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soaring

The word soaring is often used interchangeably with gliding when referring to the sport. However, more precisely soaring is the art of using air currents to stay airborne.

How do you get up there?


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Winches or bungees can be used to launch gliders and sailplanes off the sides of a hill. Nowadays, aerotows are more common. A small powered aircraft tows the sailplane upwards using a 200' long polypropylene rope, about 3/8" thick. Once the planes reach 2000' (the common height for release) the sailplane releases the rope and begins what is generally referred to as "free flight".

Staying Up

Lift in the atmosphere occurs in three primary forms. Thermals are by far the most prevalent of lifting sources available to the soaring pilot. They are generated by the heat of the ground radiating upwards to the air directly above. The heated air rises in a vertical column, almost donut shaped, and eventually reaches the condensation level of the airmass, and a cloud is formed. By circling inside this rising mass of air a glider pilot can gain altitude as quickly as 1000 feet per minute, and can reach heights of 8000 feet on a good day.

Thermals

On a summer's day, you can see birds circle upwards without flapping their wings. They are "thermalling". A thermal is a volume of air that has been heated by the sun more than the surrounding air - imagine if you were standing on some sunlit concrete, you would feel warm! As you know, hot air rises, and it is circling within this air that allows birds - and gliders - to go upwards. Next you may ask "so how do you know where the thermals are?". Well, sometimes this is educated guess work, based on how you imagine ground features below you are warming up. However, often cumulus (cotton-wool type) clouds form at the top of the thermal, marking where the thermals are.

Occasionally, you may be joined in the thermal by a bird - from a swift to an eagle. You can never do it as well as they can, but it's great fun trying! Thermals are used in cross-country flying - you climb in a thermal to gain the height to move forwards to the next thermal on track (or thereabouts). The largest flight in the UK was done like this. Just over 1000 kilometres were covered in the flight which took about 12 hours.

Ridge Lift

Another way of staying up requires a hill (ridge), and the wind to blow against the face of it. Try to imagine this scenario - when the wind hits the hill, it gets forced upwards. Again, it is this upward movement of air that allows gliders to stay airborne. With a long ridge, it's possible to do large distances without turning, generally flying fast and low to stay in the best "lift" close to the ridge.

Wave Lift

Similar to ridge lift is a phenomenon called "wave lift". This is a little harder to imagine. It arises from the wind blowing against a hill again, but this time the air comes back down (on the far side of the hill) and "bounces" off the ground and goes back up again creating a very smooth upwards flow of air. Often, this form of lift is capped by a cigar shaped "lenticular" cloud.

This wave may go back down and up again for several cycles, meaning that you don't actually have to be close to any hills to use it! The furthest flights in gliders have been done using this lift - the best being 2463 kilometres (1530 miles) which was done along the Andes, all in one flight and one day. Wave lift is also known to go very high - the world height record in a glider is just a little short of 50,000 feet!

How do you get down?

Landing an airplane is the same, whether you have an engine or not, but in soaring you only get one shot at it!! Most pilots use a circuit to align themselves with the runway they want to land on. They fly parallel to the runway (downwind leg), then turn across the end (base leg), and then turn final and begin their approach. As the sailplane is already descending the pilot only has to modify his decent rate using dive brakes or spoilers. The pilot has to correct for drift due to cross-winds and once done the pilot will flare the plane and then touch down onto the runway. Momentum ensures that the plane rolls evenly on its mainwheel. Only when the plane stops rolling does a wing gently touch the ground.

 
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