What is gliding? Part 2: Thermalling

May, 14, 2021 by Suhas J.

To avoid a stall, gliders utilize a gradual, continuous descent depending on speed. However, it is entirely possible to climb thousands of feet in a glider. How? Thermals.

What are Thermals? Thermals are the movement of rising hot air. Hot air rises and cold air sinks. The hot air rises from the ground, typically in a cylindrical shape. Because thermals are in a cylindrical shape, in order to stay in a thermal, pilots have to enter it and then continuously turn to stay inside. How do they find thermals? Thermals are typically located near Cumulus clouds, above hills, and above open fields. Thermals aren’t visible, but once a glider pilot enters one, their variometer will show a positive climb rate. If the climb rate continues to stay steady, the pilot has flown into a thermal.

A typical thermalling method is the ‘Easy as 1, 2, 3’ turn. Once the pilot has determined they have flown into a thermal, they will count to 3 and then turn continuously left or right until they find the thermal. This may mean they fly out of the thermal occasionally, but they will continue until they center the thermal, as seen above.

Continuous, steady turns are much harder than they look. It is essential to keep a steady turning rate once in a thermal, and to not let your nose or airspeed dip too low. My instructor taught me to ‘pin the nose to the horizon’ – and keep the nose level to the horizon while turning. If the variometer indicates a higher level of climb, a shallower bank is utilized, and a steeper bank for a lower level of climb to return to the thermal.

After the pilot has finished with one thermal, they will find another, or return to the airfield for landing.

Have you ever practiced continuous turns? Try it in Infinite Flight with any lightweight GA aircraft. Continuous turns are easier in powered aircraft, because if the nose is dipping or the airspeed is too low, more thrust can be used. Practice continuous turns while keeping the nose steady on the horizon and try to look outside but also keep an eye on your airspeed.

References: Image

Suhas is a writer for the IFATC Education Group. He is a long time Infinite Flight user, IFATC Officer and Tester. In the real world, he’s a student pilot on both glider and powered aircraft. He's also an IFVARB Board Member.