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!

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