Wednesday, July 24, 2013

Video: Record Setting Electric Airplane Preparing For 250 MPH Flight

Electric vehicle pioneer Chip Yates is back in the air with his record setting airplane. He spent much of the past year testing his electric Long-EZ for a series of flights this summer, and in the process broke his own speed records, all while testing new equipment for his grand plan of flying across the Atlantic in an electrified plane.
During his record setting flight last July, Yates managed to be the first pilot to top 200 miles per hour in an electric airplane. But he fried the battery in the process. It was an old battery, and Yates told us last year he knew its death was a likely outcome of pushing the lever that far forward for the fast flight.
The new battery from EnerDel is a 450-volt, 80 amp-hour pack capable of 600 amps continuous output, the equivalent of 258 horsepower, and twice the output of the old battery pack. It weighs 525 pounds and takes up the entire back seat. If he were patient, Yates could leisurely cruise at around 100 miles per hour drawing only 40 amps, giving him two hours range. But as always. Yates has speed on his mind, and during the first flight with the new pack he managed 175 miles per hour, though he wasn’t at full power.
“Fifty percent throttle, I swear,” Yates told us after the flight.
But he was actually exaggerating. The electric Long-EZ was able to hit 175 mph with the new system on just 41 percent power.
Last year Yates went from being a newly minted pilot, to setting the electric airplane speed record in a matter of days. He experienced his first dead stick landing after frying his battery in his second flight in the Long-EZ. This year, with a few hundred hours of flying experience under his belt and a year of planning and preparation, he’s taking things a bit more slowly in an effort to meet his multiple goals of setting records and testing new designs.
“Our new EnerDel pack can go up to 450 Volts,” Yates says. “But we started it at 416.8 Volts to be conservative for these early flights.”
Yates uses custom built software to control the electrical system that powers his airplane, and he keeps track of it all with the data logger that records more than 150 channels of data. He shared a few of those channels with us, along with the video from his most recent test flight last Saturday.
The highest throttle setting Yates used during the flight was just under 53 percent, which translates to 4,909 RPM for the motor. Because the electric motor can spin much faster than would be efficient for a propeller, Yates uses a gearbox with roughly a 2:1 reduction.
The propeller is a critical component of Yates’ record setting attempts. On an average airplane, the propeller is designed for a wide range of speeds, and because of that, isn’t particularly good at any specific speed. The propeller on the electric Long-EZ was designed by Craig Catto specifically for the speed flights. Catto is a legend in the aviation community and his propellers are found on everything from the fastest airplanes at the Reno Air Races, to the slowest airplanes capable of leaping off the ground. The carbon-fiber prop on Yates’ airplane is designed specifically to operate at maximum efficiency at 3,100 RPM, about 20 percent faster than a typical propeller found on your average Cessna. During the test flight the propeller reached a maximum of about 2,500 RPM while pulling just 211 of the 600 available amps from the battery.
Catto calculates that at 3,100 RPM, the propeller should be pushing Yates along at 250 miles per hour. If his calculations are correct, and Yates can keep all the other parts on the airplane flying together in formation, he plans on breaking his own record some time next month, and maybe set a few more while he’s at it.
The new recharging probe Yates will be testing on his Long-EZ is part of his plan for crossing the Atlantic Ocean in an electric airplane. Photo: Brent Baer