A spiral dive allows for a very rapid controlled descent. Using a steep continual 360° turn you can achieve descent rates of 1600-2000 fpm, with up to 4000 fpm possible. To begin, a pilot applies weight shift and brake input in the desired turn direction and gradually increases the control pressure, keeping pressure on the outside wing as in any turn. After a few rotations, you should start to feel the G-forces press you into your harness. You can maintain the dive at this point by holding the brake input, or you can exit. To exit a spiral dive, ease up on the inside control and start to lean out of the turn. The glider will start to decelerate and will want to climb up to expend the excess speed. You can avoid this climb and have a smoother transition back to level flight, if you continue another turn as soon as you start to decelerate. This takes a little practice to perfect but shows control and understanding of the energy in your glider. It’s important to have a few thousand feet to experiment with spiral dives. A maneuvers clinic is the best choice, but you can learn them on your own, or with instructor supervision.
The risk involved with spiral dives is unintentionally entering a stable spiral, where centrifugal force exceeds the force of gravity. Prior to this happening, if you were to let up on the controls, gravity would pull you back under the glider, and you would resume level flight. In a stable spiral, centrifugal force takes over, and releasing the controls allows the glider to go faster toward the ground. A stable spiral can take a lot of altitude and aggressive control input, possibly a full flare, to slow down enough for gravity to pull you back underneath the glider. At this extreme descent rate, you may not have enough altitude to recover in time and will have to throw your reserve. You may also experience dizziness or loss of blood to your brain in a stable spiral. Stable spirals should not be attempted without instructor supervision.
Quick Review
Entry: Weight shift and brake input in direction of desired turn.
Exit: Release inside brake and cease weight-shifting.
Dangers: In wind you may find yourself drifting downwind toward obstacles. In steeper spirals you may become dizzy and disoriented. In stable spirals releasing brake input will not exit. You may become dizzy, disoriented, and eventually black out.