Building a Better Aircraft

That Renaissance mastermind -- Leonardo Di Vinci -- apparently was onto something when he set about trying to design an airplane. Take a look at reproductions of Di Vinci's drawings and diagrams and you'll notice that his idea of manned flight was actually "winged flight". 'Ol Leonardo understood that "flapping" is really where it's at when it comes to manned flight and aerodynamics. Unfortunately, Leo could never overcome the problem of weight differential, meaning that a human could never flap the wings of his contraption fast enough to get off the ground, much less maneuver in the sky.

Fortunately for us -- several hundred years later -- aerodynamic engineers are finally realizing that Di Vinci's theories about flight are pretty well-grounded (pardon the pun). Namely, that "natural flyers" like birds, bats and insects outperform man-made aircraft in aerobatics and efficiency. In fact, according to a 9 Feb 2008 article on ScienceDaily.com, a team of University of Michiganengineers are studying these animals as a step toward designing flapping-wing airplanes -- although with wingspans smaller than a deck of playing cards.

It's really just a matter of common physics. Consider this: a Blackbird jet flying nearly 2,000 miles per hour covers 32 body lengths per second. But a common pigeon flying at 50 miles per hour covers 75. The roll rate of the aerobatic A-4 Skyhawk plane is about 720 degrees per second. The roll rate of a barn swallow exceeds 5,000 degrees per second. Or how about this: select military aircraft can withstand gravitational forces of 8-10 G. Many birds routinely experience positive G-forces greater than 10 G and up to 14 G.

Wei Shyy -- who chairs the UMich Aerospace Engineering Department and is the author of the new book "The Aerodynamics of Low Reynolds Number Flyers." Feels that, "...Natural flyers obviously have some highly varied mechanical properties that we really have not incorporated in engineering..."

According to Shyy, birds are not only lighter, but also "...have much more adaptive structures as well as capabilities of integrating aerodynamics with wing and body shapes, which change all the time...""Natural flyers -- relates Shyy -- have outstanding capabilities to remain airborne through wind gusts, rain, and snow." Not a bad combination when you're flying over all types of terrain in all types of weather.

The secret to a bird or bats success? Sciencedaily.com relates that pressure generated during flight cause the flapping wings to deform. In turn, the deformed wing tells the air that the wing shape is different than it appears in still air. If appropriately handled, this phenomenon can delay stall, enhance stability and increase thrust.

Explains Shyy, "....Flapping flight is inherently unsteady, but that's why it works so well. Birds, bats and insects fly in a messy environment full of gusts traveling at speeds similar to their own. Yet they can react almost instantaneously and adapt with their flexible wings".

To this end, Shyy and his colleagues at UoM have garnered several grants from the United States Air Force totaling more than $1 million a year to research small flapping wing aircraft. Such aircraft would fly slower than their fixed wing counterparts, and more importantly, they would be able to hover and possibly perch in order to monitor the environment or a hostile area. Shyy's current focus is on the aerodynamics of flexible wings related to micro air vehicles with wingspans between 1 and 3 inches. O-k, granted - that's not exactly big enough to carry a payload of bombs, but we gotta crawl before we can walk.

Or maybe it's better to say we gotta flap before we can fly.