Hang Gliding and Paragliding Volume 44 / Issue 12:December 2014 | Page 57

enough to perform a more normal, steady thermal 360. Figure 2 provides a picture of this procedure. Note that because of the presence of the hill the thermal is not drifting much downwind, so the center of my turn needs to be essentially stationary. This practice is similar to making a turn to stay over a point on the ground in wind. You can’t make a 360 evenly banked all the way around or you will drift with the wind. So we have to make a steeper bank on our downwind leg to remain in front of the hill. It should be clear that a safe thermal turn low in front of takeoff is not a steady, uniform process. The obvious reason is that you need more control to handle the unexpected near the terrain. Another reason is that thermals bulling up a steep face are not generally uniform. The presence of the ground tilts them and also turbulates their downwind border as shown in figure 3. The upwind portion of your turn tends to take place in lift that is getting stronger, while the downwind portion is usually in diminishing lift. We should all recognize that it is easier to turn a hang glider in building lift than in steady air, while it is harder (slower to react, heavier forces) when the lift is diminishing. This is another reason for gaining airspeed when you pass into the downwind portion of the 360. To be sure, using this turning technique is not apt to result in as much height gain as a turn that is at minimum speed all the way around. But, the severe (as severe as you can imagine) consequence of hitting the ground going downwind in the back side of your turn trumps performance any day. I have never come close to hitting the ground with this technique, although I know I have come closer to the hill with comfort than some pilots who aren’t aware of the benefit of carrying extra maneuvering speed. As with all our learning, all pilots should learn this variable-turn technique well away from the terrain. You can try it in a thermal up high. Simply determine the upwind direction and go slow upwind and faster with a steeper bank downwind. Practice until you have the timing down and are intimately familiar with your glider’s response. The first time you try it nearer the hill, use a wide thermal so you can be well clear. Eventually you will be able to make a safe decision when to turn in the first thermal with ample safety margin. Remember, you are judging a dynamic situation in three dimensions with a bit of unknown—the sink and turbulence at the downwind points are not necessarily the same every time around. Of course, if you boat out off launch and the lift is gentle and widespread, much to your joy, your 360 may be a normal leisurely circle. In this case, you will probably be above launch by the time you are on the back side of the turn anyway. Go in peace. But when the lift is weak or broken or small or turbulent or any combo of these characteristics, you need to use the variedcircle trick. Sometimes I find that I can get two or three 360s in a weak thermal that I may have latched onto below launch, but the drift takes me too close to the hill to keep circling. In this case I make ^H\