# Difference between revisions of "How Gliders Fly"

Most people have misconceptions about how flight works, you don't have to understand the details of flight to fly but having a grasp of the basics helps.

Forces on a glider in flight

As long as the wings are moving forward they will produce lift. Lift is one of the the forces on the glider. The others being drag (friction) and weight (gravity). Weight always pull the glider towards the ground, and drag always tries to slow the glider down.

The lift from the wings pushes the glider up and forward. This lift keeps the glider in the air; unfortunately, as the glider moves though the air, drag slows the glider down. To maintain a constant speed, the glider must therefore fly slightly ‘downhill’. Hence the glider slowly loses height over time. A typical training glider will have a glide ratio of 30:1 (it will lose one unit of height for every thirty it moves forward) while a high performance glider will have a glide ratio of 60:1 or more.

This video on the CUGC YouTube channel explains this.

## Lift and Soaring

If you want to fly further than your glider’s glide ratio, you must then gain height. This is done by finding rising air, confusingly also called lift. The act of flying in lift is called soaring. While flying in lift, the glider is still going 'downhill' but as the air around it is rising, the glider gains height, like walking down an up escalator.

### Thermal lift

The most common form of lift is thermals. Thermals are bubbles of air that are slightly warmer than the surrounding air; because of this, the bubbles rise. An experienced glider pilot can identify thermals and then fly within them. While in a thermal, the glider can gain height and therefore continue flying. Thermals vary in strength and the maximum height they rise to, but a typical good thermal in the UK could be rising at 400 ft/min (0.5 kph) to a height of 5,000 ft (1,500 m).[1]

### Ridge lift

Ridge lift is created when a wind strikes a mountain ridge or cliff that is large and steep enough to deflect the wind upward. This creates and area of rising air, which when flown in allows the glider to gain height. Although the glider cannot go very high on ridge lift (up to about 2× the height of the ridge), it is very reliable so gliders can travel great distances by flying along long mountain ranges or hills.[1]