Camera wings and line twists

[skydave238 0]

Had an interesting cutaway today. I was doing camera work for a tandem. Freefall was normal. On opening the main (Katana 120) opened hard to one side, goes into line twists and starts spiraling. Tried kicking out to no avail. I was thinking simple, reserve drill. Glanced down to locate the handles and couldn't see them properly. The wings from my camera jacket had folded over them.
After looking at the video I found that the line twists had me flying "backwards" under the canopy. This seems to have caused the wings to be pushed forward over the handles instead of backwards behing the rig.
I did get my hands under the wings to my handles and from there onward had no further problems.

I just thought I'd post this so other jumpers know that this can happen and/or maby to find out if I did something wrong and there's something you can do to prevent this from happening. I jump a custom made Tonysuit Camera Jacket and a Talon FS container.

Any thoughts??

Blue skies,
Dave

Ready...Set...Go..!

SkydiveSwakop

[rhys 0]

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/or maby to find out if I did something wrong and there's something you can do to prevent this from happening.

you wern't jumping a crossfire and you could buy a crossfire.

but seriously, well done. wings can get in the way but looking and locating instead of franticly pulling on something that you shouldn't be (it happens), is a job well done.

blue skies over namiba damn i wanna go there!

"When the power of love overcomes the love of power, then the world will see peace." - 'Jimi' Hendrix

[VideoFly 0]

Wings obscuring handles is certainly one of the many hazards added to skydiving when shooting video. Personal recommendations include a thorough familiarization with your wings and the appropriate size for you, your main canopy and the appropriate choice for video work, deployment techniques, and a sufficient deployment altitude, which allows for handling inconveniences and emergencies. Video equipment can definitely add dangerous variables and difficulties to a jump and videographers need to be aware of that. It sounds like you were heads up and did a great job handling your EP’s.

[pchapman 261]

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After looking at the video I found that the line twists had me flying "backwards" under the canopy.

I'm not really experienced in this but:

It seems common enough for someone with spiralling line twists to be 'spiralling on their back'.

Once a jumper gets under canopy he may adopt a normal after-opening 'sitting' position in the harness. Sitting in the harness is fine under a normal canopy, but when lines are twisted (providing almost zero resistance to further twisting), and someone is spiralling down at a higher airspeed, the sitting position is in effect a huge unstable de-arch.

So the relative wind turns them to a stable position, back to the wind!

[ficus 0]

Before my first jump with wings, a couple of the camera fliers on the DZ briefed me on EPs with wings thusly:

1) Put your hands flat on your chest so that your middle fingers are touching the center of your collarbone.

2) "Wipe" down the front of your suit toward your handles. Even if you miss, this will at least get you to the lift webs and you can find the handles from there by touch.


If you can find a way to guarantee you won't spin on your back in line twists, please let us know :)

[Chris_K 0]

How are your wing clipped?

Mine are clipped into the inside of my thighs so that there is always tension on the outside of the wing. this prevents the wind from pushing in too much material. If I need to you can pull out your wrist and roll your elbow inside the wing to catch material.

the downside to this system is the i need to un-clip to reach my toggles (I can reach enough riser to move if i need to, but not he toggles as they are located higher. I have practiced enough to grab risers as they open and once clear of any obsticals reach down and unclip then grab toggles.

Whats your set up?

Downsizing is not the way to prove your manhood.

[Pulse 0]

Not to be nit-picky but.....you didn't realize you were on your back until you reviewed the video?

I had the same experience last summer with a cutaway. It comes with the territory.

"Any language where the unassuming word fly signifies an annoying insect, a means of travel, and a critical part of a gentleman's apparel is clearly asking to be mangled."

[skydave238 0]

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Whats your set up?

I clip my wings just above the leg strap buckle. Basically I've put an old rsl ring through a piece of old line and tied it to the rig. My wings also have rsl links.

No I didnt realise I was on my back during the mal. I guess I was too preoccupied with trying to get my hands under the wings. I could/should have maby been a bit more aware of what was going on?!

Ready...Set...Go..!

SkydiveSwakop

[davelepka 4]

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No I didnt realise I was on my back during the mal. I guess I was too preoccupied with trying to get my hands under the wings. I could/should have maby been a bit more aware of what was going on?!

No, you did fine. The fact that you didn't let the canopy spin you into the ground is proof of that.

Everyone shits a little brick during a mal. Everyone. The fact that you were faced with an unusual situation only adds to that.

In the end, you did respond correctly, and took care of business in a timely fashion. You performed above and beyond when you were able to recall the situation (which I'm willing to bet only lasted a few seconds) and accurately indentified a problem, and then reported it here so others could avoid, or at least be informed of it.

There's a video on here of an AFF 1, I think somewhere in Europe. The student deploys, and the video guy catches one of the JMs dumping a Velo into a high speed spin. It's a great illustration of just how fast these things happen.

Anyone who claims to be clam and composed, and fully aware of what's happening during this type of mal is full of shit. Right up to the rim full of shit.

[980 0]

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So the relative wind turns them to a stable position, back to the wind!

an interesting theory, but I disagree and rather offer the following explanation for this phenomenon:

-your harness rings (biggest of the 3 rings)are located in front of you

-a good spinning mal will get you horizontal with the lines and canopy or close

-this puts your centre of gravity on top of your centre of pressure(support from the risers in this case), which makes for an unstable configuration

-this configuration will naturally rotate around your long axis (kicking out helps this happen) to a stable configuration, which is centre of gravity below centre of pressure, i.e. you on your back hanging from the 3-rings rather than balancing on top of them

-I think this is the mechanism responsible for this phenomenon as it will happen even at relatively low descent rates, therefore the forces though the risers should be much larger than aerodynamic forces on said jumper.

[pchapman 261]

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-a good spinning mal will get you horizontal with the lines and canopy or close

-this puts your centre of gravity on top of your centre of pressure(support from the risers in this case), which makes for an unstable configuration

-this configuration will naturally rotate around your long axis (kicking out helps this happen) to a stable configuration, which is centre of gravity below centre of pressure,

Hmm, nice idea. Mass distribution that accounts for the behaviour at all airspeeds rather than just aerodynamics which matter more at higher airspeed.

But I'm not convinced; I see a problem with that analysis.

(I wish I had more empirical evidence as to what happens out there in both lower and higher speed spirals.)

So you have a jumper in effect spun around at the end of a rope. The canopy lines are not vertical, but somewhat on an angle, maybe even nearly horizontal.

Let's say the situation is as you suggested: There's a 'couple' (in engineering terms), with the mass of the jumper centered behind/above the line formed by the attachment point and spun-up parachute lines.

Why is that difference not eliminated by a change in the pitch of the jumper? The center of gravity (C of G) can line up with the line of support from the risers by the jumper swinging butt forward. There's no need for a 180 degree rotation to eliminate that difference.

I think we're both agreeing that the C of G should line up with the direction the lines are pulling -- otherwise they would change angle, as they are flexible lines and not a solid beam. The lines end up at whatever angle all the forces on the canopy and jumper pull them to. The angle of the lines depends on the centrifugal apparent force (inwards towards the parachute), gravity (downwards), and some drag on the jumper.

If the C of G has to line up with the parachute lines, then with twisted lines that offer almost no resistance to twisting, it comes back to aerodynamic drag to determine which way the jumper faces.


See my sketches, which may help anyone trying to understand our words dealing with angles and directions:

Sketch #
1. The idealistic case where a jumper hangs straight below the riser attachment.
2. It is suggested that the center of gravity really tends to be towards the back. (But then the jumper should just swing butt forward so the C of G lines up with the attachment point.)
3. Representing the jumper by just a block with an aft C of G
4. Now showing the jumper in a spiral.
5. And the same, using a block instead of the jumper, showing how the center of gravity is postulated to end up above the line of support (or centre of pressure in your choice of words)
6. My suggestion that the jumper would just swing forward rather than roll 180.

[davelepka 4]

I think you both are trying to make a mole hill out of a mountain. There's no easy way analyze a 'generic' malfunction because the situation itself is wrong to begin with.

With that in mind, there is no way to suggest that sitting in the harness, or arching in the harness will create one result of the other. There are too many variables to the scenario -

Which direction is the spin?

Which direction are the line twists?

Are the lines all under tension?

Are the three rings even?

Are the other harness rings even?

Are both of the tuck tabs released?

Are the leg straps symetrical?

All of these things will influence both how the jumper will hang under the canopy, and what result one body position or another will have.

I think the more important body position to consider is the one that gives you the clearest line of sight, and physical reach to your handles. This should be the first, foremost and possible only thought a jumper should have in their head during a high speed spin.

[pchapman 261]

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I think you both are trying to make a mole hill out of a mountain. .

Other way around. But yes in any case one has to be ready to deal with whatever one is faced with, whether or not the chances of facing a particular direction or not are random. Still it intrigues me whether there is a tendency to end up "spinning on one's back".

[davelepka 4]

No, I meant it the way I wrote it. The both of you are trying to make sense of a mal, trying to simplify a situation that is anything but simple. Hence, trying to make a simple situation (a mole hill) out of a complex and varied situaiton (a mountain).

The reason that people often end up spinning on their back is because spinning mals are generally caused by, or result in line twists.

Once you get in to a situation where the canopy is not flying straight, and the lines have crossed, you're at the mercy of chance as to what direction you'll be facing.

The reason you here more about people spinning on their back is because it's an interesting and exciting part of the story. In the instances where the jumper ends up facing forwards, the story is much simpler, "I had a few lines twists, and the canopy started to spin, so I chopped it".

When it goes the other way, you get, "I threw out, and the next thing I know, I'm on my back, and the canopy was slinging me around like a rag doll, so I chopped it".

[pchapman 261]

OK, I'll accept reporting bias as the reason one always hears of people spinning on their backs.

Like I had said, I'd like to see better evidence whether or not people actually end up on their backs at a rate that's more than random.

[rwieder 0]

Cut-Away Wings??

-Richard-
"You're Holding The Rope And I'm Taking The Fall"

[980 0]

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No, I meant it the way I wrote it. The both of you are trying to make sense of a mal, trying to simplify a situation that is anything but simple. Hence, trying to make a simple situation (a mole hill) out of a complex and varied situaiton (a mountain).

honestly: "it ain't rocket surgery"

it's not that complicated a situation from a physics point of view if you have some physics education

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The reason that people often end up spinning on their back is because spinning mals are generally caused by, or result in line twists.

That hypothesis offers no explanation of the mechanism that causes you to be oriented back-to-earth.

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Once you get in to a situation where the canopy is not flying straight, and the lines have crossed, you're at the mercy of chance as to what direction you'll be facing.

I do not believe that and I think that statement only shows that you do not have a hypothesis that would explain the orientation and therefore it is just easier to say that you are at the mercy of fate, whereas you are still actually bound by the laws of physics.

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The reason you here more about people spinning on their back is because it's an interesting and exciting part of the story.

This is a good hypothesis and one worth exploring.

I believe though, that based on the empirical evidence of fellow skydivers' experiences and my own, that there is a tendency for people in that situation to end up back-to-earth more often than not.

I have a hypothesis why and so does Peter.

Exploring observed phenomenon like this and hyopthesizing as to the causes and mechanisms are part of the scientific procedure that furthers our understanding of these phenomenon.

If you have nothing to add to that process, please feel free to do so.

thanks

[davelepka 4]

Check out my first post on the subject, a few posts up from the one you quoted.

I outlined a variety or factors (and certainly not a complete list) that will contribute to the way a jumper will face while spinning with a mal.

Unless you want to account for each of these factors, you cannot come up with a logical hypothesis as to which way a jumper will face.

If you do account for all of these factors, and develop a hypothesis, you may have a valid agrument, but it will be of little use in the real world, as the chances of each of the criteria in an actual mal matching the criteria used in your hypothesis is very, very slim.

Like I said, you are daling with a malfunction, where you cannot count on the performance of any of the factors because the very essence of the situation is that one or more things are not working as they are supposed to.

If you think a jumper would hang one way or another under a mal, that would all go out the window if say, a tuck tab hang up was the cause of the mal. That would have a jumper hanging in a much different way.

Or if the twists were left, and the spin was to the right, which way would a jumper tend to face?

How about a right twist with a left spin?

What happens when a tension knot makes one line group shorter than the rest? What's the effect then?

How about a line over effectively shortening a brake line?

All of the above are realistic, and dare I say common (within the realm of spinning mals) situations that one might encounter. Unless you are preparred to account for all of these factors (and all of the ones I left out), then your hypothesis lacks any real world credibility, and I'll stand by my first conclusion which is that the only thing a jumper should be concerned with during a spinning mal is proper and timely use of emergency procedures.

[azureriders 0]

Next time you get a chance, stand on the tar mac with your back to the prop blast of a twin engine plane. Position your arms in all different places and see what the wind does to your wings and handles. Then practice getting your hands on them. I try to do this at least once a weekend.

good job saving your neck