Flying the airplane electric presented aerospace engineer a 'green' challenge

UNIVERSITY PARK, Pa. — Four years ago, Jack Langelaan scaled up his research to take on a different challenge. As he explains, "We applied the algorithms that we had developed for small unmanned aircraft to the problem of flying a large electric-powered airplane."

The Green Flight Challenge, a NASA Centennial Challenge program intended to spur private development of fuel-efficient small airplanes, was announced in 2009. To win it, an aircraft would have to fly 200 miles in less than two hours and use less than one gallon of fuel per occupant, or the equivalent in electricity. The problem seemed right up Langelaan's alley.

"Electric motors are very, very efficient," says the associate professor of aerospace engineering. "You can go from stored energy to mechanical energy with about 90 percent efficiency, compared to 30 percent for an internal combustion engine. The downside is that the energy density in a battery is a factor of 70 lower than that of gasoline."

That's a lot of extra weight to carry around, and for an airplane, extra weight means everything. "There are huge improvements in batteries coming down the line," Langelaan says, "but in the meantime, the answer is to minimize as much as possible the energy needed to fly."

That's where his work on exploiting wind and air currents came in. In 2010 he approached the Slovenian small-aircraft manufacturer Pipistrel, and over a year led a team that modified one of Pipistrel's planes, the Taurus, to meet the needs of the contest. Langelaan's technical role was to develop the plane's optimal flight plan.

In the culminating fly-off in Santa Rosa, Calif., in September 2011, Pipistrel's electric-powered Taurus G4 edged the competition by traveling the equivalent of 400 passenger miles per gallon of aviation fuel at a speed of 107 miles per hour, twice as efficient -- and twice as fast -- as a Toyota Prius. The $1.35 million winning prize is the largest ever awarded for aviation.

"It was an incredible experience," Langelaan remembers. "We were not the first to fly an electric-powered airplane. But we were the first to demonstrate that electric-powered flight can be practical."

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Last Updated March 06, 2014