Peggy learns the basics of hang gliding, then goes for a ride.
Segment length: 9:20
- How can hang gliders stay aloft for hours without motorized propulsion?
- How does a pilot steer a hang glider?
- Why must pilots know about geography and meteorology ?
Usually, when somebody tells you to "take a flying leap," they don't really expect you
to fly. But you can if you know what you're doing and have a hang glider strapped on.
Hang gliders work on the same principle as any winged aircraft. As the wings move
forward, air is deflected above and below. The air traveling over the curved wing must
travel farther--and faster--than the air below. When air speeds up, it drops in pressure,
creating a low-pressure zone above the wing. This in turn gives the air traveling
below greater relative pressure and the strength to push up the wing.
To become airborne, a hang glider's airspeed must
equal about 20 mph. Airspeed is a combination of the pilot's running speed and the
speed of the wind coming toward the pilot. Many different combinations are possible.
If a pilot is running at 20 mph, no wind is necessary. (But this is unlikely, since
the world's fastest sprinters run only about 23 mph--without carrying hang gliders.)
If the wind is blowing at 15 mph, the pilot need only run at 5 mph. A combination of
a 10 mph wind with a 10mph run is considered ideal.
As a wing lifts a glider up, gravity pulls it down. The two forces combine to create
the gliding action, which is measured by the lift to drag (L/D) ratio. For instance,
the average glider L/D ratio of 13:1 means that for every foot of drop, the glider
sails 13 feet forward. However, pilots need to find constant upward forces to stay in
the air for longer periods.
Thermals, huge masses of rising warm air, are what hang gliders ride to stay aloft.
These thermals are formed near Earth's surface and depend on warmth from the ground.
Flat fields, dark pavement, and low lying towns create heat early in the day, while
wooded areas heat up more slowly and stay warm longer. Ridge lift is another power
source. When a ridge or a hill deflects wind upward, gliders can "catch the wave!"
While suspended in the harness system, the pilot steers a hang glider by shifting his
or her center of balance. Leaning forward and backward causes the glider to dive or
climb. This motion changes the angle of
attack and is used to take off and land, as well as to control speed during
the flight. Shifting from side to side causes the glider to bank into turns. Pilots
use a control bar to move their weight in relation to the wings. Other recommended
equipment includes a helmet, parachute, variometer, and altimeter.
Breaking gliding records is difficult, but designers are always trying to glide
farther, faster, and higher. The new boomerang shaped SWIFT (swept wing with inboard
flap) is capable of an incredible L/D ratio of 25:1 and has a top airspeed of 80 mph.
- How would the altitude of your launching point affect your flight and the
equipment you would need?
- What sort of research could a pilot do before a flight to identify possible
- You've seen hang glider pilots running into the wind to take off. Hang
gliders need a total airspeed of 20 mph to take off. How fast would a pilot have to
run if there was no wind to run into?
- How fast if there was a 10 mph wind to run into?
- If the pilot was running 20 mph with a 10 mph wind coming from behind, would the
glider take off?
airspeed the speed at which a glider is passing
through the air
altimeter instrument which measures
angle of attack the angle at which a glider
meets the air flowing over it. Decrease the angle of attack, and the glider dives and
speeds up. Increasing the angle of attack slows the glider.
flare raising the nose of the glider sharply to stall
forward motion and land
ground speed the speed at which the glider is
passing over the ground. Ground speed is a result of airspeed and wind
pitch movement which increases or decreases the angle of
attack, controlled by shifting the pilot's weight forward and backward
roll side to side control movements to make the glider
bank and turn
unstable air when air temperature drops rapidly
at higher altitudes. This makes thermals rise more rapidly, offering more lift for
variometer instrument which measures altitude
gains and losses
wind speed the speed at which the wind is passing
- Cheney, P. (1990) Hang gliding for beginner pilots. Rising Fawn, GA: Matt Taber.
- Coleman, C. (1993, May 3) Flying with Pasipo. Sports Illustrated, pp. 91-95.
- Fair, E. (1993, Mar 21) Zing time! Los Angeles Times, p. 6.
- Gannon, R. (1992, Mar) Winging it. Popular Science, pp. 60-65.
- MacLachlan, S.L. (1991, Sept 27) Ride the wind. The Christian Science
Monitor, p. 10.
- On the wing. (1993, Mar 20) The Economist, p. 100.
- Plimpton, G. (1991, Dec) Four thousand feet over Africa. Esquire, pp. 87-89.
- Skow, J. (1993, July 19) Sailing seas of air. Time, pp. 56-57.
Additional sources of information
General Aviation News & Flyer
8415 Steilacoom Boulevard
Tacoma, WA 98498
Soaring Society of America, Inc.
PO Box E
Hobbs, NM 88241-1308
(publishes Soaring magazine, Technical
Soaring quarterly, and a directory of
U.S. Hang Gliding Association
PO Box 8300
Colorado Springs, CO
(publishes Hang Gliding magazine.
Can help you locate a hang gliding
school or club in your area.)
In this activity, you'll make a model of the countryside and a simple glider. Then,
using a blow dryer as a wind source, you'll recreate the air currents and thermals
that a hang glider would encounter.
- pieces of paper about 20 cm x 25 cm (about 8" x 10"). Get a few different
- a room with open floor space
- blow dryer with extension cord
- measuring tape
- items to create different structures and landmarks. Be creative! You can
use books standing on end to be buildings or lying propped open for cliffs. Cereal
boxes, milk cartons, and teapots can be city skyscrapers. Pillows can be mountains,
and so on.
- Drop the pieces of paper just as they are to the floor from a height even
with your chest. What happens? The air pressure below the paper is being released
in random spurts. Now fold the pieces of paper in half to be 20 cm x 12.5 cm
(8" x 5") and spread them open again. What happens now when you drop them, with the
fold crease down? The fold is dividing air pressure equally on either side of it.
- Open the creased pieces of paper on a table and fold a long edge back about 2 cm
(3/4"), creating a sort of lip. What happens when you drop the paper again? Keep
folding this edge over onto itself, 2 cm at a time, and keep dropping it until you
get a smooth gliding action. Why does this cause a forward motion? Can you figure
out a way to calculate the lifttodrag ratio, using the measuring tape? (Remember
the L/D definition--as the glider drops, how far does it move forward?) What thickness
of paper has the best L/D ratio? Why?
- Using the blow dryer on a low, cool setting, turn your floor into a hang
glider's paradise. Have a friend sit on the floor and hold the blow dryer even with
a structure, while you fly your gliders over, around, and through your buildings
and mountains. Create turbulence by shaking the blow dryer. Does a warmer setting
cause different flight patterns? Create the ultimate thermal by pointing the blow
dryer straight at the ceiling. Experiment using two blow dryers at once.
(Hint: If you have trouble keeping the paper gliders aloft long enough to see the
flight effects caused by your classroom countryside, try using air-filled balloons
The world records for distance in hang gliding are 488.49 km for men set by Larry
Tudor in 1990, and 335.96 km for women set by Kari Castle in 1991. Matching these
distances, where could you go if you were able to travel by hang glinder from your
Get a topographical map of your city, as well as an aerial photograph. Plan a flight
over the city in a hang glider. Can you identify which parts of the city will have
thermals rising from them and which will be cooler? What areas would you want to fly
over at 8 a.m.? Noon? 6 p.m.?
Hang gliding pilots learn to "see" the air while they are flying. Stand outside on a
breezy day. How many different ways can you determine what the air is doing? Pay
attention to things such as how sound travels, how sun and shadows look on the ground,
dust and blowing objects, plants and trees, etc. As you do this, can you anticipate
what the wind will do next, even before you feel a shift in the breeze?
Newton's Apple is a production of KTCA Twin Cities Public Television. Made possible by
a grant from 3M. Educational materials developed with the National Science Teachers