Weather Forecast


Flight Lines: By nature or man, a wing must produce lift

A female vermillion flycatcher takes flight on wings which produce both thrust and lift. Keith Corliss

You'd think by now this whole flying thing would be figured out. It's not.

Credit to the first great thinkers to ponder the possibility of manned flight goes to the venerable names we all learned, the Aristotles, the Galileos, the da Vincis, and others. That's only because they preserved their thoughts with written words and drawings. I'm confident the first humans to walk the earth also wondered and wished. With creatures all around them plying the air with moving wings, how could they not? Insects and bats were doing it. And birds, those magical feathered beasts, were doing it too.

By the late 19th century the rush to put a man in a flying machine was speeding along with leaps in understanding occurring on both sides of the Atlantic every year. Many wishing to conquer air contributed to the growing body of this infant science called aerodynamics. It culminated, of course, with the historic 120-foot, 12-second flight by Orville Wright on December 17, 1903, on a windswept beach in North Carolina called Kitty Hawk.

In the ensuing 100+ years, materials, aircraft designs, and powerplants have dramatically changed. The state-of-the-art fabric and wire designs of yesteryear have been replaced by carbon fiber structures and highly refined metals. But even the most modern of aircraft would likely be recognized as a flying machine by the Wright Brothers, perhaps even Galileo. That's because one unalterable truth remains constant. A wing has to produce lift.

For decades aviators have been schooled in the mysterious formula whereby air rushing over the top of a wing is accelerated by wing shape, while air underneath remains relatively constant. This disparity in velocity produces a low pressure area above the wing creating what we call lift. As it turns out, we were wrong.

I came across a paper written by David Anderson of Fermi Labs and Scott Eberhardt of Boeing Aircraft which not only cast doubt on the old theory of lift, it blows it out of the water. From the very first paragraph of A Physical Description of Flight; Revisited: "In reality the shape of the wing has little to do with how lift is generated...Any description that relies on the shape of the wing is wrong." Wow. This was like learning my ancestors had sailed not from England, but from Antarctica.

Let's not get too deep into this but Anderson and Eberhardt remove Bernoulli from any discussion of lift and rely upon Newton, slightly altering his second law by saying, "The lift of a wing is proportional to the amount of air diverted down times the vertical velocity of that air." Okay, enough physics.

A wing producing lift is one thing, moving the wing forward is quite another. For that we usually rely upon some sort of engine. Be it internal combustion or turbine, we need a powerplant to produce thrust. And that's where the magic and wonder of nature exceeds even our modern capabilities.

The wings of the bumble bee and barn swallow not only produce lift they also provide thrust through muscle powered movement. From the mighty to the slight, winged organisms have been effortlessly flying for thousands of years.

The bee hummingbirds, a Cuban specialty, measures barely two inches long and weighs about as much as a paper clip. On the opposite end of the weight spectrum we have two large, Old World, grouse-like birds--the Kori bustard and the great bustard. Males of these species can top 40 pounds. In terms of wing span you can't beat the wandering albatross with a reach of 12 feet.

These and myriad other flying beasts abide by the same Newtonian laws of physics an Airbus A380 does. But that's where the common ground ends. Animals do it with a beauty and a natural grace well beyond our capabilities. Maybe it's a good thing we can't achieve the complexity of God's creatures in flight. It keeps us reaching. Da Vinci supposedly wrote, "When once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been, and there you will always long to return."