How do gliders fly

Why does a glider fly?

500 kilometers in five hours with solar energy and water ballast. When you have "flooded" as a glider pilot, that is, you have made an "outland" in a meadow or a field, you are often asked: "Did you run out of wind?" or "Is there no wind for sailing today?" These questions are right and wrong at the same time. While with a sailor on the water without wind nothing really works, we glider pilots move three-dimensionally, so with us the height is added, and to slide down from a high starting point, similar to how a skier descends the slope, we can always do that, we don't need any wind at all for that. In contrast to the balloon or the airship, a glider is one of those aircraft that are "heavier than air", that is, that have no lift of their own. Because the glider also lacks the pulling power of a motor, its trajectory is always a downward glide, that is, a conversion of its static energy (the higher, the more) into the energy of movement, i.e. forward and simultaneous movement also sliding down. But how is it now that the slender white sailors keep climbing up in the sky? Suddenly the question from before, "Is the wind missing?", Is once again correct. Only it is not the wind in the usual sense, for example a strong autumn wind, which bends the trees and which you need to fly a kite, but the "updraft" that is generated by the sun and is called "thermals" and that brings us glider pilots at heights of Can carry up 3000 meters and more.

The earth is heated to different degrees by solar radiation, depending on the nature of the surface (open field, forest, bodies of water, etc.). Since the heated air, which can be compared to a soap bubble that is still clinging to a surface, is lighter than the cooler air in the area, the air bubble tears off and rises, where it is often - but not always, due to the condensation of the Moisture contained in this air bubble forms a cumulus cloud, that is, fair-weather clouds.

As a mountaineer, when descending from the mountain, you sometimes notice how this heated, warm air from the valley comes towards you. In this rising air, the thermal hose or "beard" as it is called in the glider pilot's language, the glider pilot can rise in a circle. Correctly said - as paradoxical as it may sound - the sailor glides "downwards upwards". As we heard at the beginning, a glider cannot rise like a balloon because it always glides downwards within the surrounding air mass. But if this air package moves upwards, regardless of whether as a "normal" wind on a mountain slope or as a "beard", that is, if this air rises faster than the airplane sinks in it, then the glider experiences a gain in altitude and they say: it has rises. In our latitudes, such a beard can hit the glider at up to 3 meters / sec. and also carry more. This means that you can gain almost 1000 meters in altitude in five minutes. This means that the sun's energy is stored at the height the aircraft has reached and can now be converted into speed and thus into distance. From a height of 1000 m, modern gliders can glide between 40 and 60 kilometers before they have to look for a new updraft. This glider performance is expressed in the "glide ratio", a glide ratio of 40 corresponds to a distance of 40 kilometers from a height of 1 km.

On days with good weather conditions, after a winch start, which consumes around half a liter of petrol, distances of up to several hundred kilometers can be flown without a motor, using only the sun as the "drive source". In these "cross-country flights", rising thermals and sliding altitude alternate again and again. Top experts in motorless flights have already carried out flights of up to 1000 km over the Federal Republic of Germany.

Such cross-country flights are usually carried out as so-called "triangular flights" around two or three previously determined turning points, which have to be photographed in flight, and with a return to the take-off airport.

Such a 1000 triangle would mean flying from Gerstetten to the southernmost Black Forest near Lörrach, then to the Kassel area, then to the third turning point in the Bavarian Forest, almost near Passau and back to Gerstetten. A distance that would take almost two days by car can be covered in about 10 hours by glider. Flights of 500 km from Gerstetten are no longer uncommon. It should not be left unmentioned, however, that a lot of flying skills and the correct assessment of the weather are necessary to achieve such performance. After all, a little luck is also required if the planned flight is not to end prematurely on a meadow.

Now there is another inconsistency in gliding for the layman: "Easy flies well" is our opinion, as many people noticed as children when building a kite. In the early days of gliding, this was also the top priority, so that the gliders built at the time weighed just 50 kg, while today's gliders made entirely of glass and carbon fiber reinforced plastic weighed around 250 kg. A "super orchid", a high-performance sailor with a large wingspan (up to 26 m!) Or a two-seater weighs almost half a ton. And now a visitor to the airport sees how the glider pilots pour 50 ... 100 ... and sometimes even more liters of water into the thin wings of their birds from large canisters. Why is that? He will ask in astonishment. You can use a simple comparison: if you just let go of a father and his (lighter) son on the bike on top of a mountain without pushing, who will then cover the further distance out into the plain? In the larger mass there is more kinetic energy for the same starting height. The heavy, water-laden glider will advance faster from the height it has gained and thus be able to use the next updraft earlier than a lighter sailor. This rises better in the next updraft, but the bottom line is that the aircraft loaded with ballast is faster with good updrafts and when the thermals get weaker in the evening, the water can be drained again. In this way, average speeds of up to 150 km / h can be achieved even over long distances.

Of course, you can argue about the sense and benefit of such a show of speed, as well as other top sporting performances that involve hundredths of a second. By nature, gliding is a contemplative sport that also brings fun and great experiences to those who float over the landscape for pleasure without any time pressure.

In our fast-moving and high-tech times, gliding is one of the few remaining adventures to experience the forces of nature, to play with them and also to use them for yourself and to enjoy the constantly changing impressions of a silent flight with open eyes.

By the way: even if you read about the "emergency landing" of a glider pilot in the newspaper from time to time - such an "outside landing" is completely normal and is exactly the same as a landing on a "real" airfield.

Even if, of course, one would rather end a planned flight at one's home airfield, one can still say that such an outlanding is now and then part of gliding like the icing on the cake. When it comes to this topic, some glider pilots get bright eyes and can tell of wonderful experiences that they already had "in the field" after such a landing.

Gliding as a sport

Thrill, action, fun

The engine of the glider