In 2011, Pascal Chretien, an electric and aerospace engineer from French based Solution F, achieved the first untethered electric powered helicopter flight in history. The achievement seems modest in that he hovered 1 m above the ground for just over two minutes after several weeks of tethered flight testing.
The ultra light craft employed in the historic flight weighs 544 pounds (247 kg) 374 pounds (170kg) empty. Batteries weigh 132 pounds (60kg) with an output of 43 kwh continuous and a peak of 53 kwh. Note that watts are a unit of power and kilowatt hours a unit of energy.
Sikorsky’s Electric Helicopter
Sikorsky helicopter manufacturers have been attempting the same feat but have been using a traditional main rotor and tail rotor to counteract torque. Sikorsky’s project is called Firefly and had been the only research project in the world attempting to create an all electric helicopter before Solution F.
The Sikorsky design uses a 180 hp electric engine less powerful than a Crown Victoria Sedan automobile and has a flight time maximum of 15 minutes. Engineers are using nascent technology and learn and adapt it as they conduct tests.
Chretien designed a “coaxial contra rotating twin rotor” to reduce weight, minimize power requirements and eliminate the need for a tail rotor. Traditional helicopters use rudder pedals to control yaw but Chretien’s power control and a mechanical tilt weight shifting system do the job instead . The electric powered aircraft uses lithium-ion battery technology to power its engine. Engineers are also experimenting with “lithium-air batteries.” Finally a very light drivetrain provides 87.5% efficiency in converting power to lift.
Technical Challenges to Commercial Use
The biggest obstacle to commercial use of electric powered helicopters is reducing their weight. As engineers work on this issue they will develop hybrid rotary wing aircraft that will serve as an interim step to fully electric versions.
In the meantime toy sized electric helicopters are developing quickly. Using remote control, rechargeable batteries gyroscopes and cameras these toys can be very entertaining and provide a “push” to advancing technology of larger craft.