One of the World’s First Aircraft Comes Back to Life (Bowtie Included)
Wilbur and Orville Wright get all the glory for proving powered flight is possible. But even they drew inspiration from those who laid the groundwork needed to leave the Earth behind.
Otto Lilienthal was among them. The German inventor built several gliders in the 1890s and flew them more than 2,000 times. He died in 1896 following a crash that broke his spine, but his work with curved wings, based on extensive study of birds, inspired the two famous brothers. Wilbur Wright called him “without question the greatest of the precursors.”
More than a century later, researchers at the German Aerospace Center wanted to know more about his work, how close he came to sustained flight, and what caused his fatal crash. Motivated by an American project that rebuilt the Wrights’ first plane, a small team spent six months constructing and testing a Lilienthal glider. “A dream came true for me,” says Andreas Dillmann, the aerodynamicist who led the project and is something of a Lilienthal fan.
To start, the researchers visited the Otto Lilienthal Museum in Anklamn, in the northeast corner of Germany, to obtain original drawings for the Normalsegelapparat—normal glider. That done, their task was straightforward. They spent six weeks building the frame using willow wood. The thick cotton material Lilienthal draped over the frame has long since gone out of production, so the team had a factory make more than 640 square feet of the stuff, specifically for the project.
The Normalsegelapparat weighs just 40 pounds, and stretches 20 feet from wingtip to wingtip. The pilot is meant to hang by his arms from the wings, and direct the craft by swinging his body, like a gymnast on parallel bars. Given Lilienthal’s grim end, the team approached things more cautiously, with a focus on aerodynamics. They sent the glider, complete with a mannequin pilot, to a huge wind tunnel in Emmeloord, Holland. In keeping with the 19th century vibe—and proving some Germans do have a sense of humor—they dressed the dummy in knickers, a white shirt, and a bow tie.
The next step required finding a research student who roughly matched Lilienthal’s size and putting him in the glider. The young man, who was over 6 feet tall and weighed 196 pounds, skipped the knickers and tie (“I asked him, but he refused,” Dillman says), but climbed aboard and swung his weight about as the team measured the glider’s center of gravity and how it moved with a human passenger.
Both tests validated Lilienthal’s design, Dillman says. The glider performed as they had hoped, with a glide ratio of four (moving four feet forward for every foot dropped). “It was a really airworthy sailplane,” Dillman says. “You could put the drawings in a textbook.”
One weakness they found could explain Lilienthal’s last crash: If the nose rises too far, the pilot easily loses control. Given that historical reports say Lilienthal flew into a thermal gust before crashing, that poor maneuverability could well be the cause. The next step might be a real-world flight, but Dillmann’s not sure it’s worth the effort.
This was a “small project” that he admits won’t advance modern aviation technology, but does fill in some gaps in the history books. Given the Glider King’s role in helping humanity take wing, it’s nice to be sure he knew what he was doing.
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