Wing Shapes of Birds and Airplanes

SCIENCE CONCEPT:

Birds are considered nature's perfect flying machines. Every part of a bird is adapted to flying. Their bodies are as streamlined as an airplane, enabling them to slip easily through the air. The bird's wings, with each of its feathers, are shaped much like an aircraft's wing - curved on top and flatter underneath. This allows both wings to achieve lift in the same way.

STUDENT OBJECTIVE:

The student will observe how the shape of the wing of a bird and that of an airplane are similar, causing both of them to be able to achieve lift.

OVERVIEW:

In this activity, the student will make drawings of both types of wings: the wing of a bird and the wing of an airplane. Through this exercise the student will observe that each has a similar shape and capability. As an extension the student will compare birds' wings which exhibit certain flight characteristics to an airplane wing with similar flight characteristics. For example, compare the wing of a bird of prey with a fighter aircraft or stunt aircraft wing. Or compare the wing of an albatross to a glider or transport aircraft wing.

PREPARATION TIME:

25 minutes.

LESSON TIME:

40 minutes.

TEACHER PREP:

Gather books at the library on the wings of birds and airplanes and how each uses its wings in their flight pattern and lift.

WORDS TO KNOW:

contour

tertiaries

airfoil

lift

thrust

drag

flight characteristics

TEACHER TEXT:

The wings of the airplane cause it to lift and stay in the air. Bernoulli's theory applied to flight: the curved upper surface of the wing forces the air to increase its speed as it flows over the top in order to reach the trailing edge of the wing at the same time as the air flowing in the path below the wing. With the increase in speed on top, the pressure exerted decreases. This change makes the pressure pushing up from under the wing greater than the pressure pushing down on the top of the wing, so the wing moves up naturally.

Attached to the wings of the airplane are the inside flaps that make the plane fly slower and the outside ailerons that make the plane turn. The tail of the airplane helps control its direction. Attached to the tail are the elevators that make the plane ascend and descend and the rudder makes the plane go sideways. Lift, gravity, thrust and drag are the four forces acting upon the airplane. As the airplane wing moves forward, the air moving over the curved top of the wing travels faster than the air moving under the flat bottom of the wing. Less pressure above the wing causes the airplane to lift. Lift and gravity pull against each other.

A bird's wing is the basic structure for flight. It is covered with contour feathers that are specialized for flight. It is the shape of the wing that enables a bird to fly, and the shape is determined by the feathers. The actual wing is a modified forelimb, with a skeletal structure like an arm. Man has 29 bones, most birds have 11. A bird's hand bones are much longer, fused together, and much simpler than a man's. It is the rigidity that makes the wing so strong. The bird's "elbow" is also designed so that it cannot bend in the direction that takes the most amount of stress during flight. The "shoulder" joint is also designed so that the inner wing is automatically held at the proper angle of attack for maximum lift. This section between the shoulder and the wrist moves very little during flight. It also has the airfoil shape that the airplane wing was designed after. It is this curved surface that produces the lift as the bird moves forward. The actual wing is V-shaped with two bones in the next section. The outer portion of the V is made up of long secondaries. Again the number varies by species: hummingbirds have 6 or 7 and large birds have as many as 32. The tertiaries are attached to the upper wing.

It is critical that air flows evenly around and over the wings during flight so that friction and drag are kept at a minimum. The surface of the wing is kept smooth by the overlapping placement of the flight feathers. Bernoulli's principle also applies to the bird's wing: the distinctive shape of a wing is known as an airfoil. Lift is produced by the motion of an airfoil, or wing, moving through the air. The special shape of the airfoil, or wing, is what produces a change in air pressure above the wing by deflecting or turning the air. As the wing moves through the air, air goes above and below. The upper surface has a longer surface distance. In order for the two airstreams to meet at the trailing edge of the wing at the same time, the top air must go faster. Increased speed equals decreased pressure, equals lift.

Feathers give the wing its shape and there is a direct correlation between form and function. Birds who fly fast in open air have long, narrow wings. They have difficulty taking off, but can stay in the air indefinitely, once airborne. Woodland birds must fly slowly to maneuver between branches and trees, as well as take off frequently, have short, broad wings and wide feathers. They cannot fly as fast or as long as birds with longer, streamlined wings. Finally, 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.

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Last modified: Sat Nov 15 18:59:06 PST 1997