University of Maryland engineering student Colin Gore performs a test flight in Baltimore on Wednesday. (Patrick Semansky/Associated Press)

In test flight after test flight, a group of students from the University of Maryland has labored for days to make an ungainly, 115-foot helicopter fly three meters off the ground and hover for 60 seconds, powered only by a pilot pedaling like crazy.

It’s never been done before.

The reward: the $250,000 Sikorsky Prize. The engineering contest was dreamed up by the American Helicopter Society and Sikorsky Aircraft 33 long years ago after several successful man-powered airplane flights. But this man-powered helicopter challenge — which also involves hovering in a 10-meter square — has proven far more elusive, unintentionally.

It was never meant to be so unattainable.

The competition’s developers said they would “start off with something easy, like taking off and hovering,” said Mike Hirschberg, the helicopter society’s executive director. “Well, 33 years later, it’s proved just how difficult that’s been.”

In 1989, Cal Poly students broke the flight record by hovering for 8.6 seconds. In 1994, a Japanese team had a flight of 19.46 seconds.

In 2008, graduate students from the U-Md. Alfred Gessow Rotorcraft Center decided to take up the challenge. In July 2011, the first Maryland chopper, the Gamera, flew for 11.4 seconds.

The students have developed a new craft, the Gamera II, and hold world records for height and duration of flights. The craft has flown for more than 60 seconds and in August reached a height of 2.9 meters, or about 9.4 feet.

“Almost all of our colleagues, everyone in our industry said that was not possible, not feasible,” Inder Chopra, the faculty adviser of the project, said of the height. “Now it looks like people think it is feasible.”

The challenge is putting height, duration and control together in a single flight. A new control system was added to the Gamera II to enable the pilot to essentially steer the aircraft to keep it within the 10-meter square.

One of the most difficult elements is finding a place for test flights. Elizabeth Weiner, a graduate student who has been working on the project for two years, said the footprint of the U-Md. craft is larger than that of a Blackhawk 60 helicopter.

Fifty-one students working on the project have toiled since Wednesday in a 32,000- square-foot exhibit hall in the Baltimore Convention Center.

Increasing competition from other teams has heightened the urgency for a successful flight. AeroVelo, a team in Toronto, is testing every two weeks, said Benjamin Hein of Sikorsky. Its craft has had flights of five feet and 30 seconds unofficially.

“Right now, it’s this neck-and-neck race between us and the Canadians in terms of achieving this,” Weiner said. “It’s stressful.”

Weiner said that when their Canadian counterparts test every other Friday, Maryland team members constantly check for online updates, making sure no records have been broken.

“We’ve been doing this for so long, and we’re really close,” she said. “We don’t want to be beat out at this point.”

Confidence was high Wednesday as the team prepped test flights, making small adjustments to the rotors. Team members said they thought the prize was within their reach.

More than 20 practice tests in, they had achieved a height of five feet and were ready to go for the full three meters a shot. But the first run at the prize Wednesday was unsuccessful, and the flight was cut short.

“Every time something crashes, you can tell the team just, there’s that collective sigh of disappointment because everything takes a little while to set up, it takes a little while to prepare,” Weiner said.

Another concern is the physical condition of the pilots. Each of the three pilots, all U-Md. students, is about 120 pounds, light enough to not hold the craft down. To spin the hand and foot pedals to create enough lift to continue hovering for a minute is extremely taxing.

“Once the tests get much over 30 or 40 seconds or so, they definitely can get pretty tiring,” said Duncan Enerson, 19, a freshman. “Anything past that, like once you get to like 50-, 60-second flights, after that, you’re just kind of, flat out, you’re just done.”

Enerson’s twin, Henry, and graduate student Colin Gore, are the other two pilots. Duncan Enerson said there is competition between them to be the one who pilots the prize-winning flight.

“You want to be the one to be able to say I got the world record,” he said.

Late Wednesday night, an effort to lighten to craft led the arms of the helicopter to bend, crushing the center and giving the team a major setback.

Some of the students were at the convention center working through the night to fix the problem. By about 7:15 a.m. Thursday, with a few students asleep on the concrete floor, the craft was again ready to fly.

Long hours working on Gamera is nothing new for the students. Weiner said she puts in 30-40 hours per week on the project. They are all volunteers and don’t get pay or credit for their time.

“We’re putting in 13-hour days here,” Ben Berry, a graduate student, said. “But we’re doing that because we want to. It’s not really a chore.”

Berry said some students were working on the craft even with exams or tests in a few hours. Weiner, flashing a sheepish grin, said some were skipping class to try for the prize.

Chopra said the caliber of the students working on the craft is extremely high. “The curiosity to learn new things and try to do something new, which is not routine,” he said, is very important.

Even without the Sikorsky Prize, Berry said the world records and firsts were extremely important to the team.

“This isn’t something that everyone is trying to do, but it’s just fun to say that you hold a world record, even if it’s just something kooky like this,” he said. “It is kooky in a way but we know the serious engineering that went into this. . . . A lot of brainpower, long nights, long weekends, long weeks like this flight testing have gone into this.”