Canopy collapse & airlocks question

[Raistlin 0]

Suppose there is weird turbulence coming at a weird angle, or a dirt devil, or anything else that can cause the canopy to collapse at critically low heights.

Somebody I know experienced this and in order to prevent this from happening again switched to an airlocked canopy.

This really seems something you have little control about and run a high injury risk. Will airlocks really help and keep the canopy inflated where an open-end canopy would collapse? I've heard varying opinions...

[WeakMindedFool 0]

From what I've seen airlocks absolutely stay pressurized longer (ever watch someone on the ground with one trying to deflate it...LOL) I don't know if it helps in significant turbulance though.

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[AndyMan 7]

A rigid wing will be affected by turbulence, too. Airplanes are affected by turbulence.

An wing that encouters a downdraft will... go down. This isn't such a big thing at altitude, but it sure sucks when you're at 10 feet.

Airlocked canopies are said recover faster than a normally aspirated canopy, but all this is meaningless if you've already hit something hard.

Buying an airlocked canopy after a near miss with turblence seems like the wrong answer. The correct answer is to avoid turbulence. It's usually found in predictable locations...

_Am

__

You put the fun in "funnel" - craichead.

[jose 0]

I owned the Lotus 2 135 for around 200 jumps. There are definite advantages to an airlock as compared to a normal ram air canopy without an internal closing cell.

The technology is really simple, if there is a lower air pressure outside of the cell, a flap that is sewn along the sides and bottom of the cell will flap up to the top of the cell, thus closing the cell and "trapping" air within the cell.

This will help in several situations, such as side winds, and turbulence at non-critical altitudes, but it will not help you in situations such as vorticies and dustdevils. The last two still have the ability to twist you up and send you to the ground with a fully inflated canopy, regardless of airlocks.

I have been able to collapse my Lotus with considerable effort, and I do not advocate it to anyone that is not willing to accept the possiblity of a chop. Without taking wraps on my brakes, I wasnt able to collapse it, but it did bow tie alot and it was unmanageable. After taking several wraps, at 10,000' AGL I was able to collapse it. It was different than any other canopy in the way it reinflated due to the fact that I had scrubbed all of my forward speed to get it to collapse, so it seemed to take a bit longer to reinflate (read sphincter factor here).

All in all, I believe in the airlock system. The technology has proven itself to me several times, and perhaps proven itself when I didnt even know it was. The only reason I dont jump one now is because the dont open like a Xfire does. And if it means anything to you, the Lotus flies like a dream with many many many line twists. I am an expert on the Lotus Twist.....its my own manouver that others dont seem to want to try.....

The second pic is from when my brother dropped down on the end of my canopy. See how its still fully inflated? All that happened is I made a very fast diving turn to the right and it was normal again. I can honestly say that if I was under my Xfire and that happened, that side would have collapsed and probably spun me up.

[Amazon 7]

I have about 100 jumps on a Lotus...( Think airlocked Sabre2) and about 100 jumps on a Samurai.

Both of them are very stable canopies in turbulence. On other canopies I have jumped in similar conditions.. ( thermals and small dust devils.. I would get end cell closures on the Triathalon.. and on the 9 Cell ZP Conquest. I have seen similar flexing and "breathing" on other canopies as well in the same conditions. When I go thru that with the airlocked canopy I can feel it bouncing but the airfoil remains rigid. I love jumping the airlocks.. and when I do jump my Triathalon on occassion.. it feels MUSHY in the air.

The only drawback I have seen is when you jump in 20 to 25MPH winds.. and getting the canopy collapsed is a bit of a bitch.. best bet is to dive in into the ground after you land... spin around and get the bridle under your foot. Once you do that the wind does the work of collapsing the canopy for you since you have it by the top center of the canopy.

I LOVE MY AIRLOCKED SAMURAI.

[billvon 2,434]

In my experience, an airlocked canopy is a bit more stable than a non-airlocked canopy. It's not a big difference, but it's noticeable. A lot of people believe in the "air mattress" effect, which I don't believe in. Brian Germain once did an experiement where he removed the center airlocks from a canopy and noticed very little change in the stability of it - if the internal pressure were such a big deal, that would have radically changed the stability of the canopy.

To a large degree I believe that the stability of an airlocked canopy comes from the 'cross bracing' of the nose caused by the airlocks themselves. This makes a canopy a little more resistant to side loads and sudden changes in airspeed. Nothing helps when the canopy gets toploaded by turbulence, but airlocks might give you a little edge in moderate turbulence.

[AggieDave 6]

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It's usually found in predictable locations...

Also wanted to add to this.

Even in a location that predictably calm, in high wind days objects that aren't very high can leave turbulance a LONG ways downwind.

If jumpers were smart, a quick rule of thumb is if the experienced locals that aren't getting paid to go skydive aren't skydiving, it might just be for a reason.

--"When I die, may I be surrounded by scattered chrome and burning gasoline."

[gerrcoin 0]

I think that I understand the benifits of air locked canopies, but are you aware of any possible negitive aspects.

Also is it possible to get air locking without cross-bracing. I imagined the system as a series of one-way valve type flaps on the adjoining cell walls, arranged such that positive flow is possible from the centre cell outwards.

[jerry81 10]

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Also is it possible to get air locking without cross-bracing. I imagined the system as a series of one-way valve type flaps on the adjoining cell walls, arranged such that positive flow is possible from the centre cell outwards.

Are you talking about valves on crossports? I don't know what benefits that would have and it would definitely be quite different than the airlocking system on BigAir canopies and the Vengeance- which is a series of flaps over the nose inlets. Also, the 'crossbracing' Bill is talking about is just the way these flaps are attached to the ribs in the nose, not what you'd find on high (or is it ultra?) performance canopies. It's only the leading edge of the canopy that is reinforced by the flaps, not the whole wing.

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[BETO74 0]

In my limited experience with airlocks, I think they are more responsive and in consequence more agressive, don't know about how the canopy on low wind loadings, I'll say long recovery arc but I only try my long lost Jedei for that matter, A defined down is after you cut away ( please dont' say you never will) they remain open and fliying and that's how my story ends with airlocked canopies and my first cut away. I won't recommend airlocks without experience but hey that's just me.

http://web.mac.com/ac057a/iWeb/AC057A/H0M3.html

[PhreeZone 15]

Airlocks are on canopies other then then the Jedei. The Lotus is extremely similar to a Sabre2 with Airlocks.

Airlocked canopies flying off into the sunset fullying inflated huh? I've seen an airlocked canopy just fall in a big wad an another that floated a tad longer but nothing too different then a normal cutaway.

Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

[Amazon 7]

My Samurai stayed somewhat inflated and floated a bit farther.. but I think since it was a hot muggy summer day... I think she wanted to make it to the river for a swim.
Damned if she didnt get there too and had to be pulled out of the water by a guy in a boat. No harm No foul though She still flies as gooed as ever.

[billvon 2,434]

>I think they are more responsive and in consequence more agressive . . .

I think the canopy design has far more to do with "aggression" than the airlocks. A Lotus 150 is less aggressive than a Crossfire 2 149.

>they remain open and fliying . . .

Dunno about this. I've seen non-airlocked canopies go "sailing away" with one side inflated and flying, and I've seen an airlocked canopy look like any other pile-o-rags after a cutaway from a low speed mal. I think it has far more to do with the condition of the canopy when you cut it away than any airlock issues.

[BETO74 0]

I saw my Jedei fly away after cut away, lost the canopy, the funny part is a friend told me this before jumping " What sucks about airlocks is they keep fliying after cutting away" my answer to that was " I'm never gonna cut away no worries" that jump had to cut away, that's beside the point.

I was talking to Chris from Precision canopies he told me the same thing they had to chase the xaos everytime they test the canopy when they cut it for testing proposes, I know the xaos is not presisly airlock more crossbraced but keeps a decent amount of air preassure inside the canopy.

Once again just my experience with airlocks.

http://web.mac.com/ac057a/iWeb/AC057A/H0M3.html

[riggerrob 558]

To a large degree I believe that the stability of an airlocked canopy comes from the 'cross bracing' of the nose caused by the airlocks themselves. This makes a canopy a little more resistant to side loads and sudden changes in airspeed. Nothing helps when the canopy gets toploaded by turbulence, but airlocks might give you a little edge in moderate turbulence.

[FrogNog 1]

I thought the benefit of airlocks in turbulence was not that they made the canopy better in the turbulence - as someone aptly pointed out, topload any canopy and it crumples instantly when there's no tension on the lines - but after the turbulence. That is, an airlocked canopy is supposed to start flying again faster than anything else because it has very little reinflating to do before it becomes a wing again. (It just has to feel tension on the lines again and dive for airspeed.)

Now, at "critically low heights," the ground is the limiting factor. In the dust devil video I'm thinking of, airlocks probably wouldn't make a diff. But turbulence up higher, which may be to blame for a few incidents we've read about, might have been more recoverable before the ground came up with airlocks.

That said, I don't jump airlocks because I have not yet run across an airlocked canopy that worked for me.

-=-=-=-=-
Pull.

[Praetorian 1]

I agree, at low enough level nothing is gonna save you, but up higher My Lotus deals better with turbulent air then open cell mains. I feel the jirking around a bit more but the wing holds its shape better. imagine one side of your main collapsing 500-150ft agl, now recover from that... with an air locked main it won't (or at lease is far less likely to) happen. and FrogNog your profile says you fly a sabre2 .. try a lotus (now in the MAX linset variant) I think you'll like it, a little less tapered then the Sabre2 but I think overall it flies better

Good Judgment comes from experience...a lot of experience comes from bad
judgment.

[Raistlin 0]

Thanks everyone for the traditionally great answers!

[jump23 0]

I have jumped a Jedei since 1997 and it is the best canopy I have ever had. When it used to get windy turbulant days I would quit jumping. Now I keep on, I watch other friends under different canopies bounce around but I do not and the next canopy I buy will also have airlocks I would never buy a canopy without.

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[ianmdrennan 2]

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When it used to get windy turbulant days I would quit jumping.

Smart man.

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Now I keep on,

That's an awful lot of faith to place in airlocks.

If the conditions are such that you feel you "need" airlocks then maybe jumping isn't the best thing to be doing just then.

Blues,
Ian

Performance Designs Factory Team

[kaerock 1]

Agreed,
My decision to purchase the Samurai wasn't based upon the fact that it had airlocks...I just see them as a bonus, the canopy's flight characteristics are what attracted me to it. There may have been few situations where having an airlocked canopy made a difference, where I thought "airlocks probably helped" rather than thinking, "airlocks will save me" . Airlocks move the odds slightly in your favor, they aren't a force-field.

-R


reply]

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When it used to get windy turbulant days I would quit jumping.

Smart man.

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Now I keep on,

That's an awful lot of faith to place in airlocks.

If the conditions are such that you feel you "need" airlocks then maybe jumping isn't the best thing to be doing just then.

Blues,
Ian

[JumpRu 14]

>around but I do not and the next canopy I buy will >also have airlocks I would never buy a canopy >without.

same here, I will buy my next canopy with airlocks, they helps. I have several landings on video (in a terbulent day) and my sam is solid like a rock :)

[gerrcoin 0]

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Are you talking about valves on crossports?

Er, yes, it appears that I was. So my understanding from this thread is that air-locking is a system of valves in the nose of each cell, designed to keep the cells pressurised in turbulent air. Is that accurate?

[Praetorian 1]

yep, you got it now (check out Bigairsportz.com) or the description of the PD vengence

Good Judgment comes from experience...a lot of experience comes from bad
judgment.

[alan 1]

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The only drawback I have seen is when you jump in 20 to 25MPH winds.. and getting the canopy collapsed is a bit of a bitch.. best bet is to dive in into the ground after you land... spin around and get the bridle under your foot. Once you do that the wind does the work of collapsing the canopy for you since you have it by the top center of the canopy.

I guess by now I've got nearly 1000 jumps on my Jedei, not sure cuz I quit counting a couple years ago. I mostly use it on demos now or on back to back jumps. At any rate, I ve found that nosing the canopy into the ground adds to the effect of the airlocks with the ground closing off the nose too. What has worked best for me is to pivot around after landing and at the same time, pull in both rear risers. This puts the canopy on the ground with the tail into the wind, the top to the ground, with the nose pointed downwind. In this attitude, the wind acts like your hand on a tube of tooth paste and helps "squeeze" the air out past the airlocks. The key is to not have too much pressure on the canopy because that is what causes the flap on the airlock to seal against the top skin. Work your way up to the canopy, coiling the lines as you go, and pick it up by the tail, giving it a few gentle shakes as you pick it up. This allows you to gently shake the remaining air out as you pick it up. As you said, standing on the bridle during all of this helps keep things under control as well. One other thing I've found over the years is that in 20 to 25 mph winds, the best way to control the canopy on the ground is to leave it on the ground. I have much more fun drinking beer in 25 mph winds than I do jumping. Prolly safer too.

alan