Aircraft Door Flag Mechanism for Centralized Lock Indication
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Solution Overview
Problem
Existing door locking mechanisms for vehicles, particularly aircraft, require crew members to visually inspect multiple locking members through inconveniently placed windows, and pre-catch mechanisms bias locking members away from the locked position when the door is closed, which is undesirable.
Innovation Solution
A door latching and locking system with a flag mechanism that uses bellcranks and flags to provide a visible lock indication window and a latch positioning mechanism that retains locking members in a pre-catch position until the door is securely closed, preventing biasing away from the locked position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple locking members are used to secure the door, then the door locking reliability is improved, but the difficulty of visual inspection increases due to inconveniently placed windows
Solution Approach 1:
A flag mechanism is introduced as an intermediary indicator system. The flag is mechanically linked to the locking members through arms and studs, translating the position of remote locking members into a centralized visual signal that can be observed through a conveniently located window in the cockpit.
Solution Approach 2:
The flag mechanism creates a visual copy or representation of the locking members' positions. Instead of requiring direct observation of multiple locking members through inconvenient windows, a single flag indicator replicates the locked/unlocked state information in a centrally located, easily observable position.
2Ease of operation
If pre-catch mechanisms are used to position locking members, then the door closure process is simplified, but the locking members are biased away from the locked position when the door is closed
Solution Approach 1:
The system transitions from a static pre-catch mechanism that maintains a fixed bias to a dynamic system where the flag mechanism responds to the actual position of locking members. The locking members are no longer passively biased by springs but are actively positioned and indicated by the mechanical linkage to the flag, allowing the system to adapt to the closed door state without unwanted bias.
Solution Approach 2:
The biasing function previously provided by pre-catch springs is extracted and replaced. The spring mechanism that caused unwanted biasing is removed, and its positioning function is taken over by the flag mechanism's mechanical linkage, which provides neutral positioning without active biasing forces.
Data Source
AI summary
A flag mechanism for an aircraft door includes a first arm and a second arm each having a flag on a first end and a catch on a second end. A first cam is operatively coupled to a first latching member and a second cam is operatively coupled a second latching member. The first and second latching members are each configured for latching the aircraft door, which are locked when the first and second cams are rotated to a locked position. A first stud extends from a side of the first cam and a second stud extends from a side of the second cam. The first and second studs are each configured to be received by a respective catch of the first and second arms while the first and second cams are rotated, thereby moving each respective flag from a first position to a second position for simultaneous visual inspection.