Patent Description:
Structures used on aircraft may have aerodynamic surfaces (i.e., control surfaces) that are exposed to ambient air during flight. These structures may be formed of two or more components that are joined together. An aircraft spoiler, for example, typically includes multiple components that are fastened or bonded together to form the complete spoiler. One configuration of a spoiler is a monolithic, machined body having a cover attached for aerodynamic purposes. The body has an outer surface facing away from the aircraft wing that is continuously exposed to ambient air during flight. The cover also has an outer surface that typically overlies a flap of the aircraft when in a neutral position, but may move to a deployed position in which the outer surface of the cover is spaced from the flap. Traditional methods of joining such components, such as bolting, require additional labor and expense, add to the weight of the aircraft, and introduce aerodynamic drag.

There is, therefore, a need for improved spoilers and methods of joining spoiler components.

<CIT>, in accordance with its abstract, states a precision self-locking connection mechanism and method for connecting two parts or elements to one another and a precision self-locking connection mechanism and method in combination with a further connection mechanism for connecting two parts or elements together.

<CIT>, in accordance with its abstract, states a method of friction stir welding joints with shims and an associated structural assembly is provided. The structural assembly includes one or more skin members that are disposed and friction stir welded to a substructure. A shim is disposed in a space defined by the other members of the assembly, e.g., between adjacent skin members or between a skin member and the substructure. The shim can be friction stir welded to the other members. That is, the adjacent skin members can be connected via the shim, and/or the skin members can be connected to the substructure via the shim. In some cases, the skin members and the substructure are relatively stiff, and the shim substantially fills the space to reduce flexing of the members during the friction stir welding operation.

<CIT>, in accordance with its abstract, states expanded structural assemblies and preforms and methods therefor are provided. Each preform can include at least two structural members in a stacked relationship, defining cells that can be inflated to expand the preform. Elongate members can be disposed between the structural members along the cells to define passages through which fluid can be received during expanding. Further, the structural members of the preform can be connected by friction stir weld joints, some of which can extend only partially through the preform so that the preform defines cells that can be expanded. More than one adjacent friction stir weld joint can be disposed between adjacent cells of the preform to define multiple-pass friction stir weld joints.

<CIT>, in accordance with its abstract, relates to aircraft wings, aircraft, and related methods. Aircraft wings include a spoiler constructed substantially of a monolithic structural body with an upper side that defines a portion of an airfoil surface of an aircraft wing. The monolithic structural body further includes a lower side, opposite the upper side, that includes a plurality of stiffening ribs that define a plurality of open voids. Methods of constructing a spoiler for an aircraft wing include forming a monolithic structural body of the spoiler.

The scope of protection is set out in the appended claims.

Other aspects and features will become more readily apparent upon reading the following detailed description when taken in conjunction with the accompanying drawings.

It should be understood that the drawings are not necessarily drawn to scale and that the disclosed examples are sometimes illustrated schematically. It is to be further appreciated that the following detailed description is merely exemplary in nature and is not intended to limit the disclosure or the application and uses thereof. Hence, although the present disclosure is, for convenience of explanation, depicted and described as certain illustrative examples, it will be appreciated that it can be implemented in various other types of examples and in various other systems and environments.

The following detailed description is of the best currently contemplated modes of carrying out the disclosure. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the disclosure, since the scope of the disclosure is best defined by the appended claims.

Aircraft structures having multiple aerodynamic surfaces, and methods for forming such structures, are disclosed herein having reduced weight and aerodynamic drag. An exemplary aircraft structure includes a sub-frame defining first and second aerodynamic surfaces. Skin plates are joined to the sub-frame by friction stir welded seams to form a monolithic structure. The friction stir welded seams may be continuous or intermittent about a perimeter of the skin plates. Joining the sub-frame and skin plates using friction stir welds avoids the assembly expense, weight, and aerodynamic drag associated with the use of fasteners.

As used in the examples disclosed herein, the terms "aerodynamic surface" and "control surface" are used interchangeably to refer to a component and/or a surface that defines an aerodynamic flow surface used to control flight and/or navigation of an aircraft or other vehicle based on fluid flow (e.g., airflow during movement and/or flight). For example, the term "control surface" encompasses a surface of an aerodynamic structure (e.g., a top surface of a flap) or an actively displaced and/or rotated component such as a flap, spoiler or aileron, for example. As used herein, the term "a chord length" refers to a length along a flow path or airflow direction along a direction of travel of an aircraft, unless described otherwise. As used herein the term "angle from horizontal" of an aircraft refers to an angle and/or relative angles corresponding to a reference plane defined as an angle away from a neutral position of a control surface, whereas the term "horizontal" in this context refers to the neutral position and/or angle of the control surface. As used herein, the term "upper surface" refers to a top surface (e.g., a wing top surface) of an aircraft on opposite side from landing gear of the aircraft while the term "lower surface" refers to a bottom surface side (e.g., a wing bottom surface) that corresponds to the landing gear.

<FIG> illustrates an example aircraft <NUM> in which the examples disclosed herein may be implemented. In the illustrated example, the aircraft <NUM> includes stabilizers <NUM> and wings <NUM> attached to a fuselage <NUM>. The wings <NUM> of the illustrated example have control surfaces (e.g., flaps, ailerons, spoilers, tabs, etc.) <NUM>, some of which are located at a trailing edge of the wings <NUM> and may be displaced or adjusted (e.g., angled, etc.) to provide lift during takeoff, landing and/or flight maneuvers. In some examples, the control surfaces <NUM> are operated (i.e., displaced) independently of one another. The control surfaces <NUM> include leading edge flaps <NUM>, leading edge slats <NUM>, upper surface spoilers (e.g., flight spoilers, ground spoilers, upper surface spoilers, etc.) <NUM>, and trailing edge flaps (e.g., rotatable flaps) <NUM>. The control surfaces <NUM> of the illustrated example also include ailerons <NUM> and flaperons <NUM>. In this example, the stabilizers <NUM> include elevators <NUM> and a rudder <NUM>. The wings <NUM> also define upper and lower surfaces (e.g., upper and lower sides, upper and lower aerodynamic surfaces, etc.) <NUM>, <NUM>, respectively.

To control flight of the aircraft <NUM>, the upper surface spoilers <NUM> of the illustrated example alter the lift and drag of the aircraft <NUM>. The trailing edge flaps <NUM> alter the lift and pitch of the aircraft <NUM>. The flaperons <NUM> and the ailerons <NUM> of the illustrated example alter the roll of the aircraft <NUM>. In this example, the edge slats <NUM> alter the lift of the aircraft <NUM>. The control surfaces <NUM> of the illustrated example also play a role in controlling the speed of the aircraft <NUM>. For example, the upper surface spoilers <NUM> may be used for braking of the aircraft <NUM>. Any of the control surfaces <NUM> of the illustrated example may be independently moved (e.g., deflected) to control the load distribution in different directions over the wing <NUM>, thereby directing movement of the aircraft <NUM>.

The examples described herein may be applied to control surfaces associated with any of the stabilizers <NUM>, the wings <NUM> and/or any other exterior or outboard structure (e.g., a horizontal stabilizer, a wing strut, an engine strut, a canard stabilizer, etc.) of the aircraft <NUM>. In particular, the wings <NUM> and/or the stabilizers <NUM> have control surfaces <NUM> that can be adjusted to maneuver the aircraft <NUM> and/or control a speed of the aircraft <NUM>, for example. Additionally or alternatively, in some examples, the fuselage <NUM> has control surfaces, which may be deflected, to alter the flight maneuvering characteristics during cruise and/or takeoff of the aircraft <NUM>.

<FIG> illustrates an aircraft structure in the form of a spoiler <NUM> provided on the wing <NUM> of the aircraft <NUM>. The spoiler <NUM> may have a neutral position, as shown in <FIG>, in which the spoiler overlies a wing <NUM> of the aircraft <NUM>. The spoiler <NUM>, however, may be rotated from the neutral position to alter an aerodynamic characteristic of the aircraft, such as lift, in a controlled manner. The spoiler <NUM> includes fittings, such as actuator lugs <NUM> configured for attachment to an actuator <NUM>. The actuator <NUM> may operate to move the spoiler <NUM> from the neutral position.

<FIG> illustrate a first example of a spoiler <NUM>. As best shown in <FIG>, the spoiler <NUM> generally includes a sub-frame <NUM> having a side wall <NUM>, with a first outer surface <NUM> is coupled to the side wall <NUM>. A second outer surface <NUM> is also coupled to the side wall <NUM> opposite the first outer surface <NUM>. In the illustrated example, the first and second outer surfaces <NUM>, <NUM> correspond to upper and lower aerodynamic surfaces of the spoiler <NUM>. That is, the first and second outer surfaces <NUM>, <NUM> may be directly exposed to ambient air during flight of the aircraft <NUM>, and therefore may be positioned to affect one or more aerodynamic characteristics of the wing <NUM>, such as magnitude of lift. Apertures <NUM>, <NUM> are formed in the first outer surface <NUM> while an aperture <NUM> is shown formed in the second outer surface <NUM>.

The spoiler <NUM> includes a plurality of stiffening webs that extend between the first outer surface <NUM> and the second outer surface <NUM>, thereby to improve the structural strength of the assembled aircraft structure. As best shown in <FIG>, a first stiffening web <NUM> extends between the first outer surface <NUM> and the second outer surface <NUM>, and further extends at least partially around the aperture <NUM> formed in the first outer surface <NUM>. Accordingly, the aperture <NUM>, first stiffening web <NUM>, and second outer surface <NUM> define a first stiffening recess <NUM>. A second stiffening web <NUM> also extends between the first outer surface <NUM> and the second outer surface <NUM>, and further extends at least partially around the aperture <NUM> formed in the first outer surface <NUM>. The aperture <NUM>, second stiffening web <NUM>, and second outer surface <NUM> define a second stiffening recess <NUM>. Still further, a third stiffening web <NUM> extends between the first outer surface <NUM> and the second outer surface <NUM>, and further extends at least partially around the aperture <NUM> formed in the second outer surface <NUM>. The aperture <NUM>, third stiffening web <NUM>, and first outer surface <NUM> define a third stiffening recess <NUM>.

To minimize weight, portions of the stiffening webs may border more than one stiffening recess. For example, a first common web portion <NUM> may form parts of both the first stiffening web <NUM>, which borders the first stiffening recess <NUM>, and the third stiffening web <NUM>, which borders the third stiffening recess <NUM>. Similarly, a second common web portion <NUM> may form parts of both the second stiffening web <NUM>, which borders the second stiffening recess <NUM>, and the third stiffening web <NUM>, which borders the third stiffening recess <NUM>.

The stiffening recesses may span the entire width of the spoiler <NUM> to improve the structural integrity of the spoiler. For example, as best shown in <FIG>, the spoiler <NUM> may further include a fourth stiffening recess <NUM> defined by the first stiffening web <NUM>, side wall <NUM>, and first outer surface <NUM>, and a fifth stiffening recess <NUM> defined by the second stiffening web <NUM>, side wall <NUM>, and first outer surface <NUM>. The stiffening recesses may be oriented so that adjacent recesses face opposite outer surfaces of the spoiler <NUM>, so that the stiffener webs and outer surfaces form a corrugated structure that reinforces the spoiler <NUM>. In the illustrated example, the first and second stiffening recesses <NUM>, <NUM> face toward the first outer surface <NUM>, while the third, fourth, and fifth stiffening recesses <NUM>, <NUM>, <NUM> face toward the second outer surface <NUM>. Accordingly, the first outer surface <NUM> defines a first raised stiffening section <NUM>, adjacent to both the first stiffening recess <NUM> and the second stiffening recess <NUM>, that spans across and forms a portion of the third stiffening recess <NUM>. Similarly, the second outer surface <NUM> defines a second raised stiffening section <NUM>, adjacent to both the third stiffening recess <NUM> and the fourth stiffening recess <NUM>, that spans across and defines a portion of the first stiffening recess <NUM>. Still further, the second outer surface <NUM> defines a third raised stiffening section <NUM>, adjacent to both the third stiffening recess <NUM> and the fifth stiffening recess <NUM>, that spans across and defines a portion of the second stiffening recess <NUM>.

The spoiler <NUM> further includes skin plates for closing off the stiffening recesses, thereby to complete the first and second outer surfaces <NUM>, <NUM> and improve the aerodynamic performance of the spoiler <NUM>. As best shown in <FIG>, a first skin plate <NUM> is sized to extend over the first stiffening recess <NUM> and is shaped conformally with the aperture <NUM>. Similarly, a second skin plate <NUM> is sized to extend over the second stiffening recess <NUM> and is shaped conformally with the aperture <NUM>. Still further, a third skin plate <NUM> is sized to extend over the third stiffening recess <NUM> and is shaped conformally with the aperture <NUM>. While the fourth and fifth stiffening recesses <NUM>, <NUM> are shown as being open to the exterior of the spoiler <NUM>, additional skin plates may be provided to close off these recesses.

The stiffening webs may include mating surfaces that securely position the skin plates in place to facilitate joining of the skin plates to the sub-frame <NUM>. For example, as best shown in <FIG>, the first stiffening web <NUM> includes a first mating surface <NUM>. The first mating surface <NUM> may be substantially planar (i.e., is within manufacturing tolerances associated with metal bending, cutting, rolling, and shaping techniques) to conform to a perimeter of the first skin plate <NUM>. Accordingly, in the illustrated example, the first mating surface <NUM> is a relatively narrow strip extending around a perimeter of the first stiffening recess <NUM>. The first mating surface <NUM> further may be inwardly offset from the first outer surface <NUM> by a first offset distance <NUM>. The first offset distance is substantially equal (i.e., is within manufacturing tolerances associated with metal bending, cutting, rolling, and shaping techniques) to a first skin plate thickness <NUM>, so that a first skin plate outer surface <NUM> is aligned with the first outer surface <NUM>.

Similarly, the second stiffening web <NUM> includes a second mating surface <NUM> that is substantially planar to conform to a perimeter of the second skin plate <NUM>, thereby to form a relatively narrow strip extending around a perimeter of the second stiffening recess <NUM>. The second mating surface <NUM> is inwardly offset from the first outer surface <NUM> by a second offset distance <NUM> that is substantially equal to a second skin plate thickness <NUM>, so that a second skin plate outer surface <NUM> is aligned with the first outer surface <NUM> (<FIG> & <FIG>).

Still further, the third stiffening web <NUM> includes a third mating surface <NUM> that is substantially planar to conform to a perimeter of the third skin plate <NUM>, thereby to form a relatively narrow strip extending around a perimeter of the third stiffening recess <NUM>. The third mating surface <NUM> is inwardly offset from the second outer surface <NUM> by a third offset distance <NUM> that is substantially equal to a third skin plate thickness <NUM>, so that a third skin plate outer surface <NUM> is aligned with the second outer surface <NUM> (<FIG>).

The skin plates <NUM>, <NUM>, <NUM> are joined to the sub-frame <NUM> using friction stir welded seams, thereby to form a monolithic aircraft structure having reduced weight, improved structural integrity, superior aerodynamic characteristics. Referring to <FIG>, the first skin plate <NUM> is joined to the first mating surface <NUM> of the first stiffening web <NUM> at a first friction stir welded seam <NUM>. Similarly, the second skin plate <NUM> is joined to the second mating surface <NUM> of the second stiffening web <NUM> at a second friction stir welded seam <NUM>, while the third skin plate <NUM> is joined to the third mating surface <NUM> of the third stiffening web <NUM> at a third friction stir welded seam <NUM>. The friction stir welded seams <NUM>, <NUM>, <NUM> may be formed using a friction stir welding tool having a pin. During the friction stir welding process, the pin of the friction stir welding tool is rotated and forced through the skin plate and into the associated stiffening web of the sub-frame <NUM>. Heat and pressure generated by the friction stir welding tool mechanically intermixes portions of the stiffening web and the skin plate to form the friction stir welded seam. In the illustrated examples, the friction stir welded seams <NUM>, <NUM>, <NUM> extend continuously around the perimeters of the skin plates <NUM>, <NUM>, <NUM>, however in alternative examples the friction stir welded seams <NUM>, <NUM>, <NUM> may be intermittent around the perimeter of the skin plates <NUM>, <NUM>, <NUM>. The recesses and skin plates help to provide a clearly defined path for the friction stir welding tool to follow while forming friction stir welded seams, which helps to facilitate attachment of aerodynamic skin plates. Further, the clearly defined path and the mating surfaces help to contain the weld without backside exposure (e.g., exposure of the weld at the bottom of the recess to which the skin plate is friction stir welded).

The friction stir welded seams <NUM>, <NUM>, <NUM> may be formed in different patterns as they extend around the perimeters of the skin plates <NUM>, <NUM>, <NUM>. In the examples shown in <FIG>, and the right-hand side of <FIG>, each of the first, second, and third friction stir welded seams <NUM>, <NUM>, <NUM> may be formed by weld lines having linear path segments <NUM> joined by curved corner segments <NUM>. Alternatively, the weld line used to form the first, second, and third friction stir welded seams <NUM>, <NUM>, <NUM> may be intermittently or continuously non-linear, which may limit propagation of cracks and improve structural integrity by increasing a length of the weld. The left-hand side of <FIG> and <FIG>, for example, show a non-linear weld line <NUM> that is at least partially formed in a continuous sinusoidal wave or scalloped pattern. Still other weld line patterns, such as a chevron, may be used.

Within examples, the stiffening webs are configured to direct loads to an area of the spoiler <NUM> having relatively greater structural strength, thereby to improve the performance and life of the spoiler <NUM>. More specifically, first and second lugs <NUM>, <NUM> are coupled to the side wall <NUM> to provide connection points to the wing <NUM> of the aircraft <NUM>. The first and second lugs <NUM>, <NUM> are laterally spaced to define an intermediate region <NUM> of the side wall <NUM> that extends between the first and second lugs <NUM>, <NUM>. The first and second lugs <NUM>, <NUM>, and the intermediate region <NUM> form an area of the spoiler <NUM> having relatively greater structural integrity. The stiffening webs may be configured to direct loads toward this area of the spoiler <NUM>.

Specifically, the stiffening webs may include web segments traversing paths that are aligned with the intermediate region <NUM> of the side wall <NUM>. Referring to <FIG>, the first stiffening web <NUM> includes web segments <NUM>, <NUM> and the second stiffening web <NUM> includes web segments <NUM>, <NUM>, wherein each of the web segments <NUM>, <NUM>, <NUM>, <NUM> is aligned with the intermediate region <NUM>. Referring to <FIG>, the third stiffening web <NUM> includes web segments <NUM>, <NUM> that are aligned with the intermediate region <NUM>. By providing multiple web segments that are aligned with the intermediate region <NUM>, loads applied to the spoiler <NUM> are directed to the lugs <NUM>, <NUM>, thereby improving the structural integrity of the spoiler <NUM>.

<FIG> schematically illustrates a method <NUM> of forming a monolithic aircraft structure having multiple aerodynamic surfaces. The method begins at block <NUM> by forming the sub-frame <NUM>. Within examples, the sub-frame <NUM> includes the side wall <NUM>, the first and second outer surfaces <NUM>, <NUM> coupled to the side wall <NUM>, and the first and second stiffening webs <NUM>, <NUM> extending between the first and second outer surfaces <NUM>, <NUM> and at least partially around the first and second apertures <NUM>, <NUM>. The method <NUM> may include, at block <NUM>, forming skin plates. The skin plates may include the first skin plate <NUM> sized to extend over the first stiffening recess <NUM> , the second skin plate <NUM> sized to extend over the second stiffening recess <NUM>, and the third skin plate <NUM> sized to extend over the third stiffening recess <NUM>. The method <NUM> may optionally include a dimensional inspection of the sub-frame and the skin plates at block <NUM>, to ensure that the components meet the desired size specifications.

At block <NUM>, the method <NUM> may continue by positioning the skin plates relative to the sub-frame, so that the sub-frame mating surfaces engage perimeters of the skin plates. Continuing at block <NUM>, the method <NUM> includes friction stir welding the skin plates to the sub-frame to form friction stir welded seams between the sub-frame and the skin plates, thereby to form a monolithic aircraft structure.

In an example, friction stir welding the first skin plate <NUM> to the first stiffening web <NUM> includes forming at least a portion of the first friction stir welded seam <NUM> with a continuous sinusoidal wave pattern, and friction stir welding the second skin plate <NUM> to the second stiffening web <NUM> includes forming at least a portion of the second friction stir welded seam <NUM> with a continuous sinusoidal wave pattern.

In an example, the second aperture <NUM> is formed in the first outer surface <NUM>, and forming the sub-frame <NUM> further includes a third stiffening web <NUM> extending between the first outer surface <NUM> and the second outer surface <NUM>, the third stiffening web <NUM> extending at least partially around a third aperture <NUM> formed in the second outer surface <NUM> to define a third stiffening recess <NUM>. In this example, the method <NUM> further includes joining a third skin plate <NUM> to the third stiffening web <NUM> with a third friction welded seam <NUM>, wherein the third skin plate <NUM> is sized to extend over the third stiffening recess <NUM> and shaped conformally with the third aperture <NUM>.

In an example, forming the sub-frame <NUM> at block <NUM> further includes forming a first lug <NUM> and a second lug <NUM> on the side wall <NUM> to define an intermediate region <NUM> of the side wall <NUM> extending between the first lug <NUM> and the second lug <NUM>, and wherein each of the first stiffening web <NUM> and the second stiffening web <NUM> includes at least two web segments traversing paths aligned with the intermediate region <NUM> of the side wall <NUM>.

The method <NUM> may include several optional steps after the friction stir welded seams are formed. For example, at block <NUM>, the assembled sub-frame and skin components are heat treated to improve structural integrity of the spoiler <NUM>. At block <NUM>, non-destructive inspection of the friction stir welded seams is performed to ensure that the spoiler <NUM> is structurally sound. Finally, at block <NUM>, at least one surface treatment selected from a group of surface treatments consisting of anodizing, primer coating, and topcoating is applied to the spoiler <NUM>, thereby to improve aerodynamic qualities (e.g., reducing drag) over the aerodynamic surfaces.

Beneficially, the disclosed aircraft control structure and method help to provide clearly defined paths for a friction stir welding tool to follow while forming friction stir welded seams, which helps to facilitate attachment of aerodynamic skin plates. The disclosed aircraft control structure and method also help to improve the structural strength of the assembled aircraft control structure.

The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended to illuminate the disclosed subject matter and does not pose a limitation on the scope of the claims. Any statement herein as to the nature or benefits of the exemplary examples is not intended to be limiting, and the appended claims should not be deemed to be limited by such statements. More generally, no language in the specification should be construed as indicating any non-claimed element as being essential to the practice of the claimed subject matter. The scope of the claims includes all modifications of the subject matter recited therein as permitted by applicable law.

Claim 1:
An aircraft control structure for an aircraft (<NUM>), wherein the aircraft control structure is a spoiler (<NUM>) having:
a side wall (<NUM>);
a first outer surface (<NUM>) coupled to the side wall (<NUM>);
a second outer surface (<NUM>) coupled to the side wall (<NUM>) and opposite the first outer surface (<NUM>); wherein, in use, the first and second outer surface correspond to upper and lower aerodynamic surfaces of the spoiler and are directly exposed to ambient air during flight of the aircraft;
a first stiffening web (<NUM>) extending between the first outer surface (<NUM>) and the second outer surface (<NUM>), the first stiffening web (<NUM>) extending at least partially around a first aperture (<NUM>) formed in the first outer surface (<NUM>) to define a first stiffening recess (<NUM>);
a second stiffening web (<NUM>) extending between the first outer surface (<NUM>) and the second outer surface (<NUM>), the second stiffening web (<NUM>) extending at least partially around a second aperture (<NUM>) formed in the first outer surface (<NUM>) or the second outer surface (<NUM>) to define a second stiffening recess (<NUM>);
a first skin plate (<NUM>) sized to extend over the first stiffening recess (<NUM>) and shaped conformally with the first aperture (<NUM>), wherein the first skin plate (<NUM>) is joined to the first stiffening web (<NUM>) at a first friction stir welded seam (<NUM>); and
a second skin plate (<NUM>) sized to extend over the second stiffening recess (<NUM>) and shaped conformally with the second aperture (<NUM>), wherein the second skin plate (<NUM>) is joined to the second stiffening web (<NUM>) at a second friction stir welded seam (<NUM>).