self-induced line twists at low wing loadings?

[pchapman 261]

Any comments on how easy it is to self-induce line twists at low wing loadings, below 1:1?


The method would be by the usual sudden turn or sudden turn in opposite directions, unloading the lines.

I've never personally experimented with that, although I did it accidentally at about 1:1 loading as a novice years ago.

Locally a jumper with 30-50 jumps apparently managed to accidentally self induce line twists under a rental Sabre 190. I don't know her weight, but I don't think she is big, so the wing loading should have been well under 1:1.

I'm thinking that sometimes people may not think much about teaching the risks of too-sudden maneuvering, while a novice is still at a very low wing loading. Students may be warned generally about not being too sudden and sharp on the toggles, but at some point when they transition to a more "fun" canopy one can see that they could get themselves in trouble.

[punkd 0]

I managed to do this on a Sabre 170 at roughly 1:1..
I think I had maybe 30-40 jumps at the time. Only put me into a half line twist but scared me enough that I don't snap any spiral turns anymore.

[skydude2000 3]

Hey Peter,

I can tell you I've gotten into line twists, probably on the same 190 you're talking about. I'm loading it at about 0.97. But I know, when I did it, I was in deep deep brakes and working on slow turns.

PULL!! or DIE!!

[Fast 0]

Is this not the purpose of the 180 turn follwed by 90 turn that is part of the A license card. To teach the maximum performance of a canopy to new students and the concept that they can induce problems?

Anytime someone does this I go over this exact thing happening, and that it is easier to make it happen when in more brakes combined with any kind of radical turn.

Thoughts?

~D
Where troubles melt like lemon drops Away above the chimney tops That's where you'll find me.
Swooping is taking one last poke at the bear before escaping it's cave - davelepka

[pchapman 261]

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Is this not the purpose of the 180 turn follwed by 90 turn that is part of the A license card.

Looks like that's a good thing to have (given proper instruction of course). Here in Canada where the incident happened that prompted my post, that hasn't been on the list of all the various canopy maneuvers to learn before the A license.

[rygon 0]

I managed a start of a twist on a 190 (1/4 twist or something). did a right turn, lifted off the toggle and then pulled it down again ...think as a was penduluming back it took the tension off the lines which caused it to happen

[Orange1 0]

Maybe not quite the method you are referring to, but I did it once by not keeping stable during the opening sequence, I was probably 0.85 WL - hectic twists that i finally got out of just above my hard deck.

Skydiving: wasting fossil fuels just for fun.

[DrewEckhardt 0]

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Any comments on how easy it is to self-induce line twists at low wing loadings, below 1:1?

I got line twists under my Turbo Z 205 with a wing loading of .9 pounds per square foot when I yanked on a toggle too quickly.

After that I stopped yanking; where Brian Germain's "It's ballet, not boxing" is an appropriate analogy.

[in2jumping 0]

I managed to do it on a 320sq manowar loaded .7 on my 10th jump. Just yank the toggle down very hard and fast at 3k and it spun right up. Scared the crap out of me at the time.

[ufk22 32]

10 years ago, Monarch 195, just over 1:1, I was DEEP into brakes playing with stall pt and flat turns when I thought "I wonder what would happen if....."
From deep brakes popped one toggle all the way up, then the other.
540 degrees of parachute turn later I was glad I was at 3K rather than down low.
Said to myself "self, DON'T do that again"

This is the paradox of skydiving. We do something very dangerous, expose ourselves to a totally unnecesary risk, and then spend our time trying to make it safer.

[fred 0]

Back on my 30ish jump, I was spiralling down on a navigator 260, I thought, "What if I let this toggle all the way up and try to spin the other way." I got to look behind me (about 180° line twist), but that was about it. Still scared the crap out of me.

On my current canopy, I suspect I could spin myself up pretty good if I tried.

[format 0]

Quote

Jackass
60th jump, Navigator 280 loaded 0.85
As you can see, all you gotta do is being stupid.
At the time, I used to swing right before hard left. But on this occasion I've interrupted hard left with FULL right (?!)
"I was angry nobody told me I shouldn't try that"

I still think it should be part of FJC

What goes around, comes later.

[gravitysurfer 0]

Pretty easy to do IMO.

14 years ago my tandem examiner 'sashayed' into line twists and a locked right spin while inside the landing pattern (500ft). He was under a Sabre 230 loaded approximately .82.

His next mistake was fatal. He chopped it.

aloha.

[brettski74 0]

Interesting... I think it was only two weeks ago I was having a chat with one of our novices about inducing line twists under canopy. She told me it had happened while under canopy. She'd buried the toggle and then let it up "suddenly". This prompted a short conversation about letting the toggles up under control.

I later learned when talking to another coach, she hadn't just let the toggle up suddenly. She'd actually let go of the toggle. Needless to say she also covered that point in their conversation.

I believe she was jumping her own gear, though. Not sure of wing loading, but it would be close to 1:1 and she'd have about 30 jumps. I know we typically jump at different DZs, but is this just a coincidence or are we talking about the same person?

On the instructional question, one of my coaches in my early skydiving career talked to me about the possibility of inducing line twists after opening through agressive toggle inputs. I've never actually done it myself, although I'd guess that conversation with my coach probably helped there. I'm wondering how prevalent an occurrence it is for jumpers who've never considered the possibility.

[erdnarob 1]

Hi Peter. That happened to me with a Paraflite Nimbus years ago. That parachute had a large aspect ratio (1: 2.85) and I cranked it at a 1000 ft. I got instantly a couple of line twists which fortunately got undone rapidely. But I will do that NEVER AGAIN.

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

[377 20]

On my first jump with a Triathlon 190 I yanked down hard and deep on one toggle right after my canopy check. It spun up into a line twist. Fortunately I was at 2000 ft and Tri's are forgiving. I kicked it out and got a bit smarter. I fly like a 747 now, slow steady control movements and nothing radical at low altitudes.

I think lots of people have done this early in their ram air canopy experience but few admit it. I had made many round jumps and just got carried away with how cool it was to be able to turn FAST with my new ram air canopy. Fortunately I did it high up.

377

2018 marks half a century as a skydiver. Trained by the late Perry Stevens D-51 in 1968.

[linebckr83 3]

My 32nd jump I sure did. Under a PD230. Simply yanked a toggle down hard and fast. The turn started and then I quit turning while the canopy kept going. Probably what Brian Germain refers to as "not giving your body time to catch up with the parachute". That was my lesson in initiating hard spiraling turns slowly, then speeding up once the turn is started.

"Are you coming to the party?
Oh I'm coming, but I won't be there!"
Flying Hellfish #828
Dudist #52

[CMiller 1]

It is very easy. During my progression to my A, as part of the proficiency card check, I did it by initiating a turn, then another in the opposite direction. This was under a falcon 175, loaded at .8:1

[danielcroft 2]

Jump 12, Navigator 200, dopey noob (i.e. me), "practicing" the 180 to 90 thing & messed it up. I was loading it at like .84 or something. Ended up under spinning line twists & went to my reserve.

[freeflyer58D 1]

well, as just about everyone here has mentioned, it is very easy to unload your lines and cause a wrap. i personally started going back and really exploring the deeper more aggressive portions of flight my canopy has to offer after about 150 jumps on it. i would open at 4500. try my hardest to stall it and see how it responded to slow and fast stall recovery. then i would do the 180 to 90 turns as hard as possible(with the knowledge of possible line twists!!!) and my goal was to know just where the break point was when it would wrap. i would do this from braked turns and full glide. then i worked on rear riser stalls as well and using rears to flatten out a turn. all of this work i did over about 20 jumps really payed off well. im on a saber 1 (170). so its 1:1 exactly. it isn't easy to induce line twists on my personal canopy but it sure isnt hard either:) another thing to look at is leading with a harness turn as well to get the canopy heading into the turn just prior to toggle inputs.

This is straight from the SIM:

Category G Canopy Dive Flow


Clear for traffic.

Make a sharp, balanced 90-degree turn.

Reverse the toggle position aggressively and make a balanced 180-degree turn.

Check position and traffic.

Repeat to no lower than 2,500 feet, in case of line twist.

[Gary73 8]

It's definitely possible to induce line twists, even on a properly loaded student canopy. USPA recently clarified the meaning of the A-License requirement to make a sharp turn followed "immediately" by a sharp turn in the other direction. What they want is for you to turn, ease up, let the canopy go straight, then turn the other way. The idea is to learn your canopy's limits, but to do so gradually. Start with gentle turns, then slowly make them more aggressive. When you get to the point where the canopy starts to act funny, remember where that point is and don't exceed it.

"Extraordinary claims require extraordinary evidence." - Carl Sagan

[muz 1]

It happened to me once (nearly twice) on a borrowed Sabre1 210 (loaded at ~0.8).
I think when you turn, as soon as you start swinging out the lines on the turn side get more tension than the external ones. If your weight is shifted to that side as well (e.g. a low shoulder on the turn side), you pivot around the tense lines and you get twists.
So lightly loaded wings should be more susceptible having lower tension on the outside to start with. High-aspect-ratio canopies should be more prone to it as well.

[justgo 0]

Quote

Interesting... I think it was only two weeks ago I was having a chat with one of our novices about inducing line twists under canopy. She told me it had happened while under canopy. She'd buried the toggle and then let it up "suddenly". This prompted a short conversation about letting the toggles up under control.

I later learned when talking to another coach, she hadn't just let the toggle up suddenly. She'd actually let go of the toggle. Needless to say she also covered that point in their conversation.

I believe she was jumping her own gear, though. Not sure of wing loading, but it would be close to 1:1 and she'd have about 30 jumps. I know we typically jump at different DZs, but is this just a coincidence or are we talking about the same person?

On the instructional question, one of my coaches in my early skydiving career talked to me about the possibility of inducing line twists after opening through agressive toggle inputs. I've never actually done it myself, although I'd guess that conversation with my coach probably helped there. I'm wondering how prevalent an occurrence it is for jumpers who've never considered the possibility.

I am the jumper that Brett is speaking of and yes it has happened to me. (Not the same jumper that Peter mentioned...that is a coincidence.) It's amazing what next-day recall does...I spoke too soon when trying to recall and analyze exactly what I did.

Upon reflection the day after, I realized that I let up the toggle once I already felt the canopy start to spin faster than I was. It was a weird weightless feeling in the harness and I let up the toggle to try to stop what was happening. I did let it up faster than I should have due to greatly increased toggle pressure during the turn but the twists were already starting in the direction of my initial turn before I did this. Ended up with about 3 twists right down through the risers. Luckily I was still at 2,500 feet and they were easy to get out of. I had a very experienced jumper tell me to "just bury a toggle already" after witnessing my conservative canopy flying up until that point and I decided I was ready to get more aggressive.... It was stupid of me to apply such sudden toggle input. The funny thing is, I almost did the same thing on the next jump. Then realized in time exactly what was happening and applied a bit of pressure on the opposite toggle which prevented the line twists.

I was jumping my own 190 Sabre2 with about a 0.98 wingloading. At the time had just over 30 jumps. I realize now that your parachute will do exactly what you tell it to but your body might not have time to catch up... in a sense, wouldn't this be even more true on a larger lightly-loaded canopy due to the longer lines and the greater lag time between toggle input and your body's response? Or as muz put it, lower tension on the outside? Or am I way off here?

[manchuso 3]

Many years ago I was trying a delta cloud (240sq.ft/160lbs) and one of the things I usually do testing a canopy is to bury a toggle as fast as possible. The delta immediately started turning backwards on that side. At that time, elipticals didn´t exist so a backwards spinning main was quite a novel, ugly situation...not satisfied with my reaction that first time (scared) I did it again and I tried to see what happened after that initial moment if I kept the toggle down and was happy to see the canopy right itself and start spiraling facedown as I expected it to do

blue skies, rafael

[icarusphoenix 0]

While I don't profess to be an expert on canopy flight (only 260 jumps), I did stay at a Holiday Inn Express last night.

I've noticed that a couple posts have mentioned or implied that line tension is a contributing (if not primary) factor in initiating line twists. Would any of the experienced canopy pilots be willing to expand on this issue or post links to other threads, as I think it could be a beneficial discussion here.

My line twist experience:

Jump #32, rental gear (sabre2 190 loaded at 1:1). I was flying in full brakes and let up on the toggles rather quickly, causing the canopy to surge forward and release all of the tension in the lines. At the same time I initiated a turn. The canopy responded beautifully and turned just like I asked it to. Unfortunately, since there was no tension in the system connecting me to the wing, I did not turn with it and this spun me up into 7 or 8 line twists while the canopy was still obeying my command and remaining in a hard diving turn. I went to my reserve, which ended up teaching me several other valuable lessons about cut-away handle location in a high G-force spin and altitude awareness. But that's for another thread.

As a side note, I did not understand why the situation had occurred until I read Brian Germain's The Canopy and It's Pilot. After reading a section on line tension, the light bulb went on in my head. This was nearly a year after the line twists/cutaway had happened. I have found this book to be extremely helpful in learning/understanding canopy flight, and highly recommend it as a learning tool, along with participating in a canopy piloting course.