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Reserve line twists

 

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Poll: Poll: Reserve line twists
Inconvenient 93 / 83%
Dangerous 19 / 17%
112 total votes
 
KellyF  (D 13826)

Mar 1, 2011, 9:03 AM
Post #1 of 79 (2328 views)
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Reserve line twists Can't Post

I've been seeing a lot of comments from jumpers that are choosing to disconnect their RSL/Skyhook afte cutting away from a spinning malfunction (usually spinning line twists) and having line twists on their reserves. To me, this is flawed logic considering you're going to burn through more altitude trying to get stable in freefall than you will kicking out of line twists under an open reserve.

I suspect that these comments are coming from jumpers that started jumping after tapered/elliptical canopies became the norm and spinning line twists became a common malfunction, so they view line twists as a borderline malfunction without consideration of the type of parachute on the other end of the twists. Reserve parachutes are designed to be very stable and are forgiving on harness input (the input that causes the spin in spinning line twists). A tapered or elliptical canopy is designed to be moderately to very sensitive to control inputs (including harness input) and can spin readily with just 2-3" of asymmetry, where a rectangular seven cell might change heading at a rate of ~10 degrees per second (depending on wing loading), but come no where near a nose at the earth, high descent rate spin.

I'm sure people will point out the lack of control while in line twists can contribute to a collision, but keep in mind that you probably burned through some extra altitude before you decided to cutaway, so there could be some extra vertical separation.

I encourage everyone that has never jumped their reserve or a rectangular seven cell to demo their reserve as a main and TRY to make it spin with harness input, as well as discover how it behaves in a flare, stall and all modes of flight.

(This post was edited by KellyF on Mar 1, 2011, 9:03 AM)


Premier billvon  (D 16479)
Moderator
Mar 1, 2011, 9:10 AM
Post #2 of 79 (2291 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

Inconvenient, with the huge caveat that they are inconvenient on rationally loaded reserves. Any canopy can spin up if loaded heavily enough, and many people are starting to think that if they load their main at 2.8 to 1, that they will be conservative and load their reserve at only 2 to 1. (Needless to say that's a bad idea.)


riggerpaul  (D 28098)

Mar 1, 2011, 9:23 AM
Post #3 of 79 (2277 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

Inconvenient, with the further huge caveat that some consideration must be given to the reserve deployment altitude.

Since these spinning mains seem to descend at substantially high rates, it is very possible that even a savvy heads up jumper will burn through a lot of the available altitude just getting to his cutaway.

Having to land a reserve that still has twisted lines cannot be a good thing, though it is likely to be much better than landing the spinner.

But the problem is easily addressed by raising ones altitude milestones appropriately when jumping a canopy that will spin and descend wildly.

Thanks very much, Kelly, for starting this thread.


topdocker  (D 12018)

Mar 1, 2011, 9:24 AM
Post #4 of 79 (2274 views)
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Re: [billvon] Reserve line twists [In reply to] Can't Post

Your poll needs a little more information or options. Line twists on your reserve that go from your harness to the bottom skin would be dangerous, a half line twist would be inconvenient.

Even a line-twisted reserve beats nothing out, but that still may not trump your reasons for not having/disconnecting your RSL. (CRW, etc.)

top


crotalus01  (B 28932)

Mar 1, 2011, 1:20 PM
Post #5 of 79 (2139 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

I voted inconvenient but in my case I believe they were dangerous. I chopped a spinning malfunction and ended up with linetwists all the way up. A friend later commented that he had never seen a reserve with that many twists on it (he has 15 years in and 2K+ jumps).
I opted to disconnect my RSL after that cutaway; I have had 2 more since then sans RSL and they were both textbook...


riggerpaul  (D 28098)

Mar 1, 2011, 1:35 PM
Post #6 of 79 (2119 views)
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Re: [crotalus01] Reserve line twists [In reply to] Can't Post

In reply to:
I voted inconvenient but in my case I believe they were dangerous. I chopped a spinning malfunction and ended up with linetwists all the way up. A friend later commented that he had never seen a reserve with that many twists on it (he has 15 years in and 2K+ jumps).
I opted to disconnect my RSL after that cutaway; I have had 2 more since then sans RSL and they were both textbook...

To me, "dangerous" would mean that without help, the twists would either continue, or get worse.

While "inconvenient" would mean that that they were not getting worse, and were likely getting better themselves.

This leads right back to my earlier comments that altitudes must be commensurate with the gear in use.

In your case, was it dangerous because you were too low? Or because they got worse except for your intervention?

I just want to understand why you poll one way, and then tell the story that contradicts your vote.


diablopilot  (D License)

Mar 1, 2011, 1:54 PM
Post #7 of 79 (2093 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

The logic that RSL's are causing these twists is flawed. Even in a spinning malfunction where the jumper is back to earth, once they breakaway they are slung in a strait line outward on the plane that they were rotating on, leaving them with NO SPIN. This means the airflow is from feet to head and provides THE BEST OPPORTUNITY for a clean reserve deployment.

RSL's DO NOT produce line twists. There is no physical mechanism for them to do so. Persons attempting to get belly to earth while the reserve is deploying cause line twists. People flailing around while performing a breakaway cause line twists.

The numbers don't lie. for the past 30 years an average of 6 to 8 people go in from a breakaway to no/low pull situation.

In 30 years there haven't been but 1 or 2 reliable accounts of someone dying from the use of a traditional single riser RSL.

Do the math people.

Thanks for starting the thread Kelly.


(This post was edited by diablopilot on Mar 1, 2011, 2:35 PM)


Ron

Mar 1, 2011, 1:59 PM
Post #8 of 79 (2085 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

Quote:
I suspect that these comments are coming from jumpers that started jumping after tapered/elliptical canopies became the norm and spinning line twists became a common malfunction,

My first main was a Raven II 7cell.

Quote:
I'm sure people will point out the lack of control while in line twists can contribute to a collision

Lack of control can also put you in a lake, on a highway, in trees.... Etc.

I have had line twists on a reserve and they were getting WORSE. They finally started getting better with just enough time for me to land.

Heck Lake Wales FL had a fatality due to line twist on the reserve

Quote:
Description: After a four way jump, the deceased suffered a violently spinning malfunction on his Startrac 2 main canopy, which he cutaway from at a low altitude. While unstable, at about 800-900 ft, he deployed his reserve. It (a Swift) opened into into serious line twists, potentially due to his unstable attitude during reserve deployment. He landed extremely hard under a partially-inflated reserve. The reserve was found to still have about 5 line twists. Reportedly, the risers were tangled around his throat, perhaps strangling him during decent. He weighed about 215 lbs and was jumping a Racer with a Pull-out main deployment system. He had been involved in the sport for 35 years.

What people always ignore is that you can still pull the reserve fast without an RSL.... But you cannot take a delay with an RSL.


riggerpaul  (D 28098)

Mar 1, 2011, 2:01 PM
Post #9 of 79 (2080 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

First off, JP, I basically agree with you. This is not the fault of the RSL. At least, not directly.

But we must also admit that things like wing suits and camera wings can complicate matters. They can exert forces IMMEDIATELY AFTER the chop that will indeed come into play.

This is why I want to distinguish between situations that are dangerous because the jumper was just plain too low, and situations where the claim is that the reserve would not have straightened itself out regardless of available altitude.


(This post was edited by riggerpaul on Mar 1, 2011, 2:03 PM)


Ron

Mar 1, 2011, 2:03 PM
Post #10 of 79 (2074 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

Quote:
The logic that RSL's are causing these twists is flawed.

In your opinion.

Quote:
RSL's DO NOT produce line twists.

No, but the RSL deploying while you are spinning after a cutaway sure does.


Quote:
The numbers don't lie. for the past 30 years an average of 6 to 8 people go in from a breakaway to no/low pull situation.

In 30 years there haven't been but 1 or 2 reliable accounts of someone dying from the use of a traditional single riser RSL.

Do the math people.

Saying they are safer is not the same as saying they pose no risk.


JanuszPS  (D 568)

Mar 1, 2011, 2:17 PM
Post #11 of 79 (2065 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

Quote:
The logic that RSL's are causing these twists is flawed. Even in a spinning malfunction where the jumper is back to earth, once they breakaway they are slung in a strait line outward on the plane that they were rotating on, leaving them with NO SPIN.

there is a difference between the line twist and the spin! Agree that the twist on the reserve likely will not lead to spin though.

Note: I have two rigs, one w/o rls and second (jav) where I removed the rsl and I choose not to have one.
After a severe line twist with fast spin back to earth I chopped (relating to the previous topic about fatality) with EP with two hands on both handles. Even without rls I ended up with twist(s) on the reserve. I guess that with rls I might have more twists thus less time to prepare for uneventful landing.

So rls contribute to reserve twists (not neseserly to spins though) and depending on the altitude the twists can contribute to crashed landings (eg low cutaway).

just my opinion
j.

Edit: as a side tone better crashed landing than the impact.


(This post was edited by JanuszPS on Mar 1, 2011, 2:48 PM)


jerm  (D 23994)

Mar 1, 2011, 2:52 PM
Post #12 of 79 (2026 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

In reply to:
The logic that RSL's are causing these twists is flawed. Even in a spinning malfunction where the jumper is back to earth, once they breakaway they are slung in a strait line outward on the plane that they were rotating on, leaving them with NO SPIN. This means the airflow is from feet to head and provides THE BEST OPPORTUNITY for a clean reserve deployment.

RSL's DO NOT produce line twists. There is no physical mechanism for them to do so. Persons attempting to get belly to earth while the reserve is deploying cause line twists.

you're right.. the RSL itself does not actually cause line twists. However, reserve deployment not-quite-immediately following breakaway does.

Your assertion re: "And when is the last time you have ever seen someone spin on multiple axis post breakaway? It's a myth. " is flawed on a few levels:

your logic makes sense in a vacuum where tangents are nice and clean, but in the real world, you will have very inconvenient relative wind direction and even more inconvenient bosy symmetry the moment you cutaway...

that can make someone tumble post cutaway / pre line stretch and cause all sorts of havok

your theory is more relevant with a skyhook because of how quickly you reach line stretch, but it's still naive to assert that the spin is the only relevant force variable in a spinning cutaway situation.

And all of that is ignoring any residual rotation one's body may still have with respect to the canopy -- if you were still spinning in or out of the twists when cutting away.

I'm happy that all of your chops have been picture-perfect examples of highschool physics equations, but a broader look at the variables involved in the situation and the vast anecdotal evidence quickly disprove your assertion that it just doesn't happen.


monkycndo  (D License)

Mar 1, 2011, 3:10 PM
Post #13 of 79 (2012 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

As someone mentioned during last Safety Day, I'd rather land with line twists than at line stretch.


Premier DSE  (D 29060)
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Mar 1, 2011, 4:44 PM
Post #14 of 79 (1950 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

JP, thanks for the comments.
While people may disagree (I'm no longer an RSL user), I'd much rather have my lines coming out earlier and *potentially* be spun up due to body position than not coming out at all due to someone trying to get stable when they're often likely disoriented.
Old-school wingsuit theory teaches to not use an RSL for wingsuiting. I've seen two reserve deployments that were deployed via RSL. Both were large wingsuits (greater propensity to spin up). Neither resulted in line twists. One of the two included a fairly violent spin under a Safire 149 (a fairly docile canopy). No problems getting under a straight-flying reserve.
There was a fatality at Flock n' Dock last year that could have potentially/probably been avoided had an RSL been part of the setup.


crotalus01  (B 28932)

Mar 1, 2011, 4:53 PM
Post #15 of 79 (1948 views)
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Re: [riggerpaul] Reserve line twists [In reply to] Can't Post

In your case, was it dangerous because you were too low? Or because they got worse except for your intervention?

I was very lucky that I was over a very large wide open field with no obstacles; I started kicking out as soon as I stopped spinning up (I did 3 or 4 360s before I could spread the risers enough to get stopped). I got the last twist out with just enough time to line up on a row in the soybeans and flare. Had I not been over that wide open field I would have been screwed.
FWIW I dont blame the RSL (it performed as it should), but I do believe it contributed to my linetwists. On my 2 subsequent cutaways without it I have had textbook clean reserve deployments.


pchapman  (D 1014)

Mar 1, 2011, 5:14 PM
Post #16 of 79 (1927 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

In reply to:
once they breakaway they are slung in a strait line outward on the plane that they were rotating on, leaving them with NO SPIN.

I also wanted to correct that to say (similarly to what Jerm said), is that there can be residual spin. The person isn't a point mass. When a person is spinning under canopy, their body is spinning at some speed around its own center of mass (in addition to the overall spin).

In an idealized situation of spinning purely in a flat 2-dimensional plane, in a circle, if the spin is 1 revolution per second, the person is also spinning at 1 revolution per second around their own center of mass.

When they cutaway, they are flung off at a tangent to the circle -- still spinning at 1 revolution per second!

That's of course separate from any aerodynamic issues.

Now add on the fact that a spinning, spiralling dive is 3 dimensional, so then even if there is a single spin axis, the spin will be on more than one of the axes that we normally use for a body -- there can be a pitch, roll, and yaw at the same time.

After a cutaway, there would be the same 3 perceived axes of motion, even if technically there's only a single axis of rotation.

As a simplified example of that, consider again the guy in a spin in a horizontal circle, ignoring the 3-D dimension of height. If the guy is face down, his rotation about his body mass is purely a yaw. If for some reason he is rolled 90 degrees and is spinning on his side, then it is purely a pitching motion relative to his center of mass. If he is somewhere between those two cases, rolled 45 degrees, then when he cuts away, he is flung off and has a combination of yaw and pitching, not along any single axis he is used to.

To get stable, the jumper has to apply aerodynamic inputs that he learned against both yaw (a turn) and a pitch (looping) at the same time -- multiple axes as far as he is concerned!

If anyone can explain the physics more clearly, go for it.

In reply to:
Persons attempting to get belly to earth while the reserve is deploying cause line twists. People flailing around while performing a breakaway cause line twists.

That's a point. One either wants to take the time to get reasonably stable, OR get the reserve out very quickly before much tumble can happen. Skyhook? Seems to usually do so. RSL? I'll leave that up to debate. I'm not so sure.


KellyF  (D 13826)

Mar 1, 2011, 8:03 PM
Post #17 of 79 (1859 views)
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Re: [billvon] Reserve line twists [In reply to] Can't Post

In reply to:
.... and many people are starting to think that if they load their main at 2.8 to 1, that they will be conservative and load their reserve at only 2 to 1. (Needless to say that's a bad idea.)
Funny you should mention a 2 to 1 reserve WL, we had an order come in yesterday for a 190 lb. jumper that wants an Infinity with a 99 sq.ft. reserve. I talked to the dealer today and asked him if the jumper has ever jumped that particular reserve, and he hadn't. I suggested getting a demo for him to jump and that it would be a couple of weeks before the rig was due to be cut. We'll see what happens....Smile


brettski74  (C 3197)

Mar 1, 2011, 8:12 PM
Post #18 of 79 (1850 views)
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Re: [KellyF] Reserve line twists [In reply to] Can't Post

In reply to:
I've been seeing a lot of comments from jumpers that are choosing to disconnect their RSL/Skyhook afte cutting away from a spinning malfunction (usually spinning line twists) and having line twists on their reserves. To me, this is flawed logic considering you're going to burn through more altitude trying to get stable in freefall than you will kicking out of line twists under an open reserve.

I was curious about some of those comments, also. I have cut away from spinning line twists. I have a skyhook. The reserve came out ridiculously fast with virtually no freefall of any kind and all spinning was stopped virtually immediately. I had no line twists on the reserve. I'm not sure whether a traditional RSL would be as fast or effective as a skyhook or other MARD deployment in arresting possible malfunctions on the reserve, nor am I sure whether my experience was only one of a range of possibilities that could have also included reserve line twists, but my understanding of the skyhook was, among other things, to pull the reserve out in line with the relative wind and minimize the risk of reserve malfunction.

I guess it's also worth noting that at the time I believe I was loading at about 1.4 or so.


diablopilot  (D License)

Mar 1, 2011, 9:16 PM
Post #19 of 79 (1827 views)
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Re: [jerm] Reserve line twists [In reply to] Can't Post

Quote:
I'm happy that all of your chops have been picture-perfect examples of highschool physics equations, but a broader look at the variables involved in the situation and the vast anecdotal evidence quickly disprove your assertion that it just doesn't happen.

I'll put my 79 chops against your anecdotes any day. See I've actually done real world testing to see if my theories are correct. There are 3 reasons to not jump an RSL. Cameras, CRW, and ego.


stayhigh  (F 111)

Mar 1, 2011, 9:50 PM
Post #20 of 79 (1807 views)
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Re: [diablopilot] Reserve line twists [In reply to] Can't Post

Why no rsl on camera jump?????


phoenixlpr  (D 3049)

Mar 2, 2011, 12:34 AM
Post #21 of 79 (1772 views)
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Re: [stayhigh] Reserve line twists [In reply to] Can't Post

In reply to:
Why no rsl on camera jump?????
If you get something caught with the equipment on your head it might not be a good idea to launch a reserve in the middle of the mess.


reactor

Mar 2, 2011, 2:09 AM
Post #22 of 79 (1755 views)
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Re: [stayhigh] Reserve line twists [In reply to] Can't Post

In reply to:
Why no rsl on camera jump?????

I am surprised someone with 1000+ experience is asking this question, if your profile is correct.
This has been ask and answer multiple times in the forum.


(This post was edited by reactor on Mar 2, 2011, 2:17 AM)


virgin-burner

Mar 2, 2011, 2:19 AM
Post #23 of 79 (1748 views)
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Re: [crotalus01] Reserve line twists [In reply to] Can't Post

In reply to:
In your case, was it dangerous because you were too low? Or because they got worse except for your intervention?

I was very lucky that I was over a very large wide open field with no obstacles; I started kicking out as soon as I stopped spinning up (I did 3 or 4 360s before I could spread the risers enough to get stopped). I got the last twist out with just enough time to line up on a row in the soybeans and flare. Had I not been over that wide open field I would have been screwed.
FWIW I dont blame the RSL (it performed as it should), but I do believe it contributed to my linetwists. On my 2 subsequent cutaways without it I have had textbook clean reserve deployments.

you had 3 reserve-rides in 187 jumps!? i dont think your main-problem lies in wether having an RSL or not.. Crazy


format  (B 15348)

Mar 2, 2011, 2:49 AM
Post #24 of 79 (1735 views)
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Re: [virgin-burner] Reserve line twists [In reply to] Can't Post

In reply to:
you had 3 reserve-rides in 187 jumps!? i dont think your main-problem lies in wether having an RSL or not.. Crazy

I've had 3 too, all with RSL on. Out of those events, I choose not to use it anymore.
Get it, different experience - different point of view.
It's nothing more than personal preference which comes out of personal experience.
I see no system that prevails in judgement 'what's right'.


phoenixlpr  (D 3049)

Mar 2, 2011, 3:03 AM
Post #25 of 79 (1727 views)
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Re: [reactor] Reserve line twists [In reply to] Can't Post

In reply to:
In reply to:
Why no rsl on camera jump?????

I am surprised someone with 1000+ experience is asking this question, if your profile is correct.
This has been ask and answer multiple times in the forum.

Who says? Someone with a virgin profile? Is it your real first post here or just hiding?


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