Shock Strut Latch Linkage to Prevent Landing Gear Jamming
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Solution Overview
Problem
Existing shock strut latch assemblies in aircraft landing gear can jam, causing the struts to remain in the shrunk position even after the landing gear has transitioned out of the wheel well, leading to potential operational issues during takeoff, taxiing, and landing.
Innovation Solution
A latch assembly with a first and second linkage is configured to prevent the shock strut from unshrinking while in the wheel well and to avoid jamming by transitioning between a locked, over-center position and an unlocked, under-center position based on the landing gear's position, allowing the strut to extend when necessary.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a safety latch is employed to prevent the strut from unshrinking while in the wheel well, then the safety of the landing gear retraction is improved, but the latch can jam and inadvertently hold the strut in the shrunk position after the landing gear translates to the down position
Solution Approach 1:
The latch assembly is designed to dynamically transition between locked and unlocked states based on the landing gear position. The over-center linkage mechanism automatically shifts from a locked configuration (preventing unshrinking in wheel well) to an unlocked configuration (allowing extension when gear is down), eliminating the need for manual intervention and preventing jamming.
Solution Approach 2:
The system changes the operational parameters of the latch by utilizing the positional parameter of the landing gear. When the gear transitions from up to down position, this parameter change triggers the latch to automatically switch from a restrictive state to a permissive state, ensuring safe operation at different phases of landing gear deployment.
2Stability of the object's composition
If the latch assembly is designed to lock the strut in the shrunk position, then the strut remains secure in the wheel well, but the latch may inadvertently prevent the strut from unshrinking after the landing gear exits the wheel well
Solution Approach 1:
The latch assembly employs dynamic linkage geometry that automatically adapts its locking characteristic based on the landing gear position. The over-center mechanism provides stable locking when the gear is up (securing the strut in the wheel well) but automatically becomes non-locking when the gear transitions to the down position, ensuring the strut can extend as needed.
3Device complexity
If a simple latch mechanism is used, then the device complexity is reduced, but the latch may jam and fail to release the strut properly
Solution Approach 1:
By incorporating the over-center linkage mechanism, the design achieves reliable automatic release without adding excessive complexity. The dynamic geometric transformation of the linkage ensures that the latch naturally transitions from a locked to an unlocked state based on the landing gear position, providing fail-safe operation.
Solution Approach 2:
The latch assembly is designed to automatically service itself by using the motion of the landing gear to trigger its own release. The over-center mechanism converts the gear's positional change into automatic latch state change, eliminating the need for external actuation systems or complex control mechanisms.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A latch assembly (200) for a shock strut (30) comprises a first linkage (202) coupled to a strut cylinder (110) and a shrink piston (130) of the shock strut, to regulate translation, i.e. shrinking and unshrinking, of shrink piston (130) relative to strut cylinder (110). A second linkage (204) is coupled to the strut cylinder (110) and to a static structure (101). The second linkage (204) is configured to rotate the first linkage (202) between a locked position and an unlocked position, in response to the shock strut (30) pivoting relative to the static structure (101) between a landing gear up position and a landing gear down position.