Partial Canopy Collapse

[JENNR8R 0]

When I was 180 feet from the ground the left side of my canopy collapsed. Woo doggies, now that'll make your 'A' hole draw up. Fortunately, it reinflated, and I was able to land safely.

I never realized that a canopy could do that. I asked several people what the best way to handle that situation would be. The consensus was that going to half brakes would be the best way to reinflate the canopy. This surprised me because I was taught to fly in full flight through turbulence when I was a student.

Thoughts?

What do you call a beautiful, sunny day that comes after two cloudy, rainy
ones? -- Monday.

[dbattman 0]

Have your lineset checked for trim. It may be distorting the wing and ready for replacement.

[darkwing 4]

This can happen to any canopy, and don't let anyone tell you different. The prevailing wisdom to minimize the chance of this happening is to let it fly. That is contrary to the wisdom of many years ago, but canopies and canopy designers and pilots are much advanced since then.

I have seen such "fold-unders" many times, and they virtually always self-correct very quickly. They do get your attention though. Main point is to keep your canopy flying straight when it happens.

Turbulence is one reason I choose to sit on the ground some times, even when the wind is otherwise OK. The turbulence that can cause this has several causes, including, but not limited to, wake from other canopies, thermals, and generation by ground obstacles.

-- Jeff
My Skydiving History

[billvon 2,421]

>This surprised me because I was taught to fly in full flight through
>turbulence when I was a student.

This is why these "new and improved" theories worry me . . .

It is always better to go to half brakes when your canopy is collapsing. That's how the canopy was designed to reinflate. It will also surge less as it's reinflating in half brakes. Many people think "that half brake stuff is old news! Modern canopies fly completely differently." They really don't.

In moderate turbulence, there are benefits to going to half brakes and benefits to staying in full flight. Generally most canopies do OK at full flight, but in severe turbulence (bad enough that your canopy is distorting significantly) 1/4 to 1/2 brakes can give you some additional margin for error. The twin theories "you can just blast through the turbulence if you're going fast enough" and "the air mattress effect will keep your canopy rigid" don't work.

[DougH 270]

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Woo doggies, now that'll make your 'A' hole draw up. Fortunately, it re inflated, and I was able to land safely.

It sure does!!!!!!!!!!

I experienced my first really really bad turbulence at around
I went to half brakes like I read in Bill Von's article and it started flying again. I might have just been lucky, or it might not have been as bad as it felt, but it recovered in time for me to get a nice tip toe landing. Thanks Bill!!!!!!!!!!

I wasn't the only one on the load to have a problem, another jumper on the same jump lost his canopy at the end of his swoop.

I sat out for most of the rest of the day until the conditions got better. Loads were stopped for some time too, but I waited longer then the hold.

I am definitely glad it happened though, I haven't been that scared in a long time. I think it was both humbling and a good learning experience.

"The restraining order says you're only allowed to touch me in freefall"
=P

[diablopilot 2]

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>This surprised me because I was taught to fly in full flight through
>turbulence when I was a student.

This is why these "new and improved" theories worry me . . .

It is always better to go to half brakes when your canopy is collapsing. That's how the canopy was designed to reinflate. It will also surge less as it's reinflating in half brakes. Many people think "that half brake stuff is old news! Modern canopies fly completely differently." They really don't.

In moderate turbulence, there are benefits to going to half brakes and benefits to staying in full flight. Generally most canopies do OK at full flight, but in severe turbulence (bad enough that your canopy is distorting significantly) 1/4 to 1/2 brakes can give you some additional margin for error. The twin theories "you can just blast through the turbulence if you're going fast enough" and "the air mattress effect will keep your canopy rigid" don't work.

The "theory" never was to just let the canopy fly through a collapse.


Full flight through turbulence will allow the best chance of making it through without a collapse.

If a collapse occurs, then a half brake pump, similar to inflating closed end cells is recomended.

If very low to the ground, priority must be to keep the wing over your head, and land as close to winmgs level as possible.

I fail to see how being in a braked configuration will prevent a collapse.

----------------------------------------------
You're not as good as you think you are. Seriously.

[DougH 270]

I thought the half brakes was in response to the collapse, not a preventative measure. You fly in full flight as long as all is well, but if you lose the wing you respond by going to half brakes which is the best setting for the wing to redeploy.

"The restraining order says you're only allowed to touch me in freefall"
=P

[jakee 1,257]

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I thought the half brakes was in response to the collapse, not a preventative measure.

I think that's what Diablopilot said

To what Billvon said, I don't think the problem lies with the new theories on canopy flight, it's with the Chinese whispers way in which they are passed on from person to person to person, where critical information can get left out.

Do you want to have an ideagasm?

[ChrisL 2]

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now that'll make your 'A' hole draw up. Fortunately, it reinflated.

Thoughts?

I would never have imagined that your "A" hole could reinflate

__

My mighty steed

[mnealtx 0]

You're a bad, bad person, Chris...

Mike
I love you, Shannon and Jim.
POPS 9708 , SCR 14706

[DougH 270]

Quote

Quote

I thought the half brakes was in response to the collapse, not a preventative measure.

I think that's what Diablopilot said

I think you're right... . I shouldn't post before my morning cofee!!

"The restraining order says you're only allowed to touch me in freefall"
=P

[AFFI 0]

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I would never have imagined that your "A" hole could reinflate

It can, but you need about 3 feet of hose!

Seriously though, I have seen probably hundreds (it seems) of canopies buck low to the ground an never have I seen one end in catastrophe, they always seem to re-inflate quickly whether or not the jumper goes to partial brakes or lets it fly.

One lesson I learned the hard way that resulted in a sprained ankle, it that when the canopy has a partial collapse low to the ground, don’t look up! Keep your eyes on where you are going - paying attention to the ground may help more than looking up at a problem you can do little about.
Feet and knees together and get ready to knock the earth off it’s axis!
-

Mykel AFF-I10
Skydiving Priorities: 1) Open Canopy. 2) Land Safely. 3) Don’t hurt anyone. 4) Repeat…

[JENNR8R 0]

I'm glad that I could add to your education.

What do you call a beautiful, sunny day that comes after two cloudy, rainy
ones? -- Monday.

[JohnMitchell 14]

Hi Bill,

I was wondering, and would like some input, on flying at almost no brakes, higher airspeed, and if you get hit with a partial collapse, use 1/2 or more brakes to reinflate? I lost 4 of 9 cells at about 90 feet once on a windy day, while in half brakes. Full brakes reinflated the canopy, but not before being "hooked" downwind for landing. It was a pretty serious incident. I was just thinking that more airspeed would give you more energy for reinflation, dunno.

Vskydiver, my wife, lost 3 cells at 300 yesterday, flying in quarter brakes, more brake to reinflate, pucker factor huge. Anyone with technique or tips or research results, I'm all ears.

[BillyVance 34]

It happened to me while on student status. Scared the fuck out of my instructor. I didn't even know it happened, just remember a little jerk, but I was focused on my approach and landing. Just glad it re-inflated quickly...

"Mediocre people don't like high achievers, and high achievers don't like mediocre people." - SIX TIME National Champion coach Nick Saban

[billvon 2,421]

>n flying at almost no brakes, higher airspeed, and if you get hit with
>a partial collapse, use 1/2 or more brakes to reinflate?

Yep. But the "higher airspeed" part of that worries me. If you get it by distorting the airfoil (double fronts) or a radical manuever (single front riser turn) then you are at greater risk of collapse. Such distortions/maneuvers can increase the likelihood of collapse.

The theory that higher airspeeds will let you "blast through" turbulence doesn't work, any more than aircraft can speed up to reduce their exposure to turbulence. Indeed, doing that can cause structural damage to rigid wing aircraft. Also, turbulence is just air with different velocities. The faster you go, the faster the airspeed changes in a given time, and the more turbulence the canopy sees.

On the other side of things, if you're going slower, you are moving the canopy out of its trim position above your head (by using brakes) and putting slack in a few of the D lines. You are, however, in a better position to reinflate your canopy.

Thus I generally tell people that full flight is the best way to fly through turbulence. If the canopy is actually collapsing (i.e. lines are beginning to go slack, the canopy is obviously distorted) then 1/4 to 1/2 brakes will help it reinflate.

[phoenixlpr 0]

Quote

>n flying at almost no brakes, higher airspeed, and if you get hit with
>a partial collapse, use 1/2 or more brakes to reinflate?

Yep. But the "higher airspeed" part of that worries me. If you get it by distorting the airfoil (double fronts) or a radical manuever (single front riser turn) then you are at greater risk of collapse. Such distortions/maneuvers can increase the likelihood of collapse.

I think he refered to flying in full flight - no brakes - no front riser applied. That can be the best way to keep the canopy pressurized. Higher speed - higher pressure in our RAM-air wing.

[ianmdrennan 2]

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I think he refered to flying in full flight - no brakes - no front riser applied. That can be the best way to keep the canopy pressurized.

I agree with that. I wholeheartedly disagree with Bill that flying in 1/4 brakes is better.

Now, should the canopy actually collapse then sure, do whatever you need to with the toggles, but until it does flying at full glide speed is best IMO, and my experience after lengthy discussions with PD test jumpers as well as Scott Miller.

Blues.
Ian

Performance Designs Factory Team

[billvon 2,421]

>I think he refered to flying in full flight - no brakes - no front riser
>applied. That can be the best way to keep the canopy pressurized.

Agreed.

>Higher speed - higher pressure in our RAM-air wing.

Also agreed, but that is a minor aspect of ram-air stability. The pressure in the canopy is enough to keep the canopy spread above us, but compared to the primary stabilizing force in the canopy (the normal force on the lines) it's pretty small. B Germain has demonstrated this with some experiments.

[billvon 2,421]

Something I wrote a while back concerning flight in turbulence:

------------------
Over the years I've seen a lot of skydiving myths start up. Pumping the brakes makes you go farther, putting all the weight in the plane forward helps it climb, wait until the group before you makes a 45 degree angle with the horizon and you'll have good exit separation. Some of these are good myths - the CG-forward doesn't neccessarily make the plane climb faster but can help avoid a too-far-aft CG. Some are neutral, like the pumping the brakes thing. It doesn't do anything, but so what? Some actually hurt the cause of safety - the 45 degree angle thing might cause a group to get out too soon in strong-upper conditions and potentially collide with the previous group, and a jumper might ignore advice to "leave more time" because they trusted in a myth that didn't work.

The same thing seems to be happening with turbulence. I've heard all sorts of explanations about how going fast makes turbulence less dangerous - one person even suggested using front risers to increase speed, allowing a canopy to blast through turbulence unscathed! Another suggested that ram-airs are somehow different now, so what worked 10 years ago doesn't work any more. This is getting well into myth status.

Why do myths start? I think they start because people desire a simple and straightforward plan to deal with problems. In skydiving there are a lot of these - emergency procedures are very simple and straightforward in most cases, and that's a good thing, because the lack of ambiguity saves a lot of lives. If you have a lineover you know exactly what to do. In some cases it's not so clear (PC in tow) but either choice (cutaway first or not) works more often than not, so it's not a big deal.

Other issues are not so clear-cut. Exit separation is complex, for example. It's possible to do the math and know exactly how far you'll be from someone else, but few jumpers do it. Fortunately the simple rule "wait longer if headwinds on jump run are strong" works well. So why do things like the "45 degree" rule seem to propagate? I think it's because it makes a sort of intuitive sense, anyone can do it, and it seems to 'solve' a difficult problem. The problem is that we are land animals, and while our intuitions apply well to things like jumping out of a tree, throwing a rock or chasing a dog, they don't apply well to flying or jumping out of airplanes. We just aren't set up to have good intuitions about aerodynamics or ballistics in moving frames of reference.

So on to turbulence.

First off, what is turbulence? For a detailed explanation I highly recommend Dennis Pagen's book "understanding the sky." It was written for hangglider pilots, and there is no better book I've found for understanding micrometeorology, or the winds and weather of local areas.

In general, turbulence is air moving relative to other air. Many people visualize turbulence as "pockets" of air that are somehow different, but it's all just moving air. If the air moves and changes direction and speed slowly, we call that normal wind. If it changes direction/speed more quickly we call that gusty. If it changes even more quickly than that we call it turbulence. If you fly through those changes and they happen slowly, you feel light turbulence. If you fly through them more quickly, you feel serious turbulence.

The most basic idea behind turbulence is the idea of wind shear. All turbulence is essentially wind shear, although the term is usually used to describe a large change in windspeed/direction over a short distance. A body moving through the air sees the wind of its passage (the relative wind.) If that body moves into an area that has a different wind, it sees that relative wind change. If it is relying on that relative wind to keep itself in the air, as parachutes and airplanes do, then the wing must adjust to the change in relative wind. If the wind change is dramatic the adjustment must also be dramatic. This is how we feel turbulence, through our wing's adjustment to the new relative wind condition. That new condition can be from any direction. It can come from below, from above, from the sides, even from in front or behind, which is seen as a transient increase or decrease in airspeed.

So how do we fly safely through turbulence? Let's start with a hypothetical light airplane. Like most normal category airplanes, this one has a +6.6G -3.3G design limit for its wings; the structure of the wings can take that much load at max gross weight, but beyond that, they may collapse. It can cruise at 160kts. It stalls at 50kts, and it's structural cruise, or turbulence penetration speed, is 100 kts at this weight. The plane weighs 2000 lbs.

Let's say our pilot is cruising along at 160kts. The wing is generating 2000 lbs of lift, as it must to keep the plane in stabilized flight. (Note to purists - yes, I'm neglecting tailplane and fuselage lift.) A wing can generate more lift by going faster or by increasing its angle of attack. Since he's going pretty fast, the wing's angle of attack is pretty low. If he slows down, he has to increase his angle of attack to compensate, so the wing still generates 2000 lbs. If he slows down below about 50kts, the angle of attack the wing needs to fly is so dramatic that the air no longer "sticks" to the wing, and the wing stalls.

But for now he's just cruising along at 160. He starts to feel turbulence. First he flies through an area where the wind suddenly comes from the left at 20 kts. The plane, since it's stable in yaw, 'weathervanes' into the new wind, and the plane continues along happily, but now heading slighlty to the left of where it was a moment ago.

Now he flies through an area where the wind is coming from _behind_ him at 20kts. He perceives this as a drop in airspeed from 160 to 140kts, and the plane starts to descend a bit. He might adjust power or pitch to compensate. He gets back to 160kts.

Now he flies through an area where the wind comes from beneath him at 20kts. He perceives this as a change in the relative wind from dead ahead to a wind that comes from slightly beneath him at 7 degrees. The wing doesn't know this; it just sees a change in angle of attack. 7 degrees is a big AOA change, so the wing starts generating a tremendous amount of lift - say 6000 lbs. The pilot feels 3 G's as the plane starts climbing. He quickly uses the yoke to level off.

At this point he's going to slow down. Why? Two reasons. First, because if he hits a strong enough upward gust, the AOA will change even more, the wing may generate more than 6.6 G's (13200 lbs) of lift, and the wings may fail. Similarly, if he hits a strong enough downward gust, the wing may generate more than 3.3G's of downward lift, and may likewise fail.

Secondly, wind shears are rarely 100% discontinuous. Often, the wind will change over the course of some distance, say 100 yards. If he traverses that 100 yards quickly, it will tend to hit the plane all at once. If he traverses it more slowly, the plane will see the change in relative wind more slowly, thus giving the plane (and the pilot) more time to get the nose down, add power etc.

Anyway, he slows to 100 kts. At this speed, the worst-case gust will make the wing go to 15 degrees AOA and cause a load of 6 G's or so. If it gets stronger, the wing will stall. Stalling isn't the best thing in the world but it's better than having the wings come off.

Now he's coming in to land. He's flying at 70kts. It's still turbulent. A gust from the side will cause the plane to weathervane into the wind, a bad thing when you're landing - so he's quick on the rudders to compensate. A gust from below will cause him to generate more lift and climb - so he's fast with the yoke and throttle to get the nose down to compensate. A 20kt gust from behind causes his airspeed to fall to 50kts. His stall warning horn goes off, which worries him, so he increases his speed to 80kts. That way, if that 20kt gust hits again, he will only drop to 60kts, and he won't stall. Stalling isn't _too_ big a deal at 1000 feet in the pattern (if he recovers quickly) but is a very big deal at 100 feet so he doesn't want to risk it. Note at this point he is no longer worried about his wings collapsing - he's worried about stalling.

That's an airplane. On to parachutes:

A parachute has almost infinite (for our purposes) positive load limits. There's no way you're going to tear the parachute to shreds by starting a hook turn and burying the toggles. They are built to withstand even hard (10G or so) openings, and you still have all that strength available when you're flying it. However, being a flexible wing, it has a zero negative load limit. At the slightest hint of negative lift (i.e. if the angle of attack ever goes negative) the lines will go slack and the parachute will collapse. It has no effective way to prevent this.

A parachute is relatively stable in yaw - it just turns into the relative wind. That's good since you have no rudders to control its yaw. It's very stable in pitch, which for a parachute also means stable in airspeed - if you let go of the toggles (or if airspeed changes through turbulence) it very rapidly returns to its trim airspeed and pitch.

What makes it structurally stable? The primary thing that keeps a parachute stable is the constant tension between the jumper's weight and the lift/drag generated by the canopy. A downward force on the canopy is resisted by the lift in that area of the canopy, an upward force is resisted by the tensile strength of the line (hundreds or thousands of pounds.) Cell pressure is a secondary effect; no canopy will remain stable with a lot of broken lines. Note that there are plenty of parachutes (rounds, the Paradactyl, the PC) that don't have _any_ cell pressure, since they have no cells, and they still inflate and fly. Indeed, even something like an air mattress, something that can be pressurized far more than any canopy, is no match for even a 20kt wind - but a round canopy in the same wind will inflate and remain quite stable. It is tempting to think of a pressurized canopy as a solid wing, resistant to turbulence through its rigidity, but that's just not reality. What keeps it above your head in turbulence is primarily lift, drag and the tension on the lines, and if that tension goes away, it will collapse no matter what the pressure in the canopy.

When we think of canopy instability in turbulence, we're really talking about several different things. One is canopy collapse. This is the worst result, since the wing stops flying, distorts, and must redeploy before it can generate lift again. Another is a canopy stall. In this you lose lift, but the canopy remains above your head and fully deployed, thus reducing recovery times. A third is canopy instability, where the canopy seems to want to dart in every direction. Oddly this is often due to the canopy's _stability_ - the turns and dips you feel is the parachute wanting to face into the wind and resume its previous airspeed and attitude.

So let's consider two people trying to land their canopies at a DZ. One has a large 7-cell, the other has a small 9-cell. The small canopy is twice as fast as the large canopy at trim speed - 30kts vs 15kts. There is an infinite number of types of turbulence we can consider, so let's concentrate on three: a tailwind gust, a side gust, and a downdraft.

If both people are near the ground and get hit by a very sudden 10kt tailwind, the larger canopy will immediately be near stall, with an airspeed of 5kts. The jumper could respond by burying both toggles, which will give him a little bit of flare - but probably not too much. If he's high enough the canopy will recover before impact. If he's really low (10 feet) it will just drop him on his butt. At 30 feet he might be seriously injured. The guy on the faster canopy will be much better off IF he responds well. His canopy will lose some airspeed and drop. If he adds a little less brake than is needed to arrest his descent, the canopy will not dive too hard and will recover. If this happens below 50 feet he'll have to do a braked approach, which he will probably survive uninjured if he's done it before. Since his canopy had more speed to begin with, the gust affects him less.

A side gust is similar, although the larger canopy now has something of an advantage. Both canopies will weathervane into the wind. The larger canopy will turn more degrees but the smaller canopy will react more violently. The jumper has to be _very_ quick to turn the sudden swerve into either a flat turn or a flare turn. The larger canopy will turn more but not dive very much, giving the jumper more time to deal with the problem.

It may be, of course, that the gust is so strong or so sudden that the canopies cannot weathervane quickly enough to keep the relative wind flowing over the tops of their noses, and will instead suffer partial collapses from the unexpected side loads. If that happens near the ground, the jumper going slower will make out better, due to simple physics. He will hit at a slower speed.

The final turbulence example takes some explaining. There's a 30fps downdraft that both canopies fly through near the ground. When downdrafts hit the ground, they don't just disappear - they sort of "splash out" and create winds flowing away from the downdraft. This low level tail/headwind is part of what makes microbursts so dangerous to pilots. Around the shaft of the downdraft is a 25 foot area where the downdraft transitions from zero to 30fps.

The fast canopy hits it and is through the transition area in less than a second. Even in freefall you can't pick up more than 20 feet per second every second, so even if his canopy dives hard, by the time he hits the center of the downdraft the wind is coming from _above_ him by about 5fps. His canopy collapses; there's no way around that. His momentum carries him forward, and he continues to drop. Once he exits the downdraft he has to get his canopy open again and get 10-20 kts of airspeed to let him land safely. Unfortunately, on the far side of the downdraft, he's got that wind 'splash' that he sees as a tailwind. His best chance of survival will be to hold 1/4 to 1/2 brakes - that's the brake position that canopies open best in, which is why brakes are stowed there for opening. If it does open, that's also the best compromise between a stall (full brakes) and a sudden dive for the ground (no brakes.)

The slow canopy hits the same downdraft and takes two seconds to pass through the transition area. In that two seconds you could pick up 40fps if the canopy dove hard. You only need to pick up 30fps to 'match' the speed of the downdraft, so you have a good chance of keeping a canopy above your head. Once in the downdraft you may still have an inflated canopy, but you're still not that happy, because you're descending at 35fps. Once you start leaving the downdraft you are not only descending at 35fps but you now have a tailwind, which could potentially cause a stall. 1/4 to 1/2 brakes will help keep the canopy in the air. You're near stall now but at least you're still flying; with some luck and a PLF you may pull it off.

These are just a few cases. You can make up a lot of them. Generally, if your concern is survival after getting hit by a downdraft, canopy size is your friend. A larger canopy will do a better job of saving you if you have to land without your normal flare, or in an unusual state (stalled.) If your concern is survival after a stall due to a sudden tailwind, then speed is your friend. A smaller canopy will carry more speed to prevent a stall. In the downdraft example, had the smaller canopy made it through the core without collapsing, it would have had more airspeed to work with. A smaller canopy, however, is a lot more dangerous if you stall it at 20 feet. They stall more abruptly, and take much longer to recover, than a larger parachute.

The advice I usually give to people is to let their canopy fly - canopies are generally most stable at full flight, since the loadings on their lines are close to design specs at full flight, and it's that loading that helps keep them stable. The extra speed may help them if they get a tailwind that threatens to stall their canopies. I also tell people to make very smooth and gradual corrections, and don't be afraid to let the wind push you around a bit. Those little twists left and right are not your canopy screwing up, it is your canopy doing its best to stay headed into the wind. As long as you keep yourself on an approximate heading (into the wind for landing, for example) you can deal with a 5 degree turn without too much worry.

If they start feeling really bad turbulence then I usually suggest going to a little (1/4 or so) brakes. This slows down their canopies and thus gives the canopy more time to adjust to the new wind direction. If they have to steer to remain into the wind, having some tension on the brakes also helps the canopy make smooth corrections. Also, if it gets really bad and the canopy is beginning to collapse, 1/4 to 1/2 brakes is the best position to get a rapid reinflation.

And, of course, if they ever feel a sudden drop, IMMEDIATELY go to 1/4 to 1/2 brakes to get reinflation and/or lift. What they feel at that point will tell you a lot. If they feel little to no resistance in their brake lines, their canopy may well not be flying any more. If they feel normal resistance, they may have survived entry into a downdraft - and have a good shot at flying out of it. They can go back to full flight, but be prepared for a hairier than normal landing.

Front risers in _any_ sort of turbulence is a really bad idea. Using front risers distorts the canopy and unloads some lines (C's and some D's.) Since that play of line tension vs lift is what gives you stability in the first place, avoid front and rear riser manuevers in turbulence.

The effect of things like airlocks is minor, but it is there. Samurais and the like are slightly more resistant to turbulence than their equivalent elliptical nine-cells, but pilot skill is much more important - both in avoiding turbulence and handling it once you're in it. Aspect ratio seems to matter, too. 7 cell canopies are slightly more resistant to turbulence than 9 cells of equal loading.

So if anyone's still reading by this point, there are a lot of considerations for flying safely in turbulence. Despite some people's beliefs, ram-airs still fly the same as they did 10 years ago. 1/4 to 1/2 brakes still work under some conditions, and may save your life if you _do_ find yourself with a collapsing canopy above your head. Full flight, or a slight amount of brakes, works in most moderate turbulence. Front riser is almost never a good idea. But the main skills you need to fly in turbulence are just basic canopy flying skills - make small smooth corrections, let the canopy weathervane and bop around to adjust to new winds, and be ready to flare, flat turn, flare turn or PLF if something unexpected happens.

[dorbie 0]

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If a collapse occurs, then a half brake pump, similar to inflating closed end cells is recomended.

Pump?

[phoenixlpr 0]

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Also agreed, but that is a minor aspect of ram-air stability. The pressure in the canopy is enough to keep the canopy spread above us, but compared to the primary stabilizing force in the canopy (the normal force on the lines) it's pretty small. B Germain has demonstrated this with some experiments.

How can you have more than 1G force on lines for longer period of time if you fly strait?

[billvon 2,421]

>How can you have more than 1G force on lines for longer period of time if you fly strait?

?? You generally won't.

[yeyo 1]

warning: the usual "might be strong for some audiences" thing...

Heres a video of a canopy collapsing near the ground at high speeds. From what I found it was at a NY dz in 2001 during a swooping comp. The accident was fatal. Turbulence off the nearby tree line is believed to have caused the disruption to the canopy. Happened too fast to recover. No time to try anything to re-inflate canopy.

edit: remove video, didnt knew

HISPA #93
DS #419.5

[dragon2 0]

That video was already removed from this website once.

ciel bleu,
Saskia