Aircraft Door Latch Positioning With Pre-Catch Lock Release
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Solution Overview
Problem
Existing door locking mechanisms in vehicles, particularly aircraft, require manual visual inspection of locking members for confirmation of the locked position, which is inconvenient for crew members due to obstructed views, and prior pre-catch mechanisms bias locking members away from the locked position when the door is closed.
Innovation Solution
A latch positioning mechanism using bellcranks and cams to maintain locking members in a pre-catch position until the door is fully closed, with automatic release and re-engagement, and a flag mechanism for visual lock indication, allowing crew members to confirm the locking status without obstructed views.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual visual inspection of locking members is required for confirmation of locked position, then locking status can be confirmed, but crew members experience obstructed views and inconvenience
Solution Approach 1:
A flag mechanism serves as an intermediary indicator that translates the position of locking members into a visible signal. The flag is mechanically linked to the locking members through linkages, allowing crew members to view the locking status from a remote location without needing to visually inspect the locking members directly, thus resolving the contradiction between reliable status confirmation and crew convenience
2Ease of operation
If pre-catch mechanisms bias locking members away from locked position when door is closed, then locking members can be easily released when door opens, but locking members cannot remain securely in locked position
Solution Approach 1:
The mechanism dynamically adjusts the biasing force applied to locking members based on door position. When the door is closed, the pre-catch mechanism is disengaged, allowing locking members to remain securely locked without being biased away. When the door opens, the pre-catch mechanism engages and biases the locking members toward the unlocked position, facilitating easy release. This dynamic behavior resolves the contradiction between secure locking and easy release
3Speed
If locking members are held in pre-catch position by biasing mechanism, then locking members are ready for quick release, but additional mechanisms are required to control the biasing
Solution Approach 1:
The pre-catch mechanism is merged with the existing door latching system, utilizing the same mechanical linkages and movement paths. The biasing mechanism is integrated into the door frame structure, sharing components with the overall latching system. This merging reduces the number of separate control mechanisms needed while maintaining the ability to quickly release locking members when required
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
Enables convenient visual confirmation of locking status and prevents biasing of locking members away from the locked position during door closure, ensuring secure latching and locking without manual intervention.
Implementation Method 1
a biasing member operatively coupled to the catch bellcrank, wherein the biasing member biases rotation of the catch bellcrank to bias the frame bumper into the pre-catch position
Implementation Method 2
the frame bumper is configured to contact the frame upon the door being closed thereby counterrotating the catch bellcrank to overcome the biasing member
Data Source
AI summary
A latch positioning mechanism for an aircraft door includes one or more locking members configured to be partially driven into a frame around the door via rotation of a pivot pin. A frame bumper extends outside of the door in a pre-catch position for contacting the frame. A catch bellcrank is operatively coupled to the frame bumper, and a biasing member biases rotation of the catch bellcrank to bias the frame bumper into the pre-catch position. The catch bellcrank is configured to contact a catch cam when the catch bellcrank is biased into the pre-catch position such that the catch cam prevents release of the one or more locking members for locking the door. Upon the frame bumper contacting the frame when the door is closed, the catch cam is released enabling the one or more locking members to be moved into a locked position.