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wolfriverjoe

Cutaway cable failure

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The recent fatal in Georgia is currently thought to be caused (at least in part) from the failure of the cutaway cable.

The cable reportedly got jammed in the housing, and the jumper pulled hard enough on the handle to extract the steel cable core from the teflon coating (this was the orange teflon coated cable, not the yellow ones).

This is the first time I've heard of it happening. I know there is a SB out there somewhere about the coating cracking and potentially causing a hangup from the white loop catching on the cracks.

But I've never heard of the coating stripping off of the cable before.

Has it happened to anyone before?

Note: I'm going off the preliminary info that is posted in the thread in Incidents. There may well be other things found out during the course of the investigation.
"There are NO situations which do not call for a French Maid outfit." Lucky McSwervy

"~ya don't GET old by being weak & stupid!" - Airtwardo

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It is important to note here that the cutaway cable was not made from the industry standard yellow Lolon coated cable. As far as I know this has never been an issue with the yellow cable. Everyone should be doing their monthly maintenance on all cutaway cables.
Always remember the brave children who died defending your right to bear arms. Freedom is not free.

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Yes, it has happened before. The 3 ring system has been around for a long time. I have seen the coating on older cables get brittle and crack, then if you flex the cable back and forth you could get it to split completely, seperate, and slide down the cable. These were always grounded once any cracks were found.
The only time I have seen the coating on cutaway cables crack or split was on the older clear or red coated cables. (even some home made blue ones) I have never seen this happen with modern yellow cables.

I have honestly not serviced or even seen a rig with clear or red cutaway cables in years, even on Racers (pretty rare around here) If you still have these on your rig I would get a new handle with the yellow industry standard cables.
Onward and Upward!

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This comment is more about the force that you can potentially put on the sheath of the cable then on the coating it self.

Interesting story, I once had some thing similar happen to me but by chance I got to live. The short story is that I was in a canopy collision. The end of the housing got bent over squeezing the cable against the edge of the housing. I had fallen through his lines and had one line of his canopy looped around all of mine. I really needed to cut away. I pulled as hard as I could and stripped/scraped 2 inches of yellow off one side of the cable before I just couldn't get it to move any farther. In the mean time the other guy was trying to find his handle. I got a hold of the line and started looking for a hook knife but it was a borrowed rig that we were using for testing and the knife was missing. Right about then the lines on my canopy sawed through the line on his and I was free. He had found his handle and cut away a second later. If he had been a bit quicker I would have been out of options.

Point is that the adhesion of the coating to the cable is important. You would think that it's no big deal because normally they pull so easy. But under the right circumstances you can put a lot of load on it. I actually couldn't pull it at all. It almost killed me. On the other hand if I had striped the cable or if it had been on the other side I might have released one riser and not the other which also could have killed me.

So pinched housings have happened before. Been their, done that, lived to wear the t-shirt.

Lee
Lee
[email protected]
www.velocitysportswear.com

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I do find this interesting. I jump Racers, and over my 10k of jumps I have had 22-23 cutaways. 4-5 on yellow, the rest on red. The red cables are CRAZY easier to cutaway on - I have had to use two hands on yellow before to be able to pull it, but the reds were shockingly easier. So much so that I have recommended to smaller females who may not have as much strength as other to get red cables because it made such an amazing difference.

I don't have any of the orange cables, but most of my rigs have red cables. I will inspect them, but I have never had an issue.. My handles are all standard pillow - not sure how they are designed inside. This fatality is a scary one...

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I have seen videos of the cutaway and reserve handles (modern “bulky” pillows) flipping back and forth in a free fall with amazingly high frequency. The said “oscillation” of the handles was mainly observed for the handles that were not seated very well/deep in the corresponding Velcro pockets. Also, it seemed like it was happening mainly during belly jumps.
I am not a rigger and do not know the exact details of the construction for pillow type cutaway handles. However, I am always wondering whether the constant flipping of the handles could lead progressive weakening of the attachment point between yellow lolon cable(s) and the pillow.

Of course in the case of D-ring handles the the above potential failure mode is much harder to imagine.
The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.

Stephen Hawking

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Divalent

I'm thinking you could get a lot more force onto the cable with a d-ring, as a hooked thumb in a loop is more secure than a hand grip.



maybe not, in wrestling/BJJ I was always taught not to use the thumb because you are stronger with out it, but not sure if it would apply here... the "gable grip" is an example of this

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Most cutaway pillows are made by taking a long piece of cable and using a Nicopress or swedge on it to basically make a little loop at about the 1/4 point around a piece of webbing. The short side then goes to the users right side (shorter cable) and the long side is for the left side. The webbing is what gets sewn into the fabric pillow. The swedge changes the entire geometry of this compared to the hard metal handle that was in use on this fatality since it allows for a more gentle bend and no sharp edges for the cable coating to wear against.
Yesterday is history
And tomorrow is a mystery

Parachutemanuals.com

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I doubt if vibration alone would cause a coating fatigue failure on a soft handle. Soft coatings (Teflon or nylon) have great resistance to fatigue failure.

OTOH Stainless steel cable fatigues far quicker. The tighter the bend, the more likely the fatigue failure. Just look at the large radii used to install control cables in light airplanes. Cessnas use the same stainless steel cables as ripcords are made of. Stainless steel control cables last about 50 years.
Similarly, burying a swage inside a soft cutaway handle reduces smooths the flex arc as the cable exits the swage, extending the cable's fatigue life.

Worst-case scenario is a steel cable exiting a steel handle, with a sharp edge on the steel handle. The sharp edge forces the cable to flex through a narrow arc, increasing the risk of fatigue failure.

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riggerrob

I doubt if vibration alone would cause a coating fatigue failure on a soft handle. Soft coatings (Teflon or nylon) have great resistance to fatigue failure.

OTOH Stainless steel cable fatigues far quicker. The tighter the bend, the more likely the fatigue failure. Just look at the large radii used to install control cables in light airplanes. Cessnas use the same stainless steel cables as ripcords are made of. Stainless steel control cables last about 50 years.
Similarly, burying a swage inside a soft cutaway handle reduces smooths the flex arc as the cable exits the swage, extending the cable's fatigue life.

Worst-case scenario is a steel cable exiting a steel handle, with a sharp edge on the steel handle. The sharp edge forces the cable to flex through a narrow arc, increasing the risk of fatigue failure.



Most aircraft including Cessna's use galvanized carbon steel for control cables not stainless.

Mechanic's Toolbox Software a listing of cable specifications, and just about everything you ever wanted to know about aircraft control cable.

Galvanized steel is slightly stronger.
Galvanized steel has less wear.
Galvanized steel is easier to inspect for corrosion damage.
Galvanized steel has a short life due to corrosion in high-salt areas.

Stainless steel is more corrosion resistant.
Stainless steel cannot be inspected for corrosion damage.
Stainless steel has considerably less service life in bending applications due to high wear.
Stainless steel is hard to inspect for wear (wears internally).

Stainless steel cable wears faster and has resulted in aircraft control problems:

"This Special Airworthiness Information Bulletin (SAIB) alerts you, an owner or operator of certain Piper models listed below, about possible corrosion, fraying and/or failure, and subsequent loss of control authority that may occur due to a considerably shorter life of the stainless steel cables compared to galvanized cables."


http://www.askbob.aero/content/aircraft-control-cable-comparison-wear-behavior-stainless-and-galvanized-carbon-steel
Replying to: Re: Stall On Jump Run Emergency Procedure? by billvon

If the plane is unrecoverable then exiting is a very very good idea.

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