Integral Subfloor Hull for Rotary Wing Aircraft Weight Reduction
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Solution Overview
Problem
Current rotorcraft subfloor structures face challenges in reducing structural weight, design complexity, assembly work, and production costs due to increasing cruising speeds, payload demands, and the need for lighter, cleaner, and longer-range aircraft, while also dealing with high local stress levels and inefficiencies in composite material usage.
Innovation Solution
A subfloor structure featuring an integral U-shaped subfloor bowl hull with upward web portions and external extensions, made from composite or metal materials, which integrates main load-bearing components to reduce assembly workload and increase mechanical performance, eliminating discrete load deflections and stress concentrations by providing a continuous, tangentially smooth load path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a classical framework construction with discrete longerons and ribs is used, then the subfloor structure provides adequate structural support, but the structural weight and assembly complexity increase
Solution Approach 1:
The patent merges the discrete longerons and bottom shell into a single integrated load-bearing structure. The continuous curved load path integrates what were previously separate components (longerons, ribs, bottom shell) into one unified structure, eliminating the need for discrete connections and reducing overall structural weight while maintaining strength.
Solution Approach 2:
The integrated structure is segmented into functional zones: the bottom shell portion, upward web portions, and upper external extensions. This segmentation allows optimization of material distribution in different regions while maintaining the continuous load path, reducing weight compared to a fully discrete framework.
2Shape
If discrete longerons with kink locations are used to adapt to outer loft geometry, then the structure fits the aircraft envelope, but local stress concentrations increase
Solution Approach 1:
The patent employs continuous curved surfaces throughout the load-bearing structure, eliminating sharp kinks and angular transitions. The bottom shell, web portions, and extensions are all defined by smooth continuous curves that adapt to the outer loft geometry while distributing stresses uniformly without local concentrations.
Solution Approach 2:
By integrating the longerons into the bottom shell as a continuous structure, the patent eliminates the discrete kink locations where stress concentrations occurred in classical designs. The merged structure provides smooth transitions that adapt to the aircraft envelope while maintaining structural integrity.
3Adaptability or versatility
If multiple separate components are assembled to form the subfloor structure, then manufacturing flexibility is maintained, but assembly workload and production costs increase
Solution Approach 1:
The patent combines multiple load-bearing components into a single integrated structure that can be manufactured as one piece using composite material processes. This merging eliminates the need for assembling discrete longerons, ribs, and bottom shells, dramatically reducing assembly workload and production costs while maintaining adaptability through tailored composite layups.
Solution Approach 2:
The integrated structure is manufactured using composite materials that allow for complex three-dimensional shapes to be formed in single-piece construction. The composite manufacturing process provides the flexibility needed to adapt to different outer loft geometries while enabling the integration of multiple functions into one component.
4Reliability
If classical framework construction is used, then structural reliability is maintained through discrete connections, but the number of joints and potential failure points increases
Solution Approach 1:
By merging the discrete longerons and bottom shell into a single continuous structure, the patent eliminates numerous joints and connection points that served as potential failure points in classical designs. The integrated structure maintains reliability through continuous material paths while reducing complexity by removing the need for discrete connections.
Data Source
AI summary
The invention relates to a subfloor structure with an integral hull, for a rotary wing aircraft. The subfloor structure comprises an integral subfloor hull that defines in one piece, upward web portions acting as longerons and a bottom central portion offering both load bearing capabilities and aerodynamical loft features. The subfloor structure is useful for rotary wing aircrafts such as helicopters, and is e.g. made of composite and/or light alloy such as aluminum.