Hang Gliding - Soaring Flight and Cross-country Flying

Soaring Flight and Cross-country Flying

A glider is continuously descending through nearby air, yet glider pilots can stay airborne for hours by flying in areas of rising air. Once this skill has been mastered, pilots can glide long distances to fly cross-country (XC). Rising air masses derive from the following sources:

Thermals

The most commonly used source of lift is created by the sun's energy heating the ground which in turn heats the air above it. This warm air rises in columns known as thermals. Soaring pilots quickly become aware of land features which can generate thermals; and of visual indications of thermals such as soaring birds, cumulus clouds, cloud streets, dust devils, and haze domes. Also, nearly every glider contains an instrument known as a variometer (a very sensitive vertical speed indicator) which shows visually (and often audibly) the presence of lift and sink. Having located a thermal, a glider pilot will circle within the area of rising air to gain height. In the case of a cloud street, thermals can line up with the wind, creating rows of thermals and sinking air. A pilot can use a cloud street to fly long straight-line distances by remaining in the row of rising air.

Ridge lift

Ridge lift occurs when the wind meets a mountain, cliff or hill. The air is deflected up the windward face of the mountain, causing lift. Gliders can climb in this rising air by flying along the feature. Another name for flying with ridge lift is slope soaring.

Mountain waves

The third main type of lift used by glider pilots is the lee waves that occur near mountains. The obstruction to the airflow can generate standing waves with alternating areas of lift and sink. The top of each wave peak is often marked by lenticular cloud formations.

Convergence

Another form of lift results from the convergence of air masses, as with a sea-breeze front. More exotic forms of lift are the polar vortexes which the Perlan Project hopes to use to soar to great altitudes. A rare phenomenon known as Morning Glory has also been used by glider pilots in Australia.