Sustained, level flight powered solely through the use of human muscle.
Although it will never be an efficient mode of transportation, human-powered flight satisfies an innate human desire to emulate the freedom of birds. Unfortunately, using arms to flap attached wings cannot generate adequate lift and propulsion, as bird wings do, but well-conditioned athletes can maintain fractional horsepower outputs for long periods of time using their legs, and this, in the late twentieth century, led to a series of remarkably long, controlled flights over both land and water. The earliest truly successful flights were made by entrepreneurs in response to monetary prizes. Unfortunately, it does not appear that the resulting aircraft are practical flying machines for the vast majority of fliers and homebuilders, requiring too much muscle power and being far too large, too fragile, too expensive and too vulnerable to being upset by atmospheric turbulence.
The earliest seekers of human-powered flight were the tower and bridge jumpers, dating from at least 1000 c.e. Stability and control, as well as wing-flapping propulsion, were always in question, although some glides were at least partially successful. The key insight, as it was for motor-powered human flight, was to separate lift and propulsion: use fixed wings for lift and an engine and a propeller for propulsion. Monetary prizes eventually stimulated gifted teams of designers and enthusiasts and they have transformed the almost universal dreams of human-powered flight into reality.
The first prize offered for human-powered flight, the Prix Peugeot of 1912, was won in Paris in 1921 by bicycling champion Gabriel Poulain and his Aviette when he flew 40 feet in a straight line, using biplane wings attached to a bicycle to glide forward after he abruptly increased his wing angle to lift him into the air. By 1937, a 154-pound German bicycle racer, who was able to generate a momentary power output of 1.3 horsepower, had upped the straight-line distance to almost 0.5 miles using a 75-pound sailplanelike airplane, called Mufli, with a pedal-powered propeller.
Late-blooming enthusiasm for human-powered flight in England resulted in seven men forming the Cranfield Man-Powered Aircraft Committee in 1957. Industrialist and philanthropist Henry Kremer was then inspired, in 1959, to offer a £5,000 prize for the first British human-powered aircraft that could take off and fly a figure-eight course between two turning points not less than 0.5 miles apart and fly over a 10-foot height marker at the beginning and end of the flight. In response, three postgraduate students of Southampton University formed SUMPAC (for Southampton University Man-Powered Air Craft) and made the first British human-powered flight of 50 feet in 1961. But SUMPAC was unable to exceed 2,000 feet in flight length and could not turn more than about 80 degrees.
A second effort, backed by the famous De Havilland Aircraft Company, flew about 3,000 feet at an average height of over 6 feet in 1962 in Puffin, creating a world record that was to stand for ten years, but the craft could not be turned more than about 80 degrees. The distance record, still a British record, was made in 1972 by John Potter with a 3,513-foot flight in Jupiter. Meanwhile, Professor Hidemasa Kimura of Nihon University was working with his students, and in 1966 their Linnet made Japan’s first human-powered flight; the flight was only 49 feet in length but this began a long-term commitment to human-powered aircraft. By 1977 their Stork B had established a new world record of 6,869.75 feet in a flight of over four minutes and was a strong contender for the Kremer Prize.
By 1967, the Kremer Prize for a figure-eight human-powered flight had been doubled and opened to entrants from any country. Then, in 1973, with still no winner in sight, Henry Kremer raised the award to £50,000 (about $129,000 at that time), the largest prize in the history of aviation.
The human-powered movement was very slow to reach the United States. Finally, in 1973, Professor Eugene Covert and students at the Massachusetts Institute of Technology (MIT) built a two-person biplane named Burd, which apparently never even left the ground under its own power. Credit for the first human-powered flight in the United States is therefore given to Joseph Zinno, retired from the U.S. Air Force, for his 77-foot flight in 1976 in Olympian ZB-1, which he had designed, built, and flown.
It was in that same year of 1976 that fifty-one-year-old Californian Paul MacCready decided that he knew how to design a human-powered aircraft that could win the Kremer Prize. He had impressive credentials for the challenge. As a teenager, MacCready was a Junior National Champion in model airplanes; at the age of sixteen, he soloed a Piper Cub; in 1947, he graduated from Yale with a degree in physics; in 1948 and 1949, he was the National Soaring Champion; in 1952, he received a doctorate in aeronautics from California Institute of Technology; in 1957, he decided to go into business for himself, eventually forming AeroVironment in 1971 to solve energy and environmental problems.
MacCready’s initial design was inspired by observations of soaring birds and the Rogallo hang glider. He realized that the low power output from a human meant that the airplane had to have a very large wing area (around 1,000 square feet) and have a very high aspect ratio (a large span of about 100 feet with a chord of only about 10 feet) in order to minimize lift-induced drag. The drag of the required bracing wires for an extremely light, fragile aircraft with these huge dimensions would be acceptable if flight speeds and flight altitudes were very low. The structure would have to be designed to be easily repaired, the same rule practiced by the Wright brothers. Aerodynamicist Peter Lissaman convinced MacCready that a canard surface had to be added to his wing for pitch stability. Turning the aircraft was a major hurdle, because the outer wing always wanted to stall; wing warping and a rolling front (canard) surface eventually solved this problem.
MacCready thought it would take six weeks to win the prize; it took a year. Flight control, weather, power, and structural problems kept cropping up. Finally, on August 23, 1997, the Kremer Prize was won by MacCready’s team with an official flight time of 6 minutes, 22.5 seconds. Their huge airplane, the Gossamer Condor, weighed 70 pounds and the pilot and engine, bicycle racer Bryan Allen, weighed 137 pounds. On September 22 of that year, Maude Oldershaw piloted the Gossamer Condor. It is interesting to note that all of the principal members of the team were model aircraft builders; many were also hang-glider enthusiasts. The Gossamer Condor is now the property of the National Air and Space Museum in Washington, D.C.
Retired British Rear Admiral Nicholas Goodhart had developed a huge (138-foot wingspan) twin-powered airplane, Manflier, for the Kremer Prize and, beaten to the prize, he suggested that the next great project should be a human-powered flight across the English Channel. Henry Kremer responded with a doubled award of £100,000 for the first such successful human-powered flight. It would require remaining in the air for more than one hour.
MacCready quickly rose to the new challenge with a new, lighter, stronger, more streamlined design, the Gossamer Albatross, using high-technology materials (carbon fiber-reinforced plastic, DuPont Kevlar, and a new, superthin DuPont Mylar for the covering), a new cruise prop designed by aerodynamicist Eugene Larabee of MIT, and new cockpit instrumentation, including a Polaroid sonar altimeter. By June, 1978, guided in his rigorous physical training by physiologist Joseph Mastropaolo, Allen was able to generate 0.31 horsepower for 2.5 hours, enough time, MacCready thought, to make a successful flight. However, two months later, the warp control jammed and Gossamer Albatross suffered the worst crash of the program, although the pilot was only bruised. Some eight months later, on April 25, 1979, Allen flew a record flight of over one hour and the decision was made to go to England and try for the prize. After weeks of waiting on the English coast for suitable weather, at 5:51 a.m. on June 12, 1979, pilot/power plant Allen lifted off from England. Slowed by a headwind, out of his crucial water supply, and cockpit instrumentation out of battery power, Allen felt at four different times that he would have to give up the effort. Somehow, fighting cramping legs and nearing exhaustion, he struggled on and, at 7:40 a.m., touched down lightly in France, winning the second large Kremer Prize for the team. He had flown Gossamer Albatross 22.25 miles in 2 hours, 49 minutes (an average speed over the water of less than 8 miles per hour).
Meanwhile, in 1978, the MIT Model Rocket Society, led by student John Langford, decided to see if they could get the hangar-evicted MIT Burd to fly with the addition of two 1.5-horsepower model airplane engines. The attempt failed, but the society pledged to build something that would fly by springtime, a craft that would compete for Kremer’s Channel prize. The society’s Chrysalis made its first flight on June 5, 1979, just one week before Allen won the English Channel prize. They had built a real flying machine, however, one that ended up being flown by more than forty-five pilots before the end of the summer.
Two years later, Langford had returned to MIT as a graduate student and led an effort to win a new Kremer prize, this one for flying around a 1,500 meter (4,185 feet) course in less than three minutes, requiring a speed of 21 miles per hour. Energy storage before takeoff was allowed. The group’s Monarch won the $33,000 prize on May 11, 1984, narrowly beating MacCready’s latest effort. Inspired, the Langford team vowed to pursue the “ultimate” human flight challenge: to emulate the fabled flight of the exiled Daedalus and son Icarus from the island of Crete to Greece. Thus began a four-year effort that ended up requiring more than $1 million worth of corporate and institutional sponsorship.
Key members of the team included builder Juan Cruz, Mark Drela (completing a thesis on low-speed aerodynamics), physiologist Ethan Nadel, and a group of highly trained and conditioned superathletes, as well as leader Langford. The result was a plane that weighed 70 pounds without pilot, power plant, or fuel, 29 feet in length, with a wingspan of 112 feet, and with a cruising airspeed of 15 miles per hour. On April 23, 1988, piloted and powered by a Greek bicycle champion racer, Kanellos Kanellopoulos, they flew their Daedalus the more than 70 miles from Crete over the sea to Santorini in about four hours, breaking up just 90 feet off shore when the craft encountered a strong headwind with turbulent air.
The next frontier in human-powered flight appears to be the helicopter. In 1980, a prize of $25,000 was offered by the American Helicopter Society for the first human-powered helicopter that could hover for a full minute, rising to at least 10 feet above the ground at some point during that period. Successful hovers have so far not exceeded about 24 seconds and the height requirement appears to be even more difficult.
Allen, Bryan. “Winged Victory of Gossamer Albatross.” National Geographic, November, 1979, 640-651. The 26-year-old biologist/pilot/bicycle racer/who pedaled the Albatross across the English Channel describes his flight in this picture essay. Dorsey, Gary. The Fullness of Wings: The Making of a New Daedalus. New York: Viking, 1990. A well-written account of the efforts of the team led by John Langford and associated with the Massachusetts Institute of Technology. The contributions of members of the team and their interpersonal conflicts are well covered. Grosser, Morton. Gossamer Odyssey: The Triumph of Human-Powered Flight. Boston: Houghton Mifflin, 1981. The author presents an engaging, blow-by-blow discussion of the successful efforts of the team lead by Paul MacCready to make the first significant human-powered flights. Also covers the contributions of the many hang-glider and model-airplane enthusiasts who made it possible, as well as the history of previous human-powered flight efforts. Langford, John S. “Triumph of Daedalus.” National Geographic, August, 1988, 191-199. The manager and spark plug for the re-creation of the flight of Icarus uses pictures and text to tell the story of their success to a large audience. A video was also made and shown on public television. Long, Michael E. “Flight of the Gossamer Condor.” National Geographic, January, 1978, 131-140. An easily accessed description of the problems and successes of the winner of the first Kremer Prize for human-powered flight and the driven, inventive people who made it possible. An acclaimed documentary video was also made by Ben Shedd.
Forces of flight