IN AN abandoned brewery in downtown Montreal this week, the first rotor of a
revolutionary human-powered helicopter will be slotted into place. The move
marks a major milestone in an ambitious attempt to win the US$20,000
Sikorsky Prize for human-powered helicopter flight.
The helicopter鈥檚 unique design uses a pair of rotors above and below the
pilot, which counterrotate to provide undreamed stability. To win the prize, it
will have to hover above a 10-metre square for 60 seconds, reaching an altitude
of 3 metres. It鈥檚 a tough task. Out of 17 attempts since the prize was first
offered in 1980, 15 failed to get off the ground and the two that did fly failed
to stay aloft for more than 25 seconds.
But the multidisciplinary team of 15 graduate engineers from the 脡cole de
Technologie Sup茅rieure (脡TS) in Montreal has high hopes. Its design,
called H茅lios, places a recumbent pilot between a pair of rotors 35
metres in diameter (see Diagram)
which turn in opposite directions to give the craft stability. The blades taper from
1.25 metres wide to just 10 centimetres at the tips.
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鈥淟ow weight is crucial,鈥� says Simon Joncas, the project leader. The finished
carbon-fibre composite helicopter will weigh 73 kilograms, and the pedalling
pilot another 70 kilograms. He will have to deliver 750 watts to make the huge
rotors turn at seven revolutions per minute.
鈥淲e have tested many cyclists but only one performs as we need,鈥� said Joncas.
鈥淔ran莽ois Maisonneuve has trained for four years to pedal at maximum
power for just two minutes.鈥� Maisonneuve previously piloted the 脡TS
human-powered submarine, the Omer 3, to a world-beating 6.55 knots (3.37 metres
per second) in a pool near Washington DC in June 1997.
H茅lios has also borrowed the sub鈥檚 highly efficient drive system,
which can transfer 90 per cent of the pedaller鈥檚 energy to the rotors. Instead
of an endless bicycle-style chain, which would have high frictional losses, it
uses a steel cable wound around a large wheel 14 times. It takes two minutes for
the pilot to pedal to the end of the cable.
In flight, a computer will vary the pitch of the rotors, and motors will move
masses to compensate for the movements made by the pilot as he shifts in his
seat.
The first human-powered helicopter to get off the ground was the Da Vinci
III, on 10 December 1989, built by a team from California Polytechnic State
University. It flew for 7.1 seconds, but didn鈥檛 rise more than a few
centimetres. The second was the Yuri I, which reached 20 centimetres in a
19-second flight in 1994.
The coordinator of the Sikorsky Prize, Bob Huston, admires the novel Montreal
design but doubts it will succeed. 鈥淚 like their odds but I suspect they will
fail with this configuration,鈥� he says. The attempt on the prize will take place
in Montreal鈥檚 Olympic Stadium next summer.