Vented Fastener Cap Geometry for Aircraft Ignition Quenching
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Solution Overview
Problem
Aircraft fasteners pose an ignition risk during lightning strikes due to electrical currents passing through composite materials, which can generate electromagnetic effects that interact with combustible fuel vapors, and existing polysulfide cap seals are labor-intensive to install and maintain, increasing production and inspection time.
Innovation Solution
A cover is designed to position an exclusion zone over the fastener, with holes aligned to prevent straight-line trajectories from the exterior environment to the fastener, venting gas and particles while removing thermal and kinetic energy to prevent ignition, and constructed from materials like polymers and ceramics to ensure a resilient, airtight seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polysulfide cap seals are used to seal fuel mixtures from arcs and hot particles, then ignition risk is reduced, but installation and inspection time increase production cost and time
Solution Approach 1:
The patent removes the polysulfide seal material from the cap structure entirely, replacing it with a sealless design where the fastener shank passes through a sealed cavity in the cap. This extraction eliminates the labor-intensive sealing process while maintaining ignition protection through the sealed cavity geometry that prevents fuel vapor contact with the fastener and arc paths.
2Reliability
If an airtight seal is required to prevent fuel contact with fastener and arc paths, then ignition prevention is improved, but seal durability deteriorates due to environmental exposure and electromagnetic effects
Solution Approach 1:
The patent extracts the vulnerable polysulfide seal from the system, replacing it with a sealless design where the cap cavity itself provides the barrier. The sealed cavity geometry, combined with the cap material's inherent properties, prevents fuel vapor contact without relying on degradable seal materials that are susceptible to environmental and electromagnetic damage.
Solution Approach 2:
The patent replaces the durable-but-vulnerable polysulfide seal with a simpler, sealless design that achieves protection through geometry and material selection rather than relying on a seal that degrades over time. The cap structure itself becomes the protective element, eliminating the need for maintenance of seal components.
3Reliability
If fasteners are covered to prevent ignition during lightning strikes, then safety is improved, but the complexity of the fastener system increases
Solution Approach 1:
The patent merges the protective cap function with the fastener system by integrating the sealed cavity design into the cap structure itself. The cap serves both as a protective cover and as the sealing mechanism through its geometry, eliminating the need for separate seal components and reducing overall system complexity while maintaining lightning strike safety.
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 cover effectively prevents ignition by isolating the fastener within an interior space, reducing the risk of hot particles igniting the combustible exterior environment and simplifies the installation and maintenance process, thereby reducing production and inspection time.
Implementation Method 1
venting gas and particles while removing thermal and kinetic energy to prevent ignition
Implementation Method 2
venting gas and particles while removing thermal and kinetic energy to prevent ignition
Implementation Method 3
positioned over a fastener to quench ignition... isolating the fastener within an interior space
Data Source
Figure 1
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AI summary
A cover that extends over a fastener and methods of installing the cover over the fastener. The cover includes an open end positioned at a member from which the fastener extends. The cover also includes a closed end that extends over the fastener and shields the fastener from the exterior environment that can be combustible. A plurality of holes extend through the cover from the interior space to an exterior environment external to the cap.