Aircraft Fuselage Frames with Normal-Aligned Webs for Pressurization Resistance
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Solution Overview
Problem
The existing aircraft fuselage structures with double curvature in the nose and tail sections do not provide optimal resistance to pressurization forces due to non-orthogonal webs of circumferential frames, which compromises structural integrity.
Innovation Solution
The structural assembly features circumferential frames with webs and flanges orthogonal to the fuselage skin, where a virtual straight line segment intersecting the skin is substantially orthogonal, ensuring the web extends close to the normal of the skin, providing enhanced resistance to pressurization forces. These frames are designed with specific angular orientations and extents to maximize resistance, and are connected to stringers and windshield frames for additional support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If circumferential frames with T-shape, I-shape or L-shape sections are used in double curvature regions, then the frames can be manufactured with standard shapes, but the webs are not orthogonal to the fuselage skin resulting in suboptimal resistance to pressurization forces
Solution Approach 1:
The patent applies local quality by making the web orientation angle specific to each location on the fuselage. The web is oriented at an angle α relative to the transverse plane, where α varies depending on the local double curvature geometry. This ensures that at each point, the web is substantially orthogonal to the fuselage skin surface, optimizing pressurization resistance locally while accommodating the overall double curvature shape of the nose or tail section.
Solution Approach 2:
The patent changes the geometric parameter of the web orientation angle α from a fixed value (as in cylindrical sections) to a variable parameter that adapts to the local curvature. The angle α is determined by the requirement that the web be orthogonal to the fuselage skin at each location, transforming the frame geometry to match the local surface normal direction in double curvature regions.
2Strength
If the web of circumferential frames is oriented orthogonal to the fuselage skin in double curvature regions, then resistance to pressurization forces is optimized, but the frame geometry becomes more complex and difficult to manufacture
Solution Approach 1:
The complexity is localized to specific regions. In cylindrical fuselage sections, standard frames with webs orthogonal to the skin are used. In double curvature regions (nose and tail sections), the web orientation angle α is adjusted locally to maintain orthogonality to the skin. This localized adaptation limits the complexity to only where double curvature exists, rather than complicating the entire fuselage structure.
Solution Approach 2:
The fuselage is segmented into different regions: cylindrical sections with standard frame geometry and double curvature sections (nose and tail) with adapted frame geometry. Each segment uses the appropriate frame configuration, allowing standard manufacturing processes to be used where possible while applying optimized geometry only where structurally necessary.
Data Source
AI summary
In order to allow an aircraft fuselage structure to provide optimum resistance to pressurization loads in a fuselage region with a double curvature, the fuselage structure includes a circumferential frame oriented so that the web of the circumferential frame has an orientation close to the local normal to the skin of the fuselage.