In my previous blog from Oshkosh, I talked about Sikorsky’s ambitious Firefly project, an all-electric helicopter powered by batteries. Sikorsky had planned for first flight sometime in 2012, but apparently someone has beaten them to the punch! Pascal Chretien, a French electrical/aerospace engineer and helicopter pilot, has designed and built a fully electric coaxial rotor helicopter by himself (almost) and took his machine into the air for a two minute flight.
The challenges for electric fixed-wing flight are well documented, and they are even greater for electric rotary-wing flight. For a fixed-wing aircraft, it will only require max power during takeoff, but once in flight, the power requirement is reduced. On the other hand, a helicopter requires high power throughout its flight profile, so it will require a tremendous amount of energy to stay in the air.
For Pascal, he had to design a helicopter with minimum weight, so he had to adopt a different configuration than the standard single main rotor. He picked the coaxial design so all the power is going toward lifting the vehicle off the ground, versus a 90:10 split with the conventional helicopter. Instead of cyclic for directional control, he uses a weight shifting system. This design is particularly dangerous for two reasons. The first reason is that you are shifting the C.G. of the vehicle, which could be catastrophic if the weight is shifted beyond design envelope. The second reason is that the control is now backwards compared to the regular cyclic.
As a throwback, perhaps homage, to the early aviation pioneers, Pascal did not recruit a test pilot to fly his contraption. Instead, he took it to the air himself. So far the flight testing has been limited to within ground effect while he makes final tweaks. Eventually, Pascal and his sponsor, Solution F, is targeting 10 to 12 minute flight time, which is similar to the Firefly.