Methods, systems, and devices for detachable vehicle structures

Abstract

An aircraft is disclosed. The aircraft includes a body and a structure coupled to the body. The structure having a first portion proximal to the body and a second portion distal to the body, and a breakaway feature disposed between the first and second portions. The breakaway feature includes an aperture and a doubler. The breakaway feature is configured to fail upon exceeding a threshold load, such that the second portion detaches from the first portion.

Description

METHODS, SYSTEMS, AND DEVICES FOR DETACHABLE VEHICLE STRUCTURESCROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 618,247, filed January 5, 2024, the entire contents of which are hereby incorporated by reference as if fully set forth in this description.BACKGROUND

[0002] Aircraft wings are often subjected to significant forces, such as sustaining in-flight loads. To resist these loads, many wings include an internal support structure, such as a series of spars and ribs coupled together, that forms a torque box or wingbox. The internal support structure of the wing helps to sustain and transfer loading from the wings throughout the aircraft structure.

[0003] One type of aircraft configuration is a high wing aircraft. High wing aircraft are popular because of the visibility they afford passengers, the ease of egress and ingress without the need for stepping on a wing, and efficient structures that carry an aircraft’s weight on the wings while also providing mounting locations for propellers, rotors, fuel, batteries, and the like. Consequently, the wings of the aircraft may be required to bear substantial loading conditions. However, if a high wing structure is critically loaded, it may present a hazard for a compartment or a body of an aircraft if the weight or load of the wing overcomes a threshold of one or more wing structures. For example, passengers, cargo, or other aircraft structure could be damaged.

[0004] Moreover, although aircraft can nominally withstand the loads from devices and structures on a wing during normal operations, certain conditions such as extreme weather (wind, rain, snow, and the like) or a hard landing may present additional challenges to the supportability of a wing. For example, when the loads from devices andstructures affixed to a wing increase due to severe weather, a hard landing, a crash landing, or the like, the wing structure may transfer these additional loads through the body structure. The body structure can then be damaged, as discussed above. Such damage may result in structural failure, which may be a significant concern as it can result in loss or damage to the aircraft, including its ability to fly or move. Damage to the wing may also block passengers’ ability to safely egress from the vehicle.

[0005] Accordingly, improvements to airframe structure to avoid significant structural damage are desirable.SUMMARY

[0006] In the following description, certain aspects and embodiments will become evident. It is contemplated that the aspects and embodiments, in their broadest sense, could be practiced without having one or more features of these aspects and embodiments. It is also contemplated that these aspects and embodiments are merely exemplary.

[0007] In a first example embodiment, an aircraft is provided. The aircraft includes a body and a structure coupled to the body. The structure has a first portion proximal to the body and a second portion distal to the body, and a breakaway feature disposed between the first and second portions. The breakaway feature includes an aperture and a doubler. The breakaway feature is configured to fail upon exceeding a threshold load, such that the second portion detaches from the first portion.

[0008] In some embodiments, the structure comprises a web and at least one cap coupled to the web, wherein the aperture is disposed on the web and the at least one cap, and the aperture forms an arcuate notch in the web.

[0009] In some embodiments, the doubler is disposed across the aperture on the at least one cap.

[0010] In some embodiments, a thickness of the web at a cross-section having the aperture is greater than a thickness of the web on the first and second portions.

[0011] In some embodiments, the structure includes a web and at least one cap coupled to the web, wherein the aperture is disposed solely on the web.

[0012] In some embodiments, the aperture is a first aperture and the web further includes a second aperture adjacent to the first aperture and defining a portion of the web therebetween.

[0013] In some embodiments, the doubler forms an H-shape and is coupled to the portion of the web between the first and second apertures.

[0014] In some embodiments, upon exceeding the threshold load, the doubler and the portion of the web between the first and second apertures is configured to fail prior to the at least one cap.

[0015] In a second example embodiment, an aircraft is provided. The aircraft includes a body, a wing coupled to the body, and a spar disposed longitudinally within the wing. The spar includes a first portion, a second portion, and a third portion, wherein the first portion is proximal to the body, the second portion is between the first and third portions, and the third portion is distal to the body. Each of the first, second, and third portions include a web and at least one spar cap coupled to the web, where a thickness of a portion of the web and the at least one spar cap of the second portion is less than a thickness of the first and third portions. The spar also includes a doubler coupled to the at least one spar cap of the second portion. Upon exceeding a threshold load, the spar is configured to fail at the second portion.

[0016] In some embodiments, the doubler is a first doubler and the aircraft further includes a second doubler coupled to the web of the second portion.

[0017] In some embodiments, the first doubler is coupled to the at least one spar cap of the second portion solely using an adhesive, and the second doubler is coupled to the web of the second portion solely using at least one fastener.

[0018] In some embodiments, the spar includes a composite laminate and the thickness of the portion of the web and the at least one spar cap of the second portion includes locally reduced plies such that the thickness of the second portion is non-constant.

[0019] In some embodiments, the spar includes an upper and lower spar cap, and the upper spar cap includes the locally reduced plies.

[0020] In some embodiments, a thickness of the first doubler is non-constant and a thickness of the second doubler is constant.

[0021] In some embodiments, the first and second doublers each include a composite laminate.

[0022] In some embodiments, the first and second doublers each include a metal.

[0023] In some embodiments, the first and second doublers are part of a single doubler, and the first doubler forms an angle with the second doubler.

[0024] In some embodiments, the first and second doublers form a perpendicular angle with each other.

[0025] In some embodiments, upon exceeding the threshold load, the at least one fastener of the second doubler is configured to fail before the adhesive of the first doubler.

[0026] In some embodiments, the threshold load produces a shear stress at the second portion greater than a shear strength of the at least one fastener.

[0027] These as well as other aspects, advantages, and alternatives will become apparent to those of ordinary skill in the art by reading the following detailed description, with reference, where appropriate, to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate multiple embodiments of the presently disclosed subject matter and, together with the description, serve to explain the principles of the presently disclosed subject matter; and, furthermore, are not intended in any manner to limit the scope of the presently disclosed subject matter.

[0029] Figure 1 illustrates a craft in a vertical take-off and landing configuration, according to exemplary embodiments of the present disclosure.

[0030] Figure 2 illustrates a front view of a craft having a structure in a detached state, according to exemplary embodiments of the present disclosure.

[0031] Figure 3 A illustrates a perspective view of a portion of a spar configured to be positioned on a craft, according to exemplary embodiments of the present disclosure.

[0032] Figure 3B illustrates a cross-sectional view of a second portion of the spar of Figure 3 A, according to exemplary embodiments of the present disclosure.

[0033] Figure 4A illustrates a perspective view of another embodiment of a spar portion configured to be positioned on a craft, according to exemplary embodiments of the present disclosure.

[0034] Figure 4B illustrates a cross-sectional view of the spar portion of Figure 4A, according to exemplary embodiments of the present disclosure.

[0035] Figure 5A illustrates a perspective view of another embodiment of a spar portion configured to be positioned on a craft, according to exemplary embodiments of the present disclosure.

[0036] Figure 5B illustrates a perspective view of the spar portion of Figure 5 A including a doubler, according to exemplary embodiments of the present disclosure.

[0037] Figure 6 illustrates a perspective view of another embodiment of a spar portion configured to be positioned on a craft, according to exemplary embodiments of the present disclosure.

[0038] Figure 7 illustrates a perspective view of another embodiment of a spar portion including a doubler configured to be positioned on a craft, according to exemplary embodiments of the present disclosure.DETAILED DESCRIPTION

[0039] Disclosed herein are devices, systems, and methods for vehicles, craft, aircraft, and aircraft structure. In some examples, vehicle or aircraft structure may be configured to selectively detach, avoiding significant structural damage. For example, the disclosed vehicle or aircraft structure may include breakaway regions that are configured to deform and / or fracture before vehicle or aircraft structure or other components are damaged. Vehicle or aircraft structure may include wings that include the breakaway feature.

[0040] The disclosed systems, methods, and devices may be utilized in any device or application where selective detachment of a first structure from a second structure may occur. For example, the breakaway regions may be used to join structures of a vehicle, including but not limited to a ground vehicle (e.g., an automobile), a sea vehicle (such as a boat), or a flying craft (such as an aerial, floating, soaring, hovering, airborne, aeronautical aircraft, airplane, plane, spacecraft, a helicopter, an airship, or an unmanned aerial vehicle, a vertical take-off and landing (VTOL) craft, or a drone).

[0041] Figure 1 illustrates a craft 100 in a vertical take-off and landing configuration, according to an exemplary embodiment of the present disclosure. As shown in Figure 1, the craft 100 may include, among other things, a body 110, one or more lift rotors 104, one or more proprotors 106 which may be mounted on respective hubs 107, oneor more boom assemblies 150, one or more lift surfaces 102, and a tail 114. In some examples, the craft 100 may be manned or unmanned. It is envisioned that the craft 100 may be used for any purpose known to those skilled in the art, including for example, as a taxi, a delivery vehicle, a personal vehicle, a cargo transport, a short or long-distance hauling aircraft, and / or a video / photography craft. Thus, in some examples, the craft 100 may be a manned and / or unmanned aerial vehicle (e.g., aircraft).

[0042] The body 110 may be any suitable shape, size, or configuration suitable for the purpose of the craft, as will be understood by a person of ordinary skill in the art. For example, the body 110 may be oval, square, triangular, or otherwise any appropriate shape sufficient to hold cargo and / or passengers while remaining structurally sound. Moreover, the body 110 may include gear 116 for landing on land and / or water, which may or may not be retractable. The gear 116 may be included at both the front and the back of the craft 100, and may include wheels, treads, pontoons, or other components that may aid the craft in landing in land and / or water. The body 110 may also include a cockpit 118 configured to hold a pilot, passenger(s), and / or cargo. In one example, the pilot may be located at the front of the aircraft and the passengers and / or cargo may be located behind the pilot. However, in other examples, the pilot could be located at any location within the body (or that the craft could be maneuvered without a pilot at least some of the time).

[0043] The body 110 may also include a windshield 120 of any suitable shape and size; one or more doors configured to open and / or close (e.g., by swinging, sliding, and / or raising / lowering) to allow ingress / egress of persons and / or cargo; one or more seats; and controls and / or a computer system configured to communicate and / or control craft systems for the craft, including for example, the proprotors 106, the lift rotors 104, and / or one or more control surfaces (e.g., elevator, rudder, ruddervator, actuator, spoiler, or other known control s / surfaces). The body 110 may include a fuselage configured to provide structure toconnect and / or link a lift surface structure of the lift surface 102. In some examples, the fuselage may be of truss, monocoque, or semi-monocoque construction. The fuselage may be constructed of any suitable material, such as metal and / or a composite laminate. In some examples, the fuselage may include aluminum, while in other examples the fuselage may include a carbon fiber composite laminate. In further examples, the fuselage may include a combination of metal and composite laminate.

[0044] The proprotors 106 and / or the lift rotors 104 may be positioned above or away from control surfaces and / or portions of the body 110 such that a blade strike is unlikely or not possible. For example, the proprotors 106 may be spaced above a proprotor hub 107 and / or the lift rotors 104, when in a vertical take-off and landing configuration. The proprotors 106 may be spaced along the lift surface 102 and substantially above the body 110, and / or the lift rotors 104 may be spaced along the boom assemblies 150 and substantially above the body 110. The proprotors 106 may be spaced along the lift surface 102 away from the tail 114 (e.g., outboard) to avoid a blade strike on the tail 114. For example, each proprotor 106 may be positioned at more than half the distance of one wing from the body 110 or, in some examples, more than two-thirds the distance of one wing from body 110.

[0045] The proprotors 106, the lift rotors 104, and / or controls may be operable by an onboard pilot, an onboard computer (e.g., autonomously), from a control outside of the craft (e.g., remotely), or a mixture of one or more of an onboard pilot, an onboard computer, and / or a control outside of the aircraft. The proprotor 106 may be configured to be controlled through a power control (e.g., throttle), a pitch control (e.g., collective) and / or an angle of attack control (e.g., cyclically), or any suitable combination of these controls. Each of these controls may comprise mechanical and electrical actuators, switches, or other controls known to one of ordinary skill in the art, in conjunction with one or moreprocessors (e.g., within controllers, computers) to effect operation and management of each individual control or as a subset of controls or all controls altogether.

[0046] The lift surface 102 may extend relatively horizontally, when the craft is at rest, from one end to another. The lift surface 102 may include an airfoil configured to generate lift when air flows past it. The lift surface 102 may be a single continuous surface, or may include sections of lift surfaces, for example with one or more sections arranged inboard (e.g., towards the body 110) of the boom assemblies 150 (discussed below) and one or more sections arranged outboard (e.g., away from the body 110) of the boom assemblies 150. The lift surface 102 may incorporate portions of, or include shaped portions of, the body 110, the boom assemblies 150, and / or the proprotors 106 to generate lift and / or reduce drag as air flows past. In some examples, the lift surface 102 may be a wing.

[0047] The boom assemblies 150 may provide a structure for the tail structure 114, one or more electric motors for the one or more lift rotors 104, and / or one or more batteries to power the one or more lift rotors 104, and / or the one or more proprotors 106. The lift rotors 104 may also be connected to the craft's electrical and control systems. The boom assemblies 150 may be supported by the lift surface 102 and the internal structure of the lift surface. Thus, the structure of the lift surface 102 may efficiently provide lift to the craft 100 to carry persons or cargo while incorporating structure to support the boom assemblies 150, and / or additionally to support the proprotors 106 in horizontal thrust and vertical take-off and landing configurations. Additionally, the proprotors 106 can create stress on structure as it rotates, and it is thus advantageous to support the proprotors 106 through the lift surface 102 that comprises internal structural components, such as spars and ribs, that are capable of withstanding the stress from the proprotors 106 as they operate to generate thrust and as they rotate between configurations. Efficient use of the structure inthe lift surface 102 can provide for a lighter craft, leading to less use of fuel and travel at greater speeds.

[0048] While Figure 1 illustrates four lift rotors 104, any suitable number of lift rotors 104 may be incorporated in a craft (for example, the craft may utilize more or less than four lift rotors 104). Lift rotors 104 may be configured to generate substantially vertical thrust. Lift rotors 104 may operate at a fixed pitch and / or a fixed revolutions per minute (RPM). In some examples, the lift rotors 104 may be positioned on either side of a lift surface and along the boom assemblies 150. In some examples, the lift rotors 104 may be positioned on the lift surface 102.

[0049] The lift rotors 104 and the proprotors 106 may be mechanically powered by one or more electric motors. In some examples, each lift rotor 104 and / or proprotor 106 may be powered by a dedicated motor, or one or more lift rotors 104 and / or proprotors 106 may be powered by a shared motor. As one example, two lift rotors 104 along one boom assembly 150 may share a motor. The motors discussed herein may be traditional fuel powered motors, electric motors, and / or hybrid motors. In some examples, a motor and rotor may be connected to a transmission that controls the use power generated by the motor. The transmission may be a continuously variable transmission (CVT), or an automatic transmission, or a manual or semi-manual transmission to shift one or more gears to output differing amounts of power.

[0050] The lift rotors 104 and / or the proprotors 106 may be constant speed rotors or variable speed rotors. The lift rotors and / or the proprotors may be at a constant angle of attack or have a changeable angle of attack (e.g., changeable through one or more actuators).

[0051] Speed, position, and / or angle of attack may be changed and / or gear may be shifted individually, as a set at the same time, or for all proprotors 106 and / or all lift rotors104 simultaneously. For example, four lift rotors 104 may all change speed at once to initiate a takeoff sequence and / or landing sequence. As another example, the proprotors 106 may be shifted from a take-off and landing configuration to a cruise condition simultaneously. As another example, two proprotors 106 and four lift rotors 104 may all change speed and / or angle of attack to affect a take-off and landing sequence simultaneously.

[0052] In some examples, the proprotors 106 may be puller rotors or pusher rotors. The proprotors 106 may include a thrust rotor (e.g., a propeller). In some examples, the proprotors 106 may be configured to move between a horizontal thrust configuration, a vertical thrust configuration, and / or any position in between. In such examples, the vertical thrust configuration may allow for slow flight (e.g., hovering and / or sub-horizontal stall velocity flight) and / or take-off and / or landing (e.g., verti cal / short take-off and landing (V / STOL)).

[0053] The lift rotors 104 may be located at any position on the craft 100. As illustrated in Figure 1, a first lift rotor 104 may be positioned forward of the lift surface 102 on a first side of the body, a second lift rotor 104 may be positioned aft of the lift surface on the first side of the body, a third lift rotor 104 may be positioned forward of the lift surface on a second side of the body, and a fourth lift rotor 104 may be positioned aft of the lift surface on the second side of the body. The lift rotors 104 may also be mounted on the one or more boom assemblies 150. The one or more boom assemblies 150 may include a battery pack configured to supply electrical power to one or more electric motors or may be utilized for storage of goods, electrical or mechanical components of the craft, or any other items known to those skilled in the art. While Figure 1 illustrates two boom assemblies 150 configured substantially perpendicular to the top or bottom surface of the lift surface 102, in other examples more or less than two booms may be utilized, and they may be attachedusing known attachment techniques and / or arranged in any suitable configuration. The one or more boom assemblies 150 may include or connect to the tail 114 that comprises one or more control surfaces (e.g., one or more of an elevator, a rudder, a ruddervators, a spoiler, or similar).

[0054] Control surfaces may be on relatively vertical portions of the tail 114 or relatively horizontal portions 126 of the tail 114. The tail 114 may be linked aft of the boom assemblies 150. In some examples, the tail 114 may be linked aft of the lift surface 102. The tail 114 may comprise an elevator along the link between one boom assembly 150 and another boom assembly 150. The tail structure 114 may be aft of the body 110. The tail structure 114 may comprise control surfaces such as rudders and / or ruddervators, where the control surfaces extend upwards and / or downwards from the boom assemblies 150. In some examples, at least one control surface may be positioned at least partially above a rotation plane of the lift rotors. For example, a rudder, an elevator, or a ruddervators of the tail 114 may extend partially above the body 110 and / or the lift rotors 104. The tail 114 may be configured to provide control to the craft 100 through control surfaces that are positioned in a freestream (e.g., relatively undisrupted air) when the craft is in a horizontal thrust configuration.

[0055] A number of tail configurations are contemplated, including a T-tail, cruciform tail, dual tail, triple tail, V-tail, Bronco tail, low boom tail, or high boom tail. A Bronco tail may have relatively perpendicular vertical and horizontal surfaces. The tail 114 may have rounded edges between substantial vertical and horizontal surfaces to provide efficient support of substantially horizontal surfaces by the substantially vertical surfaces, considered when the craft 100 is at rest on a ground surface. In some examples, the tail 114 may extend from the body 110 and the boom assemblies 150 may be connected above the tail 114 extending from the body 110, where the connection of the boom assemblies 150 isseparate from the tail 114 extending from the body 110 or connected to the tail 114 extending from the body 110.

[0056] The proprotors 106 may be connected to the lift surface 102 through a rotating linkage such as a rotating spar, and / or extending linkages. In some examples, the rotating spar may be actuated to rotate the proprotor 106 relative to the lift surface 102. The proprotors 106 may be positioned at any suitable location on the craft, including on the lift surface, on one or more sides of the body 110, on the boom assembly 150, or any other location. In some examples, extending linkages may be actuated to rotate the proprotor 106 relative to the lift surface 102. Actuators configured to actuate spars and / or rotating linkages may comprise one or more of a rotating actuator or a linear actuator.

[0057] The proprotors 106 may be configured in one configuration to rotate around and / or relative to an axis 108 substantially parallel with a ground surface and / or a lift surface, considered when the aircraft is at rest on the ground surface. As shown in Figure 1, the axis 108 may extend along or within the lift surface 102 from one end of the lift surface 102 to another end of the lift surface 102. The lift surface may include a first partial lift surface 122 at a first end of the lift surface 102 and a second partial lift surface 122 at a second end of the lift surface 102. The first and second partial lift surfaces may have any shape suitable to maximize lift and minimize drag, thereby reducing fuel consumption. For example, the partial lift surface may be rectangular, circular, triangular, or any combination thereof.

[0058] In some examples, a first proprotor 106 may be attached to the first partial lift surface such that the first partial lift surface moves with the proprotors 106 during movement of the proprotor 106 relative to and / or rotation about axis 108. A second proprotor 106 may be attached to the second partial lift surface such that the second partial lift surface moves with the proprotors 106 during movement of the proprotor 106 relative toand / or rotation about axis 108. The partial lift surfaces 122 may include one or more control systems which may be operable by the pilot located in the cabin 118. The partial lift surfaces 122 may be operated via actuators, active inceptors, sidesticks, switches, and / or buttons and may be configured to generate lift for vertical take-off and / or landing craft in a horizontal thrust configuration.

[0059] In some examples, the partial lift surfaces 122 may be configured to generate lift in a vertical thrust configuration. In some examples, the partial lift surfaces 122 may comprise a wing portion with a similar cross-sectional area and / or airfoil shape to the rest of the lift surface 102 (e.g., partial lift surfaces 122 may comprise a continuation of the lift surface 102). In some examples, the partial lift surfaces 122 may comprise winglets, may consist of winglets, and in other examples, the partial lift surfaces 122 may not have winglets. Whether the partial lift surfaces 122 have winglets may depend on the type of cargo, travel time, and / or proprotor size. The partial lift surfaces 122 may each comprise a winglet 124 and a wing portion, as shown in Figure 1. The winglets 124 may extend generally vertically from the end of the wing portions. In some examples, the winglets 124 may be configured to reduce drag.

[0060] In some examples, the proprotors 106 may be configured to rotate or move about the axis 108 along with the partial lift surfaces 122, where the proprotors 106 and the partial lift surfaces 122, 124 rotate outboard of the boom assemblies 150. In some examples, where the lift surface 102 is a separate structure from the boom assemblies 150, the proprotors 106 may move or rotate with the lift surface 102 aside from portions of the lift surface 102 that include the body 110. In some examples, the proprotors 106 may move or rotate such that only a portion of the proprotor hub 107 and the blades 106 move or rotate. In some examples, the proprotor hub 107 may move or rotate with the partial lift surface 122 about axis 108. Based on the shape of the lift surface 102, the lift surface notincluding the body 110 may rotate with the proprotors 106 to increase lift and decrease drag, thereby reducing fuel consumption. The lift surface 102 shape may also vary throughout a root to tip length. For example, the lift surface 102 may be rectangular shaped to support the weight of the body 110, and may be thinner out to the proprotor 106 to reduce drag when the proprotor 106 is configured for horizontal operation and wider when the proprotor 106 is configured for vertical operation.

[0061] Figure 2 illustrates a front view of a craft 200 having a structure in a detached state, according to exemplary embodiments of the present disclosure. In some examples, the craft 200 may include a body 210, a lift surface 202 coupled to the body 210, and a spar 202 A disposed within the lift surface 202. The spar 202 A may include a first portion 220, a second portion 240, and a third portion 230. The first portion 220 may be proximal to the body 210, the third portion 230 may be distal to the body 210, and the second portion 240 may be disposed between the first and third portions 220 and 230. In some examples, the craft 200 may be the same and / or similar to the craft 100 described in Figure 1.

[0062] As shown, the lift surface 202 of the craft 200 is in the detached state. In some examples, the second portion 240 of the spar 202A may be configured to fail causing the third portion 230 to detach (e.g., breaking away) from the first portion 220 and / or deform relative to the first portion 220. Failing of the second portion 240 may result in the lift surface 202 deforming and / or detaching along a cross-section at the second portion 240. By selectively detaching and / or deforming the spar 202A at the second portion 240, the location of failure of the lift surface 202 may be easier to predict and / or control which may result in increased safety to occupants within the craft 200. In some examples, the second portion 240 may be designed to fail (e.g., yield and / or fracture) upon exceeding a threshold load.

[0063] For example, the lift surface 202 (e.g., the wing) may be designed to sustain a specific load factor (G-force) while coupled to the body 210. Certain conditions, such as hard landing conditions, may exceed the design limit load factor of the lift surface 202. Exceeding the design load factor may cause damage to the lift surface 202 and / or the body 210 as the loading is transferred through the craft 200. It may be desirable to shed weight from the lift surface 202 to reduce the load factor on the lift surface 202 and thus mitigate potential damage to the aircraft 200. Further, in the event of a hard landing condition the loading experienced by the lift surface 202 may cause deformation of the lift surface 202 relative to the body 210, such as breaking and / or detaching. It may be desirable for occupants within the craft 200 to have an unobstructed ingress / egress after the hard landing condition. By including a portion of the lift surface 202 that selectively deforms / detaches upon exceeding the threshold load, such as the second portion 240 of the spar 202A, failure of the lift surface 202 may be better controlled and / or predicted to allow for ingress / egress of the craft 200 after the hard landing. In some examples, the threshold load may be any load, which when exceeded, causes deformation and / or detachment of a first portion of a component from a second portion of the component or deformation and / or detachment between one or more coupled components.

[0064] In some examples, weight may be shed from the lift surface 202 and / or failure of the lift surface 202 may be controlled by selectively detaching structures within the lift surface. For instance, the spar 202A may be a single continuous structure that includes the first, second, and third portions 220, 240, and 230. The second portion 240 of the spar 202A may be designed to fail upon exceeding the threshold load such that loading between the first and third portions 220 and 230 is reduced and / or terminated. Reducing and / or terminating load flow between the first and third portions 220 and 230, may allow for the cross-section of the lift surface 202 to deform and / or detach at the second portion240 location. For example, the second portion 240 may be designed to deform (e.g., break, fracture, shear, and / or plastically deform) at a load factor greater than the design load factor of the spar 202 A and / or the lift surface 202 such that weight (W) from the lift surface 202 is shifted off of transferring to the body 210. The deformation of the lift surface 202 may also be better predicted such that the lift surface 202 may be designed to fail while still allowing for safe occupant ingress / egress from the craft 200.

[0065] Figure 3 A illustrates a perspective view of a portion of a spar 202A configured to be positioned on the craft 200, according to exemplary embodiments of the present disclosure. The spar 202A may include a first spar cap 242A, a second spar cap 242B, and a web 244. The second portion 240 of the spar 202A may include a first doubler 260 and a second doubler 270.

[0066] As shown, the first and second spar caps 242A and 242B are coupled at opposite ends of the web 244, such as an upper and lower end. Thus, the first spar cap 242A may be the upper spar cap and the second spar cap 242B may be the lower spar cap. The first and second spar caps 242A and 242B and the web 244 together may be a single continuous structure forming the spar 202A. In some examples, the spar 202A may be made from a composite laminate, while in other examples the spar 202A may be made from a metal. The spar 202 A may be coupled to another structure of the craft 200, such as another structure of the lift surface 202. For example, the first and / or second spar caps 242A and / or 242B may couple to a skin of the lift surface 202. In examples where the first and / or second spar cap 242A and / or 242B are coupled to the skins of the lift surface 202, loading experienced by the lift surface 202 may be transferred through the skin to the first and / or second spar cap 242 A and / or 242B and throughout the spar 202 A. In such examples, a surface of the first and / or second spar cap 242A and / or 242B may lie flush with a surface of the skin to facilitate load transfer.

[0067] In some examples, a cross-sectional thickness the first spar cap 242A on the second portion 240 may be less than a cross-sectional thickness of the first spar cap 242A on the first and third portions 220 and 230. In such examples, the cross-sectional thickness of the first spar cap 242A may be locally reduced to allow for coupling of the doubler 260. Similarly, a cross-sectional thickness of the web 244 at the second portion 240 may be less than a cross-sectional thickness of the web 244 at the first and third portions 220 and 230. In such examples, the cross-sectional thickness of the web 244 may be locally reduced to allow for coupling of the doubler 270. In the example shown, and discussed further in Figure 3B, only a portion of the second portion 240 includes the locally reduced thickness on the web 244, however in other examples the entire thickness of the web 244 at the second portion 240 may be reduced. Further, in some examples, the second spar cap 242B on the second portion 240 may include a reduced cross-sectional thickness similar to and / or the same as the first spar cap 242A.

[0068] In order to reduce the presence of stress concentration factors forming, the thickness reduction on either the first spar cap 242A and / or the web 244 may be gradually reduced from the third portion 230 to a midpoint (shown by dashed line 240 A) of the second portion 240 and gradually increased from the midpoint of the second portion 240 to the first portion 220. In such examples, a maximum cross-sectional thickness of the second portion 240 may occur where the second portion 240 couples to either the first and / or third portions 220 and 230. A minimum cross-sectional thickness of the second portion 240 may occur at the midpoint of the second portion 240.

[0069] In examples where the spar 202A includes a composite laminate, plies may be gradually reduced along the second portion 240 to taper the thickness of the first spar cap 242A and / or the web 244. Thus, in some examples the thickness of the portion of the web 244 and the first spar cap 242A of the second portion 240 may include locally reducedplies such that the thickness of the second portion 240 is non-constant. In such examples, the ply reduction may be a tapered or a stepped pattern. For example, a thickness change along a length of the second portion 240 may include a ply reduction every 1 ply. In other examples, the ply reduction may occur in increments of multiple plies to form the stepped pattern, such as reducing the thickness by increments of 2 plies, by increments of 3 plies, by increments of 4 plies, by increments of 5 plies, by increments of 6 plies, by increments of 7 plies, by increments of 8 plies, by increments of 9 plies, and by increments of 10 plies over a respective length.

[0070] In examples where the spar 202A includes a metal, the thickness of the first spar cap 242A and / or the web 244 may be gradually reduced. For example, the thickness of the metal may be reduced in a stepped pattern such that the thickness of the second portion at the step closest to the first and third portions is greater than the thickness of the step at the midpoint of the second portion. In other examples, however, the thickness of the metal may have a linearly reduced pattern.

[0071] While the spar 202A shown resembles a U-beam configuration, in other examples the spar 202 A may be another configuration. For example, the spar 202 A may be a T-beam, an I-beam, an L-beam, a C-beam, and / or a box beam.

[0072] As shown, the first doubler 260 may be coupled to the first spar cap 242A of the second portion 240 and the second doubler 270 may be coupled to the web 244 of the second portion 240. In some examples, the first and / or second doubler 260 and 270 may include a metal, while in other examples the first and / or second doubler 260 and 270 may include a composite laminate. For example, the first and / or second doubler 260 and 270 may include one or more plies (P1-P4) and a resin. A shape of the first doubler 260 may mirror the shape of the first spar cap 242A on the second portion 260 such that a surface of the first doubler 260 lies flush with a surface of the first spar cap 242A. A shape of thesecond doubler 270 may mirror the shape of the web 244 on the second portion 240. In examples where the spar 202A is a composite laminate, the one or more plies (P1-P4) of the first and / or second doubler 260 and 270 may mirror the pattern of reduced plies of the mating structure (e.g., the first spar cap 242A and / or the web 244).

[0073] For example, the location and number of plies (P1-P4) included on the first and / or second doubler 260 and 270 may correspond to every ply and / or increments of ply groupings reduced on the second portion 260. In such examples, the first doubler 260 together with the first spar cap 242A may have a total cross-sectional thickness that is constant across the second portion 240. Similarly, the second doubler 270 together with the web 244 may have a total cross-sectional thickness that is constant across the second portion 240. The first and second doublers 260 and 270 together with the first and second spar caps 242A and 242B and the web 244 may allow the second portion 240 to operate at design load conditions. While P1-P4 is shown, any number of plies and / or increments of ply groupings may be used. Thus, the first and / or second doubler 260 and 270 may include one or more plies and / or increments of ply groupings, where each ply grouping may include one or more plies.

[0074] However, in other examples the web 244 first and / or second doubler 260 and 270 may have a constant thickness across a length. For example, the second doubler 270 may have a constant material thickness (e.g., ply count or laminate thickness) across the second portion 240. In such examples, the second doubler 270 together with the web 244 may be designed to carry a threshold load.

[0075] In some examples, a single doubler may include a first doubler portion and a second doubler portion. In such examples, the first doubler portion may be the first doubler 260 and the second doubler portion may be the second doubler 270. For example, the first and second doublers 260 and 270 may form a single L-Shaped doubler. Thus, insome examples the first and second doublers 260 and 270 are disposed at an angle to one another and form the single doubler. Including the first and second doublers 260 and 270 on the single doubler may allow the first and second doublers 260 and 270 to function as a single part when transferring loading throughout the doubler.

[0076] Figure 3B illustrates a cross-sectional view of the second portion 240 of the spar 202A of Figure 3 A, according to exemplary embodiments of the present disclosure. As shown, the first and second doublers 260 and 270 may be a single doubler coupled to the second portion 240. The first doubler 260 may be coupled to the first spar cap 242A and the second doubler 270 may be coupled to the web 244.

[0077] In some examples, the first doubler 260 may be coupled to the first spar cap 242A using adhesives (e.g., adhesively bonded), and the second doubler 270 may be coupled to the web 244 using one or more fasteners 272. The adhesive coupling between the first doubler 260 and the first spar cap 242A may allow for loading to be transferred between the first spar cap 242A and the first doubler 260. Similarly, the fastener coupling between the web 244 and the second doubler 270 may allow for loading to be transferred between the web 244 and the second doubler 270. A type, quantity, and / or fastener pattern chosen for the one or more fasteners 272 may be based on design needs for the second portion 240. In some examples, it may be desired to selectively detach and / or deform the spar 202A at the second portion 240. In such examples, the one or more fasteners 272 may be designed to facilitate selective detachment and / or deformation at the second portion 240.

[0078] For example, the one or more fasteners 272 may be designed to fail (e.g., shear) upon exceeding the threshold load, such as the design load of the spar 202A. Upon failing of the one or more fasteners 272, load transfer between the web 244 and the second doubler 270 may be significantly reduced (e.g., nominal). The reduced load carrying capabilities of the second portion 240 may cause the adhesive bond between the firstdoubler 260 and the first spar cap 242A to fail (e.g., due to peel stresses) which may result in a reduction of load transfer to the first doubler 260. For example, prior to failing of the one or more fasteners 272 the effective cross-section of the web 244 at the location of the second doubler 270 may be T4, which may be equal to the effective cross-section of the web 244 away from the second doubler 270, represented by T3. Upon failing of the one or more fasteners 272 the effective cross-section may be reduced to Te. This may result in more loading being transferred through the first spar cap 242A, having a thickness TI=T2, which may cause the adhesive bond 262 between the first doubler 260 and the first spar cap 242 A to fail. Failing of the adhesive bond 262 may reduce the effective cross-section of the first spar cap 242A from Ti to Ts. In some examples, upon failing of the first and / or second doubler 260, 270 the effective cross-section at the doubler location may be reduced by between 0 to 25 percent, between 25 to 50 percent, or between 50 to 75 percent. A thinner doubler may provide for easier manufacturing and reduce a likelihood of ineffective load transfer between parts, while a thicker doubler may allow for more definitive failure modes at the respective cross-section.

[0079] In some examples, the reduced cross-section of the web 244 and the first spar cap 242A may be greater than the yield strength and / or fracture strength of the second portion 240, which may result in failing of the second portion 240. Thus, the spar may be configured to selectively fail at the second portion 240 upon exceeding the threshold load.

[0080] As an illustrative example, during the hard landing condition a loading may be produced in the spar 202A that exceeds the threshold load, such as the design load. The loading on the spar 202A may produce a bending moment (M) that results in the first spar cap 242A being in tension, the web 244 being in shear, and the second spar cap 242B being in compression. Shear forces in the web 244 may exceed a shear strength of the one or more fasteners 272 coupling the second doubler 270 to the web 244, which may result infailing of the one or more fasteners 272. Similarly, the tension on the first spar cap 242A produced by the bending moment (M) may exceed a bond strength, such as a peel strength, of the adhesive bond 262 coupling the first doubler 260 to the first spar cap 242A, which may result in failing of the adhesive bond 262. The spar 202A may fail (e.g., buckle or cripple) due to the threshold load being greater than the load carrying capabilities of the reduced cross-section of the first spar cap 242A and / or the web 244. In examples, where the first spar cap 242A is the top spar cap and the second spar cap 242B is the bottom spar cap, the top spar cap may fail in tension, the bottom spar cap may fail in compression, and the web may fail in shear. However, in other examples a different failure mode may be present.

[0081] In some examples, the first doubler 260 may be coupled to the first spar cap 242A using solely adhesives (e.g., adhesively bonded without the addition of fasteners), and the second doubler 270 may be coupled to the web 244 using solely fasteners 272. For example, on an L-shaped doubler a first doubler portion may be coupled to a first area on a spar solely with adhesives and a second doubler portion may be coupled to a second area on the spar solely with fastener. Thus, the adhesive coupled portion between the doubler and the spar may be distinct from the fastener coupled portion between the doubler and the spar. By including solely adhesively coupled portions and solely fastener coupled portions between the doubler and the spar, load transfer and resulting stresses between each part may be better predicted which may allow for failure modes to be better predicted. More accurately predicting load transfer, stresses, and failure modes between the coupled parts, may allow for determining parameters of the adhesive and / or the fasteners to fail upon exceeding the threshold load.

[0082] Figure 4A illustrates a perspective view of another embodiment of a spar portion 340 configured to be positioned on a craft, according to another embodiment of thepresent disclosure. Figure 4B illustrates a cross-sectional view of the spar portion 340 of Figure 4A. The spar portion 340 may include a first spar cap 342A, a second spar cap 342B, an aperture 380, and a web 344 coupled to, and disposed between, the first and second spar caps 342A, 342B. A doubler 360 may be coupled to the spar portion 340 by way of one or more fasteners 364. In some examples, one or more aspects of the spar portion 340 may be the same and / or similar to those described with respect to the second portion 240 in Figures 3A and 3B. For example, the first spar cap 342A, the second spar cap 342B, and / or the web 344 may be the same and / or similar to the first spar cap 242A, the second spar cap 242B, and / or the web 244, respectively. In some examples, the spar portion 340 may be included on the craft 100 or 200.

[0083] In some examples, the spar portion 340 may be included on the craft 100 or 200. For example, the spar portion 340 may be a breakaway feature disposed between a first portion and a second portion of a lift surface, where the first portion is proximal to the body and the second portion is distal to the body. In such examples, the breakaway feature (e.g., the spar portion 340) may be configured to fail upon exceeding the threshold load such that the second portion detaches from the first portion.

[0084] As shown, the aperture 380 may be defined by a portion of the web 344 and at least one spar cap, such as the first spar cap 342A. The aperture 380 may be a cutout, having a portion of material at a cross-section absent from the web 344 and the first spar cap 342A. While in the example shown the aperture 380 has an arcuate notch profile, in other examples the aperture 380 may be defined by another profile, such as a V-shape. The design / profile of the aperture 380 may allow for stresses to concentrate at a particular location. For example, with the arcuate notch profile the aperture 380 resembles a parabola, where stresses may concentrate at the bottom of the parabola. In V-shaped aperture designs, stresses may concrete at the notch formed by the V in the web 344. Byconcentrating stresses at desired locations, failure of the spar portion 340 may be better predicted and / or controlled.

[0085] The doubler 360 may be disposed across the portion of the aperture 380 defined by the first spar cap 342A. One or more fasteners 364 may couple the doubler 360 to the first spar cap 342A on either side of the aperture 380. In some examples, the doubler 360 may transfer loading through the first spar cap 342A at the location of the aperture 380, such as by transferring loading through the first spar cap 342A from a first side of the aperture 380 to a second side of the aperture 380. For example, loading on the first side of the first spar cap 342A may be transferred to the doubler 360 by way of the one or more fasteners 364, carried through the doubler 360 over the aperture 380, then transferred from the doubler 360 to the first spar cap 342A on the second side by way of the one or more fasteners 364. Thus, the doubler 360 may account for material absent in the first spar cap 342A due to the presence of the aperture 380. Using the doubler 360 may provide a load path for transferring the loading through the first spar cap 342A which may reduce stresses from increasing in the web 344 and / or the second spar cap 342B at the cross-section having the aperture 380. While the doubler 360 is shown in Figure 4A on the spar portion 340, in some examples the doubler 360 may be coupled to and / or integrally formed on a mating structure, such as a skin.

[0086] In some examples, where the spar portion 340 is the breakaway feature and the spar portion includes the aperture 380, a thickness of the web 344 at the crosssection having the aperture 380 may be greater than a thickness of the web 344 on the first and second portions. For example, the spar portion 340 may include an increased web thickness 346, relative to the web thickness on the first and second portions. The increased web thickness 346 may extend from the second spar cap 342B to a lowest point, such as a tangent point, of the aperture 380 on the web. In some examples, the increased webthickness 346 may be constant along width (e.g., a height) of the spar portion 340, while in other examples the increased web thickness 346 may be non-constant (e.g., tapered). For example, the increased web thickness 346 may have a thickest cross-section at a midpoint between the lowest portion of the aperture 380 and the second spar cap 342B, and have a thinnest cross-section proximal to the aperture 380 and / or the second spar cap 342B. Similarly, in some examples the increased web thickness 346 may be constant along a length (e.g., inboard to outboard) of the spar portion 340, while in other examples the increased web thickness 346 may be non-constant, such as tapered. For example, the increased web thickness 346 may be tapered both inboard and outboard, gradually increasing to a midpoint having the thickest cross-section. By tapering the thickness, loading transferred through the web 344 may be gradually increased and / or decreased along the spar portion 340 which may reduce the occurrence and / or severity of peak stresses.

[0087] In some examples, the spar portion 340 may be configured to fail upon exceeding the threshold load. For example, upon exceeding the threshold load, stresses concentrated at specified portions of the aperture 380 may form a crack in the web 344. The crack may propagate through the cross-section of the web 344 at the spar portion 340 which may result in failure of the spar portion 340. Further, upon exceeding the threshold load, the doubler 360 on the first spar cap 342A may fail. For example, the threshold load may cause shear tear out of the one or more fasteners 364 coupling the doubler 360 to the spar portion 340. In such examples, the doubler 360 may no longer transfer loading through the first spar cap 342A. In some examples, the doubler 360, including the one or more fasteners 364, may be configured to fail prior to the web 344. For example, the doubler 360 may fail first, resulting in more load transferring through the web 344 and concentrating at the specified portion of the aperture 380 which may cause the crack to form and propagate in the web 344. Thus, upon exceeding the threshold load, the sparportion 340 may fail. In examples where the spar portion 340 is the breakaway feature, controlling failure to occur at the spar portion 340 may allow for weight to be safely shed from the craft while providing more predictability to the location of failure.

[0088] Figure 5A illustrates a perspective view of another embodiment of a spar portion 440 configured to be positioned on a craft, according to another embodiment of the present disclosure. The spar portion 440 may include a first spar cap 442A, a second spar cap 442B, a plurality of apertures 480, and a web 444 coupled to, and disposed between, the first and second spar caps 442 A, 442B. In some examples, one or more aspects of the spar portion 440 may be the same and / or similar to those described with respect to the second portion 240 in Figures 3A and 3B. For example, the first spar cap 442A, the second spar cap 442B, and / or the web 444 may be the same and / or similar to the first spar cap 242A, the second spar cap 242B, and / or the web 244, respectively. In some examples, the spar portion 440 may be included on the craft 100 or 200.

[0089] As shown, the plurality of apertures 480 may be defined on the spar portion 340 by the web 344. The plurality of apertures 480 may be located adjacent to one another, such as along a same cross-section, and separated by a web strip 444A. The plurality of apertures 480 may be mirrored about the web strip 444A such that a first aperture located on a first side of the web strip 444A may resemble a mirror image of a second aperture located on a second side of the web strip 444A opposite the first side. In some examples, each of the plurality of apertures 480 may have the same dimensions, while in other examples one or more apertures may have dimensions different from another aperture. For example, a first aperture may have a first size and a second aperture may have a second size different than the first size. In other examples, a first aperture may have a first shape, such as a trapezoid, and a second aperture may have a second shape differentthan the first shape, such as a triangle. While the plurality of apertures 480 shown in Figure5A are trapezoids, in other examples the plurality of apertures 480 may be another shape.

[0090] In some examples, the plurality of apertures 480 may have rounded, chamfered, and / or filleted edges along the perimeter, such as at corners. By rounding the comers of the aperture perimeter, stress concentration factors may be reduced which may reduce a likelihood of cracks forming at undesirable locations.

[0091] As illustrated, the web strip 444A may be disposed between two or more of the plurality of apertures 480. The web strip 444A together with first and second spar caps 442A, 442B and the remaining portion of the web 444 at the spar portion 440 may serve to transfer loading around the plurality of apertures 480. For example, a portion of loading in the web 444 may be transferred around the plurality of apertures 480 and a portion of loading in the web 444 may be transferred through the web strip 444A. A width and / or a thickness of the web strip 444A may be designed to fail upon exceeding the threshold load. This is further discussed below in Figure 5B.

[0092] Figure 5B illustrates a perspective view of the spar portion 440 of Figure 5A including a doubler 470, according to exemplary embodiments of the present disclosure. The doubler 470 may be coupled to the web 444 by way of one or more fasteners 472. For example, the one or more fasteners 472 may couple the doubler 470 to the web 444 on one or more sides of the plurality of apertures 480, as well as couple the doubler 470 to the web strip 444A. In some examples, the doubler 470 forms an H-shape and may be coupled to the portion of the web between two of the plurality of apertures 480, such as the web strip 444A between a first aperture and a second aperture. While the doubler 470 shown forms the H-shape, in other examples the doubler 470 may form another shape. For example, the doubler 470 may have a shape corresponding to a portion of the perimeter of one or more of the plurality of apertures 480. Further, a portion of the doubler 470 may have a dimensionmatching a dimension of the web strip 444A, such as a width of the doubler 470 may match a width of the web strip 444A. The doubler 470 may assist in transferring loading through the web 444 around the cross-section including the plurality of apertures 480. For example, the one or more fasteners 472 may transfer a portion loading from the web 444 into the doubler 470 which may increase an effective cross-sectional thickness of the spar portion 440.

[0093] In some examples, the doubler 470 and / or the portion of the web (e.g., the web strip 444A) between the first and second apertures may fail prior to the first and / or second spar cap 442A, 442B. In such examples, the doubler 470 and / or the web strip 444A may fail upon the spar portion 440 exceeding the threshold load. As an illustrative example, upon exceeding the threshold load, stresses (e.g., shear stresses) transferring through the doubler 470 and the web strip 444A may cause cracks to form and propagate in the web strip 444A, which may result in failure occurring, such as by shear tear out. Upon failing of the web strip 444A and / or the doubler 470, the first and second apertures (shown as the plurality of apertures 480) may effectively become a single aperture in the web 444. Forming the single aperture may further reduce an effective cross-sectional area of the web 444 which may result in load paths being redirected around the single aperture to the reduced portion of the web 444 and first and second spar caps 442 A, 442B. In such examples, a load carrying capability of the remaining cross-section of the spar portion 440 at the single aperture may be less than the threshold load, which may result in failure of the spar portion 440. In some examples, the spar portion 440 may fail in buckling, crippling, or fracture. In some examples, dimensions and / or materials used for the web strip 444A, the one or more fasteners 472, and / or the doubler 470 may be selected based on a desire for failure to occur upon exceeding the threshold load.

[0094] Figure 6 illustrates a perspective view of another embodiment of a spar portion 540 configured to be positioned on a craft, according to another embodiment of the present disclosure. The spar portion 540 may include a first spar cap 542A, a second spar cap 542B, and a web 544 that may be similar to and / or the same as the first and second spar caps 442A, 442B and the web 444 described with respect to Figure 5A. The web 544 on the spar portion 540 may define an ovular shaped aperture 580. In some examples, the ovular aperture 580 may be narrowed or pointed at one or more ends, such as vertically disposed ends closest to either the first and / or second spar caps 542A, 542B. In such examples, the narrowed or pointed ends may form points of stress concentration. It may be desirable to predict where a crack may form and / or direct where the crack forms. Including narrowed or pointed ends on the ovular aperture 580 may allow for crack formation to be directed to a desired location.

[0095] In some examples, the spar portion 540 may be configured to fail upon exceeding the threshold load. In such examples, upon exceeding the threshold load, cracks may form in the web 544 between the ovular aperture 580 and the first and second spar caps 542 A, 542B. As the crack propagates from the ovular aperture 580 toward the spar caps, loading through the web 544 may be transferred to the first and second spar caps 542A, 542B which may cause failure to occur in the first and second spar caps 542A, 542B as previously described. In some examples, a doubler may be included on the spar portion 540 and function to transfer loading over the aperture 580. In examples where the spar portion 540 includes the doubler, the doubler may be designed to fail upon exceeding the threshold load such that the web 544 may fail prior to failure in the first and second spar caps 542 A, 542B. In some examples, the aperture 580 may be used on the spar portion440.

[0096] Figure 7 illustrates a perspective view of another embodiment of a spar portion 640 including a doubler 670 configured to be positioned on a craft, according to exemplary embodiments of the present disclosure. As shown, the spar portion 640 includes a first and second aperture 680A, 680B on the web 644 having the doubler 670 coupled between the first and second apertures 680 A, 680B by way of one or more fasteners 672. One or more aspects of the example shown in Figure 7 may function similar to those described with respect to Figures 5A, 5B, and / or 6.

[0097] It should be understood that any of the examples shown in Figures 3 A through 7 may be combinable with each other or with different examples. As such, various aspects from the description of examples in one figure may be combinable with various aspects from the description of examples in another figure. For example, a doubler from one example may be combined with an aperture from another example, or multiple apertures and / or multiple doublers may be combined. Thus, the examples are not intended to be limited to the Figures with which they are described, but rather with reference to the detailed description as a whole.

[0098] In operation, an aircraft structure coupled to a body of the aircraft may be selectively detached from the body. For example, the aircraft structure may include a first portion distal to the body, a second portion proximal to the body, and an interface between the first and second portions. The interface may include a web and a cap coupled to the web, where a thickness of the web and the cap of the interface is less than a thickness of the first and second portions. A doubler may be coupled to the interface by an adhesive bond at the cap and by one or more fasteners at the web.

[0099] A load may be produced in the aircraft structure that exceeds a threshold load of the interface between the first and second portions. In some examples, shearing may occur in the fasteners coupling the doubler to the web. In such examples, shearing thefasteners may be based on exceeding the threshold load. For example, the threshold load may result in a shear stress that is greater than a maximum shear strength of the fasteners.

[0100] In some examples, the adhesive bond between the doubler and the cap may de-couple. In such examples, the de-coupling of the adhesive bond may be based on the shearing of the fasteners. For example, the shearing of the fasteners may result in more load transferring between the doubler and the cap which may produce a stress that exceeds the adhesive bond strength resulting in the adhesive bond failing.

[0101] In some examples, the cap and the web may fracture at the interface. In such examples, fracturing the cap and the web may be based on de-coupling the adhesive bond. For example, de-coupling of the adhesive bond may reduce an amount of loading transferred between the cap and the doubler which may increase an amount of loading that is transferred through the cap and / or the web. In some examples, the amount of loading that is transferred through the cap and / or the web exceeds the load carrying capabilities of the respective parts, resulting in fracturing.

[0102] In some examples, the first portion may be detached from the second portion. In such examples, detaching the first portion from the second portion may be based on fracturing of the cap and web at the interface. For example, fracturing of the cap and the web at the interface may result in the interface no longer being able to support loading produced by the first portion. This may cause the first portion to detach from the second portion.

[0103] While the above detailed description describes various aspects of the breakaway feature with respect to a spar, in other examples another structure may include the breakaway feature. For example, the breakaway feature, one or more doublers, and / or one or more apertures may be included on a longeron, a keel, a stiffener, a rib, and engine nacelle, a tail joint, and / or a cabin. Thus, the above described examples are not intended tobe limited to application on a spar and may be incorporated onto any suitable structure to form the breakaway feature.

[0104] The above detailed description describes various features and functions of the disclosed systems, apparatus, and methods with reference to the accompanying figures. In the figures, similar symbols typically identify similar components, unless context dictates otherwise. The example embodiments described herein and in the figures are not meant to be limiting. Other embodiments can be utilized, and other changes can be made, without departing from the scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, separated, and designed in a wide variety of different configurations, all of which are explicitly contemplated herein.

Claims

WHAT IS CLAIMED IS:

1. An aircraft comprising: a body; a structure coupled to the body having a first portion proximal to the body and a second portion distal to the body, and a breakaway feature disposed between the first and second portions, wherein the breakaway feature comprises an aperture and a doubler, the breakaway feature being configured to fail upon exceeding a threshold load, such that the second portion detaches from the first portion.

2. The aircraft of claim 1, wherein the structure comprises a web and at least one cap coupled to the web, wherein the aperture is disposed on the web and the at least one cap, and the aperture forms an arcuate notch in the web.

3. The aircraft of claim 2, wherein the doubler is disposed across the aperture on the at least one cap.

4. The aircraft of claim 2, wherein a thickness of the web at a cross-section having the aperture is greater than a thickness of the web on the first and second portions.

5. The aircraft of claim 1, wherein the structure comprises a web and at least one cap coupled to the web, wherein the aperture is disposed solely on the web.

6. The aircraft of claim 5, wherein the aperture is a first aperture and the web further comprises a second aperture adjacent to the first aperture and defining a portion of the web therebetween.

7. The aircraft of claim 6, wherein the doubler forms an H-shape and is coupled to the portion of the web between the first and second apertures.

8. The aircraft of claim 7, wherein upon exceeding the threshold load, the doubler and the portion of the web between the first and second apertures is configured to fail prior to the at least one cap.

9. An aircraft comprising: a body; a wing coupled to the body; a spar disposed longitudinally within the wing, the spar comprising: a first portion, a second portion, and a third portion, wherein the first portion is proximal to the body, the second portion is between the first and third portions, and the third portion is distal to the body; wherein each of the first, second, and third portions comprise a web and at least one spar cap coupled to the web, and wherein a thickness of a portion of the web and the at least one spar cap of the second portion is less than a thickness of the first and third portions; and a doubler coupled to the at least one spar cap of the second portion; wherein upon exceeding a threshold load, the spar is configured to fail at the second portion.

10. The aircraft of claim 9, wherein the doubler is a first doubler and the aircraft further comprises a second doubler coupled to the web of the second portion.

11. The aircraft of claim 10, wherein the first doubler is coupled to the at least one spar cap of the second portion solely using an adhesive, and the second doubler is coupled to the web of the second portion solely using at least one fastener.

12. The aircraft of claim 9, wherein the spar comprises a composite laminate and the thickness of the portion of the web and the at least one spar cap of the second portion comprises locally reduced plies such that the thickness of the second portion is non-constant.

13. The aircraft of claim 12, wherein the spar comprises an upper and lower spar cap, and the upper spar cap comprises the locally reduced plies.

14. The aircraft of claim 10, wherein a thickness of the first doubler is non-constant and a thickness of the second doubler is constant.

15. The aircraft of claim 14, wherein the first and second doublers each comprise a composite laminate.

16. The aircraft of claim 14, wherein the first and second doublers each comprise a metal.

17. The aircraft of claim 10, wherein the first and second doublers are part of a single doubler, and the first doubler forms an angle with the second doubler.

18. The aircraft of claim 17, wherein the first and second doublers form a perpendicular angle with each other.

19. The aircraft of claim 10, wherein upon exceeding the threshold load, the at least one fastener of the second doubler is configured to fail before the adhesive of the first doubler.

20. The aircraft of claim 10, wherein the threshold load produces a shear stress at the second portion greater than a shear strength of the at least one fastener.

Images