Fuel Tank Fastener Sparking: Development of a Threshold Database and the Benefits of Computational Electromagnetics Simulation for Certification

Prevention of catastrophic effects due to fuel vapor ignition is
a key part of any aircraft certification effort. One potential
fuel vapor ignition source is arcing and sparking resulting
from lightning currents conducted through airframe
components, such as fasteners and joints. The most common
method of demonstrating adequate ignition source prevention
involves extensive testing of a large variety of fasteners and
fastener configurations. Fastener test levels are based on
current densities distributed throughout the aircraft, obtained
through full-vehicle lightning testing and simulation.

The fastener design handbook [4] contains a sample of the
testing and simulation effort used to identify potential ignition
sources in fuel tanks. Findings and data published in the
project reports handbook serve as baseline engineering
evaluation for industry to reduce the overall quantity of tests
required during the fuel tank design process. Several factors
were studied for their impact on fastener non-sparking
thresholds. There are three phases associated with this study.

Phase 1 of this project focused on developing a public fastener
database for non-sparking thresholds due to conducted
lightning currents in coupon level tests representing metal fuel
tanks. This included both nominal and faulted fastener
installations.
Phase 2 involved the development of a metal fuel tank
lightning design handbook and was carried out by
EMA. The focus of this phase was to demonstrate how
lightning environments could be established in aircraft fuel
systems using validated numerical simulations.
Phase 3 of this project focused on developing a public fastener
database for lightning non-sparking thresholds in coupon level
tests in carbon fiber reinforced plastic (CFRP) fuel tanks for
both nominal and faulted fastener installations.
This paper provides the background for the project, findings
of each phase of this study, and opportunities for future work.
All work done during this project is publically available to be
used as a design guide. This project was funded by KART
grants and done in partnership with EMA.