AOPA Pilot Magazine - October 2022 - 22

WAYPOINTS
On a lighter note
Hydrogen-powered aircraft. Really?
BY THOMAS B. HAINES /
AOPA Foundation Legacy Society member
ONE OF MY FAVORITE subjects to cover over these past 36 years
is emerging technologies. Of course, some of those then emerging
technologies are mainstream today-GPS navigation; WAAS (widearea
augmentation system, which allowed GPS position to be good
enough for low approaches); RNAV approaches; ADS-B; electronic
cockpit displays (EFIS); in-cockpit weather; synthetic vision; terrain
awareness; collision avoidance systems; and many more.
The other side of the ledger is almost as full-technologies that
either failed or, more often, have not yet been fully realized such as
very light jets (VLJs), light sport aircraft, diesel propulsion, electric
propulsion, autonomous flight, and vertical takeoff and landing
(electric and otherwise).
I remember covering the rollout of the Sikorsky S-72 X-Wing
in 1986. Funded by the Defense Advanced Research Projects
Agency (DARPA), the X-Wing was to demonstrate the ability to
take off and land near vertically under a large X-shaped rotor and
then stop the rotor in cruise to have it act as an X-wing, greatly
increasing speed and efficiency over a conventional helicopter.
Despite the big rollout event at the Sikorsky factory in Connecticut,
the X-Wing never flew and was canceled in 1988. I can imagine
the test pilots there in the briefing room pondering that transition
from rotary flight to fixed-wing flight and saying, " Ahh, no thanks! "
As is often said in R&D, if you're not failing occasionally, you're
not trying hard enough.
Today, the hype around VTOL, eVTOL, and electric propulsion
in general is near epic proportions (see " eVTOLs: The Promise
and the Risk, " p. 66). It even eclipses the predictions we heard in
the early 2000s about very light jets darkening the sky-and if you
get that little double entendre, you know what I'm talking about.
The difference today is that rather than just a handful
of small GA companies or start-ups attempting to build simple,
low-cost personal jets, the advanced air mobility movement
(AAM), which mostly leverages VTOL and electric propulsion,
is backed by some of the largest companies in the world. Rather
than serving a relatively small number of wealthy individuals,
as would be the case with the VLJs, AAM's goal is to serve the
masses. The AAM movement comes at an interesting intersection
of technological advances and societal demands. As is often
the case with major advances, progress is in fits and starts. There
is no one simple achievement that will have everyone Jetson-ing
22
AOPA PILOT / October 2022
around in their personal VTOL as it folds into a briefcase on the
way into the meeting with Mr. Spacely.
A few years ago, most AAM companies were focused strictly
on autonomous short-haul urban eVTOL aircraft powered by batteries.
Today, most companies have broadened their focus to also
include regional transportation, almost always including a pilot
and hybrid power, mostly with a turbine generator providing at
least part of the electricity to drive the rotors or propellers during
certain phases of flight.
The latest trend is the embracing of hydrogen as a primary
fuel source. The first hydrogen-powered airplane flew in 1957-for
20 minutes on just one engine of a Martin B-57B. More recently,
ZeroAvia has been using a hydrogen fuel cell to power a variety
of aircraft during its development phase. When hydrogen is the
only fuel used, ZeroAvia claims those are zero-emission flights.
This, of course, is where the intersection with society comes into
play. Climate change warnings have been driving all manner
of societal changes, from the types of cars we drive to how we
generate electricity. The airlines in particular are facing immense
pressure to reduce or eliminate carbon emissions. Hydrogen is
an efficient fuel for generating electricity, emitting only water.
The problem is that with today's technology, creating hydrogen
is highly inefficient. And even if we had an efficient way to generate
it, the infrastructure changes to support a transition would
be enormous. Some have dismissed it as impossible.
However, if we stop and think about what is needed to get
a gallon of avgas or Jet A into our fuel tanks, perhaps the future
of hydrogen isn't so preposterous. No more drilling holes in the
ground to get a barrel of dinosaur juice that must be transported
to a refinery where it is brewed down into a variety of products,
only a small portion of which is usable in an airplane, and then
transporting that via rail, pipe, ship, or truck to a distributor
where it goes on a truck to a local airport for ultimately pumping
into our airplane wings. No small task. If the Industrial Age had
come about powered by hydrogen, we would look askance at what
might be needed to switch to
petroleum fuels.
Emerging technologies:
Easy to take pot shots at.
Sometimes life changing.
Former AOPA Editor in
Chief TOM HAINES has
been covering the aviation
and aerospace industry
for 36 years.
AOPA Pilot Magazine - October 2022

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