Aircraft Seat Track Fitting With Shear Pads
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Solution Overview
Problem
Conventional seat track fittings in aircraft structures have limited strength capabilities, often failing under loads between 11,000 lbs and 14,000 lbs due to bending stresses caused by cantilevered load paths, which poses a challenge in meeting the strict weight restriction requirements of aircraft designs.
Innovation Solution
The development of seat track fitting assemblies with shear pads that protrude outwardly from a central flange, featuring integrally formed tensile and shear flanges, which can react both shear and tensile loads, and a retention mechanism that secures the fitting to the seat track, enhancing the load-carrying capacity beyond conventional designs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional cantilevered shear pad design is used, then the structure is simple and easy to manufacture, but the load-carrying capacity is limited to 11,000-14,000 lbs due to bending stresses
Solution Approach 1:
The shear pad is divided into two distinct functional segments: a shear flange for resisting horizontal shear loads and a tensile flange for resisting vertical tensile loads. This segmentation allows each flange to be optimized for its specific load type, eliminating the bending stresses that limited conventional cantilevered designs while maintaining manufacturability through integral forming.
Solution Approach 2:
The invention transitions from a single-plane cantilevered configuration to a multi-dimensional structure with flanges extending in different directions. The shear flange extends horizontally to resist shear loads, while the tensile flange extends vertically to resist tensile loads, creating a three-dimensional load path that eliminates bending moments and significantly increases load-carrying capacity to over 14,000 lbs.
2Strength
If the shear pad size is increased to handle higher loads, then the load-carrying capacity improves, but the weight increases which violates aircraft weight restrictions
Solution Approach 1:
Different portions of the shear pad are given different geometric qualities optimized for their specific function: the shear flange has a geometry optimized for shear resistance, while the tensile flange has a geometry optimized for tensile resistance. This local optimization allows the structure to achieve high load-carrying capacity with minimal material, reducing weight while maintaining strength capabilities exceeding 14,000 lbs.
Solution Approach 2:
The shear pad functions as a composite structural element combining two different flange configurations (shear and tensile) in a single integrated component. This composite approach allows the fitting to efficiently distribute and resist multiple types of loads simultaneously, achieving high strength-to-weight ratio that satisfies both load-carrying requirements and aircraft weight restrictions.
3Reliability
If conventional shear pads are used, then the design is straightforward, but the fittings fail at loads between 11,000-14,000 lbs due to bending stresses
Solution Approach 1:
By segmenting the shear pad into distinct shear and tensile flanges, each optimized for its specific load type, the invention eliminates the bending stress concentration that caused conventional fittings to fail at 11,000-14,000 lbs. This segmentation creates reliable, predictable load paths that significantly improve fitting reliability while the integral forming process keeps the configuration manageable.
Data Source
AI summary
A seat track fitting assembly can include a seat track having a channel sized and shaped to removably, coupleably receive a seat track fitting, which seat track fitting can include a central flange having a lug aperture which is sized and shaped to be coupleable to a payload component, and at least a pair of shear pads, with each one of the shear pads protruding outwardly from opposing sides of the central flange and including a shear flange, and a tensile flange, wherein the tensile flange and the shear flange are integrally formed with the central flange. Related methods are also provided.