Finding Power for Human-Powered Aircraft

The world was electrified in 1977 when a human-powered aircraft named Gossamer Condor first flew a mile. Two years later, Bryan Allen powered another such aircraft, the Gossamer Albatross, across the English Channel in a flight of 36 km (22 mi) that required almost 3 h. Human-powered aircraft fly at altitudes of about 6 m. At these heights, even a few seconds of loss of power are out of the question, because without continuous power the aircraft will quickly land or crash. Thus the feat achieved by Bryan Allen required 3 h of truly uninterrupted effort at a very high work intensity.

The physiological properties of human exercise discussed in this chapter dictate that the rate of O₂ consumption of a pilot must be no higher than 65%–70% of his or her V̇_O2max for there to be a reasonable chance that a very motivated pilot will be able to maintain uninterrupted effort for 3 h. This biological fact set the engineering goals for the design of the Gossamer Albatross: The aircraft could not demand more power from its “power plant” than 65%–70% of V̇_O2max. Box Extension 9.2 discusses pilot selection and the next stage in human-powered aircraft following the Gossamer Albatross.

Bryan Allen powering the Gossamer Albatross over the English Channel on June 12, 1979

Engineering innovations in the 1960s and 1970s led to the invention of the Gossamer Albatross design, which required about 4.2 watts of power for each kilogram of pilot body weight to fly. A person could be expected to require an actual rate of O₂ consumption of 50–55 mL O₂/kg•min to provide this much power to the machine. Thus, for pilot effort not to exceed 65%–70% of V̇_O2max, Gossamer Albatross required a pilot with a V̇_O2max of 74–81 mL O₂/kg•min. The engineers knew that people with such high V̇_O2max values, although unusual, actually exist (see Table 9.4). Thus they needed to find such a person, who would also have the high motivation to succeed in this particular project. Bryan Allen, an amateur cyclist, was found and provided the needed V̇_O2max and motivation for the first human-powered 3-h flight. A decade later, in 1988, Kanellos Kanellopoulos, a Greek cyclist, achieved a still-greater record by powering the aircraft Daedalus for a flight of 119 km (74 mi), requiring almost 4 h.