Preventing and Curing Line Twists

[Hooknswoop 19]

Preventing and Curing Line Twists
Line twists have gone from a common nuisance to a common malfunction requiring a cutaway. There are techniques for reducing the chances of incurring line twists and correcting them if you do get them.
The first step to handling line twists is to prevent them in the first place. The looser the chest strap is the wider the 3 rings will be on deployment, which makes it harder for line twists to develop. Of course, be sure that your harness is secure enough to keep you from sliding out of it. Make sure your leg straps are even. For free flyers, a piece of bungee or elastic between your leg straps will help keep the leg straps from creeping to the back of your knees and keep the risers loaded evenly on deployment. Evenly loading the harness on deployment by keeping your hips and shoulders level with the ground will help keep the canopy opening on heading. Take care when setting the brakes of your canopy and take out any twists in the steering lines, which shorten the line. A pre-mature brake release can easily cause line twists and limits your ability to steer away from others immediately after deploying. When stowing the lines on the deployment bag, one side will have less excess in the line from bottom of reserve container to last stow on deployment bag lines than the other. If your last stow was on the left of the bag, the right side would have the least amount of excess lines in the bottom of the pack tray and vice versus. Leave 12 to 18 inches of excess line between the side with the least amount of excess and the corner of the reserve container. This will prevent the lines from hanging up on the reserve container on deployment and twisting the deployment bag as it leaves the container. A worn out pilot chute can spin on deployment, which can spin the deployment bag. Replace a pilot chute that has holes in the fabric or tears in the mesh. Re-line a canopy that is out of trim. If one end cell “A” line (the line that attaches to the nose of the canopy) has shrunk more than the opposite side, the canopy will open turning in the direction of the shorter line. Also, if one steering line has shrunk more than another, the canopy will want to turn in the direction of the shorter line on opening. Pulling the slider down to the 3 rings can prevent self-induced line twists (caused by jerking on a toggle and the canopy turning faster thant he jumper) and most importantly, smooth control inputs.
Even if you take all possible precautions, line twists still happen. If you find yourself under canopy with line twists and the canopy is flying straight, simply kick out of the twists. Make sure you are kicking in the right direction. You can also twist the risers to bring the twists closer to you and reach above the twists for leverage to get yourself out of the twists.
If the canopy is spinning with line twists, react quickly, look up at your links and make them even by shifting your weight in the harness. Be careful not to overdo it and cause the canopy to spin in the opposite direction. At the same time, make sure your brakes are still set. You can use any reference you want, but I’ve found using the links to make the risers even is easiest. The canopy should stop spinning and fly straight. Now kick out of the line twists. Again, make sure you are kicking in the right direction. A canopy that is spinning in line twists loses altitude rapidly, so watch your altitude. Remember under a highly loaded elliptical, you don’t have much time and you do not want the twists to include the excess cutaway cable in the back of your risers. This can make for an impossible or difficult cutaway.
Derek

[Gravitymaster 0]

All excellent suggestions. I would also add to make sure your rubber bands or tube stoes hold the lines tight. I use tube stoes on the first 2 grommets and rubber bands on the rest. I double loop the rubber bands around the lines. This will help prevent an out of sequence deployment which can cause line twists or a slammer opening. (OUCH)
Bob

[Hooknswoop 19]

"All excellent suggestions. I would also add to make sure your rubber bands or tube stoes hold the lines tight. I use tube stoes on the first 2 grommets and rubber bands on the rest. I double loop the rubber bands around the lines. This will help prevent an out of sequence deployment which can cause line twists or a slammer opening. (OUCH)
Bob"
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I personally (and this is DEFINATELY open for discussion) believe that as long as the last stows that hold the d-bag closed are secure until line stretch, the other stows are more of a cause of line twists than they prevent them. If you were to stow only the locking stows and coil the rest of the line in the bottom of your container you woulb be less likely to have line twists. Tight line stows pull on one side of the bag, then the other which can turn the bag. Reserves are more or less packed this way. The canopy will open in less time because the bag will come open sooner, but the canopy won't open any harder. The canopy comes out of the bag at line stetch either way. If you watch a main d-bag deploy, it rocks from side to side as each stow come undone. A reserve free-bag doesn't do this, helping to prevent line twists. I make my locking stows secure and the rest of the stows small and just enough to keep the lines in the tube stows for an in-sequence deployment.
Derek

[AndyMan 7]

Quote

If you were to stow only the locking stows and coil the rest of the line in the bottom of your container you woulb be less likely to have line twists. Tight line stows pull on one side of the bag, then the other which can turn the bag. Reserves are more or less packed this way.

Isn't this the textbook definition of Line Dump?
No thanks,
_Am
5578905 @ ICQ
AndyMan! @ MSN Messenger
ametcalf_1999 @ Yahoo IM

[Hooknswoop 19]

"Isn't this the textbook definition of Line Dump?"
No, line dumb is when the D-bag is open and canopy has started to inflate before line stretch. The locking stows would have to come undone for this to happen. Reserves are packed with the lines in a pouch on the freebag and a safety stow keeping the reserve in the bag until line stretch, no line dump.

[Zennie 0]

I was talking to Bill Lee about this one night and he called it and out of sequence deployment.
Are these both describing the same thing or are there subtle differences between the two?
"Zero Tolerance: the politically correct term for zero thought, zero common sense."

[Hooknswoop 19]

An out of sequence deployment would be anytime the deployment steps didn't go in the exact order it was supposed to. Line dump is a specific out of sequence deployment.
Derek

[AndyMan 7]

Hrm Quoting PD's "How to prevent hard openings"

Quote

Lines should be released one stow at a time. That sounds obvious, but it isn’t as simple as it may seem. When the pilot chute first pulls the bag out of the container, it rapidly decelerates the bag. At that instant, the laws of motion say that the lines stowed on the bag will tend to continue with the jumper, rather than decelerate with the bag, unless a forge opposes that motion. That force is supplied by the stow bands. If the lines aren’t stowed to the bag securely enough, they can all slip out at once. That means the stow bands attached to the bag are literally yanked right off the stowed lines. This is known as “line dump”, and can lead to a very dangerous out of sequence opening. If the locking stows fall off, the canopy is released from the bag and will start to open before it has reached line stretch. It starts filling with air almost instantly while canopy and lines go everywhere! When the jumper traveling at terminal velocity finally reaches line stretch, he already has an open canopy and receives a brutal opening shock. This scenario can damage lines, canopies, risers, and really cause serious injuries.

The pertinent line being the one that says each stow should be released one at a time.
Again, no thanks. It might work for reserves, but reservers are SUPOSED to slam you, and are designed for it.
_Am
ICQ: 5578907 @
MSN Messenger: andrewdmetcalfe at hotmail dot com
Yahoo IM: ametcalf_1999

[Hooknswoop 19]

"If the locking stows fall off, the canopy is released from the bag and will start to open before it has reached line stretch."
I think that is the key line. Think of it this way: If the d-bad takes 1000 ft for all but the locking stows to come off the bag or 100ft- will the canopy open any harder or softer? No. The reason the lines should come off the d-bag one at a time, in order, is to prevent the lines from entangling.
PD also says Sabres don't open hard........
Line dump is more likely to happen on large d-bag w/ Dacron lines. There can be 12-16 inches of line between the rubber bands and usually 4-8 inches outside the rubber bands. Most of the weight of the line is in the center. On deployment, if there is enough airspeed and a big enough pilot chute, the lines can come out of the stows in rare cases. On smaller d-bags and lighter lines, line dump is even more rare.
Again, as long as the locking stows are in place, and the lines don't entangle, normal opening
They started putting diapers on rounds for this very reason, keep the canopy from inflating until lines stretch.
I am not suggesting you coil your lines in the bottom of your container, only that the stows only need to be secure enough to prevent line dump, not slow the bag down.
Derek

[hookit 0]

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PD also says Sabres don't open hard........

Damn that was funny! Unfortunately, Derek, you're not allowed to be funny in this forum. I believe that's only allowed in 'Skydiving Talk Back'! -Trey

[Kris 0]

With my Stiletto (and even with my old Sabre) I am happy if everything past the locking stows is somewhat snug. I am more concerned with the lines being even & clear from each other.
But you better believe that my locking stows won't let go until they are ready. I can pick up my d-bag with the locking stows done if I am careful but the tension is not so high that I am worried about a bag-lock. Even then, it takes a lot more locking force than you think to cause a bag-lock. Any respectable pilot chute will have more than enough force to pull the lines from the stows (and even rip a few in the process) in order to initiate deployment.
For line-dump to happen you would have to have some kind of "bag-strip" mal. Picture a deployment with a snatch force so high it literally rips the bands and dumps the canopy out of the bag before the lines have any real tension on them. When that canopy grabs air before you hit the end of the lines... well, I hope you have a great chiropractor and money to have your main repaired. If you get tension (your suspended weight) on the lines before the canopy starts to inflate then it's all good.
Derek had it nailed when he made the comparison to a reserve free-bag and how the lines are stowed. The locking stows are what matters, the rest are there for neatness.
Now that I think about it, I usually leave 18-24 inches between my last stow and my risers to make sure that my d-bag clears my larger burble (yeah, I'm built like a God, it just happens to be Buddha). Never had a problem with that either in any of my deployments.
Kris