Page 2 - 2005 DT 12 Issues

Taking Flight airfoil, a surface or structure that in- down-turned tail, changing wing
teracts with the air passing over and angles and lowered flaps drastically re-
under it to provide lift. According to duce lift. By combining wing angles,
bird’s life is lived in the fast Bernoulli’s Law of Fluid Dynamics manipulated feather surfaces, flapping,
lane, literally. Its heart (air is a fluid through which the airfoil tail-braking and gravity, birds are mas-
Abeats faster and it breathes passes), the force produced by the air- ters of fluid dynamics.
faster than any other animal. Its body foil against the flow of incoming air Every bird can change its speed,
temperature is higher, too. Once air- exerts a pressure perpendicular to the but its maximum flight speed depends
borne and at cruising speed, it is faster leading edge of the airfoil. Because the on its overall design. Large birds may
than anything on four feet. Just how air must travel farther over the upper flap once a second to reach top speed.
fast depends on the bird. But fast or surface than the lower surface, it must Small birds may flap several times per
slow, a bird’s amazing mastery of the move faster to catch up to the air flow- second to reach their top speed. The
skies is one of nature’s miracles. ing under the humming-
Size, weight, wing shape, skeletal wing. This bird can flap
design, flight muscles and feathers all causes higher its wings 50
play a part in how speedily a bird zips pressure on the times per
around the sky. The relationship of all under surface second and
these elements to each other not only and lower fly at 60
determines speed, but whether a bird pressure on the mph. But the
can fly at all. The bigger and heavier upper surface, speed cham-
the bird, the bigger its wings must be. making lift pos- pion is the
This, in turn, means more muscle and sible. The peregrine
bigger bones. Flight muscles are the faster a bird can falcon,
biggest and strongest, providing move forward whose top
the power to lift the entire body from through the air, speed is 100
the ground. The largest flying bird on the more lift it mph in level
the planet is the Great Bustard, which can generate. By flapping its wings and flight. When it folds its wings close to
can average 45 pounds and reach a using the feathers attached to its its body in a dive, it can reach
height of a small deer. “hand” bones, a bird produces forward 200 mph.
Feathers and wings are the most thrust. The amount of thrust deter- A bird’s amazing mastery of flight
obvious characteristics related to mines the speed. The “hand” part of just became even more amazing. Un-
flight. Not all feathered birds fly, but the wing at the tip produces the actual til now, Bernoulli’s Law was the only
all flying birds must have feathers and thrust that moves the bird forward. In accepted explanation of how birds can
(of course) wings. Light but strong, slow motion, you will see the bird ro- fly. In a recent series of video experi-
tough but flexible, feathers protect the tate its wings and flex it’s “hands”—a ments using models of gliding swifts’
bird’s skin, provide insulation and en- movement accomplished in an instant. wings, scientists at the University of
able the bird to make minute adjust- Birds are also able to manipulate their Groningen and Leiden University in
ments in speed, steering and landing. feathers in flight, creating “slots” in the Netherlands, have determined that
They are responsible for the wing’s those “hand” feathers to get the the leading edge of a fast-flying swift’s
shape. Strictly speaking though, feath- most lift. delta-shaped wing creates whirlpools
ers aren’t necessary for flight unless Takeoff and landing are the most of air called leading-edge vortices.
you’re a bird. Bats, the only mammals dangerous parts of flight. Sheer muscle Until now, it was believed that the
capable of true flight, are featherless power, a good wind or jumping-off vortex mechanism was only associated
but possess what passes for “wings.” point is needed to get up enough speed with the small scale of insects. Accord-
Wing design is crucial to both to create lift from the ground. Coming ing to the researchers, all aspects of
speed and lift. The shaped wing is an down, slower speed, drag created by a bird flight are influenced by these vor-

Page 2 FORRC/JANUARY 2005