A Quiet Hum Behind Electric Aircraft

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Electric aircraft are very quiet – and they’ve gone very quiet at Oshkosh this year.

They were all the rage here two to three years ago, when the EAA sponsored the Electric Aircraft World Symposium, the Lindbergh Foundation awarded its aviation prize for electric aircraft, and NASA and the Comparative Aircraft Flight Efficiency (CAFE) Foundation announced a competition for battery-powered flight.

Only three or four electric aircraft could be found at this year’s Oshkosh without the draw of competitions, prizes and symposiums. And it’s apparent the EAA didn’t expect many, as it provided only four or five plug-in charging stations in the aircraft parking areas.

Where have the electric aircraft gone?

Perhaps with Airbus Group’s announcement two months ago that it would enter the general aviation market with two all-electric models, the two-seat and four-seat e-Fan, they have suddenly become mainstream.

“Let’s face it, electric aircraft are still only marginally useful,” says Mark Beierle, owner of Earthstar Aircraft, who has experimented with different batteries, motors and propulsion systems for the last five years. “We started with golf cart batteries and model aircraft engines. They worked, but not well.”  

Now Beierle is flying a Joby Energy Inc. engine that he helped develop with 20-kilowatt output (about 27 hp), powered by two 2.8 kW hour lithium-polymer batteries from Zero Motorcycles. They allow an endurance of 40 minutes, although using a larger 11.4 kW hour battery allows the aircraft to stay up for 1 hr 10 min. An on-board charger allows the batteries to recharge in seven hours, but a larger ground unit can give a one-hour turnaround.

Beierle maintains that electric aircraft are now viable for sport aviation, given that a recent survey of ultralight pilots showed their average flights were only 40 minutes, with a minority claiming they stayed up for an hour.

So why haven’t they caught on? The batteries are expensive, he says, and just as with computer technology, buyers are putting off a decision into the future as they know the battery technology is advancing rapidly.

Perhaps, and just perhaps, Airbus’s new venture with the eFans will bring electric aircraft to a much broader market.

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