first untethered, fully electric manned helicopter flight

sk8norcal

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Pascal Chretien

http://www.gizmag.com/first-successful-manned-electric-helicopter-flight/19716/

http://www.pprune.org/rotorheads/462709-world-s-first-manned-electric-helicopter-takes-off.html
http://rotaryforum.com/forum/showthread.php?p=435913

The World’s first manned flight of a 100% electric powered helicopter was conducted on the 12th of August 2011, after 2 weeks of tethered flight tests. This machine, designed and test flown by Pascal Chretien, for the French based company Solution F, is the outcome of a remarkably short development period that was initiated in August 2010.

This ultra light coaxial helicopter weighs 170-Kg empty, including 60 Kg of high performance air-cooled Li-ion polymer batteries that can deliver 43 KW continuous, and 52 KW peak. The craft weighs 247-Kg at takeoff and offers 10 to 12 minutes flight time. To save weight, conventional cyclic and flight controls were replaced by a weight shifting system, as well as a specific design for rotor inertia, and blade pitch. Collective and yaw are achieved via electrical flight controls.

An advanced MOSFET based feather light drive train offers astounding 87.5% end to end efficiency, from batteries terminals to rotor mast.

This helicopter is a demonstrator intended to pave the way for hybrid rotary wing aircraft and is a test bed for new technologies. Flight envelope expansion is ongoing.
 
Chretien chose brushed DC motors for the rotor shafts, even though the required power output was "just on the edge of what can be achieved with brushed motors" - because brushed motors are exceptionally efficient, and their simple controller units are significantly lighter than those of more powerful, less efficient brushless motors
 
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