Understanding Paraglider Collapses

Active Piloting

The PPG Bible goes into great detail about this. Besides avoidance, there is no better prevention of collapses than active piloting: the fine control inputs required to keep your wing overhead in a smooth fashion. The book details how to practice, what to practice and how to know when you've mastered it. 

Here's an important point: if you don't know how to do active piloting, trying to do so in strong turbulence will likely make matters worse! Use constant pressure instead.

Active piloting should be practiced in light turbulence until keeping the wing overhead, using minimum brake input, is second nature. The the dynamics are such that body movement is opposite the wing in turbulence, rendering your natural reaction to be exactly wrong. The other common malady is using too much brakes which slows down your wing's airspeed to the point where the brakes become ineffective or worse. 

And I've seen numerous accidents and collapses that were aggravated by the pilot's attempt at using brakes when he would have been far better served by reducing brake pressure to let the wing fly and concentrating on direction.

You can do a lot to avoid collapses in the first place. Staying out of turbulence is the best prevention. 

Free flyers in strong thermal conditions get collapses a lot, relatively speaking, so avoid such conditions. A good start is to only fly in the first 3 and last 3 hours of the day. Don't fly in rotors—downwind of obstructions. Stronger wind=stronger turbulence.

Don't fly too slow, though. Speed is life especially once you're already in turbulence. If you're getting bounced around a lot, reduce brake pressure a bit, especially if you feel the airflow on your face decrease. After all, once you give up speed, those brakes are worthless. Except for heavily reflexed wings, have them trimmed slow and do not use the speedbar. Flying faster means that, once a fold starts, the extra airspeed will tend to pull it under farther.

Resistant Wings & The Reflex

High performance wings (higher than DHV 1-2 or equivalent), especially when lightly loaded, will behave the worst during large folds (collapses)—they are more susceptible and less likely to recover cleanly. Their higher certification, in fact, comes from how long they take to recover from various upsets. These long, skinny wings are favored by cross-country pilots for their great glide at the expense of higher risk. Don't think that skill alone will make them safe, either. It will certainly make a huge difference but free flight has lost some awesome pilots in the powerful thermic cauldron called "big-air." Small folds, less than 50%, seem to affect higher performance wings less than lower performance wings.

Having said the above, realize that any wing, when confronted with a sufficiently strong vertical gust will fold. A heavily loaded wing will be the most resistant but it's recovery will be sportier. A highly skilled pilot flying a small, moderate performance wing actively is quite resistant but only if he is actively piloting it.

Recovery

1. Let it fly first by reducing brake pressure slightly for a second. The good side will accelerate some.

2. Add the least amount of pressure required to steer your course straight. The hand on the collapsed side will be loose, there is no point pumping it in most cases. However, one large pump can sometimes clear things up AFTER some speed is gained. But always use pressure—as the pressure in the collapsed side comes back you MUST let that hand go up.

3. For smaller collapses, weight shift away from the turn, if able. Don't waste time with it, though, during a large collapse.

4. React to pressure. If you feel the pressure build, in most cases it is best to let your hands up to allow the wing to accelerate.

5. React to fore/aft swing. If you're pointed at the ground, you may need FULL brakes. As soon as you start swinging back under though, you must get off the brakes. More advanced techniques exist for dissipating the energy resulting from such a dive but you certainly won't remember that from a one-time read here. That requires expert instruction and practice.

6. In a severe collapse there are many potential complications that may defy correction. Each situation is different, that is why avoidance is so important. There are thermals and windshears and rotors out there that no amount of pilot technique will counter. A good SIV (maneuver/safety)  course will help prepare you but, even then, without rehearsal it's doubtful you'll be that much more prepared for the most severe deformations.

Weight Shift (skip this if time is important)

Conventional wisdom suggests weight shifting to steer during a collapse and, to the extent possible, I agree. During smaller collapses it is quite beneficial—I've demonstrated turning away from a 50% collapse using weight shift alone on the Spice. However, experience and observation suggest that for large collapses it's impractical and even contrary to a rapid recovery.  Here's why.

1. In a truly large collapse your body will fall towards the folded side. A turbulence induced collapse is quite different than an intentional one. When you induce it, usually by pulling the A's on one side, you know it's coming and will likely start weight shifting immediately if not a hair in advance. Plus, just hanging on those A's gives some support and you won't fall as much, if at all. 

2. The surprise version will give neither support nor warning. You won't prepare and will likely fall towards the down side making it harder to move back up for effective weight shift. 

3. When the wing initially folds, in most cases your body will actually swing briefly away from the fold and then you'll fall towards it. It can be quite confusing. A simple procedure, such as "reduce brake pressure for a second then steer with the least input required," will yield more consistent results until you've gained experience with the requisite timing.

4. Weight shift works by differentially moving the risers. Cool foot crossing and body contorting may impress the babes, but if the risers don't move, neither will the wing. In a large collapse, the collapse-side riser is barely in play, if at all.

I've never been able to induce a collapse as bad as what nature has. Even pulling down one side as fast and hard as possible has never done more than about 60%. While that was attention-getting and turn-inducing, it was not as bad as what Mother Nature's turbulence served up. So we shouldn't think that just because we can handle self-inflicted versions, we'll easily tame natures fury. Prevention is still the best medicine. 

In the 3 major asymmetric collapses that I've experienced, two during thermal free flight and one while motoring, I fell immediately to the down side and recovered from that position mostly using the above technique. One was from launch at Marshal. Alan Chuculate, launching behind me, described that event as a 70% collapse. Another, also at Marshal, cascaded. That is, one side folded then the other. Airspeed dropped and I was successively falling to each side. That side would load and the other side collapsed. After 3 repetitions I dropped out of the harness into the landing configuration to prevent weight shifting and the cascading stopped. Scary. In that case eliminating the possibility for weight shift allowed a recovery. Of many dozens that I've induced, mother nature took the cake for collapse severity.

Cravats, Complications

Severe wing deformations can defy correction. For example, while most cravats (where a tip gets tangled in the lines) are non-events, some can quickly induce a spiral. Even small ones can be problems if the pilot allows a spiral to develop.

It's important that, after reducing brake pressure momentarily, you steer, especially before it wraps up into a steep turn. That can happen fast.

Such problems are incredibly rare except for those exploring the boundaries of conditions or maneuvering. If you've seen Risk and Reward then you've seen some examples of this. Minding the conditions and flying only when it's mellow, and forecast to remain so, will avoid the vast majority of this kind of risk.

A Reflex style wing These wings load the A's and B's very heavily with the trimmers set to fast. They are  less prone to collapse in that condition because the leading edge is less subject to "blow down," where relative wind aggravates the collapse as the leading edge is blown down and back, taking more of the wing as it goes. The effect is seen in all three of these pictures and the video below.

But any wing, going real fast, will be wilder on the recovery. So even the reflex wings will frequently earn (or deserve) a DHV 2 or performance rating at their faster settings.

The pilot was about 200 yards inland from the the Salton Sea which exhibits calming on-shore winds like an ocean beach. He was descending on speedbar which is a more vulnerable condition.

Pilots had been reporting only light thermal activity and wake turbulence did not appear to be a factor. This was a fluke. 

Fortunately, he was a very competent pilot who managed this properly, keeping his cool and using the minimum brake required to recover which he did with about a 30 foot altitude loss. This was on a DHV 1-2 wing. 

Photo by Jim Farrell