Patent ID: 12240627

DETAILED DESCRIPTION

The present disclosure relates to repair of hat stringers. In some instances, a hat stringer, which can support a skin member of an aircraft, can be become damaged or otherwise in need of structural reinforcement, e.g., due to an impact event during service. Hat stringers can also sometimes be removed to make room for a skin repair. In accordance with inventive aspects of the present disclosure, hat stringer repair techniques and repair stringers that facilitate repair or reinforcement of a hat stringer are provided herein. Such repair stringers can include an internal geometric profile that matches the internal cavity profile of a stringer, e.g., of a type 1, 2, and/or 3 stringer. The repair stringers can be arranged so that segments of the repair segments physically overlap one another, e.g., along a cap section or a web section of the hat stringer. The inventive aspects disclosed herein can advantageously minimize the amount of parts that are needed, and can eliminate or reduce the need for shimming. A reduction in parts also reduces weight of the aircraft, which is also beneficial. Further, the unique geometric profile of the repair stringers disclosed herein can improve applicability of repair solutions across a larger portion of the body of an aircraft and can making stocking repair parts easier for airline operators, among other advantages.

In the current disclosure, reference is made to various aspects. However, it should be understood that the present disclosure is not limited to specific described aspects. Instead, any combination of the following features and elements, whether related to different aspects or not, is contemplated to implement and practice the teachings provided herein. Additionally, when elements of the aspects are described in the form of “at least one of A and B,” it will be understood that aspects including element A exclusively, including element B exclusively, and including element A and B are each contemplated. Furthermore, although some aspects may achieve advantages over other possible solutions and/or over the prior art, whether or not a particular advantage is achieved by a given aspect is not limiting of the present disclosure. Thus, the aspects, features, aspects and advantages disclosed herein are merely illustrative and are not considered elements or limitations of the appended claims except where explicitly recited in a claim(s). Likewise, reference to “the invention” shall not be construed as a generalization of any inventive subject matter disclosed herein and shall not be considered to be an element or limitation of the appended claims except where explicitly recited in a claim(s). In addition, as used herein, a repair stringer is positioned primarily on a side of a hat stringer (as defined by a sagittal or central plane) when greater than fifty percent (50%) of the cross section of the repair stringer is positioned on that side.

While the foregoing is directed to aspects of the present disclosure, other and further aspects of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Referring now to the drawings,FIG.1depicts a top plan view of an aircraft100according to example aspects of the present disclosure. As shown, the aircraft100includes a pair of wings110,112and a fuselage114. The wings110,112extend laterally outward from the fuselage114. The aircraft100also includes a tail section116having a horizontal stabilizer118and a vertical stabilizer120. The wings110,112, the horizontal stabilizer118, and the vertical stabilizer120all include control surfaces122(e.g., ailerons, elevators, rudder, etc.) that can be controlled to maneuver the aircraft100during flight. The aircraft100further includes propulsion units124,126mounted to respective wings110,112. InFIG.1, the propulsion units124,126are gas turbine engines configured as turbofans. However, in other example aspects, the propulsion units124,126can be other types of propulsion units, such as electrically-driven fans.

The wings110,112each include skin members128that can be internally supported by various structures, such as stringers130and ribs136as illustrated by the cutaway portion of the wing112inFIG.1. The stringers130are positioned in spaced relation to one another and generally extend spanwise from an inboard portion132to an outboard portion134of their respective wings110,112. One or more of the stringers130can have a hat-shaped cross section, e.g., as viewed along a spanwise direction of its associated wing. In this regard, the stringers130can be “hat stringers” in some example aspects. As further depicted inFIG.1, the ribs136are positioned in spaced relation to one another and generally extend chordwise, e.g., from a forward structure, such as a front spar138, to a rear structure, such as a rear spar140, of their respective wings110,112.

FIG.2is a cross-sectional view of a hat stringer200. The hat stringer can be one of the hat stringers130of the aircraft100ofFIG.1, for example. For reference, a first direction D1(extending into and out of the page inFIG.2), a second direction D2, and a third direction D3are defined. The first, second, and third directions D1, D2, D3are mutually perpendicular and form an orthogonal direction system. InFIG.2, the first direction D1is a spanwise direction along a wing of an aircraft. In this regard,FIG.2depicts a cross section of the hat stringer200as viewed along a spanwise direction of a wing. The third direction D3can be a vertical direction.

As illustrated inFIG.2, the hat stringer200is coupled with a skin member202to provide support thereto. The skin member202can be a lower wing skin of a wing, for example. The hat stringer130includes a base stringer210. The base stringer210can be formed of one or more plies, such as one or more Carbon Fiber-Reinforced Polymers (CFRP) plies. The base stringer210can be formed as a monolithic unitary structure, for example. The base stringer210has, from left to right inFIG.2, a first flange segment212, a first web segment214, a cap segment216, a second web segment218, and a second flange segment220. The first and second flange segments212,220are coupled with the skin member202. The first and second web segments214,218extend from their respective first and second flange segments212,220and converge toward one another as they extend away from their respective first and second flange segments212,220. The cap segment216connects the first and second web segments214,218and generally extends parallel to the first and second flange segments212,220and the skin member202.

The base stringer210and the skin member202collectively define an internal cavity222. A profile224of the internal cavity222is defined by the base stringer210. Particularly, the profile224of the internal cavity222as viewed along the first direction D1is defined by an internal surface226of the base stringer210(e.g., when in serviceable condition). InFIG.2, the profile224of the internal cavity222is represented by a dashed line extending along the internal surface226of the base stringer210, or more specifically, along the internal surfaces of the first and second web segments214,218and the cap segment216. The profile224has a first web portion224A, a cap portion224B, and a second web portion224C. The first web portion224A extends along the internal surface of the first web segment214, the cap portion224B extends along the internal surface of the cap segment216, and the second web portion224C extends along the internal surface of the second web segment218. The base stringer210has an external surface228opposite the internal surface226. Moreover, for reference, the hat stringer200defines a central plane230demarcating a first side232and a second side234of the hat stringer200. The central plane230is orthogonal to the second direction D2.

In some instances, a hat stringer, such as the hat stringer200ofFIG.2, can be become damaged or otherwise in need of structural reinforcement, e.g., due to an impact event during service. For instance, a segment of the hat stringer200may be damaged to an extent that its structural integrity is compromised, or in some extreme cases, missing completely. This may present a safety issue or render the aircraft unfit for service. In accordance with inventive aspects of the present disclosure, hat stringer repair techniques and repair stringers that facilitate repair or reinforcement of a hat stringer are provided herein. Example restoration techniques and repair stringers are provided below.

With reference now toFIGS.3A and3B,FIGS.3A and3Bdepict the hat stringer200ofFIG.2undergoing a full stringer restoration with repair stringers having a “lazy Z” shape. Particularly, the base stringer210is in the process of undergoing full stringer restoration by using a first repair stringer300and a second repair stringer310, which both have a lazy Z shape. The first and second repair stringers300,310can both be formed of one or more plies, such as one or more carbon fiber plies. Full stringer restoration can be implemented in response to the base stringer210becoming damaged or otherwise structurally unsound.

As depicted inFIGS.3A and3B, the first repair stringer300has a flange segment302, a web segment304, and a cap segment306. The web segment304extends between and connects the cap segment306and the flange segment302. The flange segment302and the cap segment306both extend generally parallel to one another. The first repair stringer300has an internal profile308that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.3A, the internal profile308of the first repair stringer300is represented by a dashed line extending along the internal surface of the first repair stringer300. Stated another way, the internal profile308of the first repair stringer300matches or is shaped complementary to at least a portion of an external surface of the stringer to which the first repair stringer300will be arranged adjacent. For instance, as depicted inFIG.3A, the internal profile308of the first repair stringer300matches or is shaped complementary to at least a portion of the external surface228of the base stringer210. In addition, a cross-sectional area of the first repair stringer300as viewed along the first direction D1(e.g., a spanwise direction of a wing) is less than a total cross-sectional area of the hat stringer200as viewed along the first direction D1. In this regard, the first repair stringer300can be deemed to have a partial cross section with respect to the hat stringer200.

The second repair stringer310has a flange segment312, a web segment314, and a cap segment316. The web segment314extends between and connects the cap segment316and the flange segment312. The flange segment312and the cap segment316both extend generally parallel to one another. Like the first repair stringer300, the second repair stringer310has an internal profile318that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.3A, the internal profile318of the second repair stringer310is represented by a dashed line extending along the internal surface of the second repair stringer310. Stated another way, the internal profile318of the second repair stringer310matches or is shaped complementary to at least a portion of an external surface of the stringer to which the second repair stringer310will be arranged adjacent. For instance, as depicted inFIG.3A, the internal profile318of the second repair stringer310matches or is shaped complementary to at least a portion of the external surface228of the base stringer210and at least a portion of the external surface of the first repair stringer300. Moreover, a cross-sectional area of the second repair stringer310as viewed along the first direction D1is less than a total cross-sectional area of the hat stringer200as viewed along the first direction D1. In this regard, the second repair stringer310can be deemed to have a partial cross section with respect to the hat stringer200.

Further, in the depicted example ofFIGS.3A and3B, the first repair stringer300and the second repair stringer310have a same cross-sectional shape as viewed along the first direction D1. The second repair stringer310is oriented so as to be flipped horizontally with respect to the first repair stringer300, or rather, the second repair stringer310is rotated one hundred eighty degrees (180°) about a rotation axis extending along the third direction D3with respect to the first repair stringer300.

For a full stringer restoration using repair stringers having a “lazy Z” shape, the full stringer restoration can be implemented by arranging the first repair stringer300in a first mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.3A, the first repair stringer300is shown being arranged in a first mounting location as denoted by arrow1. In the first mounting location, the first repair stringer300is arranged so that the flange segment302, the web segment304, and the cap segment306respectively confront or are respectively positioned adjacent to the first flange segment212, the first web segment214, and the cap segment216of the base stringer210. The flange segment302, the web segment304, and the cap segment306of the first repair stringer300respectively extend parallel with the first flange segment212, the first web segment214, and the cap segment216of the base stringer210when the first repair stringer300is arranged in the first mounting location.

The full stringer restoration using repair stringers having a “lazy Z” shape can further be implemented by arranging the second repair stringer310in a second mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.3A, the second repair stringer310is shown being arranged in a second mounting location as denoted by arrow2. The flange segment312, the web segment314, and the cap segment316of the second repair stringer310respectively extend parallel with the second flange segment220, the second web segment218, and the cap segment216of the base stringer210when the second repair stringer310is arranged in the second mounting location. Moreover, in the second mounting location, the second repair stringer310is arranged so that the web segment314confronts or is positioned adjacent to the second web segment218of the base stringer210and so that the cap segment316confronts or is positioned adjacent to the cap segment306of the first repair stringer300. In this regard, the cap segment316of the second repair stringer310physically overlaps the cap segment306of the first repair stringer300. The cap segment306of the first repair stringer300and the cap segment316of the second repair stringer310each extend parallel with the cap segment216of the base stringer210. Further, as depicted, the cap segment306of the first repair stringer300is sandwiched between the cap segment316of the second repair stringer310and the cap segment216of the base stringer210, e.g., along the third direction D3.

As further shown inFIGS.3A and3B, the flange segment312of the second repair stringer310and the second flange segment220of the base stringer210are spaced from one another, e.g., along the third direction D3. Accordingly, a gap G or vertical offset is defined between the flange segment312of the second repair stringer310and the second flange segment220of the base stringer210. The full stringer restoration using repair stringers having a “lazy Z” shape can further be implemented by placing one or more shims320between the second flange segment220of the base stringer210and the flange segment312of the second repair stringer310. That is, one or more shims320can be arranged to fill in the gap G. For instance, as shown in FIG.3A, the one or more shims320are shown being placed within the gap G as denoted by arrow3. The added shims320can improve the structural integrity of the restored hat stringer200. Further, notably, due to the shapes of the first and second repair stringers300,310and the arrangement of them in their respective mounting locations, the need for shims on both sides of the hat stringer200can be eliminated or otherwise reduced. For example, in the example inFIG.3A, no shims are needed between the flange segment302of the first repair stringer300and the first flange segment212of the base stringer210.

The full stringer restoration using repair stringers having a “lazy Z” shape can further be implemented by coupling the first repair stringer300and the second repair stringer310with the base stringer210in their respective mounting locations. For instance, as shown inFIG.3B, a plurality of fasteners330are used to couple the first and second repair stringers300,310with the base stringer210. One of the plurality of fasteners330can couple the flange segment302of the first repair stringer300with the first flange segment212of the base stringer210. One of the plurality of fasteners330can couple the web segment304of the first repair stringer300with the first web segment214of the base stringer210. One of the plurality of fasteners330can couple the cap segment306of the first repair stringer300, the cap segment316of the second repair stringer310, and the cap segment216of the base stringer210together. One of the plurality of fasteners330can couple the web segment314of the second repair stringer310with the second web segment218of the base stringer210. Finally, one of the plurality of fasteners330can couple the flange segment312of the second repair stringer310with the second flange segment220of the base stringer210. Any suitable type of fastener can be utilized, including but not limited to, rivets, bolts, screws, anchors, etc. In alternative example aspects, the first and second repair stringers300,310can be coupled with the base stringer210in other manners, such as by a combination of compression and thermal processes.

With the first and second repair stringers300,310coupled with the base stringer210as depicted inFIG.3B, the hat stringer200can be deemed a restored or repaired hat stringer.

Notably, due at least in part to the geometric arrangement or cross-sectional shape of the first repair stringer300, the first mounting location is one of a plurality of possible mounting locations along the cross section of the hat stringer200in which the first repair stringer300can be arranged. In each of the plurality of possible mounting locations, the internal profile308of the first repair stringer300matches the profile224of the internal cavity222defined by the hat stringer200.

As a first example alternative mounting location, the first repair stringer300can be arranged so that the flange segment302, the web segment304, and the cap segment306respectively confront or are respectively positioned adjacent to the second flange segment220, the second web segment218, and the cap segment216of the base stringer210. In such a first alternative mounting location, the flange segment302, the web segment304, and the cap segment306of the first repair stringer300can respectively extend parallel with the second flange segment220, the second web segment218, and the cap segment216of the base stringer210. To arrange the first repair stringer300in the first alternative mounting location, the first repair stringer300can be flipped horizontally with respect to its orientation shown inFIGS.3A and3B(or rather, the first repair stringer300can be rotated from its orientation inFIGS.3A and3Bone hundred eighty degrees (180°) about a rotation axis extending along the third direction D3). In the first alternative mounting location, the internal profile308of the first repair stringer300would still match the profile224of the internal cavity222defined by the hat stringer200. Accordingly, the first repair stringer300is geometrically shaped to be mountable to the hat stringer200at least in a first possible mounting location in which the first repair stringer300is positioned primarily on the first side232of the hat stringer200(i.e., greater than fifty percent (50%) of the cross section of the first repair stringer300is positioned on the first side232) and in a second possible mounting location in which the first repair stringer300is positioned primarily on the second side234of the hat stringer200(i.e., greater than fifty percent (50%) of the cross section of the first repair stringer300is positioned on the second side234).

As a second example alternative mounting location, as shown inFIG.3C, the first repair stringer300can be arranged so that the flange segment302, the web segment304, and the cap segment306of the first repair stringer300respectively extend parallel with, but do not contact, the first flange segment212, the first web segment214, and the cap segment216of the base stringer210when the first repair stringer300is arranged in the second alternative mounting location. Moreover, in the second alternative mounting location, the first repair stringer300is arranged so that the web segment304confronts or is positioned adjacent to a first web segment of another repair stringer340(e.g., a first existing repair stringer) and so that the cap segment306confronts or is positioned adjacent to the cap segment of yet another repair stringer350(e.g., a second existing repair stringer). In this regard, the cap segment306of the first repair stringer300physically overlaps, e.g., the cap segment of the second existing repair stringer350. In the second alternative mounting location, the internal profile308of the first repair stringer300would still match the profile224of the internal cavity222defined by the hat stringer200. Accordingly, the first repair stringer300is geometrically shaped to be mountable to the hat stringer200in a mounting location in which the first repair stringer300is stacked on other stringers (e.g., existing repair stringers) that are not the base stringer210.

As a third example alternative mounting location, the first repair stringer300can be arranged in the second mounting location, or rather, the mounting location in which the second repair stringer310is located inFIGS.3A and3Band the second repair stringer310can be mounted in another mounting location of a plurality of possible mounting locations. Accordingly, like the first repair stringer300, the second repair stringer310can likewise be mountable in a plurality of possible positions as will be appreciated by the teachings above.

In some example aspects, in each of the plurality of possible mounting locations in which the first repair stringer300can possibly be mounted, the web segment304of the first repair stringer300extends parallel with a web segment of the base stringer210. Stated differently, in some example aspects, in each of the plurality of possible mounting locations in which the first repair stringer300can possibly be mounted, the internal surface of the web segment304of the first repair stringer300extends parallel with a web portion of the profile224. The same is true for the second repair stringer310. That is, in each of the plurality of possible mounting locations in which the second repair stringer310can possibly be mounted, the web segment314of the second repair stringer310extends parallel with a web segment of the base stringer210. Stated differently, in some example aspects, in each of the plurality of possible mounting locations in which the second repair stringer310can possibly be mounted, the internal surface of the web segment314of the second repair stringer310extends parallel with a web portion of the profile224.

In yet other example aspects, in each of the plurality of possible mounting locations in which the first repair stringer300can possibly be mounted, the cap segment306of the first repair stringer300extends parallel with the cap segment216of the base stringer210and the flange segment302of the first repair stringer300extends parallel with a flange segment of the base stringer210. The same is true for the second repair stringer310. Specifically, in each of the plurality of possible mounting locations in which the second repair stringer310can possibly be mounted, the cap segment316of the second repair stringer310extends parallel with the cap segment216of the base stringer210and the flange segment312of the second repair stringer310extends parallel with a flange segment of the base stringer210.

Restoring a hat stringer with one or more repair stringers each having a lazy Z cross-sectional shape can present certain advantages. For instance, the partial cross section of the lazy Z shape allows for repair stringers to be mounted in a plurality of mounting locations along the cross section of the hat stringer, which provides flexibility in the repair process. Further, the shimming needed for the repair can be reduced compared to conventional techniques. For example, inFIG.3B, shims320are needed on only one side of the hat stringer as the flange segment302of the first repair stringer300can be arranged directly on or adjacent the first flange segment212of the base stringer210. Also, a repair stringer having a lazy Z cross-sectional shape includes three segments that are capable of contacting three corresponding segments of one or more other stringers. The three points of contact can provide structural stability to a repaired hat stringer. Further, a restoration of a hat stringer with a plurality of lazy Z-shaped repair stringers is advantageous in that such hat stringers can be stacked (e.g., as shown inFIG.3C) without need to change the shape or angle of the repair stringers, which can greatly reduce or eliminate the need for custom repair stringers for a stacked arrangement. Stated differently, a plurality of same shaped lazy Z repair stringers can be used for a stacked repair. Such an advantage can improve the ease of performing the repair process for operators and stocking and storing repair parts, among other benefits.

With reference now toFIGS.4A and4B,FIGS.4A and4Bdepict the hat stringer200ofFIG.2undergoing a full stringer restoration with repair stringers having a “lazy L” shape. Particularly, the base stringer210is in the process of undergoing full stringer restoration by using a first repair stringer400, a second repair stringer410, a third repair stringer420, and a fourth repair stringer430, which all have a lazy L shape, or rather, a lazy L cross section as viewed along the first direction D1. The first, second, third, and fourth repair stringers400,410,420,430can each be formed of one or more plies, such as one or more carbon fiber plies. Full stringer restoration can be implemented in response to the base stringer210becoming damaged or otherwise structurally unsound.

As depicted inFIGS.4A and4B, generally, the first, second, third, and fourth repair stringers400,410,420,430each include a web segment and a second segment, which can be flange segment or a cap segment depending on the orientation of the repair stringer. The second segment of a given repair stringer is non-parallel with its web segment. An obtuse angle is defined between the web segment and the second segment of respective ones of the first, second, third, and fourth repair stringers400,410,420,430. Particularly, as shown, the first repair stringer400has a web segment404and a second segment, which is a flange segment402in this example. The second repair stringer410has a web segment414and a second segment, which is a cap segment416in this example. The third repair stringer420has a web segment424and a second segment, which is a flange segment422in this example. The fourth repair stringer430has a web segment434and a second segment, which is a cap segment436in this example.

The first repair stringer400has an internal profile408that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. In FIG.4A, the internal profile408of the first repair stringer400is represented by a dashed line extending along the internal surface of the first repair stringer400. As depicted, the internal profile408of the first repair stringer400matches or is shaped complementary to at least the first web portion224A of the profile224. Stated another way, the internal profile408of the first repair stringer400matches or is shaped complementary to at least a portion of an external surface of the stringer (or stringers) to which the first repair stringer400will be arranged adjacent. For instance, as depicted inFIG.4A, the internal profile408of the first repair stringer400matches or is shaped complementary to at least a portion of the external surface228of the base stringer210.

The second repair stringer410has an internal profile418that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.4A, the internal profile418of the second repair stringer410is represented by a dashed line extending along the internal surface of the second repair stringer410. As illustrated, the internal profile418of the second repair stringer410matches or is shaped complementary to at least the first web portion224A and the cap portion224B of the profile224. Stated differently, the internal profile418of the second repair stringer410matches or is shaped complementary to at least a portion of an external surface of the stringer (or stringers) to which the second repair stringer410will be arranged adjacent. For instance, as depicted inFIG.4A, the internal profile418of the second repair stringer410matches or is shaped complementary to at least a portion of the external surface228of the base stringer210along the cap segment216and to at least a portion of the external surface of the first repair stringer400.

The third repair stringer420has an internal profile428that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.4A, the internal profile428of the third repair stringer420is represented by a dashed line extending along the internal surface of the third repair stringer420. As depicted, the internal profile428of the third repair stringer420matches or is shaped complementary to at least the second web portion224C of the profile224. Stated another way, the internal profile428of the third repair stringer420matches or is shaped complementary to at least a portion of an external surface of the stringer (or stringers) to which the third repair stringer420will be arranged adjacent. For instance, as depicted inFIG.4A, the internal profile428of the third repair stringer420matches or is shaped complementary to at least a portion of the external surface228of the base stringer210.

The fourth repair stringer430has an internal profile438that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.4A, the internal profile438of the fourth repair stringer430is represented by a dashed line extending along the internal surface of the fourth repair stringer430. As illustrated, the internal profile438of the fourth repair stringer430matches or is shaped complementary to at least the second web portion224C and the cap portion224B of the profile224. Stated differently, the internal profile438of the fourth repair stringer430matches or is shaped complementary to at least a portion of an external surface of the stringer (or stringers) to which the fourth repair stringer430will be arranged adjacent. For instance, as depicted inFIG.4A, the internal profile438of the fourth repair stringer430matches or is shaped complementary to at least a portion of the external surface of the third repair stringer420and to at least a portion of the external surface of the second repair stringer410.

Further, in the depicted example ofFIGS.4A and4B, a cross-sectional area of the first repair stringer400as viewed along the first direction D1(e.g., a spanwise direction of a wing) is less than a total cross-sectional area of the hat stringer200as viewed along the first direction D1. The same is true for the second, third, and fourth repair stringers410,420,430. Accordingly, the first, second, third, and fourth repair stringers400,410,420,430can each be deemed to have a partial cross section with respect to the hat stringer200.

Moreover, in some example aspects, such as in the example ofFIGS.4A and4B, the first, second, third, and fourth repair stringers400,410,420,430can each have a same cross-sectional shape as one another as viewed along the first direction D1. InFIGS.4A and4B, the second repair stringer410is oriented so as to be flipped vertically with respect to the first repair stringer400, or rather, the second repair stringer410is rotated one hundred eighty degrees (180°) about a rotation axis extending along the second direction D2with respect to the first repair stringer400. The third repair stringer420is oriented so as to be flipped horizontally with respect to the first repair stringer400, or rather, the third repair stringer420is rotated one hundred eighty degrees (180°) about a rotation axis extending along the third direction D3with respect to the first repair stringer400. The fourth repair stringer430is oriented so as to be flipped vertically and horizontally with respect to the first repair stringer400, or rather, the fourth repair stringer430is rotated one hundred eighty degrees (180°) about a rotation axis extending along the third direction D3with respect to the first repair stringer400for the horizontal flip and the fourth repair stringer430is rotated one hundred eighty degrees (180°) about a rotation axis extending along the second direction D2with respect to the first repair stringer400for the vertical flip.

For a full stringer restoration using repair stringers having a “lazy L” shape, the full stringer restoration can be implemented by arranging the first repair stringer400in a first mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.4A, the first repair stringer400is shown being arranged in a first mounting location as denoted by arrow1. In the first mounting location, the first repair stringer400is arranged so that the flange segment402and the web segment404respectively confront or are respectively positioned adjacent to the first flange segment212and the first web segment214of the base stringer210. The flange segment402and the web segment404of the first repair stringer400respectively extend parallel with the first flange segment212and the first web segment214of the base stringer210when the first repair stringer400is arranged in the first mounting location.

The full stringer restoration using repair stringers having a “lazy L” shape can further be implemented by arranging the second repair stringer410in a second mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.4A, the second repair stringer410is shown being arranged in a second mounting location as denoted by arrow2. In the second mounting location, the second repair stringer410is arranged so that the web segment414and the cap segment416of the second repair stringer410respectively extend parallel with the first web segment214and the cap segment216of the base stringer210. Moreover, in the second mounting location, the second repair stringer410is arranged so that the web segment414confronts or is positioned adjacent to the web segment404of the first repair stringer400. In this regard, the web segment414of the second repair stringer410physically overlaps the web segment404of the first repair stringer400, with the web segment404being sandwiched or positioned between the web segment414and the first web segment214of the base stringer210. Further, in the second mounting location, the second repair stringer410is arranged so that the cap segment416confronts or is positioned adjacent to the cap segment216of the base stringer210.

The full stringer restoration using repair stringers having a “lazy L” shape can further be implemented by arranging the third repair stringer420in a third mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.4A, the third repair stringer420is shown being arranged in a third mounting location as denoted by arrow3. In the third mounting location, the third repair stringer420is arranged so that the flange segment422and the web segment424respectively confront or are respectively positioned adjacent to the second flange segment220and the second web segment218of the base stringer210. The flange segment422and the web segment424of the third repair stringer420respectively extend parallel with the second flange segment220and the second web segment218of the base stringer210when the third repair stringer420is arranged in the third mounting location.

The full stringer restoration using repair stringers having a “lazy L” shape can further be implemented by arranging the fourth repair stringer430in a fourth mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.4A, the fourth repair stringer430is shown being arranged in a fourth mounting location as denoted by arrow4. In the fourth mounting location, the fourth repair stringer430is arranged so that the web segment434and the cap segment436of the fourth repair stringer430respectively extend parallel with the second web segment218and the cap segment216of the base stringer210. Moreover, in the fourth mounting location, the fourth repair stringer430is arranged so that the web segment434confronts or is positioned adjacent to the web segment424of the third repair stringer420. In this regard, the web segment434of the fourth repair stringer430physically overlaps the web segment424of the third repair stringer420, with the web segment424being sandwiched or positioned between the web segment434and the second web segment218of the base stringer210. Further, in the fourth mounting location, the fourth repair stringer430is arranged so that the cap segment436confronts or is positioned adjacent to the cap segment416of the second repair stringer410. The cap segment436of the fourth repair stringer430is spaced from the cap segment216of the base stringer210, e.g., along the third direction D3.

The full stringer restoration using repair stringers having a “lazy L” shape can further be implemented by coupling the first, second, third, and fourth repair stringers400,410,420,430with the base stringer210in their respective mounting locations. For instance, as shown inFIG.4B, a plurality of fasteners440are used to couple the first, second, third, and fourth repair stringers400,410,420,430with the base stringer210. One of the plurality of fasteners440can couple the flange segment402of the first repair stringer400with the first flange segment212of the base stringer210. One of the plurality of fasteners440can couple the web segment404of the first repair stringer400, the web segment414of the second repair stringer410, and the first web segment214of the base stringer210. One of the plurality of fasteners440can couple the cap segment416of the second repair stringer410, the cap segment436of the third repair stringer430, and the cap segment216of the base stringer210. One of the plurality of fasteners440can couple the web segment424of the third repair stringer420, the web segment434of the fourth repair stringer430, and the second web segment218of the base stringer210. Finally, one of the plurality of fasteners440can couple the flange segment422of the third repair stringer420with the second flange segment220of the base stringer210. Any suitable type of fastener can be utilized, including but not limited to, rivets, bolts, screws, anchors, etc. In alternative example aspects, the first, second, third, and/or fourth repair stringers400,410,420,430can be coupled with the base stringer210in other manners, such as by a combination of compression and thermal processes.

With the first, second, third, and fourth repair stringers400,410,420,430coupled with the base stringer210as depicted inFIG.4B, the hat stringer200can be deemed a restored or repaired hat stringer.

Notably, due at least in part to the geometric arrangement or cross-sectional shape of the first repair stringer400, the first mounting location is one of a plurality of possible mounting locations along the cross section of the hat stringer200in which the first repair stringer400can be arranged. In each of the plurality of possible mounting locations, the internal profile408of the first repair stringer400matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. For instance, the first repair stringer400can be flipped vertically and/or horizontally to be mounted in any one of the mounting locations in which the second, third, and/or fourth repair stringers are shown inFIGS.4A and4B, and in any of these other possible mounting locations, the internal profile of the first repair stringer400matches or is shaped complementary to at least a portion of the profile224of the internal cavity222. The same is true for the second repair stringer410, the third repair stringer420, and the fourth repair stringer430. In this way, each one of the first, second, third, and fourth repair stringers400,410,420,430are mountable in a plurality of mounting locations along the cross section of the hat stringer200.

Restoring a hat stringer with one or more repair stringers each having a lazy L cross-sectional shape can present certain advantages. For instance, the partial cross section of the lazy L shape allows for repair stringers to be mounted in a plurality of mounting locations along the cross section of the hat stringer, which provides flexibility in the repair process. Further, the shimming needed for the repair can be eliminated or otherwise significantly reduced. For example, inFIG.4B, no shimming is needed to restore the hat stringer. Also, a repair stringer having a lazy L cross-sectional shape includes two segments that are capable of contacting two corresponding segments of one or more other stringers. The two points of contact can provide structural stability to a repaired hat stringer. Further, a restoration of a hat stringer with a plurality of lazy L-shaped repair stringers is advantageous in that such hat stringers can be stacked without need to change the shape or angle of the repair stringers, which can greatly reduce or eliminate the need for custom repair stringers for a stacked arrangement. Such an advantage can improve the ease of performing the repair process for operators and stocking and storing repair parts, among other benefits.

FIG.4Cis a cross-sectional view of another hat stringer undergoing a full stringer restoration with repair stringers having a “lazy Z” shape and one repair stringer having a “lazy U” shape. Particularly, the base stringer210is in the process of undergoing full stringer restoration by using a first repair stringer400, a second repair stringer420(configured and oriented in a similar manner as the third repair stringer420ofFIGS.4A and4B), and a third repair stringer450. The first and second repair stringers400,420both have a lazy L shape, or rather, a lazy L cross section as viewed along the first direction D1. The third repair stringer450has a lazy U shape, or rather, a lazy U cross section as viewed along the first direction D1. The third repair stringer450can be arranged in an upside orientation or as an upside-down lazy U, e.g., as shown inFIG.4C. The first, second, and third repair stringers400,420,450can each be formed of one or more plies, such as one or more carbon fiber plies. Full stringer restoration can be implemented in response to the base stringer210becoming damaged or otherwise structurally unsound.

The first and second repair stringers400,420can be arranged as described above with reference toFIGS.4A and4B. The third repair stringer450includes a first web segment454, a cap segment456, and a second web segment458. The cap segment456extends between and connects the first web segment454and the second web segment458. A first obtuse angle is defined between the first web segment454and the cap segment456. A second obtuse angle is defined between the second web segment458and the cap segment456. InFIG.4C, the third repair stringer450does not include flange segments.

The third repair stringer450has an internal profile460that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.4C, the internal profile460of the third repair stringer450is represented by a dashed line extending along the internal surface of the third repair stringer450. As depicted, the internal profile460of the third repair stringer450matches or is shaped complementary to the first web portion224A, the cap portion224B, and the second web portion224C of the profile224. Stated another way, the internal profile460of the third repair stringer450matches or is shaped complementary to an external surface of the stringer (or stringers) to which the third repair stringer450will be arranged adjacent. For instance, as depicted inFIG.4C, the internal profile460of the third repair stringer450matches or is shaped complementary to at least a portion of the external surface of the first repair stringer400, at least a portion of the external surface of the baseline stringer210, and at least a portion of the external surface of the second repair stringer420.

Accordingly, a repair stringer having a lazy U shape can be arranged so that a first web segment thereof couples to a web segment of one repair stringer, a cap segment thereof couples to and spans the full length of a cap segment of a baseline stringer, and a second web segment thereof couples to a web segment of another repair stringer. Such an arrangement can provide advantageous structurally integrity at the cap and web segments of the repaired hat stringer, among other benefits.

With reference now toFIG.5,FIG.5depicts the hat stringer200ofFIG.2undergoing a partial stringer restoration with at least one repair stringer having a “lazy L” shape. Particularly, the base stringer210is in the process of undergoing partial stringer restoration by using a single repair stringer (in this example a first repair stringer500), which has a lazy L shape, or rather, a lazy L cross section as viewed along the first direction D1. The first repair stringer500can be formed of one or more plies, such as one or more carbon fiber plies. Partial stringer restoration can be implemented in response to the base stringer210becoming damaged or otherwise structurally unsound, e.g., as represented by a damaged portion204inFIG.5. The damaged portion204is located at the transition between the first flange segment212and the first web segment214in this example but may be located in other areas along the cross section of the hat stringer200in other instances. Moreover, in some alternative example aspects, a repair stringer having a “lazy Z” shape can be used for a partial stringer restoration.

As depicted inFIG.5, like the repair stringers400,410,420,430ofFIGS.4A and4B, the first repair stringer500includes a first segment (e.g., a web segment) and a second segment, which can be flange segment or a cap segment depending on the orientation of the first repair stringer500. The second segment of the first repair stringer500is non-parallel with its first segment. An obtuse angle is defined between the first segment and the second segment of the first repair stringer500. In the example ofFIG.5, the first segment of the first repair stringer500is a web segment504and the second segment is a flange segment502.

The first repair stringer500has an internal profile508that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. InFIG.5, the internal profile508of the first repair stringer500is represented by a dashed line extending along the internal surface of the first repair stringer500. As depicted, the internal profile508of the first repair stringer500matches or is shaped complementary to at least the first web portion224A of the profile224. Stated another way, the internal profile508of the first repair stringer500matches or is shaped complementary to at least a portion of an external surface of the stringer (or stringers) to which the first repair stringer500will be arranged adjacent. For instance, as depicted inFIG.5, the internal profile508of the first repair stringer500matches or is shaped complementary to at least a portion of the external surface228of the base stringer210. Further, in the depicted example ofFIG.5, a cross-sectional area of the first repair stringer500as viewed along the first direction D1(e.g., a spanwise direction of a wing) is less than a total cross-sectional area of the hat stringer200as viewed along the first direction D1.

For a partial stringer restoration using a repair stringer having a “lazy L” shape, the partial stringer restoration can be implemented by arranging the first repair stringer500in a first mounting location along the cross section of the hat stringer200. For instance, as shown inFIG.5, the first repair stringer500is shown being arranged in a first mounting location as denoted by arrow1. In the first mounting location, the first repair stringer500is arranged so that the flange segment502and the web segment504respectively confront or are respectively positioned adjacent to the first flange segment212and the first web segment214of the base stringer210. The flange segment502and the web segment504of the first repair stringer500respectively extend parallel with the first flange segment212and the first web segment214of the base stringer210when the first repair stringer500is arranged in the first mounting location.

The partial stringer restoration using a repair stringer having a “lazy L” shape can further be implemented by coupling the first repair stringer500with the base stringer210in the first mounting location. For instance, as shown inFIG.5, a plurality of fasteners520are used to couple the first repair stringer500with the base stringer210. One of the plurality of fasteners520can couple the flange segment502of the first repair stringer500with the first flange segment212of the base stringer210. One of the plurality of fasteners520can couple the web segment504of the first repair stringer500and the first web segment214of the base stringer210. Any suitable type of fastener can be utilized, including but not limited to, rivets, bolts, screws, anchors, etc. In alternative example aspects, the first repair stringer500can be coupled with the base stringer210in other manners, such as by a combination of compression and thermal processes. With the first repair stringer500coupled with the base stringer210as depicted inFIG.5, the hat stringer200can be deemed a restored or repaired hat stringer.

Notably, due at least in part to the geometric arrangement or cross-sectional shape of the first repair stringer500, the first mounting location is one of a plurality of possible mounting locations along the cross section of the hat stringer200in which the first repair stringer500can be arranged. In each of the plurality of possible mounting locations, the internal profile508of the first repair stringer500matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200. The first repair stringer500can be flipped vertically and/or horizontally to be mounted in another possible mounting location.

As one example, the first repair stringer500can be flipped horizontally and arranged so that the web segment504and the flange segment502are respectively aligned parallel with the second web segment218and the second flange segment220of the base stringer210, e.g., to restore damage to a transition between the second web segment218and the second flange segment220of the base stringer210. As another example, the first repair stringer500can be flipped vertically and arranged so that the web segment504and its second segment are respectively aligned parallel with the first web segment214and the cap segment216of the base stringer210, e.g., to restore damage to a transition between the first web segment214and the cap segment216of the base stringer210. As yet another example, the first repair stringer500can be flipped both vertically and horizontally and arranged so that the web segment504and its second segment are respectively aligned parallel with the second web segment218and the cap segment216of the base stringer210, e.g., to restore damage to a transition between the second web segment218and the cap segment216of the base stringer210. In any of the possible mounting locations, the internal profile of the first repair stringer500matches or is shaped complementary to at least a portion of the profile224of the internal cavity222.

Partially restoring a hat stringer with a repair stringer disclosed herein, such a repair stringer having a lazy L cross-sectional shape or a lazy Z cross-sectional shape, can present certain advantages. For instance, the repair stringers of the present disclosure have a partial cross section with respect to the total cross section of the hat stringer, which allows for a repair stringer to be strategically arranged or localized to the damaged section of the hat stringer. This allows for less material to be used for the repair, which may advantageously reduce the weight of the aircraft.

With reference now toFIG.6A,FIG.6Adepicts the hat stringer200ofFIG.2undergoing a splice restoration with repair stringers having a “lazy L” shape. Particularly, the base stringer210is in the process of undergoing a splice restoration by plurality of strategically arranged and oriented repair stringers, including a first set600of repair stringers arranged primarily at the first side232and a second set602of repair stringers arranged primarily at the second side234of the hat stringer200in need of splice restoration. The first set600includes a first repair stringer610, a second repair stringer620, a third repair stringer630, and a fourth repair stringer640. The first, second, third, and fourth repair stringers610,620,630,640are each shaped to have an internal profile that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200, regardless of their respective mounting positions or orientations. In some aspects, the first, second, third, and fourth repair stringers610,620,630,640all have a same cross-sectional shape as one another, e.g., as viewed along the first direction D1, which can be a spanwise direction along a wing of an aircraft.

The second set602includes a first repair stringer650, a second repair stringer660, a third repair stringer670, and a fourth repair stringer680. The repair stringers610,620,630,640,650,660,670,680(or610-680) can each be formed of one or more plies, such as one or more carbon fiber plies. The first, second, third, and fourth repair stringers650,660,670,680are each shaped to have an internal profile that matches at least a portion of the profile224of the internal cavity222defined by the hat stringer200, regardless of their respective mounting positions or orientations. In some aspects, the first, second, third, and fourth repair stringers650,660,670,680all have a same cross-sectional shape as one another, e.g., as viewed along the first direction D1, which can be a spanwise direction along a wing of an aircraft.

A splice restoration can be implemented in response to the base stringer210becoming damaged with a missing section, such as the missing section206depicted inFIG.6A. In the example ofFIG.6A, the first web segment, the cap segment, and the second web segment of the base stringer210are missing and thus collectively form the missing section206or void in the base stringer210. A plane208can be defined where the missing section206of the base stringer210was previously positioned. The plane208is defined by dashed lines inFIG.6A.

For a splice restoration using repair stringers having a “lazy L” shape, the splice restoration can be implemented by constructing the first set600of repair stringers. Particularly, constructing the first set600can include arranging the first repair stringer610so that a segment (e.g., a web segment614) of the first repair stringer610is positioned in or adjacent the plane208where the missing section206of the base stringer210was previously positioned. InFIG.6A, the web segment614of the first repair stringer610is positioned, at least in part, in the plane208where the first web segment of the base stringer210was previously positioned.

Constructing the first set600can further include arranging the second repair stringer620and the third repair stringer630so that segments of the second repair stringer620and the third repair stringer630(e.g., a web segment624of the second repair stringer620and a web segment634of the third repair stringer630) sandwich the segment (e.g., a web segment614) of the first repair stringer610positioned within the plane208. As depicted inFIG.6A, the third repair segment630has a flange segment632that confronts or is positioned adjacent to the first flange segment212of the base stringer210. The second repair segment620has a flange segment622that confronts or is positioned adjacent to the flange segment632of the third repair segment630. The flange segments622,632are arranged relative to the first flange segment212so that a space or gap is defined between the web segments624,634. The gap between the web segments624,634is sized so that the web segment614of the first repair segment610can be received therein, or rather, so that the web segment614can be sandwiched therebetween. Positioning the web segment614between the web segments624,634can advantageously enhance the structural integrity of the hat stringer200.

Constructing the first set600of repair stringers along the first side232can further include arranging the fourth repair stringer640so that a segment (e.g., a web segment644) of the fourth repair stringer640and a segment (e.g., the web segment614) of the first repair stringer610sandwich the second repair stringer620(e.g., the web segment624. As shown inFIG.6A, the first repair stringer610and the fourth repair stringer640are arranged so as to define a space or gap between their respective web segments614,644. The gap between the web segments614,644is sized so that the web segment624of the second repair segment620can be received therein, or rather, so that the web segment624can be sandwiched therebetween. Positioning the web segment624between the web segments614,644can advantageously enhance the structural integrity of the hat stringer200.

As illustrated inFIG.6A, with the first, second, third, and fourth repair stringers610,620,630,640arranged as noted above, the second and third repair stringers620,630have a same mounting orientation and the first and fourth repair stringers610,640have a same mounting orientation. As shown, the second and third repair stringers620,630are oriented so as to be flipped vertically and horizontally with respect to the first and fourth repair stringers610,640.

Constructing the first set600of repair stringers along the first side232can further include coupling the first, second, third, and fourth repair stringers610,620,630,640with the base stringer210. For instance, as shown inFIG.6A, a plurality of fasteners690are used to couple the first, second, third, and fourth repair stringers610,620,630,640of the first set600with the base stringer210. One of the plurality of fasteners690can couple the flange segment622of the second repair stringer620and the flange segment632of the third repair stringer630with the first flange segment212of the base stringer210. One of the plurality of fasteners690can couple the web segments614,624,634,644of the first, second, third, and fourth repair stringers610,620,630,640. As the first and fourth repair stringers610,640are coupled with the second and third repair stringers620,630, which are coupled with the base stringer210, the first and fourth repair stringers610,640are consequently also coupled with the base stringer210. Any suitable type of fastener can be utilized, including but not limited to, rivets, bolts, screws, anchors, etc. In alternative example aspects, the first, second, third, and/or fourth repair stringers610,620,630,640of the first set600can be coupled with the base stringer210in other manners, such as by a combination of compression and thermal processes.

With the first, second, third, and/or fourth repair stringers610,620,630,640of the first set600arranged in place and coupled with the base stringer210, the first set600can be deemed to repair the first web segment and a first portion of the cap segment of the base stringer210.

The splice restoration can further be implemented by constructing the second set602of repair stringers. Particularly, constructing the second set602can include arranging the first, second, third, and fourth repair stringers650,660,670,680as described above with respect to the first set600, and also coupling them to the base stringer210, e.g., to the second flange segment220thereof.

With the first repair stringer610and the fourth repair stringer640of the first set600arranged as noted above, a gap is defined between their respective cap segments616,646. For the example ofFIG.6A, the gap defined between the cap segments616,646is arranged along the plane208of where the missing section206of the base stringer210was previously positioned. The gap is sized (e.g., along the third direction D3) so as to be capable of receiving a portion of another repair stringer, e.g., a cap segment656of the first repair stringer650from the second set602as shown inFIG.6A. Further, with the first repair stringer650and the fourth repair stringer680of the second set602arranged as noted above, a gap is defined between their respective cap segments656,686. For the example ofFIG.6A, the gap defined between the cap segments616,646is arranged along the plane208of where the missing section206of the base stringer210was previously positioned. The gap is sized (e.g., along the third direction D3) so as to be capable of receiving a portion of another repair stringer, e.g., the cap segment646of the fourth repair stringer640from the first set600as shown inFIG.6A.

As further depicted inFIG.6A, an internal surface of the cap segment686of the fourth repair stringer680of the second set602confronts or is positioned adjacent to an external surface of the cap segment646of the fourth repair stringer640of the first set600. In this regard, the cap segment686of the fourth repair stringer680of the second set602physically overlaps the cap segment646of the fourth repair stringer640of the first set600. The cap segment646of the fourth repair stringer640of the first set600physically overlaps the cap segment656of the first repair stringer650of the second set602. The cap segment656of the first repair stringer650of the second set602physically overlaps the cap segment616of the first repair stringer610of the first set600.

Moreover, as shown inFIG.6A, the cap segments616,656,646,686of each of the repair stringers610,650,640,680extend from their primary sides across the central plane230. For instance, the first repair segment610is primarily positioned on the first side232of the hat stringer200but an end of the cap segment616extends across the central plane230to the second side234. The first repair segment650is primarily positioned on the second side234of the hat stringer200but an end of the cap segment656extends across the central plane230to the first side232. Similarly, the fourth repair segment640is primarily positioned on the first side232of the hat stringer200but an end of the cap segment646extends across the central plane230to the second side234. The fourth repair segment680is primarily positioned on the second side234of the hat stringer200but an end of the cap segment686extends across the central plane230to the first side232. One of the plurality of fasteners690can couple the cap segments616,656,646,686as shown inFIG.6A, which couples the first set600with the second set602.

With the first, second, third, and/or fourth repair stringers650,660,670,680of the second set602arranged in place and coupled with the base stringer210, the second set602can be deemed to repair the second web segment and a second portion of the cap segment of the base stringer210. With the first and second sets600,602coupled together as noted above, the first flange segment212and the second flange segment220can be deemed to be spliced together to complete the splice restoration.

In some further example aspects, a hat stringer can undergo a splice restoration with only a single set of repair stringers, such as a set of “lazy Z” repair stringers. For instance, with reference briefly toFIG.6B, the first set600of repair stringers is shown being utilized to repair the first web segment and a portion of the cap segment216that is missing from the cross section of the hat stringer200. In this example, the base stringer210is not damaged or otherwise structurally compromised. Accordingly, in the example ofFIG.6B, a second set of repair stringers (e.g., the second set602ofFIG.6A) is not needed to complete the splice restoration.

In yet other example aspects, a hat stringer can undergo a full, partial, or splice restoration using at least one lazy Z-shaped repair stringer and at least one lazy L-shaped repair stringer.

In some example aspects, a repair stringer that can be used to repair or restore a hat stringer according to any of the techniques disclosed herein is provided. The repair stringer can include a web segment. The web segment has an internal profile shaped to match a web portion of a profile of an internal cavity defined by a hat stringer. The repair stringer can further include at least one of a cap segment and a flange segment extending from the web segment. The repair stringer can have a partial cross section with respect to a total cross section of the hat stringer. The repair stringer can be mounted in a plurality of possible mounting locations along the cross section of the hat stringer, e.g., as viewed along a spanwise direction of the hat stringer. In each of the possible mounting locations, the repair stringer is shaped to have an internal profile that matches at least a portion of a profile of an internal cavity defined by the hat stringer. The repair stringer can be formed of one or more plies, such as one or more Carbon Fiber-Reinforced Polymers (CFRP) plies. Examples of such a repair stringer are provided in the examples ofFIGS.3A and3B,FIG.3C,FIGS.4A and4B,FIG.5, andFIGS.6A and6B.

In yet other example aspects, a hat stringer, or rather a repaired or restored hat stringer, is provided. The hat stringer includes a stringer, such as a base stringer or an existing repair stringer. The hat stringer further includes at least one repair stringer coupled with the stringer. The repair stringer is coupled with the stringer in a mounting location that is one of a plurality of possible mounting locations along a cross section of the hat stringer, and in each of the plurality of possible mounting locations, the repair stringer is shaped to have an internal profile that matches at least a portion of a profile of an internal cavity defined by the hat stringer. A cross-sectional area of the repair stringer is less than a total cross-sectional area of the hat stringer. Examples of such a repaired hat stringer are provided in the examples ofFIG.3B,FIG.3C,FIG.4B,FIG.5, andFIG.6B.

In some aspects, a repaired hat stringer can include at least one lazy Z repair hat stringer and at least one lazy L repair stringer.

FIG.7provides a flow chart for a method700of repairing a hat stringer, such as a hat stringer of an aircraft wing.

At702, the method700includes arranging a repair stringer in a mounting location that is one of a plurality of possible mounting locations along a cross section of a hat stringer, and in each of the plurality of possible mounting locations, at least a portion of an internal profile of the repair stringer matches at least a portion of a profile of an internal cavity defined by the hat stringer, and wherein a cross-sectional area of the repair stringer as viewed along a first direction is less than a total cross-sectional area of the hat stringer as viewed along the first direction. In this regard, the repair stringer can be deemed to have a partial cross section with respect to the hat stringer. The repair stringer can be arranged relative to a base stringer and/or another stringer, such as another repair stringer.

In some implementations of the method, in each of the plurality of possible mounting locations, the repair stringer has a web segment that extends parallel with a web segment of the stringer. Stated another way, in each of the plurality of possible mounting locations, the repair stringer has a web segment that extends parallel with a web portion of the profile of the internal cavity. In some further implementations, in each of the plurality of possible mounting locations, the repair stringer has at least one segment that extends parallel with a cap segment or with a flange segment of the stringer. Stated another way, in each of the plurality of possible mounting locations, the repair stringer has at least one segment that extends parallel with a cap portion of the profile of the internal cavity or with a flange segment of the stringer. In yet other implementations, in each of the plurality of possible mounting locations, the repair stringer has one segment that extends parallel with a cap segment of the stringer and one segment that extends parallel with a flange segment of the stringer. Stated another way, in each of the plurality of possible mounting locations, the repair stringer has one segment that extends parallel with a cap portion of the profile of the internal cavity and one segment that extends parallel with a flange segment of the stringer.

In yet further implementations, the hat stringer defines a central plane demarcating a first side and a second side of the hat stringer. In such implementations, the plurality of possible mounting locations include a first possible mounting location in which the repair stringer is positioned primarily on the first side of the hat stringer and a second possible mounting location in which the repair stringer is positioned primarily on the second side of the hat stringer. In this way, the repair stringer is shaped to be mountable to the first side or to the second side of the hat stringer, and regardless of whether the repair stringer is mounted in the first possible mounting location or the second possible mounting location, at least a portion of the internal profile of the repair stringer matches at least a portion of the profile of the internal cavity defined by the hat stringer.

In further implementations, the repair stringer has a cap segment, a flange segment, and a web segment extending between and connecting the cap segment and the flange segment. For instance, the repair stringer can have a “lazy Z” cross section. In such implementations, in arranging the repair stringer in its mounting location, the cap segment, the web segment, and the flange segment of the repair stringer respectively extend parallel with a cap segment, a web segment, and a flange segment of the stringer. Stated another way, in arranging the repair stringer in its mounting location, the cap segment, the web segment, and the flange segment of the repair stringer respectively extend parallel with a cap portion of the profile of the internal cavity, a web portion of the profile of the internal cavity, and a flange segment of a flange segment of the stringer.

In some additional implementations, the plurality of possible mounting locations include at least four possible mounting locations. In such implementations, the hat stringer can define a central plane demarcating a first side and a second side of the hat stringer, and the at least four possible mounting locations can include at least two possible mounting locations in which the repair stringer is positioned primarily on the first side of the hat stringer and at least two possible mounting locations in which the repair stringer is positioned primarily on the second side of the hat stringer.

In some implementations, the at least two possible mounting locations in which the repair stringer is positioned primarily on the first side of the hat stringer include a first mounting location and a second mounting location, and in the first mounting location, one segment of the repair stringer extends parallel with a first flange segment of the stringer and one segment of the repair stringer extends parallel with a first web segment of the stringer, and in the second mounting location, one segment of the repair stringer extends parallel with a cap segment of the stringer and one segment of the repair stringer extends parallel with the first web segment of the stringer. Further, in such implementations, the at least two possible mounting locations in which the repair stringer is positioned primarily on the second side of the hat stringer include a first mounting location and a second mounting location, and in the first mounting location on the second side, one segment of the repair stringer extends parallel with a cap segment of the stringer and one segment of the repair stringer extends parallel with the second web segment of the stringer, and in the second mounting location on the second side, one segment of the repair stringer extends parallel with a second flange segment of the stringer and one segment of the repair stringer extends parallel with a second web segment of the stringer.

In some further implementations in which the plurality of possible mounting locations include at least four possible mounting locations, the stringer includes a first flange segment, a first web segment, a cap segment, a second web segment, and a second flange segment, and wherein the plurality of possible mounting locations along the cross section of the hat stringer include a first mounting location, a second mounting location, a third mounting location, and a fourth mounting location. In the first mounting location, one segment of the repair stringer extends parallel with the first flange segment of the stringer and one segment of the repair stringer extends parallel with a first web segment of the stringer. In the second mounting location, one segment of the repair stringer extends parallel with the cap segment of the stringer and one segment of the repair stringer extends parallel with the first web segment of the stringer. In the third mounting location, one segment of the repair stringer extends parallel with the cap segment of the stringer and one segment of the repair stringer extends parallel with the second web segment of the stringer. In the fourth mounting location, one segment of the repair stringer extends parallel with the second flange segment of the stringer and one segment of the repair stringer extends parallel with the second web segment of the stringer. In such implementations, the first repair stringer can be a first repair stringer and the mounting location can be the first mounting location, and the method can further include arranging a second repair stringer in the second mounting location; arranging a third repair stringer in the third mounting location; arranging a fourth repair stringer in the fourth mounting location; and coupling the second repair stringer, the third repair stringer, and the fourth repair stringer to the stringer in the second mounting location, the third mounting location, and the fourth mounting location, respectively, the first repair stringer being coupled with the stringer in the first mounting location.

In some further implementations, the first and second repair stringers physically overlap one another, the second and third repair stringers physically overlap one another, and the third and fourth repair stringers physically overlap one another (such as in the example ofFIGS.4A and4B). In yet other implementations, the first, second, third, and fourth repair stringers all have a same cross-sectional shape, and wherein the second repair stringer is oriented so as to be flipped vertically and horizontally with respect to the first repair stringer, the third repair stringer is oriented so as to be flipped vertically with respect to the first repair stringer, and the fourth repair stringer is oriented so as to be flipped horizontally with respect to the first repair stringer (such as in the example ofFIGS.4A and4B).

In some implementations of the method700, the repair stringer can have a “lazy Z” cross-sectional shape and can be mountable in a plurality of mounting locations along the cross section of a hat stringer, and regardless of its mounting location, at least a portion of an internal profile of the repair stringer matches at least a portion of a profile of an internal cavity defined by the hat stringer. For example, the repair stringer can be mounted in the mounting location in which the first repair stringer300is mounted inFIGS.3A and3B, in the mounting location in which the second repair stringer310is mounted inFIGS.3A and3B, or some other mounting location. In each of these mounting locations, the internal profile of the repair stringer matches at least a portion of a profile of the internal cavity of the hat stringer. In some implementations, the repair stringer is mountable in at least two possible mounting locations. In some further implementations, the repair stringer having a “lazy Z” cross-sectional shape is capable of being mounted in a plurality of possible mounting locations along a cross section of a hat stringer, and in at least two of the possible mounting locations, in different mounting orientations, e.g., a first orientation in a first mounting location in which the repair stringer is right-side-up and a second orientation in a second mounting location in which the repair stringer has been flipped horizontally with respect to the first orientation. In each of the mounting orientations, at least a portion of the internal profile of the repair stringer matches at least a portion of the profile of the internal cavity defined by the hat stringer.

In some other implementations of the method700, the repair stringer can have a “lazy L” cross-sectional shape and can be mountable in a plurality of mounting locations along the cross section of a hat stringer, and regardless of its mounting location, at least a portion of an internal profile of the repair stringer matches at least a portion of a profile of an internal cavity defined by the hat stringer. For example, the repair stringer can be mounted in the mounting location in which the first repair stringer400is mounted inFIGS.4A and4B, in the mounting location in which the second repair stringer410is mounted inFIGS.4A and4B, in the mounting location in which the third repair stringer420is mounted inFIGS.4A and4B, in the mounting location in which the fourth repair stringer430is mounted inFIGS.4A and4B, or some other mounting location. In each of these mounting locations, the internal profile of the repair stringer matches at least a portion of a profile of the internal cavity of the hat stringer. In some implementations, the repair stringer is mountable in at least four possible mounting locations.

In some further implementations, the repair stringer having a “lazy L” cross-sectional shape is capable of being mounted in a plurality of possible mounting locations along a cross section of a hat stringer, and in at least four of the possible mounting locations, in different mounting orientations, e.g., a first orientation in a first mounting location in which the repair stringer is right-side-up, a second orientation in a second mounting location in which the repair stringer is upside down with respect to the first orientation, a third orientation in a third mounting location in which the repair stringer is right-side-up but flipped horizontally with respect to the first orientation, and a fourth orientation in a fourth mounting location in which the repair stringer is upside down and flipped horizontally with respect to the first orientation. In each of the mounting orientations, at least a portion of the internal profile of the repair stringer matches at least a portion of the profile of the internal cavity defined by the hat stringer.

At704, the method700includes coupling the repair stringer with a stringer of the hat stringer in the mounting location. For instance, the repair stringer can be coupled with the hat stringer in a suitable manner, such as by mechanical fasteners, a thermal process, a compression process, a combination thereof, etc.

In some further implementations, the repair stringer can be a first repair stringer and the method700can further include arranging a second repair stringer in a mounting location along the cross section of the hat stringer, the second repair stringer is shaped to have an internal profile that matches at least a portion of the profile of the internal cavity. Like the first repair segment, a cross-sectional area of the second repair stringer as viewed along the first direction is less than a total cross-sectional area of the hat stringer as viewed along the first direction. In this regard, the second repair stringer can be deemed to have a partial cross section with respect to the hat stringer. In some implementations, the second repair stringer has a same cross-sectional shape as the first repair stringer, e.g., as viewed along the first direction.

In some further implementations, the second repair stringer is arranged so that a cap segment of the second repair stringer and a cap segment of the first repair stringer physically overlap and each extend parallel with a cap segment of the stringer, or stated differently, each extend parallel with a cap portion of the profile of the internal cavity of the hat stringer. In yet further implementations, the first repair stringer has a web segment that physically overlaps a first web segment of the stringer and the second repair stringer has a web segment that physically overlaps a second web segment of the stringer.

In yet additional implementations, the second repair stringer has a flange segment that extends parallel with, but is spaced from, a second flange segment of the stringer. In such implementations, the method700can further include placing one or more shims between the second flange segment and the flange segment of the second repair stringer.

In implementations in which the second repair stringer is arranged along the cross section of the hat stringer, at704, the method700can further include coupling the second repair stringer to the stringer, e.g., by mechanical fasteners, a thermal process, a compression process, a combination thereof, etc.

FIG.8provides a flow chart for a method800of repairing a hat stringer, such as a hat stringer of an aircraft wing.

At802, the method800includes arranging a first repair stringer along a cross section of a hat stringer, an internal profile of the first repair stringer matches at least a portion of a profile of an internal cavity defined by the hat stringer. As one example, the first repair stringer can have a “lazy Z” cross-sectional shape. As another example, the first repair stringer can have a “lazy L” cross-sectional shape. The first repair stringer can be arranged so that at least a first segment thereof is arranged parallel with a web portion of the profile of the internal cavity and so that a second segment thereof is arranged parallel with a cap portion of the profile of the internal cavity or so that the second segment is arranged parallel with a flange segment of a base stringer. In some implementations, the first repair stringer can include a third segment that is connected with the second segment via the first segment. The third segment extends parallel with the second segment.

At804, the method800includes arranging a second repair stringer along the cross section of the hat stringer, an internal profile of the second repair stringer matches at least a portion of the profile of the internal cavity, the first and second repair stringers being arranged so that a segment of the second repair stringer physically overlaps a segment of the first repair stringer. As one example, the second repair stringer can have a “lazy Z” cross-sectional shape. As another example, the second repair stringer can have a “lazy L” cross-sectional shape. The second repair stringer can be arranged so that at least a first segment thereof is arranged parallel with a web portion of the profile of the internal cavity, which can be the same web portion that the first segment of the first repair segment is aligned parallel with or a different web portion. A second segment of the second repair stringer can be arranged parallel with the cap portion of the profile of the internal cavity or so that the second segment of the second repair stringer is arranged parallel with a flange segment of the base stringer. In some implementations, the second repair stringer can include a third segment that is connected with the second segment of the second repair stringer via the first segment of the second repair stringer. The third segment of the second repair stringer extends parallel with the second segment of the second repair stringer.

Further, in some implementations, the first and second repair stringers are arranged so that the segment of the second repair stringer physically overlaps the segment of the first repair stringer along a web section of the hat stringer (an example of which is shown inFIG.4A, wherein the web segment414of the second repair stringer410physically overlaps the web segment404of the first repair stringer400along a web section of the hat stringer200). In yet other implementations, the first and second repair stringers are arranged so that the segment of the second repair stringer physically overlaps the segment of the first repair stringer along a cap section of the hat stringer (an example of which is shown inFIG.3B, wherein the cap segment316of the second repair stringer310physically overlaps the cap segment306of the first repair stringer300along a cap section of the hat stringer200).

At806, the method800includes coupling the first repair stringer and the second repair stringer with a stringer of the hat stringer. For instance, the repair stringers can be coupled with the base stringer in a suitable manner, such as by mechanical fasteners (such as in the examples ofFIGS.3B,3C,4B), a thermal process, a compression process, a combination thereof, etc.

FIG.9provides a flow chart for a method900of performing a splice restoration of a hat stringer, such as a hat stringer of an aircraft wing.

At902, the method900includes arranging a first repair stringer so that a segment of the first repair stringer is positioned in or adjacent a plane where a missing section of a base stringer was previously positioned. By way of example, inFIG.6A, the first repair stringer610is shown being arranged so that its web segment614is positioned in or adjacent the plane208where the missing section206of the base stringer210was previously positioned.FIG.6Bprovides another example. In some implementations, the missing section can include one or more web segments, a cap segment, or a combination thereof of the base stringer.

At904, the method900includes arranging a second repair stringer and a third repair stringer so that segments of the second repair stringer and the third repair stringer sandwich the segment of the first repair stringer positioned within or adjacent the plane. By way of example, inFIG.6A, the second repair stringer620and the third repair stringer630are shown being arranged so that that their respective web segments624,634sandwich the web segment614of the first repair stringer610positioned within or adjacent the plane208.FIG.6Bprovides another example.

At906, the method900includes arranging a fourth repair stringer so that a segment of the fourth repair stringer and the first repair stringer sandwich the second repair stringer. By way of example, inFIG.6A, the fourth repair stringer640is shown being arranged so that its web segment644and the web segment614of the first repair stringer610sandwich the web segment624of the second repair segment620.FIG.6Bprovides another example.

At908, the method900includes coupling the first, second, third, and fourth repair stringers with the base stringer. For instance, the repair stringers can be coupled with the base stringer in a suitable manner, such as by mechanical fasteners (such as in the example ofFIG.6Aor in the example ofFIG.6B), a thermal process, a compression process, a combination thereof, etc.

In some implementations, the first, second, third, and fourth repair stringers are all shaped to have an internal profile that matches at least a portion of a profile of an internal cavity defined by the hat stringer. In some further implementations, the first, second, third, and fourth repair stringers all have a same cross-sectional shape as one another.

In some further implementations, the second and third repair stringers have a same mounting orientation and the first and fourth have a same mounting orientation. For instance, in the example ofFIG.6A, the second and third repair stringers620,630have a same mounting orientation and the first and fourth repair stringer610,640have a same mounting orientation. Particularly, in the example ofFIG.6A, the second and third repair stringers620,630are oriented so as to be flipped vertically and horizontally with respect to the first and fourth repair stringers610,640.

In some implementations, the missing section includes a first web segment, a cap segment, and a second web segment of the base stringer. In such implementations, the first, second, third, and fourth repair stringers form a first set of repair stringers coupled with the base stringer to repair the first web segment and a first portion of the cap segment of the base stringer. In such implementations, the method900can further include arranging a second set of repair stringers, which can include a first, second, third, and fourth repair stringer, and coupling the repair stringers of the second set with the base stringer to repair the second web segment and a second portion of the cap segment of the base stringer. An example of a first set of repair stringers and a second set of repair stringers being utilized to splice a damaged base stringer is shown inFIG.6A.