These kinds of collapses/deflations occur when the leading edge or part of it, has too low an angle of attack and is pushed down or you fly through an area of turbulence. Collapses and deflations are something you will experience if you fly paragliders for any length of time, and usually happen so fast that they are completely recovered by the time you figure out what has occurred. If the whole leading edge of your glider deflates, you would describe it as a symmetric tuck or full frontal deflation. We describe asymmetric folds in terms of the percentage of the wing that deflates. If a small part of the right side of your glider deflated, you would describe it as a 20% to 30% right asymmetric. These terms are more descriptive than the word collapse, and help others visualize and evaluate what actually happened to the glider.
New pilots tend to spend a lot of time worrying about deflations when they have no need to be. As a new pilot you should be flying in mild conditions that have a low probability of causing any deflations, however, if you find yourself in unforeseen active conditions, remember that being an active pilot and maintaining horizon reference will greatly reduce your chances of having a deflation, and help correct them when they do occur.
If the asymmetric deflation is large enough, it will alter your course. Using opposite weight- shift and opposite brake will help you maintain your heading and re-inflate the wing. Use mostly weight-shift and only as much opposite brake as you need to control your heading. If you have 1,000+ ft of altitude and the asymmetric turns you 180°, it may be a faster recovery to allow the turn and use the speed and energy of the glider turning to re-pressurize the wing. Too much brake or weight-shift can lead to problems much worse than the asymmetric, use only enough to maintain a safe heading. Be aware that when a glider experiences an asymmetric deflation, its surface area is reduced and your stall speed increases. This means that it will require less brake to stall the remaining portion of the glider. It is very important to apply only enough brake to keep your heading.
If the tuck is symmetric, you will likely feel the loss of pressure along the leading edge of your glider and in the brakes. The glider will slow down due to an increase in drag, and you may notice an increase in your sink rate. The good news is that symmetric deflations are self- correcting. When the glider slows down, the weight of the pilot continues forward, increasing the angle of attack which re-opens the wing. The glider will surge in order to resume normal airflow. Allow this to happen, only checking the dive if necessary. DO NOT add brake input when the glider is behind you or you might stall it.
Most importantly, do not overreact. If you are unsure of what to do, do nothing and let the glider sort itself out. You can make the problem worse by giving the glider the wrong input at the wrong time.
Quick Review
Asymmetric Deflation/Collapse
Cause: Too low an angle of attack on one side of the glider
Recovery: Opposite weight shift and brake input to maintain heading
Dangers: Over controlling the flying side may cause a full stall
Symmetric Deflations/Collapse
Cause: Too low an angle of attack on the middle or entire glider
Recovery: Release brakes and wait for glider to surge
Dangers: Applying brake pressure while the glider is behind you will cause full stall or prevent it from regaining necessary airspeed.