During a paragliding experience, especially in the afternoon, you will surely feel it.

An invisible force can keep you in the air or lift you up and allow you to gain altitude. As Fabien would say “it’s magic! It’s nature’s gift to us!

But what is it?

There are actually two ways to stay aloft. The first is through warm air masses called “thermals”, and the second is through the so-called “dynamic” weather wind.

For a thermal to occur, the sun must heat the ground sufficiently. Let’s take the example of a rocky mountain.

The sun heats the rock by radiation, the heated air above the rock rises in temperature compared to the ambient air. This temperature difference of about 4 degrees expands the air and makes a warm air bubble that will rise. If the sun warms up several parts of this mountain at the same time, all the little bubbles will join together and form a fairly large rising zone (the thermal). This will rise until it cools down to the same temperature as the surrounding air, only to be warmed up again, this is the cycle of convection… and of the day.

This is the reason why the best ascents are during the hottest part of the day in summer. Hence our afternoon flights called “thermal flight“!

schéma tournette
Credit: Lorenza Bertaud, view on the Tournette

As the sunshine declines at the end of the day, the heating decreases and so does the temperature contrast, making the air mass more homogeneous. For us pilots, this phenomenon is commonly known in french as “restit” (for restitution). It will make all pilots happy because it can sometimes last for hours and can cover a whole valley!

This makes it possible to optimise the flying days. The pilots “roll” the thermals, i.e. circle them to stay where the warm air rises the most. They glide from thermal to thermal and let you discover the Annécian massifs all day long!

soaring au puy de Dome
Credit: Florent Callon. Pilot: Lorenza Bertaud. Soaring au Puy de Dôme

Associated with the terrain, the wind will also allow you to stay in the air and fly for a long time.

It goes up and around the mountain, allowing us to fly close to the slope. But this only works at a certain speed, usually between 20 and 35 km/h.

By always keeping in mind where the wind is coming from, paragliders avoid flying behind the mountain. This is because of the turbulence and vortices in the air. This part of the flight, known as “downwind”, is sometimes unpleasant.

This way of flying close to the terrain and thanks to the wind is called “soaring“. Unlike thermals, there is no need to circle. You just have to fly back and forth in front of the terrain, respecting the flight priorities (article to come 😉 ).

By combining these thermodynamic phenomena, it is therefore possible to stay in the air for a long time, but also to cover long distances. Without setting foot on the ground, pilots can fly several kilometres. This discipline in paragliding is called cross country. There is nothing more satisfying for a paraglider pilot than to take off, fly around the Bauges massif or Lake Annecy and come back to the starting point.

You now know all the conditions (or almost!) that allow a paraglider to fly for a long time.

 

If you have any other questions, please feel free to ask them in the comments.

And if you want to fly with Flyeo 🤗, our tandem flights and training course are available here.

See you soon in the air!

Lorenza & FabL'équipe Flyeo

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