UM students aim for record, prize with human-powered helicopter

Engineering students tackle glitches but fail to get airborne on test day

May 11, 2011|By Frank D. Roylance, The Baltimore Sun

COLLEGE PARK — — A 110-pound competitive cyclist pedaled furiously with both hands and feet Wednesday in repeated attempts Wednesday to lift a spindly, human-powered helicopter off the floor of a gym at the Comcast Center.

But 24-year-old Judy Wexler's efforts to become the first female pilot to get airborne in such a craft went for naught as a drive chain kept jumping its sprockets, a bearing failed and the student-designed aircraft stayed stubbornly on the boards.

"It's engineering," shrugged Darryl Pines, dean of the University of Maryland's A. James Clark School of Engineering. It was his way of explaining the glitches and delays to the onlookers and news media that gathered for the spectacle, hoping to witness a red-letter day in aviation history.

The attempt, the first full-scale tests of the school's "Gamera Project," is also the culmination of a three-year bid by University of Maryland engineering students to establish a world aviation record and perhaps to claim the $250,000 Sikorsky Prize.

The Sikorsky Prize rules require that the human-powered rotor craft rise three meters off the ground (about 10 feet), and stay aloft for 60 seconds.

Although two previous engineering teams — from Japan's Nihon University in 1994 and the California Polytechnic Institute in 1989 — have managed to get their craft off the ground for a few seconds, neither feat captured the Sikorsky Prize, and neither was officially certified for a world record, according to Kristan R. Maynard, of the National Aeronautic Association.

So unless the Gamera establishes one, he said, "there is no world record."

"I don't think we're going to get the prize today," Pines conceded as Wexler tried again and again to get the Gamera off the floor of the gym. "We'll try to fly for five or 10 seconds [Thursday] … and break the record in the fall," perhaps after some re-engineering.

The students have hit upon a new design for the craft's four rotors, Pines said, but didn't have time to build them and try them out.

Named after a giant flying turtle featured in Japanese movies, the Terps' flying machine is 103 feet from rotor tip to rotor tip. The craft nearly fills the gym, with a design that only an engineer could love.

It's made of carbon fiber, balsa wood, mylar and as little metal as possible. The rotors are driven by a transmission line consisting of 200-pound test fishing line that is pulled as Wexler cranks, like the string on a toy top.

With all that, it weighs just 100 pounds. Wexler's body adds another 110.

She sits in a cockpit at the center, where she turns both hand cranks and foot pedals. The cockpit is connected by four spindly, 29-foot truss arms to the four rotors, each 43 feet long.

Maximizing power and lift while minimizing weight was the Gamera team's primary goal, said Brandon Bush, 29, a doctoral engineering student from Texas and a team leader.

"This is kind of the Wild West of engineering," he said. The students hit on a couple of key innovations after considering the craft built by prior competitors.

"We made it bigger, because helicopter theory says the larger the area covered by the rotors, the lower the power you're required to have," he said. The trick was to keep the weight from increasing with the size.

So the team came up with a novel design for the carbon-fiber spines that stiffen the rotor blades, providing strength at little additional cost in weight. They also added the hand crank, which increased the craft's power by about 10 percent.

Wexler, a doctoral candidate in evolutionary biology, said she's excited by the challenge. A competitive bike racer for five years, she has added uphill sprints to the regular long-distance workouts she rides near her parents' home in Bethesda.

Her shortest bike races, she said, typically last 45 minutes, and require a pedaling pace of 90 to 100 rpms. The Gamera tests have required 30-second sprints, with hands and feet turning at 120 rpm.

"The hardest thing was getting used to the pedal stroke," which is more forward and back than up and down, she said. "It's also not as smooth as a bike."

The official record challenge comes Thursday, when the NAA's Maynard will be present to document the craft's performance. If the Gamera gets airborne, and his report is accepted by the Federation Aeronautique Internationale in Switzerland, the Terps team would have established the first official world record for human-powered helicopter flight.

But even if they fail, the students will have gained invaluable experience, said Inderjit Chopra, director of the Clark School's Alfred Gessow Rotorcraft Center.

The goal of the Gamera Project, he said, is "to motivate these people toward aerospace and to excite them, to have them feel a sense of pride doing something that is a milestone in aviation, and to challenge them."

"They learned about teamwork, and how to build something that is enormously challenging," he said. "If it can capture the record, that would be a plus."

frank.roylance@baltsun.com

http://twitter.com/froylance

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