Spark Containment Cap With Pressure-Balanced Fastener Sealing
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Solution Overview
Problem
Large passenger aircraft are at risk of lightning strikes, which can cause sparking or plasma at metallic fasteners, potentially igniting fuel due to their lower electrical resistance compared to composite materials, and existing spark suppression methods are inadequate.
Innovation Solution
A fastening system comprising a spark containment cap that forms a sealed cavity around the fastener, using a cap body with an annular base and skirt to receive a curable sealing material, and a fastener engaging portion to secure the cap to the fastener, minimizing components and complexity while allowing air channels to prevent pressure buildup.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a spark containment cap is used to seal the cavity around the fastener, then spark ignition is prevented during lightning strikes, but pressure buildup may occur within the sealed cavity
Solution Approach 1:
The cap body incorporates porous material that allows pressure equalization between the sealed cavity and the external environment. This porous structure maintains the spark containment function while permitting gas molecules to pass through, preventing dangerous pressure buildup during lightning strikes or fuel tank pressurization events.
2Reliability
If multiple components are used to ensure reliable sealing and engagement, then sealing reliability is improved, but device complexity increases
Solution Approach 1:
The invention combines multiple functions into a single integrated cap component. The cap body simultaneously provides spark containment sealing, pressure equalization through porous material, and fastener engagement through integrated threading. This merging of functions reduces the number of separate components while maintaining reliable sealing and engagement.
Solution Approach 2:
The cap is designed as a multi-functional component that performs spark containment, pressure equalization, and fastener engagement all in one piece. The porous cap body provides both sealing and pressure relief functions, while the integrated threaded portion provides engagement capability, eliminating the need for separate sealing elements and engagement mechanisms.
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 effectively seals the cavity to prevent spark ignition during lightning strikes, ensuring the safety of aircraft fuel tanks by creating a secure, pressure-balanced environment that inhibits plasma or out-gassing products from escaping.
Implementation Method 1
an annular sealing volume extending around the base rim arranged to receive an annular bead of a curable sealing material around the opening into the cavity to provide a seal between the cap body and the structure to seal a volume of gas within the cavity
Data Source
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AI summary
A spark containment cap for forming a sealed cavity around an end of a fastener protruding from a structure, the cap comprising: a cap body defining an air cavity arranged to enclose the end of the fastener, and including an annular base terminating at a base rim which surrounds an opening into the air cavity; and an annular skirt to provide an annular sealing volume extending around the base rim arranged to receive an annular bead of a curable sealing material around the opening into the cavity to provide a seal between the cap body and the structure to seal a volume of gas within the cavity. The cap further comprises a fastener engaging portion that engages with a threaded portion of the fastener so as to secure the cap to the fastener.