Plane & Pilot
Tuesday, June 21, 2011

A New Era Dawns: Electric Flight


An update on airplanes in production, competition prizes and R&D


A Gathering Tide

As an industry, electric flight is still in toddler mode. Batteries provide, pound for pound, a mere fraction of the energy density of gasoline (see sidebar). Therein, as the Bard said, lies the rub: The culprit is weight, because one pound of avgas has roughly 40 times the energy delivery of a pound of battery.

Up to now, electric-aircraft airframes maximize flight performance through highly efficient design to compensate for that lack of sufficient electrical storage capacity. The Oil Age will, in time, give way to the Clean Power Age. For now, Li-Ion technology currently holds the performance-leading edge for mass-produced batteries. For electric aircraft to become common, battery efficiency will need to double, then double again and double again.

Still, two-seat electrics with one-hour-plus endurance already are in production, with more on the way. Randall Fishman's ElectraFlyer-X, a two-seat composite LSA with lithium powerpacks and a newly developed motor, should fly this year, possibly in time for Oshkosh AirVenture 2011.

The Electric Envelope, Please...

To spur recognition and development, several major awards and competitions now offer substantial money prizes. On the last day of this year's AERO e-flight-expo in Germany, the Berblinger Flight Competition divided 100,000 Euro ($131,000) among three proven aircraft, each with a unique application of electric power: the elegant, single-seat Lange Antares 20E self-launcher sailplane (the world's first certified electric); Eric Raymond's record-setting, solar-powered Sunseeker; and Manfred Ruehmer's Elektro-Swift, an ultralight flying wing with streamlined pod and folding pusher prop.

The 20-meter-span Antares was cited as "the only (electric) aircraft that fulfils the strict European Aviation Safety Agency (EASA) certification requirements...life expectancy of 20 years or 3,000 charge cycles." More than 70 production Antares have been delivered.

Of the three, only the slender, graceful Sunseeker isn't for sale...yet. It flies solely on electricity generated by wing-borne super-lightweight solar cells. Raymond is currently working in Slovenia on the 23-meter span (75 feet) Sunseeker Duo two-seater, which will eventually be marketed.

The Elektro Swift, produced by Italian hang-glider company Icaro, takes another tack. It's a highly optimized, single-pilot, lightweight soaring machine based on an excellent-performing rigid-wing hang glider.

Also presented were Erik Lindbergh's Lindbergh Electric Aircraft Prize (LEAP) awards. Three categories (and $60,000 in prize money) went to the Solar Impulse for Outstanding Achievement; Pipistrel Taurus Electro G2 for Best Electric Aircraft (it's the first production two-seater electric); and Best Propulsion System, to LZ for its Front End Sustainer (FES) folding prop/motor retrofit package for sailplanes.



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