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No. 1794:

For a Spanish language version of this episode, Click Here.

Today, a forgotten chapter in the history of flight. 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.

I was hooked on airplanes in the 1930s. I built models, and I created a vast mental inventory. There were two kinds of flying machines in those days: Ones that fate would permit me to see -- like DC-3s, Piper Cubs, and blimps, and those -- like flying wings and Japanese Zeros -- which I could only imagine. I knew then that I'd never see a corporeal autogiro in flight. The autogiro was a mythic creature -- my personal unicorn among horses. It was then, and still seems, destined to remain in an imagined memory.

Instead of a wing, the autogiro had a large propeller on top. A second, regular propeller drove it forward. But the big overhead propeller free-wheeled as the autogiro flew; it provided only lift. An autogiro could take off and land in a very short distance; but it couldn't rise vertically, like a helicopter. If one lost power, it spun safely back down to earth like a maple seed.

Bruce Charnov's new book, From Autogiro to Gyroplane, tells the story of this odd machine. It was developed by Spanish aerial pioneer Juan de la Cierva. Cierva and his brother began trying to build airplanes before WW-I while he was a civil-engineering student in Madrid. Juan de la Cierva built conventional airplanes for several years before he began thinking about the autogiro.

Finally one night at the opera Aida he realized how to balance lift on advancing and retreating blades of that overhead propeller. But you find no propellers in Aida, so you hear stories that he got the idea for the autogiro from windmills in the opera Don Quixote.

In any case, two decades of autogiro development followed. British and American companies built them in a huge variety. Amelia Earhart tried to make the first autogiro flight across America in 1931. After many short hops, she finally reached Oakland, only to learn that someone else had set that record nine days earlier.

In the late 1930s, the more complex helicopter appeared. It combined lift and thrust in the overhead propeller. America created the embryonic Vought-Sikorski VS300, and Germany the Focke-Wulfe Fw-61. After the war, helicopters moved to center stage, and we heard almost nothing more about autogiros.

For twenty years, autogiros had seemed to promise an airplane in every back yard. That didn't pan out, but they finally did play a functional role as WW-II scout planes. Then the helicopter appeared, and autogiros vanished as though they had never been.

Charnov finishes by telling about the new technology of the Gyroplane. It's a helicopter/autogiro composite. It, too, has both forward and overhead propellers. But now the overhead propeller can be driven or it can free-wheel -- serving as a passive wing.

I said that the autogiro was my own unicorn among horses -- an airplane which I shall always see wearing the clothes of mythology. Well, I guess the Gyroplane is the mortal spawn of a horse and a unicorn. It is something I might one day actually ride, after all.

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

(Theme music)

Charnov, B. H., From Autogiro to Gyroplane: The Amazing Survival of an Aviation Technology. (Foreword by John H. Lienhard.) Westport, CT: Praeger Publishers, 2003.

The Cierva C-40 in three views

The Cierva C-40 in three views

Kellett Autogiro

Image sources: The photo of Amelia Earhart in an autogiro is from Charnov's book (cited above), and it is used by courtesy of Stephen Pitcairn, Pitcairn Aircraft Company Archives. The Kellet Autogiro image is from a set of airplane cards that were circulating in the late 1930s. The image of the Cierva C-40 and the Fw-61 helicopter image are from the Aeronautics Aircraft Spotters' Handbook, New York: National Aeronautics Council, Inc., 1943, and the VS300 image is courtesy of the Vought-Sikorsky Archives.