Selector Lever Float Lock for Detent Pin Failure Detection
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Solution Overview
Problem
Conventional aircraft selector levers lack an effective mechanism to detect the failure of detent pins, which can lead to increased maintenance costs and reduced safety due to the lack of redundancy in pin failure detection.
Innovation Solution
A selector lever design featuring a shaft with detent pins and floats that engage with catches, where the movement of the detent pins is linked to the movement of floats, preventing rotational movement when a pin fails, thus providing a clear indication of failure and potentially allowing for a release mechanism to disengage the float, enabling continued operation or maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single detent pin is used in the selector lever, then the device complexity is reduced, but the reliability decreases because there is no redundancy to detect pin failure
Solution Approach 1:
The selector lever is segmented into multiple independent detent pins (first and second detent pins) that can be individually monitored. Each detent pin has its own float mechanism, allowing independent failure detection without requiring complete system redundancy. This segmentation enables failure detection while maintaining relatively simple overall structure.
Solution Approach 2:
Floats are introduced as intermediary elements between the detent pins and the shaft. These floats act as mediators that translate the positional state of each detent pin into a detectable mechanical condition (engagement with catches). The intermediary float mechanism enables reliable failure detection without directly complicating the core detent pin structure.
2Reliability
If multiple detent pins with individual float mechanisms are added to detect pin failure, then the reliability improves through failure detection capability, but the device complexity increases
Solution Approach 1:
The float mechanisms for multiple detent pins are merged into a compact arrangement where floats are positioned adjacent to each other along the shaft. The catches are integrated into the housing structure, and multiple floats can engage multiple catches in a space-efficient manner. This merging reduces the overall space and structural complexity that would otherwise be required for separate detection mechanisms.
Solution Approach 2:
The float-catch mechanism serves multiple functions simultaneously: it acts as a mechanical indicator for each detent pin position, provides failure detection capability, and can potentially serve as a locking mechanism. This multi-functionality reduces the need for separate dedicated detection components, thereby limiting the increase in device complexity.
3Reliability
If the float is permanently engaged with the catch to prevent rotation, then the safety improves by ensuring failure detection, but the ease of operation decreases due to potential false prevention of legitimate movement
Solution Approach 1:
The float-catch engagement is designed as a dynamic rather than static system. The floats can engage with the catches under certain conditions (such as when detent pins are in specific positions) and disengage under others. This dynamic engagement allows the system to provide safety constraints only when necessary, maintaining ease of operation during legitimate selector lever movements.
Solution Approach 2:
The float mechanism provides immediate mechanical feedback about the state of detent pins. When a detent pin fails to move to its expected position, the corresponding float remains in a position that prevents shaft rotation, providing real-time feedback to the operator. This feedback mechanism ensures safety without requiring permanent engagement, as the prevention of rotation is conditional on the actual state of the detent pins.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A selector lever (5) with two detent plates (11, 14) and corresponding detent pins (13, 16) that travel along a shaft (6) includes a float (17) that moves with each of the detent pins (13, 16). When a detent pin (13, 16) fails, a float pin (18) remains engaged with a catch (19), thereby preventing rotational movement of the shaft (6).