Fan Cowl Latch Indicator Panel for Aircraft Nacelles
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Solution Overview
Problem
Current methods for detecting improperly latched fan cowl doors on aircraft nacelles are inefficient due to low visibility of primary latches, especially in complex engine configurations, leading to potential operational issues and increased maintenance requirements.
Innovation Solution
A hinged panel device is fixed to one fan cowl door using rotating hinges and secondary locking means, which covers primary locking means, ensuring all are properly latched for closure; if not, the panel hangs vertically, providing a high visibility warning signal, and is designed to minimize aerodynamic drag and be easily replaceable.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If primary latches are installed in the lower area of fan cowls with small size, then the nacelle structure can be compact and aerodynamic, but the latch visual detectability becomes very difficult
Solution Approach 1:
The patent introduces a secondary latch mechanism as an intermediary indicator. This secondary latch is visually connected to the primary latch state through the hinge mechanism, providing an indirect but visible signal of the primary latch status. The secondary latch acts as a mediator that translates the invisible primary latch position into a visible indicator on the fan cowl door.
Solution Approach 2:
The patent employs fluorescent paint on the secondary latch to enhance its visibility. By using color changes and fluorescent materials, the secondary latch becomes highly visible against the nacelle background, allowing maintenance personnel to easily detect the status of the primary latch from a distance without requiring close inspection of the small primary latch components.
2Device complexity
If visual inspection procedures are used to detect improperly latched fan cowl doors, then no additional mechanical components are needed, but the detection process becomes time-consuming and error-prone
Solution Approach 1:
The secondary latch mechanism is designed to automatically indicate the primary latch status without requiring active inspection. The hinge mechanism self-activates based on the primary latch position, and the fluorescent secondary latch self-displays the status information. This eliminates the need for maintenance personnel to manually inspect or interpret complex latch mechanisms, making the system self-indicating and significantly reducing inspection time.
3Difficulty of detecting and measuring
If a panel device is added to indicate latch status, then visibility is improved, but the device complexity and aerodynamic drag increase
Solution Approach 1:
The patent merges the indication function with the existing fan cowl door structure. The secondary latch is integrated into the fan cowl door rather than being a separate external component. The hinge mechanism utilizes the natural movement of the fan cowl door itself as part of the indication system, combining multiple functions (latching, indicating, and aerodynamic fairing) into a unified structure that minimizes additional complexity.
4Reliability
If the panel is designed to cover primary locking means, then all primary locks must be closed for panel closure providing reliable indication, but the device complexity increases
Solution Approach 1:
Instead of having the panel actively detect or sense the latch status through sensors or switches, the patent inverts the approach: the panel's closure is physically dependent on the latch being closed. The hinge mechanism is designed so that the panel can only close and be secured when the primary latch is in the closed position. This passive mechanical interdependence ensures reliable indication without requiring complex active detection systems.
Data Source
Figure 1a~1b
Figure 2~3a
Figure 3b~4a
AI summary
Device (3) for providing a warning signal when the fan cowl doors (8, 9) of an aircraft are not properly latched by primary locking means (6), said device (3) comprising a panel (4) the panel (4) being fixed by rotating means (5) on one of the two fan cowl doors (8 or 9), the panel (4) being closed on that one fan cowl doors (8 or 9) by rotating on said rotating means (5) therefore covering at least partially the primary locking means (6), such that all the primary locking means (6) have to be properly latched for the panel (4) to be closed, and at least one of the panel (4) primary locking means (6) not properly latched prevents proper closing of the panel (4).