Patent Publication Number: US-2022212781-A1

Title: Split Cam Braking System

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/133,890, filed Jan. 5, 2021, and entitled “Split Cam Braking System;” which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND INFORMATION 
     1. Field 
     The present disclosure relates generally to actuators. More specifically, the present disclosure relates to a split cam braking system used with rotary actuators assemblies for aircraft applications. 
     2. Background 
     Aircraft often employ rotary actuators to direct movement of mechanical parts throughout the aircraft. For example, without limitation, wing flap movement systems, slat movement systems, or some door applications have rotary actuators that work to drive the aircraft part into the appropriate position during takeoff, landing and during other points of operation of the aircraft. 
     Once movement of the part is complete, it is imperative to prevent back-drive of the actuator so that the part remains in the correct position. Undesired movement of aircraft parts could present efficiency or safety concerns. 
     Braking systems are integrated into rotary actuators to solve this problem. Such braking systems are designed to prevent back-drive. Commonly used braking systems include disc or skewed roller brakes, among others. 
     Both types of braking systems rely on friction plates to generate the holding force. Drag issues associated with friction plates may generate heat which can cause wear on the system. Moreover, the use of multiple friction plates in a disc type or skewed roller type braking system assembly may be larger than desired, thus limiting its use in constrained areas of the aircraft. 
     Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues. 
     SUMMARY 
     An illustrative embodiment of the present disclosure provides a braking system for a rotary actuator comprising a housing and split cam design. A driving cam is located within the housing and is associated with an upstream side of the braking system. The driving cam is configured to rotate and transmit torque when a load is applied to the upstream side. A wedging cam is also located within the housing and is associated with a downstream side of the braking system. The wedging cam is configured to prevent back-drive when torque is applied to the downstream side. A plurality of cylindrical rollers is positioned between the wedging cam and the housing of the braking system. The plurality of cylindrical rollers is configured to wedge between a surface of the wedging cam and the housing when the torque is applied to the downstream side, thus preventing back-drive. Several pairs of cylindrical rollers may be employed. 
     Another illustrative embodiment of the present disclosure provides a method for braking for a rotary actuator. A load is applied to an upstream side of a braking system via the rotary actuator. A driving cam within a housing in the upstream side of the braking system is rotated, and torque is transmitted to a wedging cam. The wedging cam within the housing rotates in conjunction with the driving cam. The load applied to the upstream side of the braking system then stops. Back-drive of the braking system is prevented using a plurality of cylindrical rollers oriented between the wedging cam and the housing and wedged between those two structures when torque is applied to the downstream side of the braking system. 
     A further illustrative embodiment of the present disclosure provides an aircraft having a geared rotary actuator and a braking system comprising a housing and a split cam design. The braking system has a driving cam, a wedging cam, and a plurality of cylindrical rollers. The driving cam is located within the housing and is associated with an upstream side of the braking system. The driving cam rotates and transmits torque when a load is applied to the upstream side. The wedging cam is also located within the housing and is associated with a downstream side of the braking system. The wedging cam prevents back-drive when torque is applied to the downstream side. The plurality of cylindrical rollers is positioned between the wedging cam and the housing of the braking system. The plurality of cylindrical rollers wedge between a surface of the wedging cam and the housing when the torque is applied to the downstream side, thus preventing back-drive. Several pairs of cylindrical rollers may be employed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims. The illustrative embodiments, however, as well as a preferred mode of use, further objectives and features thereof, will best be understood by reference to the following detailed description of an illustrative embodiment of the present disclosure when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is an illustration of an aircraft in accordance with an illustrative embodiment; 
         FIG. 2  is an illustration of a block diagram of a platform in accordance with an illustrative embodiment; 
         FIG. 3  is an illustration of an exploded view of rotary actuator and braking system in accordance with an illustrative embodiment; 
         FIG. 4  is an illustration of a driving cam in accordance with an illustrative embodiment; 
         FIG. 5  is an illustration of a wedging cam in accordance with an illustrative embodiment; 
         FIG. 6A  is an illustration of a wedging cam in accordance with an illustrative embodiment; 
         FIG. 6B  is a free body diagram of a cylindrical roller in accordance with an illustrative embodiment; 
         FIG. 7  is an illustration of a cross-sectional view of a split cam rotary actuator and braking system in accordance with an illustrative embodiment; 
         FIGS. 8  is an illustration of a flowchart of a process for preventing back-drive in a rotary actuator in accordance with an illustrative embodiment; 
         FIG. 9  is an illustration of a block diagram of an aircraft manufacturing and service method in accordance with an illustrative embodiment; and 
         FIG. 10  is an illustration of a block diagram of an aircraft in which an illustrative embodiment may be implemented. 
     
    
    
     DETAILED DESCRIPTION 
     The illustrative embodiments recognize and take into account one or more different considerations. For example, the illustrative embodiments recognize and take into account that aircraft manufacturers are designing aircraft parts, such as wing flaps, with smaller and smaller confined spaces to place associated mechanical components. As a result, some currently employed rotary actuator braking systems may be too big for those confined spaces, necessitating a redesign of the assembly. 
     The illustrative embodiments also recognize and take into account that braking systems that use friction plates may generate undesired levels of heat that result in inefficiencies in the system, chatter, and possibly damage to one or more components. The weight, size, and complexity of these systems that require friction plates may make assembly more laborious than intended. 
     Thus, the disclosed embodiments provide a braking system for a geared rotary actuator with a split cam design that does not utilize friction plates and is simple, compact, and easy to assemble. The braking system has a housing, a driving cam, a wedging cam, and a plurality of cylindrical rollers. The driving cam is located within the housing and is associated with an upstream side of the braking system. The driving cam is configured to allow rotation and transmit torque when a load is applied to the upstream side. The wedging cam is also located within the housing and is associated with a downstream side. The wedging cam is configured to prevent back-drive when torque is applied to the downstream side. The plurality of cylindrical rollers is positioned between the wedging cam and the housing of the braking system. The plurality of cylindrical rollers is configured to wedge between a surface of the wedging cam and the housing when the torque is applied to the downstream side. Several pairs of cylindrical rollers may be employed to prevent undesired back-drive. Simply, input into the upstream side of the braking system will allow bi-directional motion of both cams; however, the wedging cam will prevent any motion from input from the downstream side. 
     With reference now to the figures and, in particular, with reference to  FIG. 1 , an illustration of an aircraft is depicted in accordance with an illustrative embodiment.  FIG. 1  depicts aircraft  100  with body  102  and wing  104  and wing  106 . Body  102  is a fuselage in this illustrative example. Wing  104  has wing flaps  108  while wing  106  has wing flaps  110 . Each of wing flaps  108  and wing flaps  110  may be controlled during operation of aircraft  100  using a rotary actuator and braking system. 
     Aircraft  100  also comprises tail section  112  with vertical stabilizer  114 , horizontal stabilizer  116 , and horizontal stabilizer  118 . Movement of those components, if any, also may be controlled by a rotary actuator and braking system in accordance with an illustrative embodiment. 
     Turning now to  FIG. 2 , an illustration of a block diagram of a platform is depicted in accordance with an illustrative embodiment. Platform  200  has rotary actuator  202  and braking system  204  in this illustrative example. 
     Platform  200  may take a variety of different forms. For example, without limitation, rotary actuator  202  and braking system  204  may be implemented in a mobile platform, a stationary platform, a land-based structure, an aquatic-based structure, or a space-based structure. More specifically, the platform may be an aircraft, a surface ship, a tank, a personnel carrier, a train, a spacecraft, a space station, a satellite, a submarine, an automobile, a power plant, a bridge, a dam, a house, a manufacturing facility, a building, a tool, a mechanical structure, or some other suitable platform or structure where the prevention of back-drive is desirable. 
     In this illustrative example, platform  200  takes the form of aircraft  100 . Aircraft  100  comprises a number of rotary actuators and associated braking systems implemented to control aircraft parts  205 . As used herein, “a number of” when used with reference to items means one or more items. Thus, a number of rotary actuators is one or more rotary actuators. 
     Aircraft parts  205  may take a variety of different forms. For example, without limitation, one of aircraft parts  205  may take the form of a leading edge flap, a trailing edge flap, a leading edge slat, a trailing edge slat, a horizontal stabilizer, a folding wing tip, a door, or some other suitable part. In this illustrative example, aircraft parts  205  includes wing flaps  108  and wing flaps  110 . 
     Wing flap  206  is one of wing flaps  108  in wing  104  of aircraft  100 . Movement of wing flap  206  is controlled by rotary actuator  202  with braking system  204  in this illustrative example. Rotary actuator  202  comprises a combination of components configured to produce rotary motion used to move wing flap  206  in a desired fashion. 
     Braking system  204  comprises components configured to prevent or substantially prevent back-drive  208 . The phrase “substantially prevent,” as used herein, means to reduce, decrease, or eliminate back-drive completely, or within selected tolerances that are sufficient to certify the part for airworthiness or meet other standards for operation of braking system  204 . 
     Back-drive  208  results in reversal of movement of rotary actuator  202  (and braking system  204 ) when movement driven by the input has been stopped. Specifically, torque  210  applied to the output side of braking system  204  causes back-drive  208 . Back-drive  208  of braking system  204  is unwanted because back-drive  208  could dislodge wing flap  206  from its desired orientation while aircraft  100  is in operation. Back-drive  208  may cause safety or efficiency issues for wing flap  206 , wing  104 , or aircraft  100 . 
     As depicted, braking system  204  comprises housing  212 , driving cam  214 , wedging cam  224 , plurality of cylindrical rollers  226 , spring cage  228 , and plurality of bearings  230 . Housing  212  is a structural component that encloses one or more parts in braking system  204 . Housing  212  may be comprised of a metal, a metal alloy, steel, composite material, a combination thereof, or any other material or combination of material, depending on the particular implementation. 
     Driving cam  214  is a component located within housing  212 . Driving cam  214  drives rotational movement within braking system  204 . It receives input from rotary actuator  202 . Driving cam  214  is associated with upstream side  216  of braking system  204  and is configured to rotate when torque  218  is applied to upstream side  216 . Driving cam  214  allows bi-directional movement of braking system  204  when torque is applied to upstream side  216 . Upstream side  216  may also be referred to as the “input side” of braking system  204 . 
     In this illustrative example, driving cam  214  has input spline  220  and central support shaft  222 . Central support shaft  222  is an axle that allows rotational movement of the cams. Both input spline  220  and central support shaft  222  may be fabricated as part of driving cam  214 . 
     As illustrated, wedging cam  224  is a component located within housing  212  and is connected to driving cam  214 . The two cams work in tandem in the system. Wedging cam  224  is associated with downstream side  232  of rotary actuator  202 . Wedging cam  224  is configured to stop back-drive  208  when torque  210  is applied to downstream side  232 . Wedging cam  224  may also be referred to as a “stopping cam” or “braking cam.” Driving cam  214  and wedging cam  224  create the “split cam” design of braking system  204  in accordance with an illustrative embodiment. 
     Wedging cam  224  comprises a first number of cutouts  234  having curved surface  236 . Instead of wedging cam  224  having a substantially circular cross section, first number of cutouts  234  are cut out in equal intervals around the circumference of the cross section of wedging cam  224 . First number of cutouts  234  have curved surface  236  such that an engaging angle for plurality of cylindrical rollers  226  can be maintained. 
     In an illustrative embodiment, the engaging angle, also known as the “wedging angle” influences the efficiency of braking system  204 . In an illustrative embodiment, the engaging angle may be, for example, without limitation, q=3°. In other illustrative embodiments, the engaging angle may be less than three degrees. In still other illustrative embodiments, the engaging angle may be more than three degrees. 
     In this illustrative example, plurality of cylindrical rollers  226  are roller bearings that employ long, thin cylindrical rollers. These rollers may resemble needles and may be referred to as “needle rollers” or “needle bearings.” Plurality of cylindrical rollers  226  may be two times, three times, or four times longer than their diameter, or more. 
     Plurality of needle rollers  226  are positioned between wedging cam  224  and housing  212  and may be used to reduce friction between wedging cam  224  and housing  212  or between driving cam  214  and housing  212  when the system is moving (input torque is greater than output torque). However, the primary purpose of plurality of cylindrical rollers  226  is to prevent back-drive  208 . To prevent back-drive  208 , plurality of cylindrical rollers  226  are configured to wedge between surface  238  of wedging cam  224  and housing  212  when torque  210  is applied to downstream side  232  of rotary actuator  202 . Specifically, plurality of cylindrical rollers  226  wedge between housing  212  and curved surface  236  of first number of cutouts  234  of wedging cam  224 . 
     As depicted, driving cam  214  comprises second number of cutouts  240 . Second number of cutouts  240  in driving cam  214  correspond to first number of cutouts  234  in wedging cam  224 . Plurality of cylindrical rollers  226  is positioned within channels  242  through rotary actuator  202  created by first number of cutouts  234  and second number of cutouts  240 . In other words, the split cam design of rotary actuator  202  comprises channels between the cams and the housing in which pairs of plurality of cylindrical rollers  226  reside. 
     In this illustrative example, plurality of cylindrical rollers  226  has first pair of cylindrical rollers  244 , second pair of cylindrical rollers  246 , and third pair of cylindrical rollers  248 . First pair of cylindrical rollers  244  is positioned in first channel  250  between the cams and housing  212 . Second pair of cylindrical rollers  246  is positioned in second channel  252  between the cams and housing  212 . Third pair of cylindrical rollers  248  is positioned in third channel  254  between the cams and housing  212 . 
     In some illustrative examples, more pairs or fewer pairs of cylindrical rollers may exist. Similarly, more or fewer than three channels  242  may cut through rotary actuator  202 . In still other illustrative examples, more than two cylindrical rollers may be present in each channel, depending on the particular implementation. 
     Spring cage  228  is part of braking system  204 . Spring cage  228  is a spring that holds a pair of cylindrical rollers together in its respective channel. Spring cage  228  prevents free play of the pair of cylindrical rollers. In other words, spring cage  228  stabilizes the cylindrical rollers and reduces backlash or lost motion. A separate spring cage  228  is used for each pair of plurality of cylindrical rollers  226 . 
     In this illustrative example, plurality of bearings  230  are associated with at least one of driving cam  214  and wedging cam  224 . Plurality of bearings  230  support the cams and promote smoother rotation of the cams within housing  212 . Any readily available bearing may be selected for use with an illustrative embodiment. 
     In these illustrative examples, braking system  204  is devoid of friction plates. As a result, less heat is produced than with currently used systems and wear to components also may be reduced. 
     In operation of braking system  204 , torque  218  comes in through upstream side  216  and causes rotation of driving cam  214 . It then transfers through plurality of cylindrical rollers  226  and into wedging cam  224  and out downstream side  232  to move wing flap  206 . Additional actuator may be present between braking system  204  and wing flap  206  to apply gear reduction as necessary. In this manner, both driving cam  214  and wedging cam  224  will rotate. However, if movement of driving cam  214  is stopped, and torque  210  tries to back-drive wedging cam  224 , plurality of cylindrical rollers  226  will move along surface  238  of wedging cam  224  until they are wedged between it and housing  212 , thus dumping the load into housing  212 . As a result, back-drive  208  will be stopped. 
     With an illustrative embodiment, the split cam design allows drive from upstream side of  216  of rotary actuator  202  but not from downstream side  232 . Rotary actuator  202  with braking system  204  could be more compact than currently used systems, thus able to fit into more confined spaces of the newly designed aircraft. The split cam design is simple with fewer components which promotes easier assembly, machining, and the like. An illustrative embodiment also reduces system chatter compared to more traditional no-back braking systems. 
     Although the illustrative embodiments in  FIG. 2  have been described with reference to wing flap  206  in wing  104 , rotary actuator  202  with braking system  204  may be configured for use with other systems in aircraft  100  or in other platforms. For example, without limitation, an illustrative embodiment may be configured for use with leading and/or trailing edge flaps and slats, horizontal stabilizer trip actuators, folding wing tips, doors or other suitable parts. The split cam design of an illustrative embodiment may be fitting for geared or even hydraulic rotary actuators. 
     With reference next to  FIG. 3 , an illustration of an exploded view of a rotary actuator and braking system is depicted in accordance with an illustrative embodiment. The components described herein are examples of physical implementations of rotary actuator  202  with braking system  204  shown in block form in  FIG. 2 . 
     In this view, split cam braking system  300  has driving cam  302 , wedging cam  304 , housing  306 , cylindrical rollers ( 308 ,  310 ,  312 ,  314 ,  316 ,  318 ) and spring cages ( 320 ,  322 ,  324 ). These components represent examples of physical implementations for braking system  204 , driving cam  214 , wedging cam  224 , housing  212 , plurality of cylindrical rollers  226  and spring cage  228  from  FIG. 2 . 
     Turning now to  FIG. 4 , an illustration of a driving cam is depicted in accordance with an illustrative embodiment. This view of driving cam  302  is shown along lines  4 - 4  in  FIG. 3  from the driving cam side of split cam braking system  300 . 
     In this illustrative example, driving cam  302  has three cutouts spaced evenly around its circumference, cutout  400 , cutout  402 , and cutout  404 . These cutouts ( 400 ,  402 ,  404 ) are examples of physical implementations for second number of cutouts  240  shown in block form in  FIG. 2 . These cutouts ( 400 ,  402 ,  404 ) may also be referred to as notches in these illustrative examples. 
     Cutout  400  creates channel  406  between driving cam  302  and housing  306 , where cylindrical roller  308  and cylindrical roller  310  are located. Cutout  402  creates channel  408  between driving cam  302  and housing  306 , where cylindrical roller  312  and cylindrical roller  314  are located. Cutout  404  creates channel  410  between driving cam  302  and housing  306 , where cylindrical roller  316  and cylindrical roller  318  are located. 
     As depicted, cylindrical rollers ( 308 ,  310 ) are separated within channel  406  by spring cage  320  to help stabilize the pair of cylindrical rollers and prevent free play. In a similar fashion, cylindrical rollers ( 312 ,  314 ) are separated in channel  408  by spring cage  322  and cylindrical rollers ( 316 ,  318 ) are separated in channel  410  by spring cage  324 . 
     In this illustrative example, input torque in the direction of arrow  412  enters the system through driving cam  302  and transfers to wedging cam  304 , shown in greater detail in  FIG. 5  and  FIG. 7 . Only friction resists the motion such that driving cam  302  causes motion. 
     In  FIG. 5 , an illustration of a wedging cam is depicted in accordance with an illustrative embodiment. This view of wedging cam  304  is shown along lines  5 - 5  in  FIG. 3  from the wedging cam side of split cam braking system  300 . 
     As shown in this view, wedging cam  304  has cutouts ( 500 ,  502 ,  504 ) with a curved surface in each one. These cutouts ( 500 ,  502 ,  504 ) are examples of physical implementations of first number of cutouts  234  with curved surface  236  shown in block form in  FIG. 2 . As depicted, channel  406 , channel  408 , and channel  410  extend through wedging cam  304  due to the shape and orientation of cutouts ( 500 ,  502 ,  504 ). Central support shaft  506  runs through the center of split cam braking system  300  to support while allowing independent rotation of the two cams. 
     With reference next to  FIG. 6 , another illustration of a wedging cam is depicted in accordance with an illustrative embodiment.  FIG. 6  shows what happens when movement torque in the direction of arrow  412  in  FIG. 4  stops. 
     In this illustrative example, back-driving torque in the direction of arrow  600  tries to move the system. Cylindrical roller  308  wedges between the surface of wedging cam  304  and housing  306 . The back-driving torque creates a force (F cam ) normal to the surface of wedging cam  304 , which is then reacted by housing  306  such that motion is stopped. 
       FIG. 6B  is a cylindrical roller free body diagram depicted in accordance with an illustrative embodiment. The free body diagram shown in this figure corresponds to cylindrical roller  308  in  FIG. 6A  when back-driving torque from output is being placed on the system. 
     Turning now to  FIG. 7 , an illustration of a cross-sectional view of a split cam rotary actuator and braking system is depicted in accordance with an illustrative embodiment. This cross-sectional view of rotary actuator  202  is taken along lines  7 - 7  in  FIG. 5 . 
     In this depicted example, torque is input from upstream side  700 , moves through driving cam  302 , through cylindrical roller  308  and into wedging cam  304  then output from downstream side  702 . When back-drive torque comes from downstream side  702 , the system reacts as described in  FIG. 6 . 
     As illustrated, wedging cam  304  is associated with output spline  704 , which interfaces with a mating component to output force used to move the wing flap or other part. Input spline  705  mates with input components to drive driving cam  302 . Bearings ( 706 ,  708 ,  710 ) can also be seen in this view. These bearings are examples of physical implementations for plurality of bearings  230  shown in block form in  FIG. 2 . 
     The different components shown in  FIG. 1  and  FIGS. 3-7  may be combined with components in  FIG. 2 , used with components in  FIG. 2 , or a combination of the two. Additionally, some of the components in  FIG. 1  and  FIGS. 3-7  may be illustrative examples of how components shown in block form in  FIG. 2  may be implemented as physical structures. 
     Other configurations of split cam braking system  300  may be implemented other than those shown in  FIGS. 3-7 . The configurations described herein are not meant to be limiting as to the placement, orientation, type, or configuration of any component in split cam braking system  300 . Split cam braking system  300  may be used with any platform, moveable or otherwise, that uses rotary actuators. 
     With reference next to  FIG. 8 , an illustration of a flowchart of a process for reducing back-drive in a rotary actuator is depicted in accordance with an illustrative embodiment. The method depicted in  FIG. 8  may be used to operate braking system  204  using braking system  204  in  FIG. 2 . 
     The process begins by applying torque to an upstream side of a braking system for a rotary actuator (operation  800 ). Next, a driving cam rotates within a housing in the upstream side of the braking system (operation  802 ). A wedging cam also rotates within the housing as the driving cam rotates (operation  804 ). The torque applied to the upstream side of the braking system stops (operation  806 ). When the driving cam stops rotating, back-driving torque is applied to the downstream side of the braking system. In response, a plurality of cylindrical rollers wedge between the wedging cam and the housing to prevent back-drive (operation  808 ), with the process terminating thereafter. 
     The illustrative embodiments of the disclosure may be further described in the context of aircraft manufacturing and service method  900  as shown in  FIG. 9  and aircraft  1000  as shown in  FIG. 10 . Turning first to  FIG. 9 , an illustration of a block diagram of an aircraft manufacturing and service method is depicted in accordance with an illustrative embodiment. During pre-production, aircraft manufacturing and service method  900  may include specification and design  902  of aircraft  1000  in  FIG. 10  and material procurement  904 . 
     During production, component and subassembly manufacturing  906  and system integration  908  of aircraft  1000  in  FIG. 10  takes place. Thereafter, aircraft  1000  in  FIG. 10  may go through certification and delivery  910  in order to be placed in service  912 . While in service  912  by a customer, aircraft  1000  in  FIG. 10  is scheduled for routine maintenance and service  914 , which may include modification, reconfiguration, refurbishment, and other maintenance, service, or inspection. 
     Split cam braking system  204  may be installed on an aircraft during component and subassembly manufacturing  906 . In addition, split cam braking system  204  may be retrofitted onto aircraft  1000  during routine maintenance and service  914  as part of a modification, reconfiguration, or refurbishment of aircraft  1000  in  FIG. 10 . 
     Each of the processes of aircraft manufacturing and service method  900  may be performed or carried out by a system integrator, a third party, an operator, or some combination thereof. In these examples, the operator may be a customer. For the purposes of this description, a system integrator may include, without limitation, any number of aircraft 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, a leasing company, a military entity, a service organization, and so on. 
     With reference now to  FIG. 10 , an illustration of a block diagram of an aircraft is depicted in which an illustrative embodiment may be implemented. In this example, aircraft  1000  is produced by aircraft manufacturing and service method  900  in  FIG. 9  and may include airframe  1002  with plurality of systems  1004  and interior  1006 . Examples of systems  1004  include one or more of propulsion system  1008 , electrical system  1010 , hydraulic system  1012 , and environmental system  1014 . Any number of other systems may be included. Although an aerospace example is shown, different illustrative embodiments may be applied to other industries, such as the automotive industry. 
     Apparatuses and methods embodied herein may be employed during at least one of the stages of aircraft manufacturing and service method  900  in  FIG. 9 . In one illustrative example, components or subassemblies produced in component and subassembly manufacturing  906  in  FIG. 9  may be fabricated or manufactured in a manner similar to components or subassemblies produced while aircraft  1000  is in service  912  in  FIG. 9 . As yet another example, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during production stages, such as component and subassembly manufacturing  906  and system integration  908  in  FIG. 9 . One or more apparatus embodiments, method embodiments, or a combination thereof may be utilized while aircraft  1000  is in service  912 , during maintenance and service  914 , inclusive of inspection, in  FIG. 9 , or both. The use of a number of the different illustrative embodiments may substantially expedite the assembly of aircraft  1000 , reduce the cost of aircraft  1000 , or both expedite the assembly of aircraft  1000  and reduce the cost of aircraft  1000 . 
     In some alternative implementations of an illustrative embodiment, the function or functions noted in the blocks may occur out of the order noted in the figures. For example, in some cases, two blocks shown in succession may be executed substantially concurrently, or the blocks may sometimes be performed in the reverse order, depending upon the functionality involved. Also, other blocks may be added, in addition to the illustrated blocks, in a flowchart or block diagram. 
     The description of the different illustrative embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different illustrative embodiments may provide different features as compared to other desirable embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the embodiments, the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.