A Human-Powered Helicopter Takes Flight(READ IT)

A University of Maryland team has succeeded in building and flying a helicopter powered entirely by a single human pilot. Next Step: The Sikorsky Prize, a human-powered-helicopter award that has been awaiting a winner for 30 years.


On June 2, the University of Maryland team's flight time was certified at 4.2 seconds. Though that time is less than half of what the team members recorded themselves, Maryland still became the first team with a certified flight time

Two years of work culminated in a few seconds of flight this month as students from the University of Maryland flew their homemade helicopter right into the record books. The event was the first-ever human-powered helicopter flight flown by a woman—and sets up the Maryland team for a run at the elusive Sikorsky Prize, an award for human-powered helicopters that's gone unclaimed for just over 30 years.

Judy Wexler, a biology graduate student at the University of Maryland, was the pilot. Wexler pedaled furiously using both hand and feet pedals to get the craft airborne for just 10 seconds. Ten seconds might not sound like much, but in the 30 years that the prize has been out there, only two other teams have even gotten off the ground. The team is now waiting for the National Aeronautic Association and the Fédération Aéronautique Internationale, an international body that maintains aviation records, to certify the time.

The helicopter is extraordinarily light—only 210 pounds, including the pilot. Crafted primarily from balsa wood, carbon fiber, Mylar and foam, the aircraft has a limited weight that belies its size. The X-shaped frame has crossbars measuring 60 feet, with a rotor at each endpoint. The rotors themselves are 42-feet in diameter, with blades that are 21 feet long and just 7 pounds each. The helicopter needed to be light enough to lift, but strong and efficient enough so that it wouldn't shudder apart with the motion of the pedals. To accommodate the huge frame, students added additional truss supports, or "baby trusses," at weak points along the structure.

The pilot pushes the pedals with both her hands and feet, requiring a transmission system capable of transmitting the two different forces simultaneously and smoothly to the rotors. The students used string, light chain and carbon-fiber gears to build the transmission; it's all held together by string: There is a spool of fishing line attached to each rotor, and all of the strings are connected through an elaborate pulley system to a central pulley underneath the pilot's legs. This central pulley links directly to the foot pedals and connects to the hand pedals via the chain.






Getting the woman-powered chopper aloft was a monumental struggle. Darryll Pines, dean of the college of engineering at the University of Maryland, calls it "an engineering soap opera." After two years of design and construction, the students assembled the helicopter in full for the first time just a few days before the flight. While the frame and rotors handled beautifully, holding together without major structural damage during the test-flight period, the team needed to reinforce the cockpit. And the transmission system had to be entirely rebuilt overnight. Plus, the students were working through final exams, sometimes leaving work on the project to take a test and coming straight back to continue work—or going two or more days without sleep. In the last possible hour before the competition window closed, the craft finally got off the ground.

The Maryland students named their helicopter Gamera after the ferocious flying turtle from Japanese monster movies. (The University of Maryland's mascot is the terrapin, also a turtle.) Fifty students from both graduate and undergraduate backgrounds spent over two years working to bring the project to this point. Project manager and Ph.D. candidate Brandon Bush says that despite all the trouble, the students stayed confident in their design. "It's just simple math," he says. "It had to fly."

But there's still a long way to go before they reach their ultimate goal: the Sikorsky Prize. The American Helicopter Society created the prize in 1980 (and PM covered the announcement) and will award $250,000 to whichever team builds a helicopter to meet four challenging criteria (along with a few other minor requirements). The helicopter must be powered entirely by its human pilot, remain aloft for 1 minute, reach an altitude of at least 3 meters (about 10 feet) during the flight and stay within a 10-meter (32.8-foot) square.

No one has succeeded yet. Of the two teams that have gotten off the ground, one, working at California Polytechnic State University in 1989, flew for 7.1 seconds. The other, built in Japan, flew for 19.46 seconds in 1994.

Officially, however, the Japanese and Cal Poly teams failed to be certified by the NAA and corresponding international record-keepers, meaning that the University of Maryland team will hold the world-record time if it passes certification. Whatever the official figures say, Pines says that the Maryland team will attempt to surpass the Japanese time. "We're learning on the fly, just like they [did]," he says.

But for now, the Gamera team is savoring the moment. V.T. Nagaraj, a faculty advisor to the group, says that everyone involved is still elated. "It was amazing," he says. "We have not yet come down to earth"