Stalling yourself into a self-gift-wrap?

[morten 0]

Is this possible?
During our 3-day Skyvan event that rained away two debaters entered a stalemate, possibly caused by too little airtime combined with too much beertime.

A: If you stall your chute there is a possibility that it will dive under you and you may fall into it and gift-wrap yourself.
B: A stalled parachute will be streaming after the much heavier jumper, with no chance of overtaking him on the way down.

A and B are both used to win arguments such as this, but obviously they can't both be right

The next question is: Can and will a stalled chute descend faster than a spiralling one, and if so, will (or rather can) it continue do so for an extended period of time?

I'm well aware that stalling the chute may lead to a malfunction, but my questions are about possibility, not about advisability

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[billvon 2,384]

If you can stall your parachute while you are above it, there's a chance of this happening. Since that's somewhat difficult, it hasn't happened very often (ever, actually.)

[morten 0]

I've only ever heard of self-gift-wrap as an unintended outcome of a barrelroll with too low speed.
That sounds like the scenario you describe - any oppinion on the second question?

[justinhawxhurst 0]

Here is a link to a video from another thread. it is of full stalls. I think it would be hard to get stuck in a canopy that is doing this.

Just click on the picture for the video:

http://pulsevisuals.com/video/details/stallram-air.html

[lilchief 0]

If somehow the nose is not catching any air it could happen. But when you stall out a canopy you pull it back, letting the cell-openings to catch air vertically , like during the opening, instead of an angle during flight. When it starts to rock to the sides you might get collapsed cells (i had the center cell collapse on me on a sabre2 190 after a stall). but there the crossports helps inflate the canopy through the other cells.

With my limited exp I think it would be almost impossible on modern canopies.

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

[billvon 2,384]

>With my limited exp I think it would be almost impossible on modern canopies.

Well, it's definitely possible. Pull the brake lines down until the tail is in your hands and it absolutely will stall. Your speed downwards will be determined by how far you've pulled it down and how long you ride it. If you completely collapse it, I'd guess your speed would be upwards of 60mph. Only thing slowing you down would be the streamer effect.

[quade 3]

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With my limited exp I think it would be almost impossible on modern canopies.

Then you should probably learn more about stalls in general.

http://www.dropzone.com/cgi-bin/safety/detail_page.cgi?ID=20

quade -
The World's Most Boring Skydiver

[pchapman 261]

The stalled chute is not the problem. It won't overtake the jumper so to speak.

The issue is coming out of a stall, where a sudden reinflation with zero brakes applied can cause it to shoot forward to the horizon and result in slack lines. This is more of a problem if the canopy was either well stalled for a long time (completely collapsed and vertical speed has picked up a lot) or the canopy had just swung far back as the jumper has entered a stall in a very dynamic manner. Proper stall recovery technique is advised.

I can't recall whether anyone has managed to gift wrap themselves with a skydiving canopy, although dropping into slack lines could easily cause problems. Who knows, you might be able to do it if you tried.

More likely with a high performance parachute would be to get an opening that isn't on heading, which when combined with lack of line tension, would result in a spinning diving line twist situation requiring a cutaway. (With much lower drag, long lined paragliders, grift wrapping has happened.)

[dragon2 0]

I did a dragplane when I passed my B lic doing CRW. I'm still not sure if you can fall into your lines if the person holding you drops you before HE's been dropped maybe they were just making me nervous telling me that, maybe... not....

ciel bleu,
Saskia

[lilchief 0]

Yes that is indeed true, but I assumed that Morten here ment under normal circumstances. If you did what you explained, you're asking for trouble. But under normal fight and circumstances(the toggle input is limited to the armlength+1turn around the hand of the jumper) as most skydivers fly their canopies, I find it hard to believe that it's possible to stall modern canopies to become streamers.

quade: Based on the article(which say the same as Brian Germain's "Parachute and it's Pilot") you would say that what morten describes is possible if you stall out your canopy in a toggleturn? wouldn't the g forces keep the line tension through out the turn? I could see a high speed stall on a wing if it has a bank angle for en axtensive period of time(speed and bank angle will determine when the stall occurs), but that is in my mind only feasible with an aircraft, not with a parachute. I've tried it a couple of times, and only got a carve turn out o it.

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

[dragon2 0]

Some questions for you... Why only on modern canopies? What is different? What is a modern canopy anyway? Why do you assume the steering line lengths of various canopies are comparable?

I cannot stall my canopies using toggles without wrapping quite a few times, because all my canopies have their steering lines lengthened so I can pull both frontrisers without deflecting the tail. Is a sabre1 modern or not? When I first got it the steering lines were so short it couldn't even fly in full flight, so completely stalling/streamering it using toggle input would have been VERY easy. A lot of canopies I see around me have their steering lines set quite short...

ciel bleu,
Saskia

[lilchief 0]

The reason I said modern canopies, is because ZP(though introduced mid 90's I think) allows the canopy to beocme a wing, and not a air-leaking wing. Also, I don't have enough info regarding the older canopies(pre -98) to draw any conclusions. But I must say, without having a degree in aero- and fluid dynamics (though it has been my hobby since I was a little kid) i find it hard to believe that if you stall your canopy, it will buckle and turn into a streamer it can't recover from. all the air will be deflected from the bottom skin towards the nose. Also, I've not yet seen a canopy stall and stay shut. They always tend to roll over to one side and therefore changing the angle so that there will always be some air going inn. here again, the crossports was designed for å reason... Even though I've seen my shear of canopies stalling no one never held it longer then 1 second max after stalling. I don't blame them since it's not recommended, specially with smaller eliptical canopies.

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

[lilchief 0]

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I can't recall whether anyone has managed to gift wrap themselves with a skydiving canopy, although dropping into slack lines could easily cause problems. Who knows, you might be able to do it if you tried.

Ask Brian Germain..he did it while testing a VERY light frontriser canopy he made for him self.

Nice info btw...

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

[winsor 186]

Aaron Britten (sp) was screwing around with his canopy - a Jedi IIRC - stalling and recovering as he approached the DZ. At maybe 100 feet, he managed to wind up encased in his canopy, where he remained until impact.

This was at Laurel, DE maybe 8 years ago.

About 15 years ago I just missed falling into a NOVA when it reinflated and surged below me after the nose folded under. This was not a stall per se, but was close enough for my liking.

In the '80s we would lose altitude by bow-tying our Furys, CruiseLites and what have you, though I never compared the rate of descent with someone doing a spiraling descent. The advantages to stalling were the lack of Gs and the fact that the factors that made a midair more likely were not as pronounced.

I think I intentionally stalled my first Blue Track once in the process of familiarization. I have not done it again, and the idea still scares the hell out of me (its recovery was VIOLENT).

In summary, reports of Aaron's demise indicate that a one-man wrap is quite possible, and one should be circumspect regarding how and with what canopy one should play with intentional stalls.

Losing altitude rapidly in the pattern, either by stalls or spiraling, is generally a bad idea as well.


Blue skies,

Winsor

[morten 0]

Thanks for the comments on the first question. I get the impression that, if stalling in a controlled manner from normal flying it's very unlikely that the jumper will get wrapped in the chute.

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The next question is: Can and will a stalled chute descend faster than a spiralling one, and if so, will (or rather can) it continue do so for an extended period of time?

Any comments on this question?

The questions came up in a discussion on possible ways to bleed off altitude without chopping the main in a premature high altitude opening.

After reading the replys here it seems a good idea to add "and will it have any chance of recovering after a substantial altitude-loss?" to my list of questions.

And please don't worry - this was a theoretical discussion about oxygen starvation while flying the main, not plans for the immediate future

[quade 3]

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quade: Based on the article(which say the same as Brian Germain's "Parachute and it's Pilot") you would say that what morten describes is possible if you stall out your canopy in a toggleturn? wouldn't the g forces keep the line tension through out the turn? I could see a high speed stall on a wing if it has a bank angle for en axtensive period of time(speed and bank angle will determine when the stall occurs), but that is in my mind only feasible with an aircraft, not with a parachute. I've tried it a couple of times, and only got a carve turn out o it.

Accelerated stalls are the same for all wings; airplanes and canopies alike. Increase the G loading and the speed at which the stall occurs increases as well. Stall is not the same thing as canopy collapse.

quade -
The World's Most Boring Skydiver

[lilchief 0]

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this was a theoretical discussion about oxygen starvation while flying the main, not plans for the immediate future

I don't recall her name, but she was on the 357 or 400 record attempt. She had a main opening at 24K during exit. Due to her full face helmet, she had some oxygen remaining in the helmet. All she did was nothing, just let the canopy fly and controll her breathing. She told this during an Skydive radio interview.

By spiraling down you use muscles and therefore oxygen. The only thing she could have done better was to release the brakes to increase her rate of decent.

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no

[billvon 2,384]

>She had a main opening at 24K during exit.

We had another jumper on the 357 way who had a reserve opening out the door, so he was open at 25K - and he had a broken rib from the opening. (150kts, reserve, 25,000 feet is a VERY hard opening.) He landed without incident and without blacking out.

[kelpdiver 2]

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this was a theoretical discussion about oxygen starvation while flying the main, not plans for the immediate future

I don't recall her name, but she was on the 357 or 400 record attempt. She had a main opening at 24K during exit. Due to her full face helmet, she had some oxygen remaining in the helmet. All she did was nothing, just let the canopy fly and controll her breathing. She told this during an Skydive radio interview.

any notion how much faster the rate of descent is at that altitude? Is it accurate enough to divide the normal canopy fall rate (say 1000ft/min) by the percentage of 1atm is present at 24k? That would suggest a descent rate well over 2000fpm, and that should be fast enough to keep ahead of the useful consciousness table, so long as the jumper didn't use most of the 4 minutes at 24k before exit.

[hackish 8]

In the canopy and its pilot it is explained that line slack often causes the parachute to move fast without taking the jumper with it. Others have already pointed out the surge of it reinflating fast can make it dive.

I've had one experience in this area. On opening the brakes both came undone. The canopy surged forward causing slack lines and a nice little tension knot. That was my first and only reserve ride but as I grabbed and buried the toggles I seriously wondered if the canopy was going to go below me. What it did is not unlike letting the toggles up too fast after stalling.

-Michael

[murps2000 86]

Aaron Britten (sp) was screwing around with his canopy - a Jedi IIRC - stalling and recovering as he approached the DZ. At maybe 100 feet, he managed to wind up encased in his canopy, where he remained until impact. ***

Pretty much true, but it happened a little higher. I saw him at about what looked like 500', and his situation had already developed. He had already pulled the reserve by then, but it entangled with the streamering main.

It would have been a difficult situation to deal with even at 2000'. i would suggest to anyone trying to fly their canopy this way that they do it way above their hard deck, bring a hook-knife, and recover from deep stalls slowly into deep brakes first.

[morten 0]

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The only thing she could have done better was to release the brakes to increase her rate of decent.

Releasing one brake would get her down even faster. The risk of passing out before releasing the other brake would make this a risky choice though.

[vpozzoli 0]

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any notion how much faster the rate of descent is at that altitude? Is it accurate enough to divide the normal canopy fall rate (say 1000ft/min) by the percentage of 1atm is present at 24k? That would suggest a descent rate well over 2000fpm, and that should be fast enough to keep ahead of the useful consciousness table, so long as the jumper didn't use most of the 4 minutes at 24k before exit.

Aerodynamic forces scale linearly with air density, but to the square power with speed. In short this means that speeds (both horizontal and vertical) increase by the square root of the air density ratio.
In your example, a 1000 ft/min descent rate at 1 atmosphere becomes, at 0.5 atmospheres, 1000 times the square root of 2 (1.0/0.5=2). That results in approximately 1400 ft/min descent rate at 18,000 ft altitude (that's 0.5 atmospheres according to the ISA standard model, reality may vary).
Cheers,

Vale

[damion75 0]

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But under normal fight and circumstances(the toggle input is limited to the armlength+1turn around the hand of the jumper) as most skydivers fly their canopies, I find it hard to believe that it's possible to stall modern canopies to become streamers.

I'm not sure that I understand your argument fully here, but I will say that with a toggle input of full arm length, pushing a fraction further (rolled shoulders) and holding for a few seconds, I most certainly could stall my last canopy (Vision 132) into a streamer like configuration. No turn of brake line around the hand required.

I haven't tried it on my Katana because it scared the crap out of me even though it was an intentional exercise on a canopy piloting course and I was at 5k. Being able to intentionally toggle stall your canopy by pushing it like this surely just proves that the full flare of the canopy is available in normal use? I am not sure that this fits within your definition of 'normal flight and circumstances' since it had to be done intentionally.

***************

Not one shred of evidence supports the theory that life is serious - look at the platypus.

[lilchief 0]

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I'm not sure that I understand your argument fully here, but I will say that with a toggle input of full arm length, pushing a fraction further (rolled shoulders) and holding for a few seconds, I most certainly could stall my last canopy (Vision 132) into a streamer like configuration. No turn of brake line around the hand required.

i.e. if you rig a canopy for stall characteristic testing, or as mentioned earlier in this thread, you pull the tail down to you. That would in my mind be not normal circumstances.

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I haven't tried it on my Katana because it scared the crap out of me even though it was an intentional exercise on a canopy piloting course and I was at 5k. Being able to intentionally toggle stall your canopy by pushing it like this surely just proves that the full flare of the canopy is available in normal use? I am not sure that this fits within your definition of 'normal flight and circumstances' since it had to be done intentionally.

Well, I'd classify this as normal circumstances since it's something you may do unintentionally. Even though this was planned, you may do the same during final if you were scared or something made you reflexes initiate hard full flare up high(possible canopy collision).

Hope I cleared it out for you...

"Once you have tasted flight, you will forever walk the earth with your eyes turned skyward, for there you have been and there you long to return." - Da Vinci
www.lilchief.no