further, the subject matter characterizing any one example may, but does not necessarily, include the subject matter characterizing any other example. Moreover, the subject matter characterizing any one example may be, but is not necessarily, combined with the subject matter characterizing any other example. 
     Referring to  FIG. 1 , by way of examples, the present disclosure is directed to a pressure bulkhead assembly  100  that includes an aft pressure bulkhead  108  and a plurality of splice angles  102 . Referring generally to  FIG. 4 , by way of examples, the present disclosure is directed to a method  1000  of making the pressure bulkhead assembly  100  by indexing and installing the plurality of splice angles  102  on the aft pressure bulkhead  108 . Referring generally to  FIG. 5 , by way of examples, the present disclosure is also directed to a system  200  for making the pressure bulkhead assembly  100 . In one or more examples, the method  1000  is implemented using the system  200 . 
     Examples of the system  200  and method  1000  use measurements of the aft pressure bulkhead  108  to determine a surface profile of the aft pressure bulkhead  108  and to determine positions of pre-drilled full-size holes in the aft pressure bulkhead  108 . Examples of the system  200  and method  1000  use measurements of the plurality of splice angles  102  to determine a surface profile of each one of the plurality of splice angles  102 . Examples of the system  200  and method  1000  use the determined surface profile of the aft pressure bulkhead  108  and the determined surface profiles of the plurality of splice angles  102  to virtually fit the plurality of splice angles  102  at an optimized position about the aft pressure bulkhead  108  for assembly of the pressure bulkhead assembly  100 . Examples of the system  200  and method  1000  use the virtual fit and the determined positions of pre-drilled full-size holes in the aft pressure bulkhead  108  to determine positions of full-size holes to be drilled in each one of the plurality of splice angles  102  so that the plurality of splice angles  102  are indexed at the optimized position when joined to the aft pressure bulkhead  108 . 
     Examples of the system  200  and method  1000  facilitate drilling the full-size holes in each one of the plurality of splice angles  102  at the determined positions so that the full-size holes drilled in the splice angles  102  correspond to the pre-drilled full-size holes in the aft pressure bulkhead  108 . Examples of the system  200  and method  1000  also facilitate installation of the splice angles  102  on the aft pressure bulkhead  108  using a plurality of fasteners inserted through aligned pairs of full-size holes in the splice angles  102  and full-size holes in the aft pressure bulkhead  108  so that the plurality of splice angles  102  are joined to the aft pressure bulkhead  108  at the optimized position. 
     Examples of the system  200  and method  1000  facilitate identifying dimensions of gaps formed between the aft pressure bulkhead  108  and the plurality of splice angles  102  and forming the plurality of shims  128  based on those gap dimensions. Examples of the system  200  and method  1000  also facilitate determining positions of full-size holes to be drilled in the shims  128  and drilling the full-size holes in the shims  128  at the determine positions. Examples of the system  200  and method  1000  further facilitate installing the plurality of shims  128  between the aft pressure bulkhead  108  and the plurality of splice angles  102  so that the plurality of splice angles  102  are joined to the aft pressure bulkhead  108  at the optimized position. 
     Referring now to  FIG. 1 , which schematically illustrates an example of the pressure bulkhead assembly  100 . The pressure bulkhead assembly  100  includes, or is formed of, the aft pressure bulkhead  108  and the splice angles  102 . The splice angles  102  are positioned adjacent to one another and are joined to the aft pressure bulkhead  108 . The splice angles  102  form a circumferential splice surface  106 . The circumferential splice surface  106  has an optimized shape  136 . 
     For the purpose of the present disclosure, the optimized shape  136  of the circumferential splice surface  106  refers to a shape of the circumferential splice surface  106  that is optimized to be as close to circular as feasible, given manufacturing tolerances. As will be described in more detail herein, the optimized shape  136  of the circumferential splice surface  106  is achieved by determining the optimized position of each one of the splice angles  102  such that a step, or offset, between mating edges of directly adjacent ones of the splice angles  102  is minimized. In one or more examples, the optimized shape  136  is approximately circular in which a step dimension  116  (e.g., as shown in  FIG. 12 ) between a mating edge  118  of each one of the plurality of splice angles  102  and the mating edge  118  of a directly adjacent one of the plurality of splice angles  102  is minimized (e.g., as shown in  FIGS. 13 and 14 ). 
     In one or more examples, the aft pressure bulkhead  108  includes a bulkhead interface surface  126  (e.g., as shown in  FIGS. 7 and 9 ) and a plurality of aft-pressure-bulkhead holes  114  (e.g., as shown in  FIGS. 6-9 ). The aft-pressure-bulkhead holes  114  are pre-drilled through the bulkhead interface surface  126 . 
     In one or more examples, the splice angles  102  are configured to be coupled to (e.g., installed on or otherwise fastened to) the aft pressure bulkhead  108 . Each one of the splice angles  102  incudes a flange surface  130 , a plurality of splice-angle holes  112 , and a splice surface  104  (e.g., as shown in  FIGS. 8, 9 and 16 ). The flange surface  130  is configured to mate with the bulkhead interface surface  126 . The splice-angle holes  112  are drilled through the flange surface  130 . The splice surface  104  extends from the flange surface  130 . With the splice-angle holes  112  aligned with the aft-pressure-bulkhead holes  114 , a plurality of splice surfaces  104  forms the circumferential splice surface  106  with the optimized shape  136 . 
     In one or more examples, splice-angle-hole positions  110  (e.g., as shown in  FIG. 16 ) of the splice-angle holes  112  are determined based on: (1) a virtual fit between the splice angles  102 , at the optimized position, and the aft pressure bulkhead  108 ; and (2) measured aft-pressure-bulkhead-hole positions  132  (e.g., as shown in  FIGS. 6 and 7 ) of the aft-pressure-bulkhead holes  114 . 
     For the purpose of the present disclosure, the “position” of a hole refers to a location (e.g., along an X-axis, a Y-axis and a Z-axis) and the angular orientation (e.g., about the X-axis, the Y-axis and the Z-axis) of the hole in three-dimensional space (e.g., relative to a three-dimensional coordinate system). 
     In one or more examples, the pressure bulkhead assembly  100  includes a plurality of fasteners  134  (e.g., as shown in  FIGS. 5 and 17 ). The fasteners  134  are inserted through the splice-angle holes  112  and the aft-pressure-bulkhead holes  114  to fasten the plurality of splice angles  102  to the aft pressure bulkhead  108 . 
     In one or more examples, the pressure bulkhead assembly  100  includes a shim  128  (e.g., as shown in  FIGS. 17 and 18 ). The shim  128  is positioned between the flange surface  130  of one of the splice angles  102  and the bulkhead interface surface  126  of the aft pressure bulkhead  108  (e.g., as shown in  FIG. 17 ). 
     In one or more examples, the aft pressure bulkhead  108  takes the form of a panel, a disk or a dome (e.g., is dome-shaped). Accordingly, the aft pressure bulkhead  108  is also referred to as an aft pressure bulkhead dome or as an aft pressure bulkhead panel. For simplicity, the aft pressure bulkhead may be referred to herein or in the accompanying figures as “APB”. Generally, the pressure bulkhead assembly  100  is sized and shaped for placement inside a fuselage  1202  of an aircraft  1200  (e.g., as shown in  FIG. 2 ) such that the aft pressure bulkhead  108  separates a pressurized portion of an interior  1204  ( FIG. 2 ) of the aircraft  1200  (e.g., a pressurized cabin) from an unpressurized portion of the interior  1204  and the splice angles  102  form a pressure seal. In one or more examples, the pressure bulkhead assembly  100  is attached to a skin  1206  ( FIG. 2 ) of the fuselage  1202  via the splice angles  102 . 
     The aft pressure bulkhead  108  and the splice angles  102  are formed of any suitable material. In one or more examples, the aft pressure bulkhead  108  and the splice angles  102  are formed of a composite material. In one or more examples, the aft pressure bulkhead  108  and the splice angles  102  are formed of a metallic material, a polymeric material, another suitable material, or a combination of materials. The material of the aft pressure bulkhead  108  and the material of the splice angles  102  may be the same or different. 
     Referring now to  FIG. 2 , which schematically illustrates an example of the aircraft  1200  in which pressure bulkhead assembly  100  is used. The pressure bulkhead assembly  100  divides a pressurized side of the aircraft  1200  from an unpressurized side of the aircraft  1200 . The splice angles  102  ( FIG. 1 ) are installed on the aft pressure bulkhead  108  ( FIG. 1 ) on the pressurized side of the aft pressure bulkhead  108 . As an example, the aircraft  1200  includes the fuselage  1202  and wings  1208  attached to and outwardly extending from the fuselage  1202 . The fuselage  1202  includes a plurality of fuselage sections (e.g., barrel sections). The fuselage  1202  (e.g., each fuselage section) has the skin  1206 , coupled to an airframe  1210 , that forms an exterior of the aircraft  1200 . The pressure bulkhead assembly  100  separates a first fuselage section  1212  (e.g., pressurized side) from a second fuselage section  1214  (e.g., unpressurized side) in an aft portion of the fuselage  1202 . For example, in  FIG. 3 , arrow  1216  indicates a direction of a forward (e.g., pressurized) portion of the aircraft  1200 . 
     Referring now to  FIG. 3 , which schematically illustrates an example of a portion of the pressure bulkhead assembly  100  attached to the first fuselage section  1212  and the second fuselage section  1214 , viewed from within the fuselage  1202 . The splice angles  102  overlap a first skin-portion  1218  of the skin  1206  of the first fuselage section  1212  and a second skin-portion  1220  of the skin  1206  of the second fuselage section  1214 . The splice angles  102  are attached (e.g., fastened by a plurality of fasteners) to the first skin-portion  1218  and to the second skin-portion  1220 . In this manner, the splice angles  102  join the aft pressure bulkhead  108 , the first fuselage section  1212  and the second fuselage section  1214  together. Accordingly, the splice angles  102  are also referred to as skin splice angles. 
     As an example, during fabrication of the aircraft  1200 , the pressure bulkhead assembly  100  is attached to the second fuselage section  1214  by fastening the splice angles  102  to the second skin-portion  1220 . The first fuselage section  1212  is then positioned adjacent to the second fuselage section  1214  such that the splice angles  102  overlap the first skin-portion  1218 . The pressure bulkhead assembly  100  is attached to the first fuselage section  1212  by fastening the splice angles  102  to the first skin-portion  1218 . The optimized shape  136  ( FIG. 1 ) of the circumferential splice surface  106 , formed by the splice angles  102 , is approximately complementary to the barrel (e.g., circular) shape of the skins  1206  of the first fuselage section  1212  and the second fuselage section  1214 . Accordingly, the splice angles  102  are positioned on the pressurized side of the aft pressure bulkhead  108  and are configured to form a pressure seal for the fuselage  1202  ( FIG. 2 ) between the first fuselage section  1212  (e.g., pressurized section) and the second fuselage section  1214  (e.g., unpressurized section). 
     In one or more examples, one or more splice-to-skin shims (not shown in  FIG. 3 ) are positioned between the circumferential splice surface  106  of the splice angles  102  and the skin  1206  to fill any gaps that exist between the splice angles  102  and the first skin-portion  1218  and/or the second skin-portion  1220 , for example, in areas where the circumferential splice surface  106  does not contact the skin  1206  of the first fuselage section  1212  and/or the second fuselage section  1214  (e.g., where the optimized shape  136 ) ( FIG. 1 ) of the circumferential splice surface  106  does not match the barrel shape of the first fuselage section  1212  and/or the second fuselage section  1214 ). 
     Referring now to  FIG. 4 , which illustrates an example of the method  1000 . In one or more examples, the method  1000  includes a step of (block  1002 ) making, or forming, the aft pressure bulkhead  108 . In one or more examples, the method  1000  includes a step of (block  1004 ) drilling aft-pressure-bulkhead holes  114  through the aft pressure bulkhead  108 . 
     Referring now to  FIGS. 6 and 7 , which schematically illustrates an example of a portion of a first bulkhead surface  138  and a portion of a second bulkhead surface  140  of the aft pressure bulkhead  108 , respectively. In one or more examples, the aft pressure bulkhead  108  is initially made, or otherwise fabricated, with the plurality of aft-pressure-bulkhead holes  114 . For example, the aft pressure bulkhead  108  can be attached to an assembly jig or support tooling for drilling the aft-pressure-bulkhead holes  114 . 
     The aft-pressure-bulkhead holes  114  are pre-drilled in the aft pressure bulkhead  108  and are full-size holes configured to receive corresponding fasteners  134  (e.g., as shown in  FIG. 17 ). Accordingly, the aft-pressure-bulkhead holes  114  are also referred to as pre-drilled, full-size holes or aft-pressure-bulkhead fastener holes. The aft-pressure-bulkhead holes  114  are drilled at pre-defined positions on the aft pressure bulkhead  108 . The pre-defined position of each one of the aft-pressure-bulkhead holes  114  refers to the pre-determined, actual (e.g., physical, real world) position of the aft-pressure-bulkhead hole  114  on the aft pressure bulkhead  108 , as drilled. 
     In one or more examples, the aft pressure bulkhead  108  includes the first bulkhead surface  138  (e.g., as shown in  FIG. 6 ) and the second bulkhead surface  140  (e.g., as shown in  FIG. 7 ), opposite the first bulkhead surface  138 . The aft pressure bulkhead  108  also has a thickness  142  ( FIG. 6 ) defined between the first bulkhead surface  138  and the second bulkhead surface  140 . 
     In one or more examples, the first bulkhead surface  138  is, or forms, an outer mold line (OML) of the aft pressure bulkhead  108  and the second bulkhead surface  140  is, or forms, an inner mold line (IML) of the aft pressure bulkhead  108 . Accordingly, the first bulkhead surface  138  is also referred to as an outer surface and the second bulkhead surface  140  is also referred to as an inner surface. With the pressure bulkhead assembly  100  installed within the fuselage  1202  of the aircraft  1200  (e.g., as shown in  FIG. 3 ), the first bulkhead surface  138  is on a unpressurized side of the aft pressure bulkhead  108  and the second bulkhead surface  140  is on the pressurized side of the aft pressure bulkhead  108 . 
     The second bulkhead surface  140  includes (e.g., a portion of the second bulkhead surface  140  forms) the bulkhead interface surface  126  (e.g., an aft-pressure-bulkhead interface surface). The bulkhead interface surface  126  is located adjacent to a peripheral edge of the aft pressure bulkhead  108  and extends along an approximately circular path. The bulkhead interface surface  126  is configured to mate with the splice angles  102  during installation of the splice angles  102  on the aft pressure bulkhead  108 . In other words, the bulkhead interface surface  126  serves as a faying surface that contacts the splice angles  102  at a joint between the splice angles  102  and the aft pressure bulkhead  108  during assembly of the pressure bulkhead assembly  100  ( FIG. 1 ). 
     The aft-pressure-bulkhead holes  114  are drilled through the thickness  142  of the aft pressure bulkhead  108  (e.g., extend between the first bulkhead surface  138  and the second bulkhead surface  140 ). The pre-defined positions of the aft-pressure-bulkhead holes  114  locate the aft-pressure-bulkhead holes  114  through the bulkhead interface surface  126 , for example, along an approximately circular path proximate (e.g., at or near) the peripheral edge of the aft pressure bulkhead  108 . 
     Only some of the aft-pressure-bulkhead holes  114  are shown in  FIGS. 6 and 7  (e.g., aft-pressure-bulkhead holes  114  in a section of the aft pressure bulkhead  108 ) for the purpose of clarity of illustration. While not explicitly illustrated in  FIGS. 6 and 7 , it should be understood that the aft-pressure-bulkhead holes  114  extend around an entirety of the aft pressure bulkhead  108  (e.g., as shown in  FIG. 1 ). 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1006 ) making the splice angles  102  ( FIGS. 8 and 9 ). The splice angles  102  are initially made, or otherwise fabricated, without a plurality of holes (e.g., pre-drilled, full size holes). 
     Referring now to  FIGS. 8 and 9 , which schematically illustrate an example of a first splice-angle surface  144  and a second splice-angle surface  146 , respectively, of one of the splice angles  102  relative to the aft pressure bulkhead  108 . The splice angle  102  illustrated in  FIGS. 8 and 9  is representative of any one of the plurality of splice angles  102 . 
     In one or more examples, the splice angle  102  includes the first splice-angle surface  144  (e.g., as shown in  FIG. 8 ) and the second splice-angle surface  146  (e.g., as shown in  FIG. 9 ), opposite the first splice-angle surface  144 . The splice angle  102  also has a thickness defined between the first splice-angle surface  144  and the second splice-angle surface  146 . 
     In one or more examples, the first splice-angle surface  144  is, or forms, an outer mold line (OML) of the splice angle  102  and the second splice-angle surface  146  is, or forms, an inner mold line (IML) of the splice angle. Accordingly, the first splice-angle surface  144  is also referred to as an outer surface and the second splice-angle surface  146  is also referred to as an inner surface. With the pressure bulkhead assembly  100  installed within the fuselage  1202  of the aircraft  1200  (e.g., as shown in  FIG. 3 ), the first splice-angle surface  144  generally faces radially outward and the second splice-angle surface  146  generally faces radially inward. 
     In one or more examples, the splice angle  102  includes a flange  148 . The flange  148  includes (e.g., a portion of the first splice-angle surface  144  forms) the flange surface  130  (e.g., a splice-angle interface surface). The flange surface  130  is configured to mates with the bulkhead interface surface  126  of the aft pressure bulkhead  108  during installation of the splice angles  102  on the aft pressure bulkhead  108 . In other words, the flange surface  130  serves as a faying surface that contacts the bulkhead interface surface  126  at the joint between the splice angle  102  and the aft pressure bulkhead  108  during assembly of the pressure bulkhead assembly  100  ( FIG. 1 ). 
     In one or more examples, the splice angle  102  includes a skin splice  150  that extends from the flange  148  at an oblique angle. The skin splice  150  includes (e.g., a portion of the first splice-angle surface  144  forms) the splice surface  104 . The splice surface  104  forms an arcuate segment of the circumferential splice surface  106  (e.g., shown in  FIG. 1 ). 
     The splice angle  102  includes an opposed pair of mating edges  118  (e.g., identified as a first mating edge  118   a  and a second mating edge  118   b  in  FIGS. 1, 8 and 9 ). During installation of the splice angles  102  on the aft pressure bulkhead  108 , one of the mating edges  118  (e.g., the first mating edge  118   a ) of one of the splice angles  102  abuts one of the mating edges  118  (e.g., the second mating edge  118   b ) of a directly adjacent one of the splice angles  102  (e.g., as shown in  FIG. 1 ). 
     In one or more examples, the splice angle  102  is fabricated with pilot holes  152  that are drilled through the skin splice  150 . The pilot holes  152  are drilled at positions that approximately correspond to locations where full-size holes will be drilled through the skin splice  150  of the splice angle  102 , the first skin-portion  1218 , and the second skin-portion  1220  during installation of the pressure bulkhead assembly  100  in the fuselage  1202  (e.g., as shown in  FIG. 3 ). 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1008 ) measuring the aft pressure bulkhead  108 . In one or more examples, the step of (block  1008 ) measuring the aft pressure bulkhead  108  provides (e.g., generates) three-dimensional (3D) measurement data representing the 3D geometry of the aft pressure bulkhead  108 . 
     In one or more examples, the step of (block  1008 ) measuring the aft pressure bulkhead  108  includes a step of measuring the bulkhead interface surface  126  and a step of measuring the aft-pressure-bulkhead holes  114 . It can be appreciated that an entirety of or other portions of the aft pressure bulkhead  108  may also be measured, such as an entirety of the first bulkhead surface  138 , an entirety of the second bulkhead surface  140 , and/or the peripheral edge of the aft pressure bulkhead  108 . 
     In one or more examples, the method  1000  includes a step of (block  1010 ) measuring the splice angles  102  (e.g., each one of the splice angles  102 ). In one or more examples, the step of (block  1010 ) measuring the splice angles  102  provides (e.g., generates) 3D measurement data representing the 3D geometry of each one of the splice angles  102 . 
     In one or more examples, the step of (block  1010 ) measuring the splice angles  102  includes a step of measuring the first splice-angle surface  144  of the splice angles  102  (e.g., of each one of the splice angles  102 ), such as measuring the flange surface  130  and measuring the splice surface  104 . In one or more examples, the step of (block  1010 ) measuring the splice angles  102  includes a step of measuring the pilot holes  152 . It can be appreciated that an entirety of or other portions of the splice angle  102  may also be measured, such as an entirety of the first splice-angle surface  144 , an entirety of the second splice-angle surface  146 , and/or the pair of mating edges  118 . 
     In one or more examples, the method  1000  includes a step of (block  1012 ) generating a plurality of splice-angle scans  120  (e.g., as shown in  FIG. 5 ). In one or more examples, the splice-angle scans  120  are generated using the 3D measurement data obtained during the measuring step (e.g., block  1010 ). Accordingly, the splice-angle scan  120  is a virtual model or 3D digital representation of the splice angle  102 , such as of the surface (e.g., a 3D surface profile) of the splice angle  102  and, optionally, other geometric features of the splice angle  102 . Each one of the splice-angle scans  120  represents (e.g., is a 3D digital representation of) a corresponding one of the splice angles  102 . 
     In one or more examples, the splice-angle scan  120  represents at least a portion of the first splice-angle surface  144  ( FIG. 8 ). Optionally, the splice-angle scan  120  represents at least a portion of the second splice-angle surface  146  of the splice angle  102 . In one or more examples, the splice-angle scan  120  includes a splice-surface scan  158  (e.g., as shown in  FIGS. 10-14 ) representing the splice surface  104  ( FIG. 8 ). In one or more examples, the splice-angle scan  120  includes a flange-surface scan  162  (e.g., as shown in  FIGS. 11, 12 and 14 ) representing the flange surface  130  ( FIG. 8 ). In one or more examples, the splice-angle scan  120  includes mating-edge scans  160  (e.g., as shown in  FIGS. 11, 12 and 14 ) representing the mating edges  118  ( FIGS. 8 and 9 ) of the splice angle  102 . In one or more examples, the splice-angle scan  120  includes pilot-hole scans  164  (e.g., as shown in  FIGS. 11 and 14 ) representing the pilot holes  152  of the splice angle  102 . 
     In one or more examples, the method  1000  includes a step of (block  1014 ) aligning (e.g., virtually aligning) the splice-angle scans  120  to a nominal model  122  ( FIG. 5 ) of the pressure bulkhead assembly  100 . The nominal model  122  is a 3D design model, such as a computer aided design (CAD) model, that represents the pressure bulkhead assembly  100  having the circumferential splice surface  106  with a nominal shape (e.g., a design shape). The step of (block  1014 ) aligning the splice-angle scans  120  to the nominal model  122  arranges the plurality of splice-angle scans  120  at an initial position in which the splice-angle scans  120  are positioned adjacent to one another and a plurality of splice-surface scans  158  of the splice-angle scans  120  represents the circumferential splice surface  106  with an initial shape  154  (e.g., as shown in  FIGS. 10 and 11 ). 
     Accordingly, the initial position of the splice-angle scans  120  is a position of the splice-angle scans  120  following the alignment of the splice-angle scans  120  to the nominal model  122 . The initial shape  154  of the circumferential splice surface  106  is the shape of the circumferential splice surface  106  represented by the splice-surface scans  158  following alignment of the splice-angle scans  120  to the nominal model  122 . 
     For the purpose of the present disclosure, the “position” (e.g., initial position, adjusted position, optimized position, etc.) of the splice angle  102  or the splice-angle scan  120  refers to a location (e.g., along an X-axis, a Y-axis and a Z-axis) and an angular orientation (e.g., about the X-axis, the Y-axis and the Z-axis) of the splice angle  102  or the splice-angle scan  120  in three-dimensional space (e.g., relative to a three-dimensional coordinate system). 
     In one or more examples, step of (block  1014 ) aligning the splice-angle scans  120  to a nominal model  122  includes a step of performing a best fit between each one of the plurality of splice-angle scans  120  and the nominal model  122 . For example, alignment parameters are calculated by performing an optimized best fit of multiple points of the splice-angle scan  120  to a portion of the nominal model  122  representing the splice angles  102  of the pressure bulkhead assembly  100 . 
     In one or more examples, the method  1000  includes a step of (block  1016 ) limiting degrees of freedom of each one of the splice-angle scans  120  relative to the nominal model  122  within a predetermined tolerance during the step of (block  1014 ) aligning the splice-angle scans  120  to the nominal model  122 , such as while performing the best fit. The predetermined tolerance limits the magnitude of motion (e.g., linearly along the X-, Y-, and Z-axes and/or angularly about the X-, Y-, and Z-axes) of the splice-angle scan  120  relative to the nominal model  122  during the best fit analysis. In one or more examples, a feature of the splice angle  102  represented by the splice-angle scan  120  is used to limit the degrees of freedom. For example, motion (e.g., linear and/or angular) of the pilot-hole scans  164  of the splice-angle scan  120  is restricted to a predefined linear and/or angular dimension relative to a fixed coordinate system shared by the splice-angle scan  120  and the nominal model  122 . 
     Referring now to  FIGS. 10 and 11 , which schematically illustrate an example of the splice-angle scans  120  arranged (e.g., virtually positioned) at the initial position following the step of (block  1014 ) aligning the splice-angle scans  120  to the nominal model  122  ( FIG. 5 ) of the pressure bulkhead assembly  100 . With the splice-angle scans  120  at the initial position, the mating-edge scans  160  of each one of the splice-angle scans  120  abut the mating-edge scan  160  of a directly adjacent one of the splice-angle scans  120 . The splice-surface scans  158  (e.g., 3D surface profile) representing the splice surfaces  104  of the splice-angle scans  120  form a virtual representation of the circumferential splice surface  106  having the initial shape  154 . 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1018 ) determining the step dimension  116  (e.g., as shown in  FIG. 12 ) between the mating-edge scan  160  of each one of the splice-angle scans  120  and the mating-edge scan  160  of a directly adjacent one of the splice-angle scans  120 . The step dimensions  116  are determined with the splice-angle scans  120  in the initial position. 
     Referring now to  FIG. 12 , which schematically illustrates an example of a portion of the splice-angle scans  120  arranged adjacent to one another in the initial position. As illustrated in  FIG. 12 , with the splice-angle scans  120  fit to the nominal model  122  (e.g., at the initial position), stepping can occur between the splice-surface scan  158  of adjacent ones of the splice-angle scans  120 . An offset distance (e.g., step) between the splice-surface scans  158  of directly adjacent ones of the splice-angle scans  120  is defined (e.g., calculated) by the step dimension  116  between the abutted mating-edge scans  160  of the directly adjacent ones of the splice-angle scans  120 . For example, in the initial position, a first mating-edge scan  160   a  of a first splice-angle scan  120   a  is offset relative to a second mating-edge scan  160   b  of a second splice-angle scan  120   b  that is directly adjacent to the first splice-angle scan  120   a . The second mating-edge scan  160   b  of the first splice-angle scan  120   a  is offset relative to the first mating-edge scan  160   a  of a third splice-angle scan  120   c  that is directly adjacent to the first splice-angle scan  120   a , opposite the second splice-angle scan  120   b.    
     As such, if the splice angles  102  were to be joined with the aft pressure bulkhead  108  at the initial position, such stepping would form one or more discontinuities along the circumferential splice surface  106  between the splice surfaces  104  of directly adjacent ones of the splice angles  102  (e.g., as shown in  FIGS. 10-12 ). Such stepping can lead to challenges when installing the pressure bulkhead assembly  100  within the fuselage  1202  of the aircraft  1200 . As an example, the initial shape  154  of the circumferential splice surface  106  may not suitably mate with the surface of the skin  1206  of the fuselage  1202 . As another example, the splice-to-skin shim (not illustrated), which is positioned between the circumferential splice surface  106  formed by the splice angles  102  and the skin  1206 , typically extends across the splice surfaces  104  two or more of the splice angles  102 . As such, fabricating the splice-to-skin shim to suitably fill the gap between the splice angles  102  and the skin  1206  can be challenging when such stepping is present. 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1020 ) determining an angular displacement of each one of the splice-angle scans  120  to minimize the step dimension  116  and a step of (block  1022 ) adjusting (e.g., repositioning) each one of the splice-angle scans  120  by the angular displacement. Adjusting the splice-angle scans  120  by the angular displacement moves the plurality of splice-angle scans  120  from the initial position to an optimized position. 
     The angular displacement of each one of the splice-angle scans  120  that minimizes the step dimension  116  is used to determine the optimized position of the splice-angle scans  120  and, thus, the optimized position of the splice angles  102  when joined with the aft pressure bulkhead  108  to form the pressure bulkhead assembly  100 . In one or more examples, the method  1000  includes a step of (block  1024 ) determining the optimized position of the plurality of splice angles  102  such that the plurality of splice surfaces  104  of the plurality of splice angles  102  will form the circumferential splice surface  106  with the optimized shape  136  (e.g., as shown in  FIGS. 13 and 14 ). The step of (block  1024 ) determining the optimized position of the splice angles  102  is achieved by adjusting the splice-angle scans  120  according to the angular displacement between directly adjacent ones of the splice-angle scans  120  to minimize the step dimensions  116 . 
     Accordingly, the optimized position of the splice angles  102  is represented by the optimized position of the splice-angle scans  120 . The optimized position of the splice-angle scans  120  is a position of the splice-angle scans  120  in which the step dimension  116  is minimized. The optimized position of the plurality of splice angles  102  is a position of each one of the splice angles  102  in which the step dimension  116  is minimized and the optimized shape  136  of the circumferential splice surface  106 , formed by the splice surfaces  104  of the splice angles  102 , is achieved. The optimized shape  136  of the circumferential splice surface  106  is the shape of the circumferential splice surface  106  following position optimization of the splice-angle scans  120  and step minimization between the splice-angle scans  120  (e.g., as shown in  FIGS. 13 and 14 ). 
     Referring again to  FIG. 12 , in one or more examples, the angular displacement of the splice-angle scan  120  represents an angle of rotation, applied to the splice-angle scan  120  about a rotation axis  156 , required to minimize the step dimensions  116  between the splice-angle scan  120  and the directly adjacent splice-angle scan  120 . For example, as illustrated in  FIG. 12 , the first splice-angle scan  120   a  is adjusted (e.g., angularly reposition) by applying an axial rotation to the first splice-angle scan  120   a  about the rotation axis  156 , according to the angular displacement, in order to: (1) minimize the step dimension  116  between the first mating-edge scan  160   a  of the first splice-angle scan  120   a  and the second mating-edge scan  160   b  of the second splice-angle scan  120   b ; and (2) minimize the step dimension  116  between the second mating-edge scan  160   b  of the first splice-angle scan  120   a  and the first mating-edge scan  160   a  of the third splice-angle scan  120   c.    
     An axial rotation, about a respective rotation axis  156  and according to a respective angular displacement, is then applied to the each remaining one of the splice-angle scans  120  to minimize the step dimensions  116  between each one of the splice-angle scans  120  and its directly adjacent neighbors. In other words, the angular displacement for each one of the splice-angle scans  120  is determined to “split the difference” between the opposed mating-edge scans  160  of each one of the splice-angle scans  120  and the respective mating-edge scan  160  of the directly adjacent, opposing pair of splice-angle scans  120  (e.g., neighboring splice-angle scans  120 ). 
     In one or more examples, the adjusting step (e.g., angular repositioning by axial rotation) of each one of the splice-angle scans  120  is performed sequentially along the circumferential splice surface  106 . For example, the second splice-angle scan  120   b  is adjusted (e.g., angularly repositioned) to minimize its step dimensions  116  following adjustment of the first splice-angle scan  120   a . The splice-angle scan  120  that is directly adjacent to the second splice-angle scan  120   b  and opposite the first splice-angle scan  120   a  is then adjusted (e.g., angularly repositioned) to minimize its step dimensions  116 . This process is repeated for each subsequent one of the splice-angle scans  120  along a circular path, corresponding to the circumferential splice surface  106 , until the third splice-angle scan  120   c  is adjusted (e.g., angularly repositioned) to minimize its step dimensions  116 . 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of sequentially repeating the step of (block  1018 ) determining the step dimension  116 , the step of (block  1020 ) determining the angular displacement for each one of the plurality of splice angles  102 , and the step of (block  1022 ) adjusting each one of the splice-angle scans  120  by the angular displacement in an iterative matter until the step dimension  116  between each one of the splice-angle scans  120  and its neighbor (e.g., directly adjacent one of the splice-angle scans  120 ) is below a predetermined threshold. Repeating the optimization steps, referred to above, for each one of the splice-angle scans  120  in an iterative manner further optimizes the position of each one of the splice-angle scans  120  to achieve a shape for the circumferential splice surface  106  that is closer to circular. 
     The predetermined threshold can be any suitable predefined value. In one or more examples, the predetermined threshold is a maximum dimension value of the step (e.g., of the step dimension  116 ) between adjacent ones of the splice-angle scans  120  that is within manufacturing tolerance. In one or more examples, the predetermined threshold is a point beyond which there is no discernable angular displacement that would further minimize the step dimension  116 . 
     Referring now to  FIGS. 13 and 14 , which schematically illustrate an example of the splice-angle scans  120  arranged adjacent to one another at the optimized positioned following the optimization steps (e.g., block  1018 , block  1020  and block  1022 ). With the splice-angle scans  120  at the optimized position, the mating-edge scans  160  of each one of the splice-angle scans  120  abut the mating-edge scan  160  of a directly adjacent one of the splice-angle scans  120 . The splice-surface scans  158  representing the splice surfaces  104  of the splice-angle scans  120  form a virtual representation of the circumferential splice surface  106  having the optimized shape  136 . 
     With the splice-angle scans  120  at the optimized position, the stepping between the splice-surface scan  158  of adjacent ones of the splice-angle scans  120  is minimized. As such, when the splice angles  102  are joined with the aft pressure bulkhead  108  at the optimized position, such minimized stepping will reduce, or eliminate, discontinuities along the circumferential splice surface  106  between the splice surfaces  104  of directly adjacent ones of the splice angles  102  (e.g., as shown in  FIGS. 13 and 14 ). Minimizing such stepping is advantageous when installing the pressure bulkhead assembly  100  within the fuselage  1202  of the aircraft  1200 . As an example, the optimized shape  136  of the circumferential splice surface  106  will more suitably mate with the surface of the skin  1206  of the fuselage  1202 . As another example, the splice-to-skin shim (not illustrated), which is positioned between the circumferential splice surface  106  formed by the splice angles  102  and the skin  1206 , typically extends across the splice surfaces  104  two or more of the splice angles  102 . As such, fabricating the splice-to-skin shim to suitably fill the gap between the splice angles  102  and the skin  1206  is less challenging when such stepping is minimized. 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1026 ) performing a virtual fit between the plurality of splice angles  102 , at the optimized position, and the aft pressure bulkhead  108 . The virtual fit is essentially a virtual joining of the splice angles  102  and the aft pressure bulkhead  108  using the splice-angle scans  120  and an aft-pressure-bulkhead scan  124  (e.g., as shown in  FIG. 15 ). For example, the step of (block  1026 ) performing the virtual fit includes a step of virtually overlaying, or aligning, the aft-pressure-bulkhead scan  124  with the splice-angle scans  120 . 
     In one or more examples, the method  1000  includes a step of virtually arranging the splice-angle scans  120  in the optimized position (e.g., as shown in  FIGS. 13 and 14 ) before performing the virtual fit (block  1026 ). 
     In one or more examples, the method  1000  includes a step of (block  1028 ) generating the aft-pressure-bulkhead scan  124  (e.g., as shown in  FIG. 15 ) representing the aft pressure bulkhead  108 . In one or more examples, the aft-pressure-bulkhead scan  124  is generated using the 3D measurement data obtained during the measuring step (e.g., block  1008 ). Accordingly, the aft-pressure-bulkhead scan  124  is a virtual model or 3D digital representation of the aft pressure bulkhead  108 , such as of the surface (e.g., a 3D surface profile) of the aft pressure bulkhead  108  and, optionally, other geometric features of the aft pressure bulkhead  108 . 
     For example, the aft-pressure-bulkhead scan  124  represents at least a portion of the first bulkhead surface  138  ( FIG. 8 ) and at least a portion of the second bulkhead surface  140  ( FIG. 9 ) of the aft pressure bulkhead  108 . In one or more examples, the aft-pressure-bulkhead scan  124  includes a first bulkhead-surface scan  166  (e.g., as shown in  FIG. 15 ) representing the first bulkhead surface  138 . In one or more examples, the aft-pressure-bulkhead scan  124  includes a second bulkhead-surface scan  168  (e.g., as shown in  FIG. 15 ) representing the second bulkhead surface  140 . In one or more examples, the aft-pressure-bulkhead scan  124  includes a bulkhead-interface-surface scan  170  (e.g., as shown in  FIG. 15 ) representing the bulkhead interface surface  126  ( FIG. 9 ). In one or more examples, the bulkhead-interface-surface scan  170  forms a portion of the second bulkhead-surface scan  168 . In one or more examples, the aft-pressure-bulkhead scan  124  includes aft-pressure-bulkhead-hole scans (e.g., not shown) representing the aft-pressure-bulkhead holes  114  ( FIGS. 8 and 9 ) of the aft pressure bulkhead  108 . 
     In one or more examples, the method  1000  includes a step of (block  1030 ) aligning the aft-pressure-bulkhead scan  124  to the nominal model  122  to virtual fit (e.g., block  1026 ) the aft pressure bulkhead  108  to the splice angles  102 , at the optimized position. For example, aligning the aft-pressure-bulkhead scan  124  to the nominal model  122  virtually overlays the aft-pressure-bulkhead scan  124  to the splice-angle scans  120 , which have been position-optimized relative to the nominal model  122 . 
     In one or more examples, according to the method  1000 , the step of (block  1030 ) aligning the aft-pressure-bulkhead scan  124  to the nominal model  122  includes a step of performing a best fit between the aft-pressure-bulkhead scan  124  and the nominal model  122 . For example, alignment parameters are calculated by performing an optimized best fit of multiple points of the second bulkhead-surface scan  168  to a portion of the nominal model  122  representing the second bulkhead surface  140  of the pressure bulkhead assembly  100 . 
     In one or more examples, the method  1000  includes a step of (block  1032 ) determining the splice-angle-hole positions  110  of the splice-angle holes  112  to be drilled in each one of the splice angles  102  such that the splice-angle holes  112  (e.g., as shown in  FIG. 16 ) will correspond to aft-pressure-bulkhead holes  114 , pre-drilled in the aft pressure bulkhead  108  (e.g., as shown in  FIGS. 8 and 9 ). The splice-angle-hole positions  110  represent the determined locations and orientations of the splice-angle holes  112 , to be drilled in each one of the splice angles  102 , such that the that the splice-angle holes  112  will axially align with corresponding aft-pressure-bulkhead holes  114  when the splice angles  102  are joined to the aft pressure bulkhead  108  at the optimized position. Alignment of the splice-angle holes  112  and the aft-pressure-bulkhead holes  114  inherently index the splice angles  102  at the optimized position relative to the aft pressure bulkhead  108 . 
     The splice-angle-hole positions  110  of splice-angle holes  112  are determined based on the measured 3D surface profile of the flange surface  130  of the splice angle  102 , the measured 3D surface profile of the bulkhead interface surface  126 , and the measured positions of the aft-pressure-bulkhead holes  114 . In one or more examples, the step of (block  1032 ) determining the splice-angle-hole positions  110  of the splice-angle holes  112  includes a step of determining location and orientation of a drilling axis, for drilling each one of the splice-angle holes  112  in the splice angle  102 , relative to the 3D profile the flange surface  130  such that the drilling axis is coaxially aligned with a center bore axis of a corresponding one of the aft-pressure-bulkhead holes  114 . 
     In one or more examples, the 3D surface profile of the flange surface  130  ( FIG. 8 ) of the splice angle  102 , which is to be joined to the bulkhead interface surface  126  ( FIG. 9 ) of the aft pressure bulkhead  108 , is determined by measuring the splice angle  102  (e.g., block  1010 ), such as measuring the flange surface  130 , and is represented by the flange-surface scan  162  of the splice-angle scan  120  (e.g., as shown in  FIG. 15 ). As described above, the splice angles  102  are initially fabricated without full-size pre-drilled holes (e.g., without the plurality of splice-angle holes  112 ), as illustrated by example in  FIGS. 8 and 9 . 
     In one or more examples, the 3D surface profile of the bulkhead interface surface  126  ( FIG. 9 ) of the aft pressure bulkhead  108 , which is to be joined to the flange surfaces  130  ( FIG. 8 ) of the splice angles  102 , is determined by measuring the aft pressure bulkhead  108  (e.g., block  1008 ), such as measuring the bulkhead interface surface  126  (e.g., the second bulkhead surface  140 ), and is represented by the bulkhead-interface-surface scan  170  of the aft-pressure-bulkhead scan  124  (e.g., as shown in  FIG. 15 ). As described above, the aft pressure bulkhead  108  is initially fabricated with full-size pre-drilled holes (e.g., with the plurality of aft-pressure-bulkhead holes  114 ), as illustrated by example in  FIGS. 8 and 9 . 
     In one or more examples, the method  1000  includes a step of (block  1034 ) determining the aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114 . In one or more examples, the aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114  are determined by measuring the aft pressure bulkhead  108  (e.g., block  1008 ), such as measuring the bulkhead interface surface  126  and the aft-pressure-bulkhead holes  114 . In one or more examples, the step of (block  1034 ) determining the aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114  includes a step of determining the locations and the orientations of the aft-pressure-bulkhead holes  114 . 
     Referring now to  FIGS. 6 and 7 , in one or more examples, the location of each one of the aft-pressure-bulkhead holes  114  is determined from a first measured location  178  of a first hole-center  172  (e.g., as shown in  FIG. 6 ) of the aft-pressure-bulkhead hole  114  formed in the first bulkhead surface  138  and from a second measured location  180  of a second hole-center  174  (e.g., as shown in  FIG. 7 ) of the aft-pressure-bulkhead hole  114  formed in the second bulkhead surface  140 . For example, the first hole-center  172  and the second hole-center  174  are measured (e.g., block  1008 ) relative to an origin O in an example three-dimensional Cartesian coordinate system XYZ. As an example, the first measured location  178  of the first hole-center  172  of the aft-pressure-bulkhead hole  114  is measured as x1, y1, z1 in the XYZ coordinate system (e.g., as shown in  FIG. 6 ) and the second measured location  180  of the second hole-center  174  of the aft-pressure-bulkhead hole  114  is measured as x2, y2, z2 in the XYZ coordinate system (e.g., as shown in  FIG. 7 ). 
     It can be appreciated that the origin O (e.g., as shown in  FIGS. 6 and 7 ) may be chosen for convenience, such as at an outer peripheral edge of the aft pressure bulkhead  108 . In other instances, the origin O may be chosen at a different location or in other instances, the measurement is made using a different coordinate system, such as a polar or spherical coordinate system, without departing from the scope of the present disclosure. 
     In one or more examples, the orientation of each one of the aft-pressure-bulkhead holes  114  is determined from the first measured location  178  of the first hole-center  172  and from the second measured location  180  of the second hole-center  174  of the aft-pressure-bulkhead hole  114 . Based on the first measured location  178  of the first hole-center  172  and the second measured location  180  of the second hole-center  174 , a measured orientation  182  of the aft-pressure-bulkhead hole  114  is determined by the angle θ formed between a plane  176 , containing a center bore axis extending between the first hole-center  172  and the second hole-center  174  through the thickness  142  of the aft pressure bulkhead  108  (e.g., as shown in  FIG. 6 ), and a reference plane of the XYZ coordinate system (e.g., XY-plane). 
     In one or more examples, the step of (block  1032 ) determining the splice-angle hole positions  110  of the splice-angle holes  112  is performed after the step of (block  1026 ) performing the virtual fit by overlaying the aft-pressure-bulkhead scan  124  to the splice-angle scans  120  at the optimized position. For example, the splice-angle scans  120  are arranged adjacent to one another and fixed at the optimized position such that the splice-surface scans  158  form a virtual representation of the circumferential splice surface  106  having the optimized shape  136 . The aft-pressure-bulkhead scan  124  can be translated and/or rotated relative to the splice-angle scans  120  to optimize the mating interface between the bulkhead-interface-surface scan  170  and the flange-surface scans  162 . A virtual overlay  184  (e.g., a portion of which is shown in  FIG. 15 ) of the aft-pressure-bulkhead scan  124  and the splice-angle scans  120  is fixed and the splice-angle-hole positions  110  are determined (e.g., computed) based on the determined aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114 . 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1034 ) drilling the splice-angle holes  112  in each one of the splice angles  102  at the splice-angle-hole positions  110 . 
     Referring now to  FIG. 16 , which schematically illustrates an example of the splice angle  102  after the splice-angle holes  112  are drilled through the flange  148 . Each one of the splice-angle holes  112  is drilled at a corresponding splice-angle-hole position  110  (e.g., indicated by x3, y3, z3 in  FIG. 16 ), as determined in accordance with the method  1000 . 
     In one or more examples, as illustrated in  FIG. 16 , additional splice-angle holes are drilled through the skin splice  150  at appropriate locations for joining the skin splice  150  to the skin  1206  of the fuselage  1202  when installing the pressure bulkhead assembly  100  within the fuselage  1202  (e.g., as shown in  FIG. 3 ). In one or more examples, the additional splice-angle holes are full size holes drilled through the skin splice  150  at the pilot holes  152  ( FIGS. 8 and 9 ). 
     In one or more examples, the method  1000  includes a step of (block  1036 ) assembling the pressure bulkhead assembly  100 . In one or more examples, according to the method  1000 , the step of (block  1036 ) assembling the pressure bulkhead assembly  100  includes a step of (block  1038 ) joining each one of the splice angles  102  with the aft pressure bulkhead  108  such that the splice surfaces  104  of the splice angles  102  form the circumferential splice surface  106  of the pressure bulkhead assembly  100  with the optimized shape  136  (e.g., as shown in  FIG. 1 ). 
     Referring now to  FIG. 17 , which schematically illustrates an example of a portion of the pressure bulkhead assembly  100 . In one or more examples, when assembling the pressure bulkhead assembly  100 , a gap can exist between the bulkhead interface surface  126  of the aft pressure bulkhead  108  and the flange surface  130  of one or more of the splice angles  102 . It can be appreciated that such gaps may be formed due to manufacturing tolerances for the aft pressure bulkhead  108  and the splice angles  102 . The shim  128  is used to fill the gap between the bulkhead interface surface  126  and the flange surface  130 . 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1040 ) determining shim dimensions of the shim  128  to be positioned between the bulkhead interface surface  126  of the aft pressure bulkhead  108  and the flange surface  130  of one of the splice angles  102 . 
     In one or more examples, the shim dimensions of the shim  128  are determined based on gaps identified in the virtual overlay  184  ( FIG. 15 ) between the bulkhead-interface-surface scan  170  and the flange-surface scan  162 . In one or more examples, the method  1000  includes a step of determining (e.g., detecting or estimating) the gaps between the bulkhead-interface-surface scan  170  and the flange-surface scan  162 , which would correspond to a gap formed between the bulkhead interface surface  126  of the aft pressure bulkhead  108  and the flange surface  130  of the splice angles  102  when assembling the pressure bulkhead assembly  100 . 
     Referring to  FIG. 15 , which schematically illustrates an example of a portion of the virtual overlay  184  between the aft-pressure-bulkhead scan  124  and the splice-angle scans  120  (only one splice-angle scan  120  is shown in  FIG. 15  for the purpose of clarity). In one or more examples, when the aft-pressure-bulkhead scan  124  and the splice-angle scans  120  are virtually overlaid, any deviations between the bulkhead-interface-surface scan  170  and the flange-surface scan  162  are identified as gaps. Computed deviations that exceed design allowances are identified as gaps that need to be filled by the shim  128  (e.g., as shown in  FIG. 16 ) and are used to determine the shim dimensions. 
     In one or more examples, the deviations are used to determine a shim outline  186  and a 3D shim-surface profile  188  of the shim  128  to be used to fill the gap between the bulkhead interface surface  126  and the flange surface  130 . The shim outline  186  and the shim-surface profile  188  represent the shim dimensions. 
     Referring again to  FIG. 4 , in one or more examples, the method  1000  includes a step of (block  1042 ) fabricating (e.g., making) the shim  128 , used to fill the gap between the aft pressure bulkhead  108  and the splice angles  102 , based on the shim dimensions. The shim outline  186  and the shim-surface profile  188  (e.g., as shown in  FIG. 15 ) of the shim  128  are determined based on dimensional data of the deviations between the bulkhead-interface-surface scan  170  and the flange-surface scan  162 . The shim outline  186  and shim-surface profile  188  represent the length, width, thickness and surface geometry of the shim  128 . 
     In one or more examples, the step of (block  1042 ) fabricating the shim  128  includes machining the shim  128  to have the determined shim dimensions (e.g., to form the shim outline  186  and the shim-surface profile  188 ) from a stock shim (not shown). The shim  128  is machined according to the shim dimensions to fill the gap between the aft pressure bulkhead  108  and the splice angles  102  (e.g., as shown in  FIG. 17 ). 
     In one or more examples, the method  1000  includes a step of determining a plurality of shim-hole positions  192  of a plurality of shim holes  190  (e.g., as shown in  FIG. 18 ) to be drilled in each one of the shims  128 . In one or more examples, the shim-hole positions  192  of the shim holes  190  are determined based on the virtual overlay  184  ( FIG. 15 ) and the determined the shim dimensions. For example, with the virtual overlay  184  of the aft-pressure-bulkhead scan  124  and the splice-angle scans  120  fixed, the shim-hole positions  192  are determined (e.g., computed) based on the determined aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114  and the splice-angle-hole positions  110  of the splice-angle holes  112 . 
     In one or more examples, the step of (block  1042 ) fabricating the shim  128  includes a step of drilling the shim holes  190  through the shim  128  at the determined shim-hole positions  192 . Each one of the shim holes  190  is drilled at a corresponding shim-hole position  192  (e.g., indicated by x4, y4 in  FIG. 18 ). 
     In one or more examples, the shim holes  190  are drilled in the shim  128  before the shim  128  is machined to the shim dimensions. For example, the shim holes  190  are drilled in the stock shim having an approximately flat configuration (e.g., a flat stock shim). In these examples, the shim-surface profile  188  is transformed to a virtual (e.g., flat or planar) profile corresponding to the flat surface of the stock shim and the shim-hole positions  192  are transformed to corresponding virtual positions on the stock shim. The shim holes  190  are drilled in the stock shim at the virtual positions such that the shim holes  190  are at appropriate shim-hole positions  192  after machining the stock shim to the shim dimensions. 
     In one or more examples, the shim holes  190  are drilled in the shim  128  after the shim  128  is machined to the shim dimensions. In these examples, the shim holes  190  are drilled in the shim  128  at the determined shim-hole positions  192 . 
     Referring now to  FIG. 18 , which schematically illustrates an example of the shim  128 . The shim-hole positions  192  of the shim holes  190  correspond to the aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108  and the splice-angle-hole positions  110  of the splice-angle holes  112  in the splice angle  102 . The shim holes  190  will axially align with corresponding aft-pressure-bulkhead holes  114  and corresponding splice-angle holes  112  when the shim  128  is positioned between the bulkhead interface surface  126  and the flange surface  130  and the splice angle  102  is joined to the aft pressure bulkhead  108  at the optimized position (e.g., as shown in  FIG. 17 ). Filling the gap between the aft pressure bulkhead  108  and the flange  148  with the shim  128  maintains the splice angle  102  at the optimized position relative to the aft pressure bulkhead  108 . 
     Referring again to  FIG. 4 , in one or more examples, according to the method  1000 , the step of (block  1036 ) includes a step of (block  1044 ) positioning the shim  128  between the bulkhead interface surface  126  and the flange surface  130  before the step of ( 1038 ) joining the splice angle  102  with the aft pressure bulkhead  108  such that shim holes  190  axially align with corresponding aft-pressure-bulkhead holes  114  and corresponding splice-angle holes  112 . 
     In one or more examples, the method  1000  includes a step of (block  1046 ) moving the aft-pressure-bulkhead scan  124  relative to the plurality of splice-angle scans  120  such that the shim dimensions of the shim  128  are greater than minimum manufacturing dimensions. In one or more examples, when the aft-pressure-bulkhead scan  124  and the splice-angle scans  120  are virtually overlaid, the computed deviations between the bulkhead-interface-surface scan  170  and the flange-surface scan  162  exceed design allowances but define a gap that is less than the minimum manufacturing dimensions for the shim  128 . In one or more examples, after the step of (block  1026 ) performing the virtual fit, the aft-pressure-bulkhead scan  124  is moved away from the splice-angle scans  120 , along an axis that is circumscribed by the circumferential splice surface  106 , to space the bulkhead-interface-surface scan  170  away from the flange-surface scans  162  until the shim dimensions of the shim  128  are greater than minimum manufacturing dimensions of the shim  128 . In these examples, the splice-angle-hole positions  110 , the shim-hole positions  192 , and the shim dimensions are determined after the aft-pressure-bulkhead scan  124  is moved (e.g., spaced) away from the splice-angle scans  120 . 
     Referring to  FIGS. 1 and 17 , in one or more example, after the splice-angle holes  112  are drilled in the splice angles  102 , each one of the splice angles  102  is joined to the aft pressure bulkhead  108  such that the splice-angle holes  112  are aligned with corresponding ones of the aft-pressure-bulkhead holes  114 . Fasteners  134  ( FIG. 17 ) are installed through the aligned aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108  and splice-angle holes  112  in the splice angles  102  to secure the splice angle  102  to the aft pressure bulkhead  108  at the optimized position. Drilling the splice-angle holes  112  at the splice-angle-hole positions  110 , as described herein, enables the fasteners  134  to index the splice angle  102  at the optimized position. Assembly of the pressure bulkhead assembly  100  in accordance with the method  1000  also reduces, or eliminates, the amount of assembly tooling required to index and hold the splice angles  102  in position relative to the aft pressure bulkhead  108  when assembling the pressure bulkhead assembly  100 , which advantageously improves cycle time and reduces manufacturing costs. 
     In one or more examples, shims  128  are used, as needed, to fill the gaps between the bulkhead interface surface  126  and the flange surface  130 . After the shim  128  is machined to the shim dimensions and the shim holes  190  are drilled in the shim  128 , the splice angle  102  and the shim  128  are joined to the aft pressure bulkhead  108  such that the shim holes  190  and the splice-angle holes  112  are aligned with corresponding ones of the aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108 . The fasteners  134  ( FIG. 17 ) are installed through the aligned aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108 , the shim holes  190  in the shim  128 , and splice-angle holes  112  in the splice angle  102  to secure the splice angle  102  and the shim  128  to the aft pressure bulkhead  108  with the splice angle  102  at the optimized position. 
     Each one of the splice angles  102  is joined to the aft pressure bulkhead  108  at the optimized position, as expressed above, so that the flange surface  130  mates with a corresponding portion (e.g., section) of the bulkhead interface surface  126  to form the circumferential splice surface  106  of the pressure bulkhead assembly  100  with the optimized shape  136  ( FIG. 1 ). The shims  128  are used as needed to fill gaps between the flange surface  130  and the bulkhead interface surface  126 . The fasteners  134  are sent through the aligned set of holes to join the aft pressure bulkhead  108  and the splice angles  102  and the shims  128 , as needed, together to form the pressure bulkhead assembly  100 . The fasteners  134  may take any desirable form, such as permanent fasteners. 
     The fasteners  134  and the shims  128  maintain the optimized shape  136  when the splice angles  102  are joined to the aft pressure bulkhead  108 . The pressure bulkhead assembly  100  may include any number of splice angles  102  needed to form the circumferential splice surface  106  and for attachment of the pressure bulkhead assembly  100  the fuselage  1202 . In an example, thirty-two splice angles  102  are coupled to the aft pressure bulkhead  108  to form the pressure bulkhead assembly  100 . 
     Referring now to  FIG. 5 , which schematically illustrates an example of the system  200 . In one or more examples, the system  200  is configured to make accurate measurements of the aft pressure bulkhead  108  and the splice angles  102  and to process those measurements, for example, to generate the aft-pressure-bulkhead scan  124  and the splice-angle scans  120 . The system  200  is also configured to determine the optimal position of the splice angles  102  from the measurements of the aft pressure bulkhead  108  and the splice angles  102 . The system  200  is further configured to determine the splice-angle-hole positions  110  of the splice-angle holes  112  such that the optimal position of the splice angles  102  is maintained when the splice angles  102  are joined with the aft pressure bulkhead  108 . The system  200  is additionally configured to machine the splice angles  102  (e.g., drill the splice-angle holes  112  in the splice angles  102 ). The system  200  is further configured to machine the shims  128  that comply with required tolerances, as needed. 
     In one or more examples, the system  200  includes a measurement machine  202  configured to take measurements of the aft pressure bulkhead  108  and the plurality of splice angles  102 . In one or more examples, the measurement machine  202  is a Coordinate Measurement Machine (CMM). 
     In one or more examples, the measurement machine  202  (e.g., CMM) is configured to measure an object in a three-dimensional (3D) coordinate system, often in comparison to a computer aided design (CAD) model of the object. For example, the measurement machine  202  makes measurements of the aft pressure bulkhead  108  and of the splice angles  102  for drilling the splice-angle holes  112  in the splice angles  102  and, optionally, adding the shims  128  and drilling the shim holes  190  in the shims  128  as necessary to fill the gaps between the aft pressure bulkhead  108  and the splice angles  102 . 
     The measurement machine  202  is any suitable metrological machine. In one or more examples, the measurement machine  202  is a Portable Coordinate Measuring machine. In one or more examples, the measurement machine  202  includes an articulated measurement arm, such as a ROMER arm machine (e.g., not shown). For example, the measurement machine  202  includes a robotic arm that operates in 3D space with six or seven joints, having six degrees of freedom, which means that the robotic arm can move in three-dimensional space forward/backward, up/down, left/right combined with rotation about three perpendicular axes (roll, yaw, pitch). The movement along each of the three axes is independent of each other and independent of the rotation about any of these axes, having the six degrees of freedom. 
     In one or more examples, the measurement machine  202  is configured to take measurements of selected areas on the aft pressure bulkhead  108  (e.g., the aft-pressure-bulkhead holes  114  and the bulkhead interface surface  126 ). In one or more examples, the measurement machine  202  is positioned adjacent to the aft pressure bulkhead  108  to be measured, such that the articulated measurement arm can take measurements of the location and orientation of the aft-pressure-bulkhead holes  114  and the bulkhead interface surface  126 . In one or more examples, the aft pressure bulkhead  108  is mounted on an assembly jig or support tooling for taking measurements by the measurement machine  202 . 
     In one or more examples, the measurement machine  202  is configured to take measurements of selected areas on the splice angles  102  (e.g., the flange surface  130  and the splice surface  104 ). In one or more examples, the measurement machine  202  is positioned adjacent to the splice angles  102  to be measured, such that the articulated measurement arm can take measurements of the flange surface  130  and the splice surface  104 . In one or more examples, one or more of the splice angles  102  may mounted on an assembly jig or support tooling for taking measurements of each one of the splice angles  102  by the measurement machine  202 . 
     It should be appreciated that other suitable types of coordinate measurement machines with sufficient accuracy may be used to take measurements of the selected areas of the structure being measured (e.g., aft pressure bulkhead  108  and splice angles  102 ), such as a handheld measuring device or a laser scanner. Further, it should be appreciated that the system  200  may use different coordinate measurement machines to take measurements of the aft pressure bulkhead  108  and the splice angles  102 . 
     In one or more examples, the system  200  includes a computer system  204 . In one or more examples, the system  200  includes a measurement apparatus  220 . In one or more examples, the measurement apparatus  220  includes, or takes the form of, a spatial relation apparatus. The measurement apparatus  220  includes the measurement machine  202  and the computer system  204  (e.g., a controller). The measurements taken by the measurement machine  202  are sent to the computer system  204 . The computer system  204  provides the interface for a user to execute a measurement plan, processes the measurements taken by the measurement machine  202 , and provides the processed measurements in an .XML format to an on demand emergent manufacturing (ODEM) application  222 . 
     The computer system  204  includes a processor  210  and memory  206 . The memory  206  stores one or more programs  208 . In one or more examples, the computer system  204  includes a measurement software platform. The measurement software platform is any suitable type that includes programs  208  adapted to take and process measurements. One exemplary measurement software platform (e.g., program  208 ) is a spatial analyzer program  224 . In one or more examples, the computer system  204  includes an optimization software platform. The optimization software platform is any suitable type that includes programs  208  adapted to process measurement data and execute optimization algorithms on the data. One exemplary optimization software platform (e.g., program  208 ) is a best-fit optimizer program  226 . 
     In one or more examples, the processor  210  is configured to execute the program  208  to determine the optimized position of the plurality of splice angles  102  such that the plurality of splice surfaces  104  of the plurality of splice angles  102  will form the circumferential splice surface  106  with the optimized shape  136 . The processor  210  is configured to execute the program  208  to perform the virtual fit between the plurality of splice angles  102 , at the optimized position, and an aft pressure bulkhead  108 . The processor  210  is configured to execute the program  208  to determine the splice-angle-hole positions  110  of splice-angle holes  112  to be drilled in each one of the plurality of splice angles  102  such that the splice-angle holes  112  will correspond to aft-pressure-bulkhead holes  114 , pre-drilled in the aft pressure bulkhead  108 . 
     In one or more examples, the processor  210  is configured to execute the program  208  to generate the plurality of splice-angle scans  120  representing the plurality of splice surfaces  104  from measurements of the plurality of splice angles  102 , taken by the measurement machine  202 . The processor  210  is configured to execute the program  208  to align the plurality of splice-angle scans  120  to the nominal model  122  representing the pressure bulkhead assembly  100  to arrange the plurality of splice-angle scans  120  at the initial position in which the plurality of splice-surface scans  158  of the plurality of splice-angle scans  120  represents the circumferential splice surface  106  with the initial shape  154 . 
     In one or more examples, the processor  210  is configured to execute the program  208  to determine the step dimension  116  between the mating-edge scan  160  of each one of the plurality of splice-angle scans  120  and the mating-edge scan  160  of a directly adjacent one of the plurality of splice-angle scans  120 . The processor  210  is configured to execute the program  208  to determine the angular displacement of each one of the splice-angle scans  120  to minimize the step dimension  116 . The processor  210  is configured to execute the program  208  to adjust each one of the plurality of splice-angle scans  120  by the angular displacement to move the plurality of splice-angle scans  120  to the optimized position. 
     In one or more examples, the processor  210  is configured to execute the program  208  to virtually arrange the plurality of splice-angle scans  120  in the optimized position before performing the virtual fit. The processor  210  is configured to execute the program  208  to generate the aft-pressure-bulkhead scan  124  representing the bulkhead interface surface  126  of the aft pressure bulkhead  108  from measurements of the aft pressure bulkhead  108 , taken by the measurement machine  202 . The processor  210  is configured to execute the program  208  to align the aft-pressure-bulkhead scan  124  to the nominal model  122  to virtually overlay the aft-pressure-bulkhead scan  124  to the plurality of splice-angle scans  120 , at the optimized position. 
     In one or more examples, the system  200  includes a Computer Numerically Controlled (CNC) machine  212 , or equivalent. The CNC machine  212  is configured to drill the splice-angle holes  112  (e.g.,  FIG. 16 ) in each one of the plurality of splice angles  102  at the splice-angle-hole positions  110 . For example, each one the splice angles  102  is secured and indexed on a drill fixture. 
     In one or more examples, the computer system  204  executes a software application to create a program to drill the splice-angle holes  112  in the splice angles  102  based on the determined splice-angle-hole positions  110  that align with the measured aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108 . In one or more examples, the CNC machine  212  drills the splice-angle holes  112  in the splice angles  102  based on the created program. In one or more examples, the CNC machine  212  drills the splice-angle holes  112  in each one the splice angles  102  based on the NC programs  228 . 
     In one or more examples, the CNC machine  212  includes a network computer (NC) controller  232  that receives the NC program  228 . The system  200  takes measurements, processes the measurements in accordance with the requirement document in an .XML format. The ODEM application  222  then updates the NC seed model with the .XML formatted data, and then automatically creates the requisite validated NC program  230 . 
     In one or more examples, the system  200  includes an assembly jig  214  configured to restrain the aft pressure bulkhead  108  for joining each one of the plurality of splice angles  102  with the aft pressure bulkhead  108  such that the plurality of splice surfaces  104  forms the circumferential splice surface  106  with the optimized shape  136 . 
     In one or more examples, the processor  210  executes the program  208  (e.g., the spatial analyzer program  224 ) to facilitate the measurement apparatus  220  in providing an interface for a user to execute the measurement plan, process the measurements, and provide the processed measurements, as described in the method  1000 , to the ODEM application  222 . In one or more examples, the processor  210  executes the program  208  (e.g., the spatial analyzer program  224 ) to direct the measurement machine  202  to execute operational measuring steps (e.g., block  1008  and block  1010 ) of the method  1000 . 
     In one or more examples, the processor  210  executes the spatial analyzer program  224  to perform an operational step of implementing a first measurement model (e.g., 3D seed model) of the aft pressure bulkhead  108  that includes a plurality of first measurement points for each one of the aft-pressure-bulkhead holes  114  and for portions of the bulkhead interface surface  126 , adjacent to the aft-pressure-bulkhead holes  114 , and a second measurement model (e.g., 3D seed model) for each one of the splice angles  102  that includes a plurality of second measurement points for portions of the flange surface  130 . The processor  210  then executes the spatial analyzer program  224  to perform further operational steps (e.g., blocks  1012 - 1020 ,  1026 - 1032  and  1040 ) of method  1000 . 
     In one or more examples, the first hole-center  172  of each one of the aft-pressure-bulkhead holes  114  ( FIG. 6 ) along the first bulkhead surface  138  of the aft pressure bulkhead  108  is measured (e.g., block  1008 ) by the measurement machine  202 , relative to an origin O in an example three-dimensional Cartesian coordinate system XYZ. The second hole-center  174  of each one of the aft-pressure-bulkhead holes  114  ( FIG. 7 ) along the second bulkhead surface  140  of the aft pressure bulkhead  108  is measured (e.g., block  1006 ) by the measurement machine  202  relative to the origin O in the example three-dimensional Cartesian coordinate system XYZ. 
     In one or more examples, the computer system  204  processes the measurements to determine the aft-pressure-bulkhead-hole position  132  (e.g., relative location and orientation) for the aft-pressure-bulkhead hole  114 . In one or more examples, the computer system  204  processes the measurements to determine the aft-pressure-bulkhead-hole position  132  for each one of the aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108 . 
     In one or more examples, the bulkhead interface surface  126  of the aft pressure bulkhead  108  is scanned by the measurement machine  202 . A three-dimensional (3D) scan of aft pressure bulkhead  108  (e.g., the aft-pressure-bulkhead scan  124 ) is generated and stored by the computer system  204 . In one or more examples, the 3D scan produces 3D point cloud surface profile data for the aft pressure bulkhead  108 . 
     In one or more examples, the 3D scan of the aft pressure bulkhead  108  is compared to a corresponding the 3D seed model, to a nominal model of the aft pressure bulkhead  108 , or to as-designed dimensions derived from drawings associated with the aft pressure bulkhead  108  to identify the measurement capability of the measurement machine  202  performing the 3D scan, to ensure that the measurement process resulted in no errors, to ensure proper alignment has been achieved and/or to confirm no anomalies are present. 
     In one or more examples, the flange surface  130  and the splice surface  104  of the splice angle  102  is scanned by the measurement machine  202 . A three-dimensional (3D) scan of the splice angle  102  (e.g., splice-angle scan  120 ) is generated and stored by the computer system  204 . In one or more examples, the 3D scan produces 3D point cloud surface profile data for the splice angle  102 . 
     In one or more examples, the 3D scan of the splice angle  102  is compared to a corresponding the 3D seed model, to a nominal model of the splice angle  102 , or to as-designed dimensions derived from drawings associated with the splice angles  102  to identify the measurement capability of the measurement machine  202  performing the 3D scan, to ensure that the measurement process resulted in no errors, to ensure proper alignment has been achieved and/or to confirm no anomalies are present. 
     In one or more examples, the computer system  204  executes a software application (e.g., the spatial analyzer program  224 ) to generate the aft-pressure-bulkhead scan  124  and the splice-angle scans  120 . For example, the aft-pressure-bulkhead scan  124  is generated using the 3D scan (e.g., measurement data and/or 3D cloud surface profile data) of the aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114 , the first bulkhead surface  138 , the second bulkhead surface  140 , and the bulkhead interface surface  126 . The splice-angle scans  120  are generated using the 3D scan (e.g., measurement data and/or 3D cloud surface profile data) of the first splice-angle surface  144  and the second splice-angle surface  146 . 
     In one or more examples, the processor  210  executes the program  208  (e.g., the best-fit optimizer program  226 ) to process the measurements of the step dimension  116  and the angular displace and facilitate optimization of the circumferential splice surface  106 , as described in the method  1000 . In one or more examples, the processor  210  executes the program  208  (e.g., the best-fit optimizer program  226 ) to direct the computer system  204  to execute operational optimizing steps (e.g., blocks  1018 - 1024 ) of the method  1000 . 
     In one or more examples, the best-fit optimizer program  226  performs a position optimization operation on each one of the splice-angle scans  120  by rotationally adjusting the angular orientation of each one of the splice-angle scans  120  according to determined angular displacement to minimize the step dimension  116  (e.g., as shown in  FIG. 12 ) and move the splice-angle scans  120  from the initial position (e.g., as shown in  FIGS. 10 and 11 ) to the optimized position (e.g., as shown in  FIGS. 13 and 14 ). 
     In one or more examples, the spatial analyzer program  224  performs the virtual fitting, for example, generates the virtual overlay  184  (e.g., as shown in  FIG. 15 ), by virtually aligning the aft-pressure-bulkhead scan  124  (representing the bulkhead interface surface  126  of the aft pressure bulkhead  108 ) with the splice-angle scans  120  (representing the corresponding flange surfaces  130  of the splice angles  102 ) at the optimized position, for example, relative to the nominal model  122 . Based on the virtual overlay  184  of the aft-pressure-bulkhead scan  124  and the splice-angle scans  120  at the optimized position, the spatial analyzer program  224  determines the splice-angle-hole positions  110  of the splice-angle holes  112  to be drilled in each one of the splice angles  102  corresponding to the aft-pressure-bulkhead holes  114  in the aft pressure bulkhead  108 . 
     Accordingly, the splice-angle-hole position  110  of each one of the splice-angle holes  112 , determined by the spatial analyzer program  224 , provides the location and orientation of a drilling axis for drilling the splice-angle hole  112 . During fabrication (e.g., assembly) of the pressure bulkhead assembly  100  ( FIG. 1 ), the splice-angle holes  112  coaxially align with the aft-pressure-bulkhead holes  114  such that the splice angles  102  are indexed at the optimized position. 
     In one or more examples, the ODEM application  222  generates network computer (NC) programs  228  and then validates the NC programs and generates validated NC programs  230  to enable drilling full-size holes in the splice angles  102 , machining or fabricating necessary shims  128 , and drilling full-size holes in the shims  128  (e.g., blocks  1034  and  1042 ) when provided with the compatibly-formatted .XML measurement files and 3D seed models from the spatial analyzer program  224 . Each hole to be drilled will have an XYZ point to be drilled and an associated plane, which determines the orientation of the hole to be drilled. Accordingly, the system  200  is configured to generate a plurality of NC programs for drilling the splice-angle holes  112  in the splice angles  102  based on obtained measurements. 
     In one or more examples, the spatial analyzer program  224  is adapted (e.g., programmed) to link a three-dimensional (3D) measurement seed model. For example, the system  200  includes 3D measurement seed models that correspond to the aft pressure bulkhead  108  and the splice angles  102  in nominal configurations that include the interfacing surfaces, nominal full-size holes, and surface geometry. As an example, for the aft pressure bulkhead  108 , the corresponding measurement seed model identifies the first bulkhead surface  138 , the second bulkhead surface  140 , the bulkhead interface surface  126  and the aft-pressure-bulkhead holes  114  (e.g., as shown in  FIGS. 6-9 ). As an example, for each one of the splice angles  102 , the corresponding measurement seed model may identify the flange  148 , the skin splice  150 , the flange surface  130 , and the splice surface  104  (e.g., as shown in  FIGS. 8 and 9 ). 
     In one or more examples, for each selected area to be measured, the spatial analyzer program  224  operates to lead the measurement machine  202  (e.g., under automated computer control or under operator control) through the measuring and processing steps needed, resulting in a coordinate system transform from an as-mounted CMM coordinate system to a 3D NC seed model in a nominal coordinate system for each one of the aft pressure bulkhead  108  and the splice angles  102 . 
     In one or more examples, the system  200  provides the processed measurements in the .XML format to the ODEM application  222 . The ODEM application  222  generates and then validates the network computer program (e.g., NC program  228  or validated NC program  230 ) for drilling the splice-angle holes  112  (e.g., full-size holes) in the splice angles  102  and, optionally, to fabricate (e.g., machine and drill full-size holes in) the shims  128 , as necessary, when provided with the compatibly formatted .XML measurement files and NC seed models. Each hole to be drilled will have an XYZ point to be drilled and an associated plane, which determines the location and orientation of the hole to be drilled. The ODEM application  222  also monitors the fabrication status of the drilled or machined part. 
     In one or more examples, the ODEM application  222  also transfers the network computer programs to a server that includes setup files that reflect the allowable tolerances of the drilled holes and the shims and the quality assurance provisions per product definition data along with measurement plans, index plans, and installation plans. 
     In one or more examples, the processor  210  is configured to execute the program  208  to determine shim dimensions of the shim  128  to be positioned between the bulkhead interface surface  126  and the flange surface  130  of one of plurality of splice angles  102 . The shim  128  is positioned between the bulkhead interface surface  126  and the flange surface  130  before joining the one of the plurality of splice angles  102  with the aft pressure bulkhead  108 . 
     In one or more examples, when the spatial analyzer program  224  overlays the aft-pressure-bulkhead scan  124  with the splice-angle scans  120 , the spatial analyzer program  224  further estimates gaps between the bulkhead-interface-surface scan  170  and the flange-surface scan  162 . The estimated gaps are representative of the gaps between the bulkhead interface surface  126  of the aft pressure bulkhead  108  and the flange surface  130  of the splice angles  102 . The estimated gaps are used to determine shimming required to fill any gaps between the bulkhead interface surface  126  and the flange surface  130  during assembly of the pressure bulkhead assembly  100 . 
     In one or more examples, the spatial analyzer program  224  minimizes the gaps and, thus, the shimming requirements by adjusting the position of the aft-pressure-bulkhead scan  124  relative to the splice-angle scans  120  during virtual overlaying and alignment, as described above. This gap minimization step is performed before the step of (block  1032 ) determining the splice-angle-hole positions  110  of the splice-angle holes  112 . 
     In one or more examples, in order to determine the shimming and/or spacing requirement, the spatial analyzer program  224  determines a set of deviations (defining the gaps) between the bulkhead-interface-surface scan  170  and the corresponding flange-surface scan  162  during overlay and compares the set of deviations with design allowances for deviations in design or nominal 3D profiles of the aft pressure bulkhead  108  and the splice angles  102 . The set of deviations between the bulkhead-interface-surface scan  170  and the flange-surface scan  162  includes, for example, dimensional and 3D surface profile data. The set of deviations that exceed (e.g., greater than) the design allowances determines mating surfaces and profiles for the shims  128  to be positioned between the aft pressure bulkhead  108  and the splice angles  102 . 
     In one or more examples, the processor  210  is configured to execute the program  208  to move the aft-pressure-bulkhead scan  124  relative to the plurality of splice-angle scans  120  such that the shim dimensions of the shim  128  are greater than minimum manufacturing dimensions. In one or more examples, the spatial analyzer program  224  sizes the dimensions of the gaps and, thus, the shimming requirements such that the shim dimensions meet minimum manufacturing dimensions by adjusting the position of the aft-pressure-bulkhead scan  124  relative to the splice-angle scans  120  during virtual overlaying and alignment. This gap sizing is performed before the determining the splice-angle-hole positions  110  of the splice-angle holes  112 . 
     In one or more examples, the CNC machine  212  is configured to fabricate (e.g., machine) the shim  128  based on the shim dimensions. The CNC machine  212  is configured to drill the shim holes  190  in the shims  128  (e.g.,  FIG. 18 ). For example, each one the shims  128  is secured and indexed on a drill fixture. 
     In one or more examples, the computer system  204  executes a software application to create a program to machine the shim  128 , according to the determined shim dimensions, and drill the shim holes  190  in the shim  128 , based on the determined shim-hole positions  192  that align with the measured aft-pressure-bulkhead-hole positions  132  of the aft-pressure-bulkhead holes  114  and the determined splice-angle-hole positions  110  of the splice-angle holes  112 . In one or more examples, the CNC machine  212  machines the shims  128  and drills the shim holes  190  in the shims  128  based on the created program. In one or more examples, the CNC machine  212  drills the shim holes  190  in each one the shims  128  based on the NC programs  228 . 
     In one or more examples, a set of .XML measurement files is generated incorporating the determinations of the splice-angle-hole positions  110  of the splice-angle holes  112  to be drilled in the splice angles  102 , the shim dimensions (e.g., shim outline  186  and shim-surface profile  188 ) of the shims  128  to be machined, and the determinations of the shim-hole positions  192  of the shim holes  190  to be drilled in the shims  128 . In one or more examples, the spatial analyzer program  224  generates the set of .XML files and transmits the set of .XML files to the ODEM application  222 . The ODEM application  222  then generates the plurality of NC programs  228  for drilling the splice-angle holes  112  in the splice angles  102 , for machining the shims  128  to fill the gaps, and for drilling the shim holes  190  in the shims  128 . The NC programs  228  are then validated, and the ODEM application  222  then transfers a set of validated NC programs  230  to the CNC machine  212  or equivalent. The NC controller  232  receives the validated NC programs  230  and the CNC machine  212  drills the splice-angle holes  112  in the splice angles  102 , machines the shims  128 , and drills the shim holes  190  in the shims  128  based on the set of validated NC programs  230 . 
     Referring now to  FIGS. 2 and 19 , examples of the method  1000 , the system  200  and the pressure bulkhead assembly  100  may be related to, or used in the context of, an aircraft manufacturing and service method  1100 , as shown in the flow diagram of  FIG. 19  and the aircraft  1200 , as schematically illustrated in  FIG. 2 . For example, the aircraft  1200  and/or the aircraft production and service methodology  1100  may utilize the pressure bulkhead assembly  100  made according to the method  1000  and/or using the system  200  described with respect to  FIGS. 1 and 3-18 . 
     Referring to  FIG. 2 , examples of the aircraft  1200  may include an airframe  1210  that forms the wings  1208  and the fuselage  1202  having the interior  1204 . The aircraft  1200  also includes a plurality of high-level systems  1222 . Examples of the high-level systems  1222  include one or more of a propulsion system  1224 , an electrical system  1226 , a hydraulic system  1228 , and an environmental system  1230  (e.g., environmental control system). In other examples, the aircraft  1200  may include any number of other types of systems, such as a communications system, a flight control system, a guidance system, a weapons system, and the like. 
     Referring to  FIG. 19 , during pre-production, the method  1100  includes specification and design of the aircraft  1200  (block  1102 ) and material procurement (block  1104 ). During production of the aircraft  1200 , component and subassembly manufacturing (block  1106 ) and system integration (block  1108 ) of the aircraft  1200  take place. Thereafter, the aircraft  1200  goes through certification and delivery (block  1110 ) to be placed in service (block  1112 ). Routine maintenance and service (block  1114 ) includes modification, reconfiguration, refurbishment, etc. of one or more systems of the aircraft  1200 . 
     Each of the processes of the method  1100  illustrated in  FIG. 19  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the purposes of this description, a system integrator may include, without limitation, any number of spacecraft manufacturers and major-system subcontractors; a third party may include, without limitation, any number of vendors, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
     Examples of the pressure bulkhead assembly  100 , the system  200  and the method  1000  shown and described herein may be employed during any one or more of the stages of the manufacturing and service method  1100  shown in the flow diagram illustrated by  FIG. 19 . In an example, implementations of the pressure bulkhead assembly  100 , the system  200  and the method  1000  may form a portion of component and subassembly manufacturing (block  1106 ) and/or system integration (block  1108 ). For example, production of the pressure bulkhead assembly  100 , made using the system  200  or according to the method  1000 , or production of the aircraft  1200  that includes the pressure bulkhead assembly  100  may correspond to component and subassembly manufacturing (block  1106 ). Further, the pressure bulkhead assembly  100 , made using the system  200  or according to the method  1000 , may be utilized in a manner similar to components or subassemblies prepared while the aircraft  1200  is in service (block  1112 ). Also, the pressure bulkhead assembly  100 , made using the system  200  or according to the method  1000 , may be utilized during system integration (block  1108 ) and certification and delivery (block  1110 ). Similarly, implementations of the pressure bulkhead assembly  100 , made using the system  200  or according to the method  1000 , may be utilized, for example and without limitation, while the aircraft  1200  is in service (block  1112 ) and during maintenance and service (block  1114 ). 
     Although an aerospace example is shown, the examples and principles disclosed herein may be applied to other industries, such as the automotive industry, the space industry, the construction industry, and other design and manufacturing industries. Accordingly, in addition to aircraft, the examples and principles disclosed herein may apply to structural component assemblies and systems and methods of making the same for other types of vehicles (e.g., land vehicles, marine vehicles, space vehicles, etc.) and stand-alone structures. 
     As used herein, a system, apparatus, device, structure, article, element, component, or hardware “configured to” perform a specified function is indeed capable of performing the specified function without any alteration, rather than merely having potential to perform the specified function after further modification. In other words, the system, apparatus, device, structure, article, element, component, or hardware “configured to” perform a specified function is specifically selected, created, implemented, utilized, programmed, and/or designed for the purpose of performing the specified function. As used herein, “configured to” denotes existing characteristics of a system, apparatus, structure, article, element, component, or hardware that enable the system, apparatus, structure, article, element, component, or hardware to perform the specified function without further modification. For purposes of this disclosure, a system, apparatus, device, structure, article, element, component, or hardware described as being “configured to” perform a particular function may additionally or alternatively be described as being “adapted to” and/or as being “operative to” perform that function. 
     Unless otherwise indicated, the terms “first,” “second,” “third,” etc. are used herein merely as labels, and are not intended to impose ordinal, positional, or hierarchical requirements on the items to which these terms refer. Moreover, reference to, e.g., a “second” item does not require or preclude the existence of, e.g., a “first” or lower-numbered item, and/or, e.g., a “third” or higher-numbered item. 
     As used herein, the phrase “at least one of”, when used with a list of items, means different combinations of one or more of the listed items may be used and only one of each item in the list may be needed. For example, “at least one of item A, item B, and item C” may include, without limitation, item A or item A and item B. This example also may include item A, item B, and item C, or item B and item C. In other examples, “at least one of” may be, for example, without limitation, two of item A, one of item B, and ten of item C; four of item B and seven of item C; and other suitable combinations. As used herein, the term “and/or” and the “/” symbol includes any and all combinations of one or more of the associated listed items. 
     For the purpose of this disclosure, the terms “coupled,” “coupling,” and similar terms refer to two or more elements that are joined, linked, fastened, attached, connected, put in communication, or otherwise associated (e.g., mechanically, electrically, fluidly, optically, electromagnetically) with one another. In various examples, the elements may be associated directly or indirectly. As an example, element A may be directly associated with element B. As another example, element A may be indirectly associated with element B, for example, via another element C. It will be understood that not all associations among the various disclosed elements are necessarily represented. Accordingly, couplings other than those depicted in the figures may also exist. 
     As used herein, the term “approximately” refers to or represent a condition that is close to, but not exactly, the stated condition that still performs the desired function or achieves the desired result. As an example, the term “approximately” refers to a condition that is within an acceptable predetermined tolerance or accuracy, such as to a condition that is within 10% of the stated condition. However, the term “approximately” does not exclude a condition that is exactly the stated condition. As used herein, the term “substantially” refers to a condition that is essentially the stated condition that performs the desired function or achieves the desired result. 
       FIGS. 1-3 and 5-18 , referred to above, may represent functional elements, features, or components thereof and do not necessarily imply any particular structure. Accordingly, modifications, additions and/or omissions may be made to the illustrated structure. Additionally, those skilled in the art will appreciate that not all elements, features, and/or components described and illustrated in  FIGS. 1-3 and 5-18 , referred to above, need be included in every example and not all elements, features, and/or components described herein are necessarily depicted in each illustrative example. Accordingly, some of the elements, features, and/or components described and illustrated in  FIGS. 1-3 and 5-18  may be combined in various ways without the need to include other features described and illustrated in  FIGS. 1-3 and 5-18 , other drawing figures, and/or the accompanying disclosure, even though such combination or combinations are not explicitly illustrated herein. Similarly, additional features not limited to the examples presented, may be combined with some or all of the features shown and described herein. Unless otherwise explicitly stated, the schematic illustrations of the examples depicted in  FIGS. 1-3 and 5-18 , referred to above, are not meant to imply structural limitations with respect to the illustrative example. Rather, although one illustrative structure is indicated, it is to be understood that the structure may be modified when appropriate. Accordingly, modifications, additions and/or omissions may be made to the illustrated structure. Furthermore, elements, features, and/or components that serve a similar, or at least substantially similar, purpose are labeled with like numbers in each of  FIGS. 1-3 and 5-18 , and such elements, features, and/or components may not be discussed in detail herein with reference to each of  FIGS. 1-3 and 5-18 . Similarly, all elements, features, and/or components may not be labeled in each of  FIGS. 1-3 and 5-18 , but reference numerals associated therewith may be utilized herein for consistency. 
     In  FIGS. 4 and 19 , referred to above, the blocks may represent operations, steps, and/or portions thereof and lines connecting the various blocks do not imply any particular order or dependency of the operations or portions thereof. It will be understood that not all dependencies among the various disclosed operations are necessarily represented.  FIGS. 4 and 19  and the accompanying disclosure describing the operations of the disclosed methods set forth herein should not be interpreted as necessarily determining a sequence in which the operations are to be performed. Rather, although one illustrative order is indicated, it is to be understood that the sequence of the operations may be modified when appropriate. Accordingly, modifications, additions and/or omissions may be made to the operations illustrated and certain operations may be performed in a different order or simultaneously. Additionally, those skilled in the art will appreciate that not all operations described need be performed. 
     Further, references throughout the present specification to features, advantages, or similar language used herein do not imply that all of the features and advantages that may be realized with the examples disclosed herein should be, or are in, any single example. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an example is included in at least one example. Thus, discussion of features, advantages, and similar language used throughout the present disclosure may, but do not necessarily, refer to the same example. 
     The described features, advantages, and characteristics of one example may be combined in any suitable manner in one or more other examples. One skilled in the relevant art will recognize that the examples described herein may be practiced without one or more of the specific features or advantages of a particular example. In other instances, additional features and advantages may be recognized in certain examples that may not be present in all examples. Furthermore, although various examples of the pressure bulkhead assembly  100 , the system  200  and the method  1000  have been shown and described, modifications may occur to those skilled in the art upon reading the specification. The present application includes such modifications and is limited only by the scope of the claims.