Saturday, February 07, 2009

Great Moments in Aviation, Part II

After the legend of Icarus and Daedalus was first told by the Greeks, many years passed. They were forgotten, then re-discovered during the Renaissance. The next man to pick up the ball and run with it was Leonardo da Vinci.

Da Vinci had a lifelong fascination with, well, damn near everything. He had that remarkable combination of a fertile creative imagination coupled with an intensely analytical mind that could look at a bird in flight and not only wonder how such a thing could be, but deduce more or less how it works. There's scarcely a field of human knowledge at the time he didn't touch, but here, we're concerned with some of his most famous inventions: his flying machines. Interestingly enough, he left enough clues in his work for us to follow his thought process.

His first thought was to mimic birds mechanically.

This is a rather ingenious device that uses pedals to work the wings, which would flap like those of a bird, producing both lift and thrust. But the problem with this design is that a human simply cannot provide enough power to achieve flight this way. Which isn't the same as saying human-powered flight is impossible -- it's been done -- but it can't be done this way.

His second thought was to build a large man-powered vertical screw, with the idea that he could pump air in the same way that a screw of Archimedes pumps water, thus lifting the man airborne. The key thing here is that da Vinci realized that air is a fluid just like water, and thus obeys the same laws. This is a key revelation, one that will be put to great use later. Today, we look at this design and see the precursor of the modern helicopter. This, also, suffered seriously from the limit of man's direct mechanical power. It also suffered from da Vinci's insistence upon providing lift and thrust with the same device. It's his sole conceptual failure in both of these powered designs.

Once he'd given both of those up as bad ideas, his thoughts turned to pure gliding flight. And here, he finally hit upon something that was practical with the technology of his time. Unfortunately, history does not tell us if he actually tried a full-scale test with a human pilot.

Despite never having worked full-scale, though, the designs in his sketchbooks served as inspirations for all the great pioneers of aviation to follow. By documenting what didn't work, he prevented later generations from pursuing blind alleys and false starts. This, too, is progress.

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