Monday, February 23, 2009

Great Moments in Aviation, Part VI

(Editor's Note: I'd meant to continue this series last week, but I forgot that it was Tour of California time again. For those of you who care, Levi Leipheimer won his third straight Tour of California. It was also Lance Armstrong's first USA appearance since coming out of retirement, and Floyd Landis' first race since finishing his suspension. It's four months and change 'till the big race kicks off on July 4 in Monaco. It's the Return of the King, baby! Be there!)

When we last left our story, Sir George Cayley had just made a key realization that would ultimately pave the way to controlled, powered flight: the functions of lift, propulsion, and control must be separated in order to be made practical. The half-century separating 1853 from 1903 would see each problem attacked in turn, with varying degrees of success. Truly, we're still contending with them. We're always finding better ways of doing things, and cannot consider these things "solved" even now.

But the obvious thing to do in the latter half of the 19th Century was to study gliding flight in detail. And by far, the biggest name in gliders would have to be that of Otto Lilienthal. Lilienthal made over 2,000 flights with his gliders between 1891 and 1896. He became sufficiently skilled that he could use an updraft against a hill to hang seemingly motionless in the air, with respect to the ground.

The key differences between Lilienthal's gliders and Cayley's original design is first that Lilienthal eliminated the "basket" that Cayley's reluctant passenger rode in, and also that Lilienthal's wings were of a more advanced design. He spent a considerable amount of time studying the gliding flight of birds, especially storks, making detailed aerodynamic diagrams. Today, we call such plots lift polars and drag polars. The data he gathered drove his designs. Among other things, he was the first to build biplane gliders, which gave twice the lifting surface for the same wingspan, and also a more rigid wing structure. He also experimented with a movable elevator for improved pitch control.

His remarkable feats of gliding brought him worldwide fame. Unfortunately, they were also his downfall. On August 9, 1896, he lost control of a glider, falling more than fifty feet to the ground. He broke his spine, and died of his injuries the next day. A grievous loss, but yet not in vain. He gave everyone who followed a firm foundation on which to build. True controlled flight was scarcely more than seven years away.

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