The aircraft weighed 70 pounds, was 96 feet wide, and allowed a human to pedal the propeller and move forward—at an anemic 11 miles per hour.

In 1977, an aircraft that looked too delicate for sustained flight took off from a short runway in California—and made aviation history. The Gossamer Condor, as that aircraft was known, was a decidedly odd-looking airplane. It had enormous wings and no conventional engine—and almost no weight whatsoever. Rather than a motor, its power plant came from the leg power of its pilot.

On August 23, 1977, pilot and (not coincidentally) avid cyclist Bryan Allen flew the strange aircraft around a prescribed figure-eight course at Minter Field in Shafter, California. The flight lasted less than 8 minutes, covering a distance of just 1.35 miles. But the achievement won designer Paul MacCready the Kremer Prize—and more importantly demonstrated that sustained, controllable human-powered flight was actually a real possibility.

Why Is Human-Powered Flight So Hard?

Human-powered flight—the notion of using human effort to power an aircraft, in much the same way that a cyclist pedals a bicycle—has fascinated inventors almost as long as aviation itself. The fundamental problem with it is very simple: aircraft require lots of power to move, and humans just don’t generate much. The average person can generate about 0.1 horsepower on a relatively sustained basis, with short bursts of energy ranging from 1–2 horsepower. By contrast, a typical Cessna has an engine ranging from around 150 to 200 horsepower. In other words, a bicycle chain connected to a Cessna propeller would need hundreds, and perhaps thousands, of people on the other end in order to sustain flight!

This obvious mismatch makes most human-powered arrangements impossible. If someone wants to build a human-powered aircraft, they must do so specifically for that purpose—namely extraordinarily light and incredibly aerodynamically efficient, like a bird rather than a conventional aircraft.

About the Kremer Prize

In the mid-20th century, British industrialist Henry Kremer made his fortune in lightweight manufacturing—particularly plywood, a composite laminated wood that was both light and strong. Kremer’s plywood was used in British aircraft during World War II—most notably the De Havilland Mosquito, a multirole fighter-bomber built almost entirely of wood. After the war, Kremer’s interest in lightweight flight continued, and in 1959, he established a prize to encourage designers to craft an aircraft light enough to take off under the power of only a human pilot.

The requirements of the prize called for a human-powered aircraft to take off under human power, fly a figure-eight course around two markers set 0.5 miles apart, and clear a 10-foot obstacle at the beginning and end of the flight. This was a simple enough challenge. Even so, the £5,000 prize (~$13,000 1959 USD, $145,000 today) remained unclaimed for nearly two decades. In 1973, it was increased to £50,000 (~$130,000 then, $977,000 today), initially to no avail.

Introducing the “Gossamer Condor”

American aeronautical engineer Paul B. MacCready approached the problem differently than those who had tried before. An accomplished glider pilot as well as an engineer, MacCready believed that rather than creating a highly sophisticated conventional airplane, the solution required extreme lightness, enormous wing area, low-speed flight, and a simple construction that could be modified quickly. The inspiration came partly from watching birds and considering the relationship between weight, wing loading, and required power.

MacCready’s team operated on a very modest budget relative to conventional aerospace programs. These limitations were reflected in the resulting product, which looked more like a giant model airplane than a normal aircraft. The Gossamer Condor was built around aluminum tubing, lightweight plastic film, and other extremely light materials. The wingspan measured approximately 96 feet—wider than many powered aircraft, despite the Condor weighing only around 70 pounds. The pilot sat in an open framework beneath the wing with pedals that drove a large propeller through a bicycle-style mechanism. Its cruising speed was only around 11 mph. 

Still, the huge wing produced the lift required at extremely low speeds, and the low weight meant Allen’s limited human power could keep the aircraft airborne. These solutions to the power problems created another problem: the Gossamer Condor was extremely sensitive to wind turbulence because the aircraft was so light. The aircraft would have struggled to remain airborne for long periods of time, in changing weather. But if the conditions could be engineered just right, it was just good enough to win the Kremer Prize.

The historic attempt took place at Shafter Airport near Bakersfield, California, during favorable conditions with low wind. Allen pedaled the Condor under his own power and flew the prescribed course, completing it in 7 minutes and 27.5 seconds, clearing the required obstacle and winning the prize. More importantly, the flight proved human-powered flight was indeed possible—though relatively few tried it again!

About the Author: Harrison Kass

Harrison Kass is a writer and attorney focused on national security, technology, and political culture. His work has appeared in Tablet, City Journal, The Hill, The Spectator, and The Cipher Brief. He holds a JD from the University of Oregon and a master’s in Global & Joint Program Studies from NYU. More at harrisonkass.com.

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