Non-jamming Shrink Latch for Aircraft Landing Gear
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Solution Overview
Problem
Retractable landing gear shock struts in aircraft can unshrink unexpectedly, causing them to jam and prevent safe extension, leading to operational hazards when the gear tries to retract into the wheel well.
Innovation Solution
A non-jamming shrink latch mechanism is introduced, comprising a detent rigidly mounted within the wheel well, rocker arms with compression members, and a cradle with stirrups, which prevents the strut piston from extending during the shrink stroke and allows safe retraction and extension by managing the arc paths of the axle and wheels, ensuring the strut remains outside the wheel well when extended.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a shrinking strut is used to fit within the wheel well, then the landing gear can be retracted into the wheel well, but the strut may unshrink when retracted and jam, preventing safe operation
Solution Approach 1:
The latch mechanism applies preliminary anti-action by engaging the detent with the rocker arm before the strut can unshrink and jam. This preventive engagement blocks the harmful motion path, ensuring the strut remains securely in the retracted position without risking uncommanded extension that would cause jamming in the wheel well.
Solution Approach 2:
The rocker arm acts as an intermediary between the strut piston and the detent. It translates the strut's shrink/extend motion into a corresponding movement that engages or disengages the detent, providing controlled position transition while preventing uncommanded movement that would lead to jamming.
2Reliability
If a latch mechanism is added to prevent unshrink, then the strut position control is improved, but the device complexity increases
Solution Approach 1:
The latch mechanism employs dynamic elements including a movable rocker arm that pivots between engaged and disengaged positions, and a spring that provides dynamic locking force. This dynamic design allows the latch to automatically engage when the strut retracts and disengage when the strut extends, providing reliable position control without requiring complex active control systems.
Solution Approach 2:
The latch mechanism is self-actuating through the interaction between the rocker arm, detent, and spring. The strut's own motion during shrink and extend operations automatically triggers the latch to engage or disengage, eliminating the need for external actuators or complex control systems while maintaining reliable position control.
3Reliability
If the strut piston is inhibited from extending over the first portion of the shrink stroke, then jamming is prevented, but the ease of operation is reduced
Solution Approach 1:
The latch mechanism performs preliminary action by securing the strut in the retracted position before any extension operation begins. The detent engages the rocker arm to lock the piston, preventing premature extension that would cause jamming. This preliminary locking ensures safe operation while the extension sequence is properly initiated.
Solution Approach 2:
The rocker arm provides mechanical feedback by translating the piston's position into detent engagement or disengagement. As the strut attempts to extend, the rocker arm moves and automatically disengages the detent at the appropriate moment, providing position-dependent control that prevents jamming while enabling proper extension operation.
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
The solution prevents jamming by inhibiting the strut piston from extending over the first portion of the shrink stroke and allows it to fully extend, ensuring safe operation and visual indication of uncommanded unshrink events, thus enhancing the reliability and safety of the landing gear deployment.
Implementation Method 1
one of the first rocker arm or the second rocker arm comprises a compression member. In various embodiments, in response to the compression member exerting a spring force, one of the first outboard pivot or second outboard pivot is driven into engagement with the detent
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A non-jamming shrink latch is provided and may comprise a cradle (204), a first rocker arm (206), a first inboard pivot (212), and a first outboard pivot (210), wherein the first inboard pivot is coupled to the first rocker arm at a first end (234) and the first outboard pivot is coupled to the first rocker arm at a second end (236) opposite the first end, and wherein the cradle is coupled to the first outboard pivot. In various embodiments, a non-jamming shrink latch (202) may further comprise a second rocker arm (208) coupled to the cradle at a second outboard pivot (211) and a second inboard pivot (213) coupled to the second rocker arm opposite the second outboard pivot.