Soaring Association of Canada

What is "LIFT"

Lift, or rising air, occurs in three primary forms; thermal lift, ridge lift, and wave lift.

Thermals are by far the most prevalent of lifting sources available to the soaring pilot. They are generated by the sun heating the ground and the ground radiating that heat upwards to the air directly above. The heated air rises in a vertical column and eventually reaches the condensation level of the air mass, 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 in Ontario.

cumulonimbus

A cumulonimbus cloud, the epitome of the thermal
in its most powerful form.

Ridge lift is another form of rising air. In this instance a prevailing wind rushes against a long hill or ridge of hills and the air is directed up the slope of the hills. If the run of hills is long enough, great distances can be covered by the sailplane without ever needing to circle in lift. Essentially, once the airspeed required to produce lift for the sailplane wings is produced, the excess airspeed is converted into extra height, or extra forward speed. In North America the best ridge system is the Appalachien Mountains which go from northern Pennsylvania into Tennessee. Distance flights of over 1500 km have been recorded along this ridge.

wave flying

Over the Columbia River, in British Columbia.

Mountain wave is the third form of lift used in soaring. If a strong wind blows over a row of mountains it may set up an undulating wave in the atmosphere, much like the ripples you may see behind a submerged rock in a stream. The air in a mountain wave can rise or descend as much as 2000 feet per minute, and the phenomenon can exist right up into the stratosphere to over 50,000 feet. The current world record for an altitudewas set in wave, and it surpasses 50,000 feet.

Waves are marked by long, smooth bars of cloud that remain in place downwind of the mountains that cause them. The immense Chinook Arch in the lee of the Rocky Mountains in Alberta is a classic example of the presence of a wave.

thermalling

Inside the cockpit, thermaling upwards... Other less common types of lift involve cloud flying (prohibited in Canada), flying the edge of a cold front, and using sea breezes to stay aloft and fly large distances.

< Prev		Next >

[ Back ]