Strut-Braced Wing Structural Arrangement
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Solution Overview
Problem
Strut-braced wings face structural inefficiencies due to large vertical moments induced by tension loads in struts, which are not effectively managed, leading to axial loads that conventional wing spars are not designed to handle, especially in high-aspect-ratio, swept-wing aircraft.
Innovation Solution
The aircraft design features a center wing structure coupled to the fuselage with outer wing structures supported by struts, where each strut is attached below and aft of the wing-fuselage joint, and the outer wing structures are connected to the center wing at mid-wing joints located between engine mounting locations and strut-wing joints, reducing axial loads and distributing spanwise bending moments efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the strut-fuselage joint is located aft of the wing-fuselage joint to reduce interference drag, then aerodynamic performance is improved, but large vertical moments and axial loads are induced on the wings and struts
Solution Approach 1:
The wing structure is segmented into a center wing structure and outer wing structures that can be independently connected. The outer wing structures are connected to the center wing structure at mid-wing joints located between the engine mounting locations and strut-wing joints, allowing the structure to segment and distribute the large vertical moments and axial loads rather than concentrating them at the wing root.
Solution Approach 2:
The center wing structure acts as an intermediary element between the outer wing structures and the fuselage. It receives the vertical moments and axial loads from the outer wing structures and transfers them to the fuselage at the wing-fuselage joint, which is positioned ahead of the strut-fuselage joint, thereby reducing the moment arm and the induced vertical moments.
2Object-affected harmful factors
If high-aspect-ratio wings are used to increase aerodynamic performance, then aspect ratio is improved, but the vertical thickness of the airfoil section at the wing root becomes shallower, reducing structural capacity to accommodate axial loads
Solution Approach 1:
The wing is divided into multiple structural segments (center wing structure and outer wing structures) connected at mid-wing joints. This segmentation allows the shallower airfoil section at the wing root to avoid carrying the full axial load by distributing it through the outer wing structures and mid-wing joints, thereby maintaining structural capacity without increasing root thickness.
Solution Approach 2:
The structural solution moves from a two-dimensional wing root thickening approach to a three-dimensional distribution system. By introducing mid-wing joints and outer wing structures, the load path is extended in the spanwise dimension, allowing axial loads to be distributed along the wing span rather than concentrated at the root, thereby accommodating loads without increasing root thickness.
3Device complexity
If conventional cantilevered wing configuration is used, then structural simplicity is maintained, but spanwise bending moments are not effectively reduced compared to strut-braced configurations
Solution Approach 1:
The wing structure is segmented into a center wing structure and outer wing structures connected at mid-wing joints. This segmentation allows the outer wing structures to be supported by struts, effectively reducing spanwise bending moments in the outer portions of the wing while maintaining overall structural integrity and simplicity.
Data Source
AI summary
An aircraft has a fuselage, a wing assembly, and a pair of struts. The wing assembly has a center wing structure and a pair of outer wing structures. The center wing structure is coupled to the fuselage at a wing-fuselage joint, and has a pair of engine mounting locations respectively on opposite sides of a wing centerline. Each of the struts is coupled to the fuselage at a strut-fuselage joint, and to one of the outer wing structures at a strut-wing joint. Each strut-fuselage joint is located below and aft of the wing-fuselage joint. Each outer wing structure is coupled to the center wing structure at a mid-wing joint located no further inboard than the engine mounting location, and no further outboard than the strut-wing joint.