Although Bar-Yohay emphasized he doesn’t believe 3D printed plastic is strong
enough to replace metal in most use cases “[but], when you want to build a light,
tough, clever piece of plastic to say, demonstrate a partition in your battery or a part
of your cabin, there’s no better way to manufacture something light and complex.”
He added, “Today there are several printed parts in Orca,” referring to several nonstructural parts of the drone’s hull and some aerodynamic fillets.
“There will be several in Alice. They’re not weight-bearing, but they are parts that
made sense to print. I believe we’ll see more of this in Eviation and other companies.”
Eviation plans to use commercially available lithium-ion batteries to power its first
production airliners, in large part because they are easiest to acquire and certify. As
a result, the first-generation battery pack will comprise 63.5 percent of the aircraft’s
maximum takeoff weight, but subsequent developments that deliver higher energy
densities will enable users to choose between a longer range or larger payload
capacity. To minimize the potential for the thermal problems that some Li-Ion
batteries are subject to, Eviation will actively cool their batteries with, as Bar-Yohay
puts it, “a clever set of vapor chambers and liquid cooling solutions.”
Eviation says that a state-of-the-art 400 kW charger will only need 40 minutes to
pump enough power into the battery pack for an hour’s worth of flight. Since nearly
all flights will only use part of the battery’s capacity, most recharge cycles will take
much less than the 2. 2 hours needed to go from fully drained to a full charge.
The company is also exploring aluminum air batteries under development by an
Israeli startup called Phinergy as a future power option. These are not chargeable in
the traditional sense, operating more like a fuel cell made of aluminum plates. Their
chemistry enables extremely high energy densities but, for the moment, it remains a
promising option to be explored once the technology matures a bit more and a path
to certification is defined.
THE ECONOMICS OF ELECTRIC FLIGHT
Although electric aviation offers many potential environmental benefits, its most
compelling argument is its ability to reduce aircraft operating costs by between 75
percent and 80 percent. Only part of the savings come from the lower cost per
equivalent gallon of electricity versus aviation fuel. Additional savings are achieved
by eliminating the complex turboprop power plants used by most competing aircraft.
Besides having a purchase price that’s a fraction of an equivalent-sized turboshaft
engine, electric motors don’t need the regular maintenance and periodic overhauls that
add hundreds of dollars per hour to a turbine’s operating costs. Even using today’s
Li-Ion battery technology, which will require replacement of the battery pack every
2-3,000 flight hours, Eviation expects that the plane’s total DOC (direct operating
costs) will fall below $200/hour in practically all territories. This translates to a per-seat-mile cost of $0.10 to $0.15, a small fraction of the cost for a Beechcraft King Air,
Cessna 400 series, or other conventional aircraft of comparable speed and capacity.
As a result, Bar-Yohay said he believes that he can pitch customers on both the
performance of their aircraft, and on what he calls “insurance” for the low direct
operating costs. While petroleum-based aviation fuels will fluctuate wildly in cost
as they inevitably become more expensive, he bets that Eviation can guarantee its
aircraft will cost less to operate as battery technology improves.
Now that the the drone has verified the basic technology and the 1/3 scale
model is complete, Eviation’s next goal is to begin the construction of a full-scale
prototype, which will be 12 meters long with a 15-meter wingspan. They hope to fly
it by mid or late-2018 and apply for FAA certification and European certification in
early 2019. Commercial production is anticipated to begin in 2021.
“You’re gonna see a lot of fun machines out there,” Bar-Yohay said when talking
about the placement of the wingtip propellers. “Sooner than you think. And that’s
because this is possible.”