Otto Lilienthal: First True Aviator

One of the points Francis Wenham made in his landmark 1866 paper was that as much work needed to be done in unpowered gliding as in engine-driven powered flight. The short-hoppers, all versed in some aspect of engine technology, concentrated on the latter, but one man, Otto Lilienthal (along with his brother), paid close attention to the engineering problems posed by glider flight. In any discussion about the history of flight, Lilienthal deserves to be mentioned alongside Cayley and the Wrights.

Otto Lilienthal was born on May 23, 1848, in Anklam, Prussia, near the Baltic Sea. As children, he and his brother Gustav would watch in wonder the gliding flight of storks at the shores of the Baltic, noticing for themselves what was already known—namely, that the storks gliding in circles as they search for fish rise when they circle into the wind (and not with the wind, as one might expect). Otto was trained as a mechanical engineer at the Berlin Technical Academy, graduating in 1870, and he set up a factory in Berlin manufacturing steam engines and the like. In his spare time, he pursued his aeronautical interests (sometimes with Gustav, now an accomplished architect) outside Berlin, and later in the Rhinower Hills near Stollen.



These photos of Lilienthal show three of the many designs he used to make more than two thousand glides. Lilienthal, a mechanical engineer  by training, had developed the bi-wing design so he could install a motor that would power propellers. It was in such a glider (without the safely bar in the top left design) that he fell to his death in 1896.


Lilienthal built rigid fixed wing gliders—more than eighteen distinct designs—and made more than two thousand glides, many longer than eight hundred feet (244m). His approach was markedly different from that of most experimenters of the day. He believed that the best way to learn to fly was to get into the air and experience flight for oneself. Whereas the others rode the machines they created, Lilienthal flew his, learning the feet of the air and the response of the aircraft.

“The manner in which we have to meet the irregularities of the wind,” he wrote, “...is by being in the air itself.” It was thus necessary, he believed, to gain experience in flying an unpowered version of an aircraft before adding a propulsion system to it. Lilienthal was planning to add a propulsion system to his gliders, thereby adding “powered” and “sustained” to his accomplishment of controlled flight. Others scoffed at his feats—Maxim derisively called him a flying squirrel.

 But improvements in photography and printing resulted in pictures and accounts of Lilienthal’s feats appearing in newspapers all over the world, including in Dayton, Ohio, where they came to the attention of the Wright brothers. Although his work in airfoil design was groundbreaking, Lilienthal’s method of control—swinging his legs and torso in order to shift the craft’s centre of gravity—was limited and difficult, certainly not a method that would become practical for anyone other than a circus acrobat.

Having studied birds so carefully (his 1889 book Bird Flight as the Basis of Aviation, was an instant aviation classic), he looked to ornithopter-like systems or engines that would, in emulation of birds, flap narrow slats at the wingtips, as methods of propulsion. Later tests showed that these would never have worked (so that claims that Lilienthal would have flown before the Wrights had he lived longer are doubtful). But Lilienthal never had the chance to test them. On Sunday, August 9, 1896, during a glide, a gust of wind turned Lilienthal and his glider upward and the aircraft stalled. (A stall is what happens when the wing cuts though the air at an angle so large that the airflow over the top surface separates from the wing. The wing becomes an obstacle to the wind and there are no longer two smooth layers of airflow creating lift. When an aircraft stalls, it suddenly loses lift and falls).

Lilienthal’s glider crashed and he died at the Bergmann Clinic in Berlin the next day. Over the centuries, many had died leaping from towers and attempting to fly, but Lilienthal’s death was the first death of a man actually flying. When people had pointed out the dangers of gliding to Lilienthal, he often said, “Sacrifices must be made.” This was the epitaph that was carved (in German) on his gravestone.