Wing Tip Device Attachment Using Pivotable Joints
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Solution Overview
Problem
Current methods for attaching wing tip devices to aircraft wings are inefficient, leading to high stresses and structural reinforcement needs due to small moment arms, increased weight, and complexity from cyclic loading and differential expansion, resulting in unpredictable load distribution and costly assembly processes.
Innovation Solution
A wing tip device attachment system with multiple mounting formations allowing relative movement in spanwise, chordwise, and vertical directions, utilizing composite wing spars for load reaction and a statically determinate assembly with pivotable joints for easy installation and reduced stress, incorporating a large moment arm to distribute loads efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If splice plates or butt straps are used to attach wing tip devices, then the wing tip device can be attached to the wing, but the moment arm available to react loads is very small and local concentrated loads require structural reinforcement
Solution Approach 1:
The patent transitions from in-plane attachment (within the wing span plane) to out-of-plane attachment by extending the wing tip device vertically. This dimensional change creates a large vertical moment arm that efficiently reacts aerodynamic loads without requiring additional in-plane structural reinforcement, thereby resolving the contradiction between load reaction capability and structural weight.
Solution Approach 2:
The patent introduces a pivotable joint that allows the wing tip device to rotate relative to the wing, transforming the rigid attachment into a dynamic system. This dynamic capability enables the structure to adapt to thermal expansions and cyclic loading while maintaining effective load reaction through the vertical moment arm, reducing the need for over-engineered reinforcement.
2Reliability
If abutting plates joined by tension bolts are used, then the wing tip device can be attached, but cyclic loading requires pre-tensioned bolts with interference fit adding complexity
Solution Approach 1:
The patent extracts the complex pre-tensioned bolt system with interference fit from the design and replaces it with a simpler pivotable joint mechanism. The pivotable joint achieves reliable fatigue resistance through its geometric configuration and load path, eliminating the need for complex pre-tensioning procedures while maintaining reliability under cyclic loading.
Solution Approach 2:
The patent introduces a pivotable joint as an intermediary element between the wing tip device and the wing structure. This intermediary component mediates the connection by providing a controlled rotation capability that accommodates thermal and fatigue effects without requiring complex pre-tensioned fasteners, thereby reducing device complexity while maintaining reliability.
3Stress or pressure
If multiple joining locations are used to spread load, then the load per joining location is reduced, but a statically indeterminate system is created making loads difficult to predict
Solution Approach 1:
The patent segments the load path into distinct components: the vertical moment arm handles aerodynamic loads, while the pivotable joint handles thermal and fatigue effects. This segmentation creates a statically determinate system where each component's function is clear and predictable, eliminating the load distribution uncertainty associated with multiple joining locations in traditional designs.
4Strength
If heavy bolting and large surface area contact are used, then the interface is sensitive to geometry differences requiring fettling
Solution Approach 1:
The patent replaces the rigid, geometry-sensitive heavy bolting system with a dynamic pivotable joint that accommodates geometric variations through controlled rotation. This dynamic approach maintains interface strength while eliminating the need for fettling, as the pivotable joint naturally compensates for minor geometry differences between components during assembly.
Data Source
AI summary
An aircraft wing subassembly including: a wing skin defining a first outer surface, and, a structural reinforcement member, the structural reinforcement member defining a second outer surface, wherein the structural reinforcement member is arranged within the wing such that the first outer surface and the second outer surface form part of an outer wing surface.