RAT Door Linkage Motion Limiter for Over-Rotation Protection
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Solution Overview
Problem
Aircraft ram air turbine (RAT) door linkages lack rotational limiters, leading to potential damage from over-rotation during handling and installation, which can result in stress concentrations and fatigue in clevis components.
Innovation Solution
A motion limiter system comprising a block with specific openings and tabs that engage the clevis cavity apex to prevent over-rotation, using a lightweight, non-marring material to absorb rotational stress and prevent metal-to-metal contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If no motion limiter is installed on the RAT door linkage, then the linkage can rotate freely during deployment and operation, but the linkage components are vulnerable to over-rotation damage and stress concentrations during handling and installation
Solution Approach 1:
A motion limiter block made of lightweight, non-marring material is introduced as an intermediary component between the door linkage arm and the clevis. This block engages with the clevis cavity apex to prevent over-rotation during handling and installation, while allowing normal operational rotation. The non-marring material prevents damage to the clevis components during abnormal conditions.
Solution Approach 2:
The motion limiter block with its non-marring material provides beforehand cushioning by preventing direct metal-to-metal contact between the clevis tang and cavity apex. The block absorbs rotational stress and prevents damage before it can occur to the critical clevis components during handling and installation operations.
2Reliability
If a traditional metal motion limiter is used, then over-rotation protection is provided, but the limiter itself can cause marring or damage to the clevis components through metal-to-metal contact
Solution Approach 1:
The material parameter of the motion limiter is changed from traditional metal to a lightweight, non-marring material. This parameter change maintains the over-rotation protection function while eliminating the harmful effect of metal-to-metal contact and marring to the clevis components.
Solution Approach 2:
The motion limiter block is designed as a sacrificial component made from inexpensive, non-critical material. If damage occurs during handling, the block can be replaced rather than the expensive clevis components, serving as a disposable protective element.
3Strength
If the motion limiter uses dense, strong material, then structural strength is improved, but the weight of the linkage system increases
Solution Approach 1:
The material density parameter is changed from high (metal) to low (lightweight material). The motion limiter block achieves sufficient strength for its protective function while maintaining low weight, as it does not need to bear structural loads like the main linkage components.
Solution Approach 2:
The linkage system is segmented into critical structural components (requiring strong, heavy material) and the non-critical motion limiter component (using lightweight material). This segmentation allows optimization of each part's material properties according to its specific functional requirements.
Data Source
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AI summary
Disclosed is an aircraft system comprising: a linkage (68) comprising a first end (120), an opposing second end (130) and a clevis (160) therebetween; a motion limiter (400) configured to engage the clevis; wherein: the first end is configured for connecting to one of a strut of a ram air turbine (RAT) and an enclosure door, and the second end is configured for connecting with another of the strut and the door; and the motion limiter limits rotation between the first end of the linkage and the second end of the linkage.