Aircraft Flag Door Spring Linkage Mechanism
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Solution Overview
Problem
Conventional flag door systems in aircraft are complex and costly due to their reliance on triggered torsion springs, and they lack a direct mechanism to provide a visual cue for incomplete latching of access doors, relying on pressure differential-based systems for pressure relief.
Innovation Solution
A system utilizing a spring and mechanical linkage to directly open and close a flag door based on the state of the access door, providing a visual cue and pressure relief through a simpler design with fewer parts, which includes a first door assembly, a spring, and a mechanical linkage that drives the flag door to open or close based on the door's state and pressure differential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional triggered torsion springs are used to open the flag door, then the flag door can provide pressure relief and visual indication, but the system becomes complex and costly with multiple components including latch release and re-arming mechanisms
Solution Approach 1:
The patent extracts and eliminates the complex triggered torsion spring mechanism, latch release mechanisms, and re-arming mechanisms from the conventional system. Instead, it uses a simple spring-loaded flag door that opens automatically when pressure differential exceeds spring force, providing pressure relief and visual indication without complex control systems.
Solution Approach 2:
The flag door system is designed to be self-actuating based on pressure differential. The spring provides the necessary force to keep the door closed during normal operation, and when pressure exceeds this force, the door automatically opens without requiring external control systems, latch releases, or re-arming mechanisms.
2Ease of manufacture
If pressure differential-based systems are used for flag door operation, then pressure relief can be achieved, but the system lacks a direct mechanism to provide visual cue for incomplete latching
Solution Approach 1:
The spring-loaded flag door serves multiple functions simultaneously: it provides pressure relief by opening when pressure differential exceeds spring force, and it provides visual indication of latch state by remaining closed only when the access door is properly latched. This multi-functional design eliminates the need for separate systems for pressure relief and visual indication.
3Reliability
If conventional flag door systems with multiple components are used, then pressure relief and visual indication functions are provided, but maintenance costs increase due to more parts
Solution Approach 1:
The patent removes multiple maintenance-prone components including triggered torsion springs, latch release mechanisms, and re-arming mechanisms. The remaining system consists of a simple spring-loaded door that can be easily replaced as a single unit, dramatically reducing maintenance complexity and cost.
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 system reduces complexity and maintenance costs by eliminating the need for latch release and re-arming mechanisms, while providing a clear visual indication of the access door's state and effective pressure relief through a direct linkage system.
Implementation Method 1
a spring configured to apply a first force to the first member and to apply a second force, via the mechanical linkage, to the second door
Implementation Method 2
a mechanical linkage coupled between the spring and the second door, the mechanical linkage configured to transmit the second force from the spring to the second door
Implementation Method 3
the second door may be configured to also open based on a latch position of the access door... open based on a pressure difference between a pressure (e.g., an interior pressure) of the portion and an exterior pressure or an ambient pressure
Data Source
AI summary
An aircraft includes a first structure between a pressure-controlled region of the aircraft and a non-pressure-controlled region of the aircraft and a second structure between the non-pressure-controlled region and an exterior of the aircraft. The aircraft also includes a first door assembly that includes a first door configured to cover a first opening between the pressure-controlled region and the non-pressure-controlled region and a second door configured to cover a second opening between the non-pressure-controlled region and the exterior. The aircraft further includes a spring coupled, via a first member, to the first door assembly and coupled, via a mechanical linkage, to the second door. The spring is configured to apply a first force to the first member and to apply a second force, via the mechanical linkage, to the second door, where the second force is applied based on a state of the first door assembly.