NFPA Journal - Fall 2021 - 32

PREPPED FOR
TAKEOFF
Beyond Batteries
The emerging urban air mobility industry will rely on battery-powered aircraft
and will likely include hydrogen-powered and hybrid gas- and-electric models-
all of which present fire safety concerns
WHEN A BATTERY-POWERED electric vehicle catches fire, it
can be a difficult beast for the fire service to control. Even so,
the instructions remain fairly simple: put water-lots of it-on
the batteries. The same principles will apply to fires involving
the batteries of electric vertical takeoff and landing (eVTOL)
aircraft, which are poised to become a reality in the next three
to five years.
But what happens when those aircraft use a hydrogen fuel
cell, instead of batteries, to generate electricity? The approach
first responders take, and the fire protection systems that are
needed, to control such a blaze will be markedly different. And
what about when the aircraft is powered mainly by batteries but
also has a gas tank on board?
These questions are currently being weighed by the technical
committee for NFPA 418, Standard for Heliports, as it works to
draft a new chapter in the standard addressing the emerging
urban air mobility (UAM) industry. Specifically, the group is
determining what fire safety measures will be needed at vertiports,
the facilities where these aircraft will operate from. While
batteries seem to be the most popular type of power source
envisioned by VTOL aircraft manufacturers, some companies
have also introduced hydrogen-powered and hybrid gas-andelectric
designs-propulsion types that will present different
challenges requiring different solutions.
" Whether you have a hydrogen leak or a gas spill or a battery
fire, you're going to need to have specific requirements for
mitigating the hazards in those
situations, " said Kevin Carr, the
NFPA staff liaison to NFPA 418.
According to Rex Alexander,
current aviation infrastructure
around the world is mainly
designed to protect against
gas fires and spills, with foam
fire suppression systems and
systems designed to contain
leaked gasoline. In addition to
being a member of the NFPA
418 committee, Alexander
is a veteran helicopter pilot
and founder and president of
Five-Alpha, an Indiana-based
consulting agency specializing
in aviation infrastructure. Alexander
said vertiports may need
to include those same systems,
plus systems designed
to handle incidents involving
batteries and hydrogen.
Some experts see hydrogen,
in particular, becoming
a prominent part of the UAM
industry in the future. According
to an article published in
January by eVTOL.com, a UAM
industry news website, the use
of hydrogen as a power source
" could significantly expand the
possibilities of air taxis beyond
the limitations posed by battery-electric
powertrains,
32 | NFPA JOURNAL * FALL 2021
according to proponents of the fuel. " Those proponents say
hydrogen " has a higher energy density than lithium batteries,
meaning it can increase operational range and flight time.
Additionally, hydrogen systems can be refueled fairly quickly,
increasing the utilization rate of those platforms. " But, the article
concedes, hydrogen is also highly flammable-it holds the
highest flammability rating on the scale described in NFPA
704, System for the Identification of the Hazards of Materials
for Emergency Response-and " creates significant challenges
for use in rooftop-based vertiports. "
As a result, the committee is making it a point to include
hydrogen and hydrogen fuel cells in its scope of work for the
vertiport chapter, Alexander said. " The application of hydrogen
will no doubt bring with it some unique challenges, " he added,
" but NFPA 2, Hydrogen Technologies Code, first published in
2011, has a significant amount of great language that can be
directly referenced by NFPA 418. "
NFPA 2 includes fire safety guidance for both liquid hydrogen
and gaseous hydrogen applications, both of which could
be utilized in VTOL designs. In general, its requirements focus
heavily on hydrogen storage quantity and distancing requirements,
pressure valves, and leak detection.
The public comment period for the 2024 edition of NFPA 418,
which will include the new chapter on vertiports, is open now
through January 22. Learn more about the standard and submit
a comment at nfpa.org/418. -A.V.
GETTY IMAGES
http://www.nfpa.org/418 http://www.eVTOL.com
NFPA Journal - Fall 2021

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