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Basic knowledge of glider

Add Date:2009-12-18  Hits:17168

     Glider aircraft are aircraft with no attached powerplant. Larger outdoor model gliders are usually radio-controlled gliders and hand-winched against the wind by a line attached to a hook under the fuselage with a ring, so that the line will drop when the model is overhead. Other methods include catapult-launching (using an elastic bungee.) The newer "discus" style of wingtip handlaunching has largely supplanted the earlier "javelin" type of launch. Also using ground based power winches, hand-towing, and towing aloft using a second powered aircraft.
     As gliders are unpowered, flight must be sustained through exploitation of the natural wind in the environment. A hill or slope will often produce updrafts of air which will sustain the flight of a glider. This is called slope soaring, and when piloted skillfully, radio controlled gliders can remain airborne for as long as the updraft remains. Another means of attaining height in a glider is exploitation of thermals, which are bubbles or columns of warm rising air created by hot spots on the ground. As with a powered aircraft, lift is obtained by the action of the wings as the aircraft moves through the air, but in a glider, height can only be gained by flying through air that is rising faster than the aircraft is sinking relative to the airflow.
     Sailplanes are flown using thermal lift. As thermals can only be indirectly observed through the reaction of the aircraft to the invisible rising air currents, pilots find sailplane flying challenging.
Hang gliders come in two categories: hang glider and paraglider. The default use of the term is for the stiffened-wing sort; the paraglider is fully flexible winged.
     Walkalong gliders are lightweight model airplanes flown in the ridge lift produced by the pilot following in close proximity.      In other words, the glider is slope soaring in the updraft of the moving pilot (see also Controllable slope soaring).
     Power sources
     Powered models contain an onboard powerplant to propel the aircraft through the air. Electric motor and internal combustion are the most common propulsion systems, but other types include rocket, small turbine, pulsejet, compressed gas and tension-loaded (twisted) rubber band.