self induced line twists causes?

[pete683 0]

i have read a lot about self induced line twists and have seen some videos of this happening. my question is: what exactly causes this to happen? are there certain canopies that are more likely to twist up? i have actually been trying to make this happen under an fx-86 (high of course) with no luck.

[tex08 0]

why in the heck would you try to induce line twist for the fun of it?? I recently did this unintentionally on a student 230 rig by making a hard right turn then changing direction hard left. Not a fun thing to happen at 1500 feet. Fortunately I was able to quickly untwist it by 1000 ft before having to cutaway.

[AMax 0]

troll

[pchapman 262]

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are there certain canopies that are more likely to twist up? i have actually been trying to make this happen under an fx-86 (high of course) with no luck.

If I'm being really casual with quick toggle motions, it is easier for me to start to unweight the lines (and get close to spinning myself up) with my Sabre 135 than with an FX 88. After jumping the FX a lot, I've had to make sure I toned down my approaches on the Sabre after snapping too quickly around a 180 turn and getting into that situation of feeling nearly weightless in the harness.

So a smaller canopy isn't necessarily more sensitive to self induced twists.

Without figuring out the actual physics, it seems like the small ground-hungry crossbraced canopy more easily immediately puts some G's on when starting into a turn, putting tension on the lines.

[towerrat 0]

assuming you're not a troll, i would guess your wing loading is keeping you from nasty toggle twists...............

Play stupid games, win stupid prizes!

[popsjumper 2]

---never feed a blatant troll---

My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239

[Baksteen 84]

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Fortunately I was able to quickly untwist it by 1000 ft before having to cutaway.

"That formation-stuff in freefall is just fun and games but with an open parachute it's starting to sound like, you know, an extreme sport."
~mom

[Ion01 1]

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why in the heck would you try to induce line twist for the fun of it?? I recently did this unintentionally on a student 230 rig by making a hard right turn then changing direction hard left. Not a fun thing to happen at 1500 feet. Fortunately I was able to quickly untwist it by 1000 ft before having to cutaway.

If you got out of the twists why did you have to cut away? Just curious.

[tex08 0]

Sorry for the confusion. I did not cutaway, since I had corrected the line twist problem in time.

[Baksteen 84]

Er.. I still have a problem here... you mean 1000 meters, right?

Below 1000 feet it's not wise to cutaway -at my experience level I'd just get as big a ball of crap over my head as possible and hope for the best..

"That formation-stuff in freefall is just fun and games but with an open parachute it's starting to sound like, you know, an extreme sport."
~mom

[JohnMitchell 14]

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Er.. I still have a problem here... you mean 1000 meters, right?

Below 1000 feet it's not wise to cutaway -at my experience level I'd just get as big a ball of crap over my head as possible and hope for the best..

If landing what you have over your head will get you seriously injured or killed, it's okay to cutaway at `1000 feet. Just make sure you pull the reserve right away. Don't do a long freefall first. that would be a good time to have an RSL.

Then try to plan ahead better on the next jump.

[pete683 0]

thanks to Pchapman and towerrat for the info.
so, is it correct that the twists are more likely to happen using toggle input on a lightly-loaded canopy?
the reason i was trying to make this happen on purpose was to prevent it from happening accidentally. like when a pilot practices stalls and spins in an airplane.
whats a troll, should i take offense?

[pwln 0]

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whats a troll, should i take offense?

I can help with this one.

http://en.wikipedia.org/wiki/Internet_troll
http://www.wisegeek.com/what-is-an-internet-troll.htm

[Baksteen 84]

Certainly - As long as it's clear that it's better never to end up in such a situation, for instance by not performing radical manoeuvres for fun while below 2.5k or whatever the recommended altitude is for you.

"That formation-stuff in freefall is just fun and games but with an open parachute it's starting to sound like, you know, an extreme sport."
~mom

[phoenixlpr 0]

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Certainly - As long as it's clear that it's better never to end up in such a situation, for instance by not performing radical manoeuvres for fun while below 2.5k or whatever the recommended altitude is for you.

Keep it simple. Keep your lines under tension and do not turn faster than you canopy can follow.

[fred 0]

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why in the heck would you try to induce line twist for the fun of it??

I believe the way to induce line twists is to do a sharp turn followed by a sharp turn in the other direction, and this is start of the ISP sign-off.

Why wouldn't you do this? When I got recurrent, I practiced flares until they were familiar to me, and then played with stalls. Stalls scare me, so I can see why they should be avoided when low, but on a new canopy, you need to know when/where/how they occur. Same thing applies to self-induced linetwists. You should practice them up high enough so that know what's required, so that you don't do them low.

And imo, you should do this early in your progression, because higher wingloadings are less forgiving of them.

[DougH 270]

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Certainly - As long as it's clear that it's better never to end up in such a situation, for instance by not performing radical manoeuvres for fun while below 2.5k or whatever the recommended altitude is for you.

Keep it simple. Keep your lines under tension and do not turn faster than you canopy can follow.

I agree Gabor, and it isn't hard to avoid. Toggle input should be gradual and progressive. You need allow your body to keep up with the turn.

If you hammer a toggle down you can end up with a turn rate that your body can't keep up and you are going to find yourself in line twists.

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

[markatich 0]

There are two factors for induced line twists. First, the canopy is at a slow forward speed, second an abrupt turn causes the chute to rotate like a top over head. Line twists can be (inadvertently) induced more easily on certain ram air canopies particularly the high aspect 9 cell variety (versus a 7 cell type).
An abrupt toggle input can result in that side of the canopy stalling. This allows the other side to fly around the stalled side in the rotating manner described above.

There have been poorly designed canopies that have killed people simply because they were susceptible to collapsing, spinning and/or twisting lines due to turbulence or from abrupt toggle input.

If you really want to induce line twists try this; bring the canopy to slow flight using full brakes followed by abruptly raising one toggle to its keeper.
If that doesn't work then try an abrupt hook turn at least 180 degrees. Depress the opposite toggle to stop the hook turn then quickly raise the first toggle to its keeper.

If that doesn't work then I imagined the two times I inadvertently induced line twists. I would recommend to anyone thinking of trying this; just take my word for it! Definitely don't try it with an elliptical canopy since they will, most likely, spiral out of control.

I love going fast and I think I can say with 7300 jumps, I've 'been there, done that'!

[BUBLHED 0]

I'm a big guy all I had too do on my PD230 was slam either toggle down while in full flight and there she goes. If you really want to do this and be able to recognize whats happening,(The point for practicing this anyway) then at a very high alt. half toggle right then release rt. toggle and slam the left one down all the way. Watch the canopy as you do this and release tension as soon as it starts to twist. If doing this two things happen. 1 you learn to feel it starting which can save your ass. 2 It's a hell of alot of fun. Be careful not to let it get away from you though. GoodLuck

ATTACK LIFE ! IT'S GOING TO KILL YOU ANYWAY!!!!

[erdnarob 1]

I have explained already on this forum what makes a self induced line twists. It was a thread where you could see it on a video.
Physics explains it. On a self induced line twists, the canopy turns faster that the jumper. That happens after a sudden important toggles input. The body of the jumper has the tendency to stay like it was (ie. not turning) because of what we call in physics the conservation of the angular momentum.
A fast reacting canopy for turn is likely to induce that kind of problem easily. I have had line twists self induced but unintentional years ago with a Nimbus canopy. This canopy wasn't comparable to elliptical canopy we jump now but his aspect ratio was near to 3 and that is why I think that happened.
To avoid such a problem, as several people said it on this thread, start depressing toggle progressively to allow your body to follow the motion.

Learn from others mistakes, you will never live long enough to make them all.