Last month, a University of Toronto student brought one of Leonardo da Vinci’s dreams to life by building (and flying!) a human-powered ornithopter capable of sustained flight.
So… what’s an ornithopter? Good question!
Ornithopters are winged aircraft that fly like birds, flapping their wings to achieve and sustain flight. Up to now, though, the only ornithopters to achieve flight are the ones from Frank Herbert’s Dune novels… but this one’s real.
Ever since da Vinci sketched the first human-powered ornithopter in 1485, engineers have tried (unsucessfully) to make one actually fly… and it was a UT student named Todd Reichert—not an established skunkworks engineer from Boeing or NASA—that would make history, flying his ornithopter for over 19 seconds at an average speed over 25 kilometers per hour.
“This represents one of the last of the aviation firsts,” says Reichert, who built and piloted the ornithopter—named Snowbird—into the history books.
The ornithopter was built using advanced processes to keep overall vehicle weight under 95 lbs., despite a wing span of 105 feet (think Boeing 737). Snowbird was built with sustainability in mind, as well, in a process that encourages “the use of the human body and spirit,” according to Reichert…
…which is all well and good, but how does it fly?
To answer that question, the team behind the Snowbird’s construction have posted a full technical brief online that documents the project in incredible detail, including an explanation of flapping-wing design theory, which I thought was interesting enough to share, below.
FLAPPING WING THEORY
In an ornithopter the wings must produce both the lift to counteract the weight of the aircraft, and the thrust to counteract the body drag. Lift is produced in the conventional way, with the oncoming air striking the wing at a positive angle of attack; thus no feathers, valves or folding of the wing is required to produce lift. The key is to produce enough thrust with the wing to keep the aircraft flying at the required forward velocity. This thrust is produced by placing the wing at a lower angle of attack, relative to the local flow velocity, on the upstroke, and at a higher angle of attack on the downstroke. It can be seen in the figure below that this results in a large amount of lift and thrust on the downstroke and a small amount of lift and drag on the upstroke. The net result is positive lift and positive thrust.
Throughout the stroke (above) the wing must twist with the proper magnitude and phase to produce the proper angles of attack. This is accomplished passively by designing the structure in such a way that the aerodynamic and inertial forces produce the proper twist.
Getting that “proper twist” is one of the hardest things about
the Macarena building a successful ornithopter, but the final movement that Reichert’s team came up with is both visually organic and hauntingly beautiful, as can be seen in the video below.
No word, yet, on whether university’s plans for Snowbird, but if they plan on a solar or electric pedal-assist model in the future, you know we’ll cover it here—stay tuned!
(If anyone can find some video of the ornithopters from SyFy’s Dune movie, post a link in the comments!)