eFlightJournal-04-2020+01-2021double issue

e Vision
The Schleicher ASK-14
circa 1965, here at the
Wallduern Aerodrome/
Germany – inspiration
for the Spark Solo
Photo: Politicus de
for my desired flight endurance. The dual-wheel landing
gear of the Taurus allows un-assisted ground handling,
without the wingtip-dragging that comes with the ASK-
14. I had also considered the use of the recently certified
Pipistrel electric motor and battery system but may
not be able to afford the sizeable price tag that it carries.
A few thoughts about battery performance
There are a number of electric aircraft coming to market,
many of which are aimed at either the initial flight training
market, or as electric self-launch competition gliders.
Electric power is well suited to these applications,
but current battery performance is not good enough to
supplant piston engines for recreational flying outside
of these specific uses. How good do they need to be?
My previously published articles and presentations for
the Electric Aircraft Symposium concluded that batteries
need to achieve a performance metric of 300 watt-hours
per kilogram of weight, when encapsulated in an airworthy
pack complete with Battery Management System
(BMS). This would require the bare battery to be capable
of around 400 W-h/Kg. I consider this performance level
the tipping point where wholesale replacement of piston
engines with electric can take place. Despite the often
wildly optimistic claims of developers seeking investment
money for their projects, the fact is that the best battery
pack level performance that a Real World customer can
purchase today is down around 180 to 200 watt-hours
per kilogram. But Wait! You say, every day I read an article
about some new super-battery that is good for 400
watt-hours per kilogram or even more. Yes, but the educated
reader will ask a few questions
- is this new wonder battery ready to be scaled up from
the research laboratory to mass production?
- is it capable of being charged and dis-charged thousands
of times without being replaced?
- is this battery available at a price that normal people
can afford?
- has anybody designed and built an airworthy pack
structure with all of the required BMS and battery cooling
systems?
While I remain eternally optimistic, the pragmatic side of
me says that it will be another 10 years before we see
these new higher-performance battery chemistries widely
available for our aeronautical experiments.
The Zero motorcycle
drivetrain of Gabriel
DeVault’sXenos motor-glider,
shown shortly
before its first flight in
summer 2020.
1 / 2021
e Flight Journal
49