Winglets in Nature

SCIENCE CONCEPT:

While gliding, some birds curl the tips of their wings upwards. This is similar to the winglets used on many modern aircraft. The winglets are designed to reduce the induced drag of the wing.

STUDENT OBJECTIVE:

The student will study how different birds curl the tips of their wings upwards when they are gliding.

OVERVIEW:

In this activity the student will pair up with one other classmate and do a study of a bird that curls the tips of its wings when gliding. Each group will choose a different bird to study. Have the groups include pictures, stories, and facts about the bird they study. Have each team share their findings with the rest of the class. As an extension have one group do a study of aircraft designs that use winglets on their planes, and another group to do a study of gliders that man has made.

PREPARATION TIME:

25 minutes.

LESSON TIME:

40 minutes.

TEACHER PREP:

Collect books from the library on birds that glide and soar for your students to use. Also, gather books on modern aircraft that utilize winglets in their design.

WORDS TO KNOW:

gliding

soaring

winglets

thermals

currents

TEACHER TEXT:

Part of the time certain birds use gliding flight. The winglets on the birds reduce the induced drag of the wing allowing them to enjoy gliding. During gliding flight a bird does not move its wings, but glides on air currents. Birds like eagles, hawks, vultures and gulls enjoy this effortless flight. They may do this to rest their wings. As they glide, they drop lower and lower until finally they must start flapping again to stay up in the air. At other times, they have been known to soar higher and higher for hours on warm air currents.

The feathers on a bird are used to increase the speed of air moving over the upper surface of the wing. When a bird curls the tips of its wings upwards it gives added life to the flight without the bird having to flap it's wings. The bird is able to take full advantage of the air currents around him to glide effortlessly. Birds that soar have broad secondary flight feathers which greatly increase the surface area of the wing so they can ride easily on the warm air currents.

While soaring and gliding, birds take advantage of upward movements of air called thermals. These bird's wings are resting on piles of air that are moving upward. We cannot usually feel these updrafts on the ground. We can, on very warm sunny days, observe that distant objects seem to quiver. This results from looking through waving currents of warm air rising from the ground. You cannot see the air itself; what you do see is the way it distorts the objects behind it. Many birds find these thermals and use them for the extra upward push they give. Added to the aerodynamic force of the wings, there is enough force to overcome the pull of gravity, and no other flapping power is necessary. These birds then, are gliding downward on a constantly rising current of air.

Warm air does not rise evenly from the ground. It is shaped more like doughnuts piled upon one another. The air moves up the center and then falls down on the outside of the ring as it cools. Eventually, the thermal thins out so it can no longer push the bird upward. When this happens, the birds glide down until they can catch another rising current of air. Riding thermals are great energy saving devices for birds when they can find them. But they don't always exist. The sun must have warmed the ground sufficiently.

Many large birds wait on the ground until 9 or 10 o'clock until the thermals form. There are other kinds of updrafts in addition to thermals. Obstruction currents form when moving air runs into an obstacle, like a cliff, hill, mountain, or even a building. The air is forced to rise up and over the obstruction. Sea birds use another kind of air movement. Ocean breezes, like trade winds, offer a steady source of power upon which they can rise and glide. This is called dynamic soaring.

Web Hosting Provided By The National Business Aviation Association.

Explore Space ... Not Drugs!
Hear what astronauts have to say about staying drug-free.
Last modified: Sat Nov 15 19:01:04 PST 1997