1977

Human-Powered Airplane

Dr. Paul B. McCready (1925–2007)

The human-powered airplane seems like such a simple, obvious idea, but in fact represents a huge engineering challenge. The problem lies in using a human as a motor.

On a bicycle, on level ground, the human motor works pretty well because the weight of the motor has minimal effects. A human being who is in fantastic shape (like a Tour de France athlete) can produce half a horsepower (375 watts) over several hours. With half a horsepower, a bicycle can move along at a good clip.

In an airplane, the weight of the motor does matter. It not only moves the vehicle forward, it keeps the vehicle in the air. Gravity is constantly pulling the airplane to the ground, and the motor must supply the power that opposes gravity. In this situation, a motor that weights ~160 pounds and produces half a horsepower becomes a huge problem. The power-to-weight ratio is horrible.

So the human-powered airplane must be as light as possible. Yet it needs big wings because it is flying so slowly with the power available.

The Kremer Prize, started in 1959 by industrialist Henry Kremer, offered £50,000 to pioneers in human-powered flight. The Gossamer Condor, designed by American aeronautical engineer Paul McCready, was the first human-powered airplane to win the Kremer Prize in 1977. To win, it flew a figure eight around two pylons half a mile (0.8 km) apart.

The engineering is amazing. Even though the plane has an unbelievable 96-foot wingspan (29 meters), a huge propeller, and a surprising front-mount canard to control it, it weighs only 70 pounds (32 kg). To do this, engineers combined thin aluminum tubes with super-lightweight foam ribs, a Mylar skin, and thin wire. The “chain” is made of steel cable and plastic.

Even more amazing was the MIT Daedalus HPA, which in 1988 flew 71 miles (115 km) from Crete to Santorini in just under four hours. Made of carbon fiber, foam, Mylar, and Kevlar, it looked like a traditional airplane. With a wingspan of 111 feet (34 meters), it is an engineering plus athletic achievement of the highest order.

SEE ALSO Carbon Fiber (1879), Hall-Héroult Process (1889), Kevlar (1971).

The Daedalus 88 human-powered airplane, with Glenn Tremml piloting, is seen here on its last flight for the NASA Dryden Flight Research Center, Edwards, California.