How do Gliders Fly?

The basic operation of a glider ithe same as any other aircraft. Lift is created by the wings as they move through the air. The big difference is that the pure glider has no engine, and so it relies on natural forces in the air to stay aloft.

The diagram opposite shows all the parts and primary controls of a basic glider. Full explanation of all the details would be beyond the scope of this web site but short explanations can be found in the glossary or by clicking on the diagram.

Click the highlighted areas on the diagram to see a description of the primary controls.

 

thermallarge

Because gliders have no power of their own, they must be launched into the air using some other means. This is usually a tow behind a powered aircraft (tug) or by a winch. 

Using natural forces, or energy, that creates rising air (lift), gliders can stay in the air for many hours at a time and cover long distances. 

The main types of lift a glider pilot uses are shown below. It can't be seen of course, but there are indications as to where lift might exist, such as land features and clouds, and it is these that the glider pilot looks out for.

 

 

Thermals are formed by the sun heating the ground, which in turn heats the air above it, causing it to rise. Gliders can use this rising air by circling in it to gain height.
What the pilot looks out for are:

  • Clouds that are growing

  • Darker patches of land

  • Birds circling

  • and of course other gliders circling!

thermal

hill

Hill or Ridge Lift

When wind blowing across the country meets a hill or cliff it is forced upwards to flow over it.  This upwards movement can be used by a glider to stay aloft by flying  up and down the length of the ridge.
What the pilot looks out for are:

  • Sharply rising ground

The pilot must also be aware of the wind direction

Under certain conditions, (wind strength & direction in relation to a range of hills), a wave system can be set up in the atmosphere. The upwards flowing air can be used to reach great heights. (The world record in a glider is just a little short of 50,000 feet) Often, this form of lift is capped by a cigar shaped "lenticular" cloud.
What the pilot looks out for are:

  • Stationary lenticular clouds

wave

H2 s

As the glider has no power of its own and is relying on natural energy (and the skill of the pilot) to stay airborne, the pilot must be constantly aware of where he/she is in relation to the airfield, or, if on a cross country flight, possible fields to land in.

All this is part of the pilots training, and you soon get to recognise how far away from the airfield you can be and still get back.

Field landings are practiced in a powered glider, so that when you are ready to turn your back on the airfield you are confident you can land the glider in a farmers field if 'the energy runs out'!

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