Glider Thermalling Technique
I have been around gliding for a number of years now and am staring to compete. I spent this off season thinking about how best to centre a thermal and how to verify and communicate this.
Speaking to others on this point, I have heard variations of "turn when you feel the kick", "turn tighter in the good air" or the BGA's "Less lift: reduce the bank and increase the bank as the lift improves".
The issue I have with all these is: Assuming you are not already centered, the "kick", "good air" or "lift" only comes once per circle. This means your feedback loop takes a circle to resolve (about 25s according the the BGA Instructor Manual). The main variant of this technique involves opening the turn in the bad air, which makes this problem worse.
This is what I came up with:
Open the turn while the needle rises, close while it falls.
More formally:
Your turn rate should be your desired turn rate with an additive proportional to your downward acceleration.
This allows you to receive and incorporate immediate feedback, it also has only two parameters (proportional weight and desired turning rate), making it fast to optimise for your aircraft/conditions.
There are a few intuitive things about this technique, generally:
Heading diagonally towards the core, with the vario value increasing -> open the turn.
Heading diagonally away from the core, with the vario value decreasing -> close the turn.
Heading at a tangent to a circle concentric with the thermal, with the vario constant (irrespective of value) -> fly your desired turn rate.
In all situations, the prescribed technique offers an immediate bettering of the glider's position in the thermal.
Finally, it is important to note that: The ideal proportionality is between the rate of change in vertical speed and the turn rate, not the control input. Therefore you would ideally preempt the vario reading to accommodate for the time it takes to change the turn rate. This may be why the technique of increasing the turn rate in the lift works well for many people. The control input may be proportional to vertical jerk, but I found this too complex to use in flight.
Less lift: reduce the bank and increase the bank as the lift improves
Open the turn while the needle rises, close while it falls
06/06/2026