Aircraft Pin Hook Lock Assembly Rigging Tolerance
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Solution Overview
Problem
Rigging tolerances can cause the pin in hook and pin lock assemblies of aircraft landing gear to engage sub-optimally, leading to potential pin fracture due to non-central loading, which is exacerbated by increasing pin size to mitigate this issue, resulting in increased weight and cost.
Innovation Solution
The pin is designed with a prominent centre portion and axially spaced outer portions, where the centre portion's contact face is radially spaced further from the longitudinal axis than the recessed faces, ensuring contact occurs at the centre even with offsets, thereby distributing load centrally and reducing the risk of fracture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pin size is increased to account for rigging tolerances and sub-optimal engagement, then the reliability of the lock assembly is improved, but the weight and cost of the landing gear assembly increase
Solution Approach 1:
The pin features a prominent centre portion with a contact face that is radially spaced further from the longitudinal axis than the outer portions. This local geometric modification concentrates the contact area at the centre portion, ensuring reliable engagement even with rigging tolerances, while the outer portions have recessed faces that reduce material where not needed, avoiding overall pin size increase
Solution Approach 2:
The pin is divided into distinct segments: a centre portion and one or more outer portions axially spaced from the centre. The centre portion defines the contact face at a greater radial distance, while outer portions define recessed faces at smaller radial distances. This segmentation allows the contact function to be localized without increasing the overall pin dimensions
2Reliability
If the pin size is increased to account for rigging tolerances and sub-optimal engagement, then the reliability of the lock assembly is improved, but the cost of the landing gear assembly increases
Solution Approach 1:
The pin features a prominent centre portion with a contact face that is radially spaced further from the longitudinal axis than the outer portions. This local geometric modification concentrates the contact area at the centre portion, ensuring reliable engagement even with rigging tolerances, while the outer portions have recessed faces that reduce material where not needed, avoiding overall pin size increase
Solution Approach 2:
The pin is divided into distinct segments: a centre portion and one or more outer portions axially spaced from the centre. The centre portion defines the contact face at a greater radial distance, while outer portions define recessed faces at smaller radial distances. This segmentation allows the contact function to be localized without increasing the overall pin dimensions
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
An aircraft assembly (10) including a first part (12) having a pin (30) and a second part (22) having a hook (26) that is movable in an engagement plane to engage the pin to hold the first part in a condition relative to the second part. The pin has a central portion (30a) and one or more axially spaced outer portions (30b), the prominent portion being prominent with respect to the outer portions in the engagement plane to cause contact to be made between the hook and the in within the central portion rather than an outer portion.