by Dr Peter Harro, Chairman, IDTechEx
It can only fly for 15 minutes but it is a breakthrough all the same. Improved batteries have finally made a manned electric helicopter a reality. It follows rapidly on announcements of all electric fixed wing aircraft from Germany (PC-Aero), France (EADS), Italy (Sky- Spark), China (Luneec) and the USA (Sonex etc) and an historic 24 hour flight by Solar Impulse powered entirely by the sun. Solar Impulse has the wingspan of an Airbus (over 200 feet) and carries 11,628 solar cells to power four motors.
For a few years, allelectric power assisted gliders and hang gliders have been available. Advantages of electric aircraft include improved manoeuvrability due to the greater torque from electric motors, increased safety due to decreased chance of mechanical failure, less risk of explosion or fire in the event of a collision, and less noise. There will be environmental and cost benefits associated with the elimination of consumption of fossil fuels and resultant emissions. As with on-road vehicles, the problem is range – the best range of both being 160- 400 km (about 100-250 miles) in practicable manned con- figuration.
Some of the fixed wing pure electric aircraft and other electric flying vehicles are now available in kit form. The SkySpark pure electric fixed wing aircraft has reached 155 mph(300 kph) though 100 mph is more typical of such aircraft, and they have flight time of 1 to 3 hours. The SkySpark experiment is based on a two-seat Pioneer Alpi 300 powered by a 75 kW (100.5 horsepower for the nostalgic) electric motor using brushless technology and lithium polymer batteries.
Electric helicopter
Sikorsky Innovations, the technology development organization of Sikorsky Aircraft, has officially introduced “Project Firefly,” an all-electric helicopter technology demonstrator.
Chris Van Buiten, Director of Sikorsky Innovations, says, “Our objectives with Project Firefly are to provide a proof of principle concept to validate the benefits of an electrically powered rotorcraft; to develop the technologies to enable the manned flight of that technology, and to drive future development of improved, state-of-theart ‘green’ technologies and practices.
In building the demonstrator, the Innovations team replaced the legacy propulsion system of an S-300CTM helicopter with a high-efficiency, 142 kW (191 horsepower) electric motor and digital controller from U.S. Hybrid, coupled with a lithium ion energy storage system from GAIA. The two GAIA 135 Ah lithium polymer hold it aloft for 15 minutes. Most other electric aircraft also employ lithium polymer traction batteries of one chemistry or another because of safety and light weight, with no heavy metal casings. GAIA uses lithium iron phosphate and lithium nickel cobalt aluminum in the cathodes of its traction batteries.
Integrated sensors provide real-time aircraft health information to the helicopter pilot through a panel integrated interactive LCD monitor. Eagle Aviation Technologies, LLC, executed the custom airframe modifications and assembly of the demonstrator aircraft.
“Many of the most significant advancements in aviation have been enabled by transformations in propulsion technology. It is exciting to be at the forefront of the exploration of electric propulsion technology for rotorcraft,” said Mark Miller, Vice President, Sikorsky Research & Engineering. “Through the electrical conversion, propulsion efficiency of the aircraft has been increased roughly 300 percent from baseline. Electric propulsion also inherently simplifies the complexity of the propulsion system by reducing the quantity of moving parts, increasing reliability while reducing direct operating costs.”
“World fuel reserves are continuing to dwindle as demand increases. This inversion of the supply/demand cycle will increase operating costs of all fuel-based vehicles, especially in the aviation industry. Nowhere is this more apparent than in the commercial helicopter market, where the critical role rotorcraft play could be threatened by spiraling fuel costs,” said Mark Miller, Vice President, Sikorsky Research & Engineering, in a statement.
