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Dartmoor Gliding Society

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What is Gliding?

Imagine you're a falcon. You effortlessly ride the airwaves, circling upwards in the thermals, just flicking a wing feather every now and again to change direction. For we mere humans, the closest approximation of flying like a bird is the sport of gliding. The motorless aircraft, called gliders (or more accurately sailplanes) provide the experience of flying without distracting engine noise, and allow for wonderful views of the countryside below. Reading the weather provides a real mental challenge for glider pilots, and yes, they sometimes do watch the birds for clues.

Do You Fall Out of the Sky when the Wind Stops?

Keeping a glider airborne is all about finding areas of rising air, known as lift. There are several different types of lift:

Thermal Soaring DiagramThermals

Thermals are the result of warm air from the earth escaping into the colder skies above. When you see birds circling high above you, they are taking a free lift from a thermal. At the top there will often be a large fluffy white cloud with a flat bottom. Think of a hot summer's day with blue skies and you're probably picturing the right sort of cloud. If you're anywhere near a gliding airfield, there may well be some large-winged sailplane circling up under the clouds.

Ridge Soaring DiagramRidge Lift

Ridge lift is caused by a hillside getting in the way of a steady flow of air. When the air stream reaches the hillside, there's nowhere to go but up. Pilots can then fly quite happily above the ridge, supported by all that rising air. With a favourable wind, you can fly back and forth for hours if you really want to.

Lee Wave SoaringWave

Wave can be King of the Skies for providing strong, steady lift. It's easiest to imagine if you consider the analogy of a stone in the middle of a river. As the water flows over the stone, standing waves form down stream. A similar thing happens to moving air as it hits mountains and hilltops sticking up into the atmosphere. Standing waves occur which can be seen in the sky in the form of lens-shaped clouds, lying still across the direction of the wind instead of moving with it. The stronger the wind, the bigger the waves and the faster they lift lucky glider pilots up, up and away.

Glider pilots watch for signs of these conditions and make the most of them to get high in the air and stay there. If there are no thermals, you might still find some ridge or even wave lift. When there really is no rising air to be found, then you'll gently glide downwards in a controlled descent. If you've calculated your height, glide angle and distance from the airfield correctly, you'll make it back home. If you've miscalculated and are too low, too far from home - then it's time to find a friendly field you can safely land in. Glider pilots on cross-country flights will be constantly scanning the ground for suitable fields in case the weather or their judgement fails.                                                                    

Dartmoor Gliding Society, Burnford Common, Brentor, Tavistock, Devon PL19 0LB