Lithium Ion in the Air


A battery-powered ultralight motor glider. Aircraft image: Electric Aircraft Corporation

Batteries have taken off this year, quite literally. They powered Airbus’s new E-fan on its maiden flight, helped stuntman Chip Yates attain five new records ratified by the The Fédération Aéronautique Internationale, and went aloft with the first flight of the second incarnation of Solar Impulse, a plane slated to circle the world later this year.

But while these media-magnetic aircraft and their high-profile pilots have drawn the spotlight, one man has continued to make quiet, cheap, electric flight available to the everypilot.

Randall Fishman’s pioneering efforts to create battery-powered flight started less than a decade ago and were for purely selfish reasons. “I used to fly hang gliders and ultralights,” he says, “The ultralights were so loud and vibrated so much—they had snow mobile engines—you had to wear earplugs. I said I wish there was another way.” Fishman, known as “Dr. Gizmo” when a lad, had long been riding to work on an electric bicycle. So it was no great stretch for him to imagine putting batteries on a light aircraft. He and a friend decided to do a few calculations.

An electric trike. Image: Electric Aircraft Corporation

“We ran all the numbers and we could see it worked easily. You could see there was enough energy to lift the little trike and me and the engine. So we made it, built it, and it worked great right away.” On his third flight with the craft, he managed to stay up for a full hour. Fishman wowed the ultralight world when the setup, now called the ElectraFlyer Trike, made its debut in Oshkosh in 2007.

But Fishman wanted something that didn’t have the hobbyist image projected by a kite on a tripod. So he began to make a sleek, single passenger, enclosed cockpit aircraft. The latest version is the ElectraFlyer ULS, capable of cruising at 40 mph and staying up for a good two-hour flight. A trip that long costs about $1.20 in electricity. “A lot of a regular working guys have airplanes, but it costs so much—240 dollars to take a trip in the afternoon—that they just don’t do it,” says Fishman. Once they’ve plunked down the initial $59,000 for the ElectraFlyer, they can kiss fuel costs goodbye.

Squeezing maximum performance from the aircraft had more to do with the design of the vehicle—carbon fiber, foam, long wingspan—than the batteries. “Today’s advances are terrific for cars, but not for airplanes,” says Fishman, noting that the energy densities have not changed much in recent years. He uses a lithium cobalt battery built for military purposes, which is to say it has a much lower failure rate.   

But they’re not particularly light. When the FAA made the first ultralight rules there were no electric planes on the horizon. So the weight limit is written as 254 pounds plus five gallons of gas. There’s no mention of whether those gallons are to be measured as weight or as volume. So, to make it all possible, Fishman took a gallon to be a measure of volume, which would allow him 100 pounds of batteries (the pack he uses comes to 90).

The decision is in keeping with the original spirit of the ultralight regulations, which wanted to give pilots enough fuel to fly a good distance safely but not so much as to cause a major fire in the event of a crash. “You can blow up a building with five gallons of gas, if you vaporize it,” points out Fishman. “A stainless steel box of batteries has a lot less potential for fire.” Some of the battery power is kept in reserve in case of emergency. But with a 22-to-1 glide ratio, a pilot out of juice has a pretty good chance of finding a place to put the craft down lightly.

Two hours of flight time makes for good sport, but doesn’t get you too far. For the more trip-oriented pilot, Fishman has a diesel-electric hybrid in mind. The power needed to put a small craft in the air usually means that they fly inefficiently once they’re cruising. Fishman’s design would use diesel to get in the air, and battery power fly at peak efficiency once there.

Michael Abrams is an independent writer.

You could see there was enough energy to lift the little trike and me and the engine. So we made it, built it, and it worked great right away.

Randall Fishman, Electric Aircraft Corporation


January 2015

by Michael Abrams,