Forums: Skydiving Disciplines: Swooping and Canopy Control:
Round and round we go

 

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runningman  (A 61275)

Nov 18, 2011, 8:13 PM
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Round and round we go Can't Post

I was hoping someone could shed some light in this subject for me.

I saw in another thread the mention of canopies that can cause GLOC, so I searched a bit but it seems like no one really had a definite answer. What I am curious about is the nature of the G-force that is experienced by a jumper under a rapidly spinning canopy. I have read that the small, highly-loaded ellipticals can spin up at a fantastic rate, and was wondering if anyone actually knew the maximum number of Gs that one could experience under such a violent malfunction? Some of the people in the threads mentioned numbers around 4-5 Gs, but these were really just guesses. I was looking to see if anyone had actually measured the true force. I understand that individual canopies have their idiosyncrasies, but I am interested to know if there is an average or any type of concrete correlation between canopy size/wing loading and the amount of Gs that one could possibly experience.

The second aspect of my question concerns the physical experience of G-force when hanging from a harness. For anyone who has experienced such a malfunction, are the G-forces rapid in their onset or are they more gradual, topping out at a sustained value? Did you experience tunnel vision or the "curtain effect?" Being such a new jumper, I have absolutely no experience jumping even moderately-sized canopies; from the few videos I have seen, however, it seems as though there may be a split second before the canopy develops into a fully established spin.

I'm sure I left out some other questions I have but I'm just intrigued to gain some insight from people who have actually been in such situations.


Calvin19  (D 29712)

Nov 18, 2011, 8:42 PM
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Re: [runningman] Round and round we go [In reply to] Can't Post

Depends largely in the person. G loc is just the point of loss of consciousness. It could be instant or take minutes to happen.

A person can GLOC on a navigator 290 if it is spinning for long enough.

In a hanging harness, I would assume the maximum even a very healthy and fit expert pilot could take is not more than about four or five Gs for a long period of time. (in a hanging harness). In a reclined and ideal position, WITH a G suit even the best pilots in the world cannot take ~9gs for more than a couple seconds.

I know I black out at about five Gs in about two seconds in the airplane I owned a few years ago, and that was in a seated position and prepared for it.

I have had only a few spinning malfunctions, on a stiletto 120 I had bad line twists and a bad spin. I cut away. I have had a few twister openings on JVXs, but nothing I could not get out of.

I have also done a lot of high-g controlled spinning maneuvers. Keeping your head in the game is the biggest part of it.
Of course, on lighter loaded parachute openings, "GLOC" is pretty much never an issue and should not be a worry.


(This post was edited by Calvin19 on Nov 18, 2011, 8:57 PM)


runningman  (A 61275)

Nov 18, 2011, 9:59 PM
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Re: [Calvin19] Round and round we go [In reply to] Can't Post

I was thinking it would be something along those lines. I guess I was wondering why there's such a discrepancy between hanging and sitting. I would venture to say that since gravity is already pulling your blood towards your feet, any additional force would simply amplify the force.

It's interesting you mentioned aircraft because I spent some time in a centrifuge (some camp when I was younger). We got up to 5 Gs and, while I wouldn't say I was terribly comfortable, I was still aware and could lift my hands if I really put in some effort. That's also why I mentioned rapid onset as opposed to gradual. I know that rapid G-loading when not adequately braced (and even when prepared) can render even the most skilled pilots unconscious within seconds whereas gradual Gs tend to be comparatively more tolerable.

Hopefully I get some more responses because this is a pretty interesting topic. Thanks for the replySmile


dqpacker  (D 32043)

Nov 19, 2011, 5:11 AM
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Re: [runningman] Round and round we go [In reply to] Can't Post

search for the Chris Martin incident.


davelepka  (D 21448)

Nov 19, 2011, 5:39 AM
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Re: [runningman] Round and round we go [In reply to] Can't Post

 
Any malfucntion that's going to cause a spin is going to come out of the bag that way. It's not going to 'develop', it's just going to start spinning, and canopies (any of them) tend to reach their maximum turn rate fairly quickly. Even if a spin doesn't start until you release the brakes, it's still going to get up to speed fairly quickly.

As for the differences between sitting and hanging in a harness, there are some obvious physical differences, but the jumper plays a big role in it. If you're not trained to avoid GLOC, you're much more susceptible to it. Another poster mentioned a personal limit of 5 Gs when he was flying, which sounds about right for a civilian pilot without a G-suit. To contrast that, I started to grey-out (the first stages of GLOC) in an Otter once when I was riding in the right seat. The pilot dove the plane after the last tandem out, and then startes a spiral dive around the tandem for a couple thousand feet. The turn was tight, but I was also leaning forward to look out of the windshield and this was for 10 to 15 seconds, and with no efforts not to GLOC, the blood started drainiing from my brain. All I had to do was sit up straight and tense the muscles in my legs/abdomen, and I returned to normal vision, but becuase I wasn't ready for it, an Otter almost put me out.

Add in other physiological factors in jumping, like fatigue from just performing a freefall, stress of being in a malfunction, dehydration, the pysical oncdition of the jumper, etc, and you can see how the threshold for GLOC can vary greatly.

The post you were reading was full of inaccuracies. That guy was just being a 'grumpy old man' and use broad sweeping strokes to paint certain canopies as being dangerous. Even bigger, student type canopies, under the right conditions, can put you out. If you have a spinning malfunction that you don't react to, the prolonged spin can induce GLOC. A bigger canopy will have a slower descent rate than a smaller one, but the G force of the spin might be similar, just for a longer time period.

There are very few canopies out there that can GLOC you so fast that you cannot cutaway. Chris Martin had this happen to him, but he was jumping an experimental 21 sq ft canopy (which he planned to cutaway before landing, and land a conventionaly sized canopy). Almost nobody jumps canopies under 50 sq ft, and the small number of jumpers who jump canopies under 80 sq ft are almost all young, in good physical shape, and aware of what they are doing. If you know your canopy will spin like a banshee if it mals, you're A) ready for that type of force, and B) aware that you need to cutaway in short order (also becauce you're probably losing altitude at a high rate).


runningman  (A 61275)

Nov 19, 2011, 8:07 AM
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Re: [davelepka] Round and round we go [In reply to] Can't Post

Hmm..that's quite interesting. I wonder if the guys flying sub-100 sq. ft. canopies have trained the HIC maneuver with any regularity.

Oh, and I read the Chris Martin incident.Unsure Very crazy.


Calvin19  (D 29712)

Nov 19, 2011, 9:06 AM
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Re: [davelepka] Round and round we go [In reply to] Can't Post

In reply to:
the small number of jumpers who jump canopies under 80 sq ft are almost all young, in good physical shape, and aware of what they are doing. If you know your canopy will spin like a banshee if it mals, you're A) ready for that type of force, and B) aware that you need to cutaway in short order (also becauce you're probably losing altitude at a high rate).

Word.


Martini  (D 23756)

Nov 19, 2011, 8:32 PM
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Re: [davelepka] Round and round we go [In reply to] Can't Post

Quote:

Any malfucntion that's going to cause a spin is going to come out of the bag that way. It's not going to 'develop', it's just going to start spinning, and canopies (any of them) tend to reach their maximum turn rate fairly quickly.

'Taint necessarily so. For example slider comes down hard and knocks a toggle off a small xbrace.


davelepka  (D 21448)

Nov 19, 2011, 8:37 PM
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Re: [Martini] Round and round we go [In reply to] Can't Post

Quote:
Any malfucntion that's going to cause a spin is going to come out of the bag that way

Let me clarify. When I said 'come out of the bag that way', I didn't literally mean it was going to come out of the deployment bag in that condition. I meant that the malfunction would present itself and almost immediately go to 'full tilt', as opposed to starting out as an 'easy going' mal, and develop into a high-g mal.

In this case, using the term 'out of the bag' might have been a poor choice.


flipper  (D 11524)

Nov 23, 2011, 7:40 AM
Post #10 of 38 (2771 views)
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Re: [runningman] Round and round we go [In reply to] Can't Post

In reply to:
Hmm..that's quite interesting. I wonder if the guys flying sub-100 sq. ft. canopies have trained the HIC maneuver with any regularity.

Oh, and I read the Chris Martin incident.Unsure Very crazy.

Sorry not sure what the HIC manouver is but with all due respect it sounds like fucking about at a time when fucking about is not what you should be doing ....The only thing to do with a spinning sub 100 sqft canopy is cutaway and deploy the reserve ... been there and done it ... there is no time


pchapman  (D 1014)

Nov 23, 2011, 11:00 AM
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Re: [runningman] Round and round we go [In reply to] Can't Post

I think a bunch of related issues may take place at times. I don't have specific evidence of any of these, but they seem plausible as factors.

There could be actual GLOC. Someone could also just be groggy from the G's and not thinking clearly. Just being spun and thrown around rapidly is going to inhibit clear thinking. (Sometimes it is more the unexpected spinning rather than many G's. Even just a popped toggle on a slightly smaller sized canopy can be quite disorientating mentally, as the canopy starts to spiral harder and faster. Jumpers cut away - better than nothing - without reaching up and fixing the problem.)

Spinning may also disturb the vestibular system and eye movement, causing problems in getting stable after a cutaway. Older less fit jumpers may be more susceptible to problems. We've seen a few accidents where an old but experienced jumper gets spun and cuts away too low, where they can't pin the accident on something specific like a heart attack.

It wouldn't be bad for jumpers on high performance canopies to understand the basics of an anti-G straining maneuver, but just in general tensing up during a spinning mal is going to help keep blood pressure up. I could see that if some just 'go with it', lowered blood pressure could make it harder to mentally focus on what needs to be done. We have the examples of students who spiral into the ground, limp under a Manta with a popped toggle. It could be a vicious circle, for if they relax mentally at some point they may relax physically, which in turn makes it harder to get the mental focus back under G's.

I also wonder if the physiological factors of suspension trauma are at work, inhibiting blood return from the legs to the torso, making G tolerance in a harness lower than when seated in a chair.

I don't want to overplay these factors. Jumpers, whether experienced or not, can get flung around in a mal and still perform necessary emergency procedures.

As for the original question, while exact G load numbers would be interesting, we don't generally have any recorded.


runningman  (A 61275)

Nov 23, 2011, 11:57 AM
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Re: [flipper] Round and round we go [In reply to] Can't Post

Oh, I don't doubt that at all. And the HIC maneuver is an anti-G straining maneuver that pilots you to counteract the force of G on the body. Basically, you tense up your legs, butt, and torso while building up air pressure in your chest (taking a deep breath). It is named "HIC" because of the sound it makes when you forcibly hold the air in your chest and strain against the extra gravitational force. There are a lot of youtube videos that show pilots in centrifuges utilizing the move.


runningman  (A 61275)

Nov 23, 2011, 12:02 PM
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Re: [pchapman] Round and round we go [In reply to] Can't Post

THAT was what I was looking for. I just figured if you knowingly jump an aggressive, potentially "spinny" canopy you should at least be familiar with anti-G straining if everything goes Tango Uniform.

And the suspension trauma, I'll have to look into that. I still don't quite understand the whole mechanics behind why I hanging harness would make that much of a difference in G-force distribution (besides the fact that you're body position is different).


davelepka  (D 21448)

Nov 23, 2011, 8:54 PM
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Re: [runningman] Round and round we go [In reply to] Can't Post

Quote:
I wonder if the guys flying sub-100 sq. ft. canopies have trained the HIC maneuver with any regularity.

I would guess no. I would actually guess nobody has ever done that for the purposes of canopy flight. There might a jumper or two (probably more) who are either involved in aircraft aerobatics and military avaiation, so they might have experience/training with that, but not for skydiving purposes.

In order to build and sustain those types of Gs, a canopy pilot would need to turn so fast for so long that they would become dizzy, lose a ton of altitude, and possibly spin themselves into line twists, and I don't see anyone doing that intentionally.

A malfunction that would spin you fast enough to require the HIC manuver would need to be cutaway before it would become a factor. Again, and spin of that speed would eat altitude, so a mal like that needs to go so you can open a reserve before impact. Also, very high G loads like that have been known to cause hard pulls due to problems with the 3-ring or cutaway cable, so you want to pull the handle before the Gs have enough time to screw up your gear.

Another factor to this is that the HIC manuver is generally done by the pilot, the same pilot who is aware of the Gs before they begin to build. A pilot can begin the HIC manuver an instant before hauling back on the stick, putting them 'ahead' of the Gs. I think non-pilots in those types of planes have a much harder time as they don't know the G load is coming until after it begins.

Canopy pilots would have to begin the HIC manuver before each deployment in order to be ready in case there is a high-G malfunction. The problem with that is that it will probably cause more malfunctions than it will help because you're better off being relaxed when you deploy a canopy, as opposed to all tensed up with your legs.


SRI85  (D License)

Nov 23, 2011, 9:03 PM
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Re: [davelepka] Round and round we go [In reply to] Can't Post

what kind of problems with the 3 ring are you talking about? like the 3 ring getting deformed with that much force?

And what about the cable?


davelepka  (D 21448)

Nov 23, 2011, 9:12 PM
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Re: [SRI85] Round and round we go [In reply to] Can't Post

 
There have been reports of hard cutaways in high-G spins, with a root cause never being determined.

There have also been hard pulls/no pull on the cutaway due to the yellow cable getting folded in half and getting sucked through the grommet. If it just begins to get sucked through, and kinks the cable, it's a hard pull. If the cable is folded in half and gets pulled completely through the grommet, it's a no pull on the cutaway.

Another high-G related cutaway problem that has been reported was jumpers having dificulty physically lifting their arms to their handles to grab them. Not gear related, but related to high-G spins, and a good reason to cutaway sooner than later.


Calvin19  (D 29712)

Nov 23, 2011, 9:35 PM
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Re: [davelepka] Round and round we go [In reply to] Can't Post

In reply to:
Quote:
I wonder if the guys flying sub-100 sq. ft. canopies have trained the HIC maneuver with any regularity.

I would guess no. I would actually guess nobody has ever done that for the purposes of canopy flight. There might a jumper or two (probably more) who are either involved in aircraft aerobatics and military avaiation, so they might have experience/training with that, but not for skydiving purposes.

In order to build and sustain those types of Gs, a canopy pilot would need to turn so fast for so long that they would become dizzy, lose a ton of altitude, and possibly spin themselves into line twists, and I don't see anyone doing that intentionally.

A malfunction that would spin you fast enough to require the HIC manuver would need to be cutaway before it would become a factor. Again, and spin of that speed would eat altitude, so a mal like that needs to go so you can open a reserve before impact. Also, very high G loads like that have been known to cause hard pulls due to problems with the 3-ring or cutaway cable, so you want to pull the handle before the Gs have enough time to screw up your gear.

Another factor to this is that the HIC manuver is generally done by the pilot, the same pilot who is aware of the Gs before they begin to build. A pilot can begin the HIC manuver an instant before hauling back on the stick, putting them 'ahead' of the Gs. I think non-pilots in those types of planes have a much harder time as they don't know the G load is coming until after it begins.

Canopy pilots would have to begin the HIC manuver before each deployment in order to be ready in case there is a high-G malfunction. The problem with that is that it will probably cause more malfunctions than it will help because you're better off being relaxed when you deploy a canopy, as opposed to all tensed up with your legs.
I agree with all that. Good post. I never was a fan of high Gs flying airplanes. Four is about as high as I want to go. My Citabria red lined at +5/-2 and anywhere near that she burned so much energy it's not worth the stress. I was always more a map of the earth guy than an acro guy anyway. Tongue

And you are talking about the grunt? I have never heard of the HIC maneuver.

I have done that on every canopy I have ever owned, paragliders and parachutes. I do it all the time on the JVX I fly now. The only times I jump that thing is high pulls. We do tandem spirals topskin-topskin for 8000' at a time. burning 6000'/min. It feels like 10gs, but it's probably only about 2.5gs.


A few canopies I have spiraled and spun to the point of accelerated stall. (high speed/accelerated spin).

It does not transfer well to malfunctions, but I have found that it helps a lot to pull up your legs and "sit" in a parachute harness. This tenses your legs, (part of the grunt) and do everything you can to maintain the CORRECT weight shift input. A spinning canopy will try to give you the OPPOSITE weight shift than you want to stop the spin. The reason it would not transfer to mals skydiving is usually the lines are so spun up you cannot control the weight shift input, and usually I assume it would happen so fast that you cannot get the correct move in before it sets in. but as soon as you can, fight it. The best way to do that is force the risers by pushing the opposite riser up and forcing the leg strap and lift web down on the correct side.


(This post was edited by Calvin19 on Nov 23, 2011, 9:36 PM)


Premier LouDiamond  (D 25931)
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Nov 24, 2011, 9:11 AM
Post #18 of 38 (2630 views)
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Re: Round and round we go [In reply to] Can't Post

For those of you who are interested in it, I have talked about grunt breathing in a few different posts over the years. A description of it can be found here.

Having seen first hand the severity and speed of this type of malfunction, I can tell you that I am not sure one would even have time to begin grunt breathing for it to be effective. IMO, the most critical moments that one needs to decide/be ready to cutaway or not, is from the moment of deployment/direct bag to line stretch/inflation of the canopy. Granted that is a very small window of time to decide and execute cutaway procedures but it is quite possibly the only time you may have where you can still physically move/control your extremities with enough dexterity to pull your handles. The longer the canopy is allowed to spin and I am not talking about 15-30 seconds but more like 4-5 seconds, the greater the G forces will be and the harder it will be for you to stay conscious and to be able to get to the handles. This is of course assuming that everything has gone to hell from the moment the canopy has come out of the D bag(as in the case of Chris's incident) and not after one is under a good or a moderately spinning canopy that is building speed.


superstu  (D License)

Nov 24, 2011, 9:48 AM
Post #19 of 38 (2623 views)
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Re: [LouDiamond] Round and round we go [In reply to] Can't Post

I've attached a picture of what happened to me on a violent hop and pop on my Comp Velo 71 loaded at 3.0 last year. Still don't know what the malfunction was that caused the spinner but the docs said I was doing close to 5 G's for a short time. I broke blood vessels in my face, eyes, nose, and mouth. By the time I chopped. probably less than 10 seconds after deployment, I was almost blacked out and I lost my vision till 1500' under the reserve. I was conscious the whole time but it was extremely hard to get to my handles and am lucky I got rid of it so quickly. Lesson I learned from that one is that it pays to practice your emergency procedures and when you're dealing the ultra small shit, there is no forgiveness so get rid of it.

Pic was taken 20 minutes after the incident and my home dz Mile-Hi Skydiving in CO.
Attachments: IMG_0764 - Copy.JPG (211 KB)


Premier ianmdrennan  (D 25821)
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Nov 24, 2011, 9:56 AM
Post #20 of 38 (2619 views)
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Re: [superstu] Round and round we go [In reply to] Can't Post

You look better than usual in that pic......

Smile

Jokes aside, that mal still freaks me out. Glad you're ok.

I was hoping you'd chime in on this thread with some first hand experience.

Ian


davelepka  (D 21448)

Nov 24, 2011, 11:03 AM
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Re: [davelepka] Round and round we go [In reply to] Can't Post

 
Does anyone remember a video posted here awhile back, it was an outside video of an AFF I having a spinning mal on a Velocity after an AFF jump? For some reason I think it was a Russian guy? The canopy spun up instantly and at an amazing rate?

I looked around Youtube and did a search on this site, but came up empty. I really only spent about 2 min total looking for it, but if anyone knows what I'm talking about and where it is, post up a link.


Mr.B  (B License)

Nov 24, 2011, 12:52 PM
Post #22 of 38 (2577 views)
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Re: [davelepka] Round and round we go [In reply to] Can't Post

In reply to:
Does anyone remember a video posted here awhile back, it was an outside video of an AFF I having a spinning mal on a Velocity after an AFF jump? For some reason I think it was a Russian guy? The canopy spun up instantly and at an amazing rate?

I looked around Youtube and did a search on this site, but came up empty. I really only spent about 2 min total looking for it, but if anyone knows what I'm talking about and where it is, post up a link.

This one :
http://underdeconstruction.net/stuff/cutaway.wmv
?

cheers,
Bart Wink


davelepka  (D 21448)

Nov 24, 2011, 12:54 PM
Post #23 of 38 (2575 views)
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Re: [Mr.B] Round and round we go [In reply to] Can't Post

 
That's the one.


Calvin19  (D 29712)

Nov 24, 2011, 2:33 PM
Post #24 of 38 (2556 views)
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Re: [davelepka] Round and round we go [In reply to] Can't Post

That canopy was heli-ing, not "spinning" in the sense we are discussing here. still not good.

-HUGE- difference.


AggieDave  (D License)

Nov 24, 2011, 2:49 PM
Post #25 of 38 (2551 views)
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Re: [superstu] Round and round we go [In reply to] Can't Post

With as high as we load our canopies, I maintain a one rotation rule. If I can't arrest the spin in a spinning linetwists malfunction within a revolution, it gets chopped.

The canopy can go zero to holy-shit in a split second. At least the canopy will start telling you that it is going to do that before it happens. Sometimes you can feel the bag come off your back wrong.


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