The aerotow starts with hooking up a rope to the tow hook on the nose of the glider.  When the glider and towplane pilots are both ready to go another person raises the wing tip of the glider, levelling the wings and uses hand signals to tell the towpilot to begin the launch.  The glider and towplane only have to accelerate a few feet before the wing runner can let go, and the aerotow is on its way.  The glider and towplane fly in formation until the glider releases the tow rope at the desired launch height.  Typically this is 2000 feet above the ground.  

 

Winch launching requires about 4,000 feet of light-weight wire or composite cable.  When the glider pilot is ready a wing runner levels the wings of the glider and signals the winch operator near the cable drum to start reeling in the cable.  Quite quickly the glider is flying on its own and flying skywards at a 45 degree angle.  The whole launch is often done in about two minutes when the cable is released by the glider.  A small parachute is deployed when the cable is released that gently guides it to the ground.  It is then stretched out to launch the next glider.

 

 

Self-launching is typically done with a small gasoline or electric engine, with the propeller mounted on a retractable boom.  Once the glider has reached the desired launch height, the engine is stopped, and the boom is retracted inside the body of the aircraft.  As it retracts, small doors close to complete the streamlining, and the glider is ready to soar.  Should the need arise if lift cannot be found, the engine can be extended again in flight and restarted, to try again or go home.

 

 

 

 

 

 

 

 

In mountainous regions wind that is deflected upwards may provide wave-like rising and falling air currents.  If glider pilots orient their sailplanes properly to these waves, flight can be sustained.  At altitudes above 12,000 feet though supplemental oxygen is required.  Also it's very cold so pilots have to dress warmly.

After a cool clear night, the next afternoon, the sky is often filled with beautiful puffy cumulus clouds.  Each of these is a marker for the rising air currents that glider pilots use to sustain their flights.

In areas that have ridges, the wind is often deflected upwards with enough force that the sailplane can sustain itself with these rising air currents.

 

A powered aircraft uses an engine to move forward and the air flowing over its wings generates lift to sustain flight.  A sailplane trades height (potential energy) for forward motion (kinetic energy) to achieve the same result.  At altitude, the weight of the sailplane is being pulled towards the earth by gravity.  Therefore, the sailplane must always descend at a minimum rate.  The weight may be considered as a force opposite of the Lift, L, called WL plus a force opposite to the Drag, D, called WT which may be combined to give the Resultant Force=Weight=Mg  The force propelling the glider forward is the force WHence the Equivalent.  Thrust=WT+Mg.sinø

 

Glide ratio - The most modern Sailplanes can reach glide ratios of 60 to 1 in still air such that if a sailplane is 1000m above ground it can glide...60Km before it will touch the ground!