Unpowered flight

Thermal soaring

A way of flying in which the aircraft rides rising currents of air – thermals. They keep a glider aloft without an engine and can carry it hundreds of kilometers, just like birds circling with their wings spread wide.

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Glider wing next to a cumulus cloud
How thermals form

From sun to cloud

  1. ☀️
    The sun warms the ground

    Fields, rocks and towns heat up faster than forests or water. The air above them gets warmer and lighter.

  2. ⬆️
    Warm air rises

    An invisible column forms – a thermal – in which the air rises at 1 to 10 m/s.

  3. ☁️
    A cumulus forms at the top

    As the rising air cools, it forms the typical fluffy “cotton-wool” cloud. For a pilot, it's a sign: the air is rising here.

  4. 🌀
    The glider circles upward

    In the thermal, the pilot circles like a bird of prey and gains height – no engine, powered by the sun alone.

How pilots find them

Reading the sky

  • Clouds – the flat base of a cumulus reveals where the air is rising most strongly.
  • Terrain – sunlit slopes, fields and towns are the best thermal “generators”.
  • Variometer – an instrument that beeps to show whether you're climbing or sinking. In the photo, it's on the right side of the cockpit.
  • Birds and other gliders – wherever they're circling, there's a thermal.
Glider instruments – airspeed indicator and variometer
The High Tatras seen from a glider
The Tatra wave

Up to 8,000 meters

Besides thermals, our aero club pilots also fly the wave behind the High Tatras. In strong winds, a wave forms in the air behind the ridge that can lift a glider to around 8,000 m – far above the clouds.

More about the Tatra wave at lzsv.sk ↗
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