Aircraft Rib Assembly Load Reaction via Stiffener
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Solution Overview
Problem
Existing aircraft rib assemblies for control surfaces require individual manufacturing for each position along the wingspan due to varying spar depth and wing skin geometry, leading to increased weight, complexity, and maintenance challenges, as well as susceptibility to damage and thermal strains.
Innovation Solution
A rib assembly with a single limb attached to the rear spar at an intermediate point, utilizing a stiffener that reacts loads through the spar, eliminating the need for multiple fasteners on the wing skin and allowing for a continuous load reaction surface, thereby reducing manufacturing variability and weight, and simplifying replacement and assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the rib is attached at the extreme top and bottom of the rear spar to provide the largest moment arm for load reaction, then the structural strength and load reaction capability are improved, but the manufacturing complexity increases because each rib must be individually manufactured for its position along the wingspan due to varying spar depth
Solution Approach 1:
The rib assembly is divided into modular components: a standardized rib body and separate stiffener elements. The stiffeners can be individually positioned and attached to the spar at different locations, allowing the system to accommodate varying spar depths without requiring custom-manufactured ribs for each position along the wingspan.
Solution Approach 2:
The rib design incorporates universal attachment features that allow the same rib component to be used at multiple positions along the wingspan. The stiffeners provide adaptable load reaction capability through their positioning relative to the spar, enabling a single rib design to serve multiple locations without individual manufacturing.
2Strength
If the rib is attached at the extreme top and bottom of the rear spar to provide the largest moment arm, then the structural strength is improved, but the weight increases due to the need for thick skin material and high diameter bolts throughout the wingspan to support the structural requirements
Solution Approach 1:
The stiffeners are positioned strategically at specific locations along the spar where additional strength is needed, rather than requiring uniformly thick skin material throughout the entire wingspan. This localized reinforcement approach provides the necessary structural strength at critical points while maintaining lighter weight in other areas.
Solution Approach 2:
The rib assembly utilizes composite construction combining the rib body, stiffeners, and attachment components to achieve high strength-to-weight ratio. The composite structure allows for optimized strength distribution without requiring excessive material thickness throughout the entire wingspan.
3Reliability
If multiple fasteners are used to attach the rib to both wing skins to provide secure fixation, then the reliability of attachment is improved, but the device complexity and assembly cost increase due to additional parts and assembly steps
Solution Approach 1:
The stiffener assembly integrates multiple attachment functions into a single integrated component structure. The stiffeners are designed to work together with the rib and spar to provide secure fixation, reducing the need for separate fasteners and simplifying the assembly process while maintaining reliable attachment.
4Reliability
If the wing skin thickness is increased throughout the wingspan to support the structural requirements for rib attachment, then the strength and reliability of the attachment system is improved, but the weight increases by approximately 10 kg per meter of wingspan
Solution Approach 1:
The structural reinforcement is applied locally at the rib attachment positions through the stiffener components rather than uniformly throughout the entire wingspan. This localized approach provides the necessary reliability at critical attachment points while avoiding the weight penalty of increased skin thickness across the entire wingspan.
Data Source
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AI summary
A spoiler rib assembly (110) comprises a rib (144) which is attached to a spar (112) on one side and a stiffener (160) on a second side which abuts the upper and lower flanges of the spar in order to react the loads. The invention is applicable to the mounting of any movable control surface.