AIRCRAFT FLOW BODY

Abstract

An aircraft flow body comprising a rib bounded by and fixedly attached to an outer skin, wherein the outer skin and the rib are configured to plastically deform when the outer skin is subjected to an impact load in a leading edge region of the airflow body, wherein the stiffness of the outer skin is greater than or equal to the stiffness of the rib when deformed by the impact load.

Claims

1. A aircraft flow body comprising: a rib bounded by and fixedly attached to an outer skin; wherein the outer skin and the rib are configured to plastically deform when the outer skin is subjected to an impact load in a leading edge region of the flow body; wherein a stiffness of the outer skin is greater than or equal to a stiffness of the rib when deformed by the impact load.

2. An aircraft flow body according to claim 1, wherein the rib comprises a first rib portion and a second rib portion; wherein the first rib portion is attached to the outer skin in the leading edge region; wherein the stiffness of the outer skin is greater than or equal to a stiffness of the first rib portion when deformed by the impact load; and, wherein the first rib portion is attached to the second rib portion by a lap joint.

3. An aircraft flow body according to claim 2, wherein the lap joint is orientated substantially perpendicular to a direction of the impact load.

4. An aircraft flow body according to claim 2, wherein the lap joint comprises a single row of shear fasteners.

5. An aircraft flow body according to claim 2, wherein the first rib portion and second rib portion are formed from dissimilar materials.

6. An aircraft comprising an aircraft flow body according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the present invention presented herein are described below with reference to the following drawings, in which:

[0017] FIG. 1 provides a schematic plan view of an aircraft comprising aircraft flow bodies according to embodiments of the present invention;

[0018] FIG. 2 provides a pair of schematic cross-sectional views vertically through the line A-A of the aircraft flow body of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] With reference to FIG. 1, an aircraft 100 is shown comprising a plurality of flow bodies such as the wing 101, horizontal tail 103, vertical tail 105, and engine nacelle 107. Each flow body comprises an internal structure comprising an outer skin attached to underlying spars and/or ribs and/or stiffeners. The aircraft comprises a set of orthogonal aircraft axes, comprising a longitudinal X axis, a lateral (spanwise) Y axis, and a vertical Z axis. The region of each flow body existing in the most positive X direction is commonly referred to as the leading edge region of the flow body and is most susceptible to impact from foreign objects travelling (relatively) in the X direction. The wing 101 further comprises a plurality of smaller flow bodies in the form of slats 109, which are movably attached the forward (leading edge) region of the wing 101. These are constructed in substantially the same way as the larger structures in that they comprise an outer skin attached to underlying spars and/or ribs and/or stiffeners.

[0020] With reference to FIG. 2, a non-impacted flow body in the form of a slat 200 is shown on the left hand side.

[0021] The slat 200 comprises an outer skin 203 that bounds, and is fixedly attached to, a rib 201 and a spar 204 that lie internally within it. The outer skin 203 is formed from a thin sheet alloy aluminum material (e.g., 2024 series aluminum alloy material), but any suitable metallic or composite material may alternatively be used. The rib 201 comprises a first rib portion 207 attached by a lap joint 211 with a single row of fasteners 213 to a second rib portion 209. The first rib portion 207 is attached to the outer skin 203 in the leading edge region 205 by fasteners (not shown) and is formed from a thin sheet alloy aluminum material (e.g., 2024 series aluminum alloy material), but any suitable metallic or composite material may alternatively be used. The second rib portion 209 is attached to the spar 204 aft of the leading edge region 205 by fasteners (also not shown) and is formed from a thin sheet alloy aluminum material (e.g., 2024 series aluminum alloy material), but any suitable metallic or composite material may alternatively be used. The second rib portion 209 comprises a connection portion 215 that attaches to a slat kinematic system for moving the slat 200 in operation. The rib 201 is oriented substantially vertically in a plane lying parallel to the XZ plane. The spar 204 is oriented substantially vertically in a plane lying parallel to the YZ plane and is constructed from a sheet aluminum alloy material (e.g., or 7010 series or 2014 series aluminum alloy), but any suitable metallic or composite material may alternatively be used. During normal operation of the slat 200, the outer skin 203 is subjected to aerodynamic pressure loads, which are transferred via spar 204, the rib 201 and the kinematic system to the wing 101. The components in the slat 200 i.e., the skin 203, rib 201 and spar 204, are also subjected to inertial loads caused by accelerations of the aircraft 100 during take-off, cruise and landing. In response to this loading the components elastically deform and deflect within predetermined limits that are pre-determined by each component's load amount, sectional properties and material mechanical properties.

[0022] Referring to the right hand side of FIG. 2, the non-impacted flow body shown on the left hand side is also shown in an impacted and plastically deformed scenario, where an impact load L acts against the leading edge region 205 of the slat 200 in a X direction.

[0023] The stiffness of the outer skin 203 is equal to the stiffness of the first rib portion 207 at the location where impact load L exerts itself on the structure, such that the skin 203 and first rib portion 207 deform uniformly in reaction to the impact load L, as shown. The impact kinetic energy is absorbed by slat 200 through deformation of the skin 203 and the first rib portion 207, and not by the second rib portion 209 and spar 204, which remain only elastically deformed in response to the impact load. In the example shown, the lap joint 211 is not sheared, however for an impact of a higher impact energy, the lap joint 211 is configured to shear at a predetermined load level, which redistributes the load back to the skin 203, which may deform further.

[0024] The stiffness of the first rib portion 207 may be tailored by changing the sectional properties of the first rib portion 207 or by choosing a material for the first rib portion 207 that has a lower mechanical stiffness in the direction of the applied loading or both. Where less deformation of the skin 203 is desired, for example to prevent rupture of the skin 203, e.g., adjacent to the attachment interface with rib 201, the stiffness of the first rib portion 207 may be reduced to a value less than the stiffness of the skin 203 but sufficient to support the loading otherwise experienced during normal operation. Similarly where more deformation of the skin 203 is desired, the stiffness of the first rib portion 207 may alternatively be increased to a value higher than the stiffness of the skin 203 but sufficient to support the loading experienced during normal operation.

[0025] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. For example, it should be appreciated that the rib 201 may be a unitary component with the required stiffness, rather than a rib 201 with separate portions. The rib 201 may further be attached to only the skin 203 or additional structural components than the skin 203 or spar 204.

[0026] This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms comprise or comprising do not exclude other elements or steps, the terms a or one do not exclude a plural number, and the term or means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.

[0027] While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure.