Experimenter Beats Sikorsky To Electric Helo Milestone
At EAA AirVenture 2010 last year, Sikorsky unveiled it's Firefly
electric helicopter proof-of-concept demonstrator, a
battery-powered electric helicopter it said it expected to fly by
the end of the year. It was essentially a legacy S-300C helicopter
with the engine replaced with a 190-HP electric motor, and honkin'
huge lithium batteries, which left enough useful load for only a
very light test pilot. This year, the Firefly was back at Oshkosh,
and still hadn't flown. Now, it will be too late for the enormous
manufacturer and military contractor to get there first.
Instead, in a story that would be an even better fit at
AirVenture, a private experimenter working in France took on an
assignment from a French company called Solution F to design, build
and fly the world's first untethered electric helicopter, (pictured
in Gizmag photo, above) and got the whole thing done in about 12
months. Pascal Chretien's first flight in his original design
happened August 12, according to Gizmag, remaining in ground effect
but reaching a height of about one meter during a flight lasting
two minutes, ten seconds.
In an irony noted by Gizmag's Loz Blain, while Sikorsky went
with an old-school combination of single main rotor with tail rotor
for anti-torque, Chretien chose to cut the waste of a tail rotor
system by using coaxial main rotors, a scheme like the one Sikorsky
has promoted as the future of high-performance helicopters with its
X2 Technology Demonstrator. He also replaced the conventional
cyclic control system with a weight-shift setup to shave some more
weight.
To make deadline, Chretien used welded 7020 aluminium for the
airframe instead of lighter composites. A major concern for the
electrical/aerospace engineer and helicopter pilot was careful
regulation of the esoteric battery system. He told Gizmag, "The
infamous thermal instability of lithium/cobalt chemistry does not
leave room for error... It is important to take it slowly, if I
don't want to wreck tens of thousands of Euros worth of hardware;
but also, in case of crash I stand good chances to end up in kebab
form, as LiPo batteries are notoriously infamous for bursting to
flames once distorted. The chemical reaction is violently
exothermic. This machine looks like a toy, and flies like a toy,
but there is a raging tiger under the seat, waiting to bite at the
first mistake."
Chretien achieved an efficiency level of over 87 percent from
battery terminals to rotor, and says he may even have enough
reserve power to use a convention cyclic control.
Your move, Sikorsky!
ANN's Daily Aero-Linx (05.02.24)
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