Aircraft Landing Gear Leaf Spring Without Drilled Attachments
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Solution Overview
Problem
Aircraft landing gear assemblies using fibre composite leaf springs face challenges such as stress concentrations, delamination, and component failure due to post-processing methods like drilling, which can lead to performance loss and increased manufacturing complexity.
Innovation Solution
The design features a fibre composite leaf spring with inner layers shorter than outer layers, arranged to prevent delamination and stress concentrations, coupled to a mounting assembly that mechanically restrains the spring to prevent twisting and ensure bending in a direction perpendicular to the composite layers, reducing the risk of failure and simplifying manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If post-processing methods like drilling are used to couple the leaf spring to landing gear elements, then the leaf spring can be securely attached, but stress concentrations and delamination occur leading to component failure
Solution Approach 1:
The invention extracts and eliminates the harmful post-processing step (drilling) from the manufacturing process. Instead of drilling holes to attach the leaf spring, the design uses a clevis-shaped fitting that attaches to the leaf spring's end without requiring holes through the composite material, thereby avoiding stress concentrations and delamination while maintaining secure attachment
Solution Approach 2:
The invention introduces a clevis-shaped fitting as an intermediary component between the leaf spring and the landing gear elements. This fitting serves as a mediator that provides secure attachment without requiring direct drilling into the composite leaf spring, thus protecting the integrity of the composite material while achieving reliable coupling
2Ease of manufacture
If the leaf spring is made with uniform layers throughout, then manufacturing is simpler, but stress concentrations occur at layer ends leading to delamination and failure
Solution Approach 1:
The invention applies local quality by varying the number of composite layers at different locations along the leaf spring. Specifically, the leaf spring has a first region with a first number of layers and a second region with a second number of layers, creating a stepped configuration. This local variation in layer structure prevents stress concentrations at layer ends and reduces delamination risk, while the overall manufacturing process remains relatively simple using conventional composite layup techniques
3Ease of operation
If conventional metal coil springs are used as down lock springs, then the landing gear assembly can be moved to deployed condition, but the profile is high increasing likelihood of impact damage
Solution Approach 1:
The invention changes the physical parameters of the down lock spring by replacing a conventional metal coil spring with a fibre composite leaf spring. This material substitution fundamentally alters the spring's profile characteristics, enabling a low-profile design that reduces the likelihood of impact damage while maintaining the functional capability to move the landing gear assembly to the deployed condition and lock it in place
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration enhances the strength and reliability of the leaf spring, reduces the risk of delamination and component failure, and simplifies the manufacturing process while maintaining the benefits of fibre composite materials like reduced vibratory loading susceptibility and low profile impact resistance.
Implementation Method 1
The fibre composite leaf spring can deflect sufficiently to accommodate articulation movement of the lock link as the landing gear assembly moves between the deployed and stowed conditions
Implementation Method 2
One or more down lock springs are generally provided to assist in moving the landing gear assembly to the deployed condition and locking it in that state
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
An aircraft landing gear assembly comprises a first landing gear element movably coupled relative to a second landing gear element to move between a first condition and a second condition. The aircraft landing gear assembly further comprises a fibre composite leaf spring formed from a plurality of composite layers and arranged between the first and second elements, the leaf spring being arranged to bend when the first element moves from the first condition to the second condition. The fibre composite leaf spring comprises a first region and a second region, wherein the number of composite layers in the first region is greater than the number of composite layers in the second region. The landing gear further comprises a mounting assembly arranged to engage the first region of the leaf spring to couple the leaf spring to the first landing gear element.