is a special kind of
that has no engine.
are the simplest aircraft to build and fly, and students can learn the
by flying paper airplanes.
Toy gliders, made of balsa wood or styrofoam, are an inexpensive
way for students to study the basics of
aerodynamics, while having
fun building and flying the aircraft.
Hang-gliders are piloted aircraft that are
launched by leaping off the side of a hill or by being towed aloft.
Piloted gliders are
launched by ground based catapults, or are towed aloft by a
powered aircraft then cut free to glide for hours over many miles.
The Wright Brothers perfected the design of the first airplane and
gained piloting experience through a series of
from 1900 to 1903.
flies as a glider during reentry and landing; the rocket engines are used only
If a glider is in a steady
(constant velocity and no acceleration) descent, it loses altitude as
it travels. The glider's flight path is a simple straight line,
shown as the inclined red line in the figure. The flight path
intersects the ground at an angle a called the glide angle.
If we know the distance flown d and the altitude change h,
we can calculate the glide angle using
tan(a) = h / d
where tan is the trigonometric tangent function. The
of the change in altitude h to the change in distance d
is often called the glide ratio.
If the glider is flown at a specified glide angle, the
trigonometric equation can be solved to determine how far the glider
can fly for a given change in altitude.
d = h / tan(a)
Notice that if the glide angle is small, the tan(a) is a
small number, and the aircraft can fly a long distance
for a small change in altitude.
Conversely, if the glide is large, the tan(a) is a large
number, and the aircraft can travel only a short distance
for a given change in altitude.
We can think of the glide angle as a measure of the
flying efficiency of the glider. On
another page, we will show that the glide
angle is inversely related to the
lift to drag ratio.
The higher the lift to drag ratio,
the smaller the glide angle, and the farther an aircraft can fly.
- Beginner's Guide Home Page