Today, let's look for the first helicopter. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them.

It's frustrating to try to find the first helicopter. Leonardo da Vinci had the idea of pulling himself into the air with a vertically mounted propeller, and the idea was seductively simple. But for the next four and a half centuries one inventor after another ran into terrible problems when he actually tried to do it.

There're three kinds of heavier-than-air flight. An airplane lifts off the ground when its propeller or jet pulls a lifting wing through the air. An autogyro also works like that. A propeller pulls it forward; but instead of a wing it has another large propeller on top. The second propeller is free-wheeling -- it's not powered. It just whirls in the wind and lifts the plane up. But a helicopter propeller is powered, and it lifts the machine directly upward. It combines both power and lift in the same propeller.

After Leonardo, the idea of the helicopter resurfaced in France in 1784 in the form of a working model driven by a bow-string -- about the same time ballooning also got its start in France. During the 19th century, all kinds of ingenious helicopter models were built throughout Europe.

In 1877, for example, Enrico Forlanini flew a large steam-powered model to a height of over 40 feet in Milan. But it wasn't until 1907 that the Frenchman Paul Cornu hovered just off the ground for 20 seconds in a strange 32-bladed helicopter. Cornu, like the Wright brothers four years earlier, was a bicycle-maker.

Several other early helicopters were made, but they were all underpowered and hard to control. When the more manageable autogyro was developed in the 20s, helicopters were abandoned. In 1936 the Germans built a successful hybrid helicopter-autogyro whose engine drove both lifting and pulling propellers.

Igor Sikorsky built the first real helicopter in the United States in 1939. He'd tried to build one in Russia 30 years before but had failed. Now after designing airplanes for 30 years, and with vastly improved technology, he succeeded. Then the Germans dropped the forward propeller on their model, making it into a pure helicopter. The Russians soon copied the Germans, and -- we all had military helicopters during WW-II.

The helicopter was in people's minds long before the airplane. But it was a hard dream to fulfill. Its history is littered with half-successes. The very simplicity of combining power and lift in one big propeller leads to awful design problems. Leonardo was drawn in by its simplicity 500 years ago. He couldn't see how hard it would be to control motion with a single propeller. This complexity, masking as simplicity, kept right on teasing and misleading designers until 1939.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

Angelucci, E., World Encyclopedia of Civil Aircraft. New York: Crown Publishers, Inc., 1982, Chapter 1.

This episode has been revised as Episode 1489.