Human-Powered Helo - Mission Possible?

The two leading teams competing for the $250,000 AHS Sikorsky Prize for human-powered helicopter flight are regrouping after back-to-back unsuccessful assaults on the challenge, which remains unclaimed after three decades. A respected rotorcraft academic, meanwhile, says the lack of success shows the prize is unwinnable. Its organizer disagrees.

Established in 1980, the AHS Sikorsky Prize for the first controlled flight of a human-powered helicopter (HPH) requires the winner to fly for 60 seconds and reach an altitude of 3 meters while remaining within a 10-meter square. The University of Maryland's (UMD) Gamera II team has flown for 65.1sec and reached a height of 9.4ft (2.86m), but not on the same flights. And all the teams have struggled to control drift.

UMD's Gamera IIXR (Photo: AHS International)

Over a series of flights on Feb 27-28 in Baltimore, the latest Gamera IIXR reached heights up to 6ft and stayed aloft for up to 60sec - but not on the same flights - while a new control system allowed it to hover within the required area. The team hopes to try again in April. Then, on Mar 8 in Toronto, the rival AeroVelo team made nine flights with the Atlas, achieving its longest flight yet of 47sec, terminated only because of drift.

"We have some work to do," says Gamera II project manager Will Staruk. "We like the changes we made, but unfortunately we've been slowly adding weight with time, not just because of modifications but also because of repairs after each and every mishap. Now our plan is to put the helicopter on a diet, try and find any place we can trim weight. We are also looking at some possible modifications to improve efficiency."

AeroVelo plans to try again this Friday (Mar 15). "We know we’re close, and we know the helicopter/pilot is capable, but to clinch this prize absolutely everything has to go right," the team says in a blog post. A stripped screw caused "strange behavior" in one of the rotors on the Mar 8 flights, but was isolated too late to be fixed. "On the plus side, our weight/drag savings from the week before proved highly effective, with even lower power numbers than we’ve seen in the past," the team says.

AeroVelo Atlas (Photo: AHS International)

But Dr Gordon Leishman, a specialist in helicopters and professor at UMD (of all places), questions whether the prize is even winnable. "Sadly, even with the most optimistic assumptions of aerodynamic efficiency, weight efficiency, and power/total energy output from a human athlete, such a 60 second flight for a human-powered vertical flight vehicle with a climb to 3 meters (in the same flight) is all but impossible," he says on organizer AHS International's Facebook page.

"The analysis has been done, several times, and by several people, and the accomplishments thus far validates the analysis," he says. "But the Sikorsky Prize was not set by carefully examining (by analysis) what was actually possible and by so then making the goal (human-powered helicopter flight) challenging but achievable. Not surprisingly then we see the prize unclaimed yet again."

“When [the competition] was first formulated in the late 1970s, the requirements were based on the analytic capabilities of the day," counters Mike Hirschberg, AHS executive director. "The tremendous progress made over the past two years has demonstrated that we are closer than ever to seeing the longest running prize in aeronautical history finally being captured. We may soon see one of our HPH teams accomplish the ‘impossible.’”

I will give Gamera's Will Staruk the last word here. "We're certainly coming close to our maximum performance," he says. "When we didn't have controls in August we got to 9 ft, but never were able to really push it because of drift. Now that we have controls, it's heavier and our altitude is limited. The trade-off there is a tough one, but I think we still have room for weight cutting and efficiency improvements."

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