Fuel Line Siphon Break for Fault-Tolerant Firebay Isolation
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Solution Overview
Problem
Traditional fuel shut-off systems in aircraft introduce a single point of failure, leading to potential catastrophic loss of propulsion due to erroneous closure during non-engine fire events, as they rely on a normally open valve that can malfunction electrically or mechanically.
Innovation Solution
Implementing a valve on the cold side of the firewall, coupled between the fuel tank's ullage and the fuel feed line, which introduces air as a vacuum break to prevent fuel siphoning, eliminating the need for a traditional shut-off valve and reducing the risk of single-point failure, with a control unit managing the system to ensure safe operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a normally open shut off valve is used in the fuel feed line to prevent fuel flow into the engine compartment during an engine fire, then fuel isolation effectiveness is improved, but system reliability deteriorates due to single point of failure risk from erroneous valve closure
Solution Approach 1:
The fuel isolation function is segmented into two independent subsystems: a traditional shut-off valve for active fire response and a passive siphon break device for redundancy. This segmentation ensures that failure of one subsystem does not compromise overall fuel isolation capability, resolving the single point of failure issue while maintaining effective fuel isolation during engine fires.
Solution Approach 2:
The system incorporates a passive siphon break device that is pre-configured to automatically break the siphon effect if the shut-off valve fails. This beforehand cushioning mechanism provides redundant protection against fuel siphoning into the engine compartment, ensuring reliability even when the primary active valve system fails erroneously.
2Object-affected harmful factors
If a normally open shut off valve is used to cut off fuel flow during engine fire, then fuel isolation is achieved, but device complexity increases due to additional valve components and control systems
Solution Approach 1:
The invention introduces a passive siphon break device as an intermediary mechanism that works in conjunction with the traditional shut-off valve. This intermediary device provides fuel isolation capability through passive physical principles (breaking the siphon effect) rather than requiring complex active control systems, thereby achieving fuel isolation while managing overall system complexity.
Solution Approach 2:
The system utilizes pneumatic principles through the passive siphon break device, which operates by introducing air into the fuel line to break the siphon effect. This pneumatic approach provides a simpler alternative to purely mechanical or electrical valve systems, reducing device complexity while maintaining effective fuel isolation capability.
3Object-affected harmful factors
If a traditionally positioned shut off valve is used on the cold side of the firewall, then fuel isolation from the firebay is achieved, but accessibility for maintenance and inspection deteriorates
Solution Approach 1:
The invention relocates the shut-off valve from the traditional position on the cold side of the firewall to an alternative position that improves accessibility while maintaining fuel isolation effectiveness. This dimensional change in valve positioning allows maintenance personnel to access and service the valve more easily without compromising its ability to isolate fuel from the firebay during engine fires.
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
This solution ensures fuel isolation from the engine firebay without introducing a single point of failure, allowing safe engine operation even if the valve malfunctions, and allows for reversible fuel isolation in case of false fire detection, maintaining propulsion and compliance with aviation regulations.
Implementation Method 1
the valve is opened to introduce air from the ullage portion into the fuel feed line, wherein the air introduced by the valve provides a vacuum break or siphon break in the fuel line
Data Source
AI summary
Fuel isolation systems, apparatuses and methods are described. In some embodiments, a system comprises a fuel tank, a fuel pump, an engine, a firewall, a fuel line from the fuel tank to the engine, a connector coupled inline with the fuel line on a cold side of the fuel line, a valve coupled to the connector, a fluid feed line coupled to a fluid source and to the valve. In the event of an engine fire condition, a control unit outputs signaling to turn off the fuel pump and operate the valve to introduce fluid from the fluid source into the fuel line. The introduced fluid provides a siphon break in the fuel line such that the only fuel that can pass the firewall is the remaining fuel in the fuel line downstream of the connector and the introduced fluid.