HMA lines- history of snapping without warning?

[dbattman 0]

Thanks Saut. Good info is coming out in this thread. Just how visible is the wear on the HMA lines? Is the wear more internal or external? Under the high tension load of flaring, would a burr on the guide rings be enough to snap the line?

Here's another thought- if the external portion of the lower control lines were sprayed with a dye or something similar, would the wear become more visible? Yes, it is the jumpers responsibility to check their gear and maintain it, but there's plenty of people out there that aren't exactly 'vigilant.' If the HMA line wear is considerably less visible, I could see this becoming a serious issue if it became a more widespread material.

[rmsmith 1]

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Who can post a little info on Vectran/HMA lines and their history of wearing from the inside out?

If this canopy has been subjected to repeated submersion in water with the silt and clay particles in suspension then some of those particles could work their way "into" the lines where they will "cut" the fibers each time a load is applied to the lines. Or one of those sandy beach landings comes to mind as I think of small sharp particles. This has been an issue in mountain climbing rope as it has frequent contact with soil particles.

[JGarcia 0]

I was just at the PIA and spoke to George Galloway and Beezy from Precision Aerodynamics and asked these same questions. I fly a Xaos-21 108 and wanted to know about the life of an HMA line set. One can, in fact, see the wear on an older line set. The outside of the lines start fraying. You've got to look close, but you can definately tell the difference between a good line set and one that's getting worn.

--Jairo

Low Profile, snag free helmet mount for your Sony X3000 action cam!

[GroundZero 0]

Jairo, the canopy you looked at (at the Symposium), has 1000+ jumps on the HMA lineset, most done at Eloy were the conditions are most severe for wear. (Jeff Provenzano's X21-91... white with blue x-braces). Wear is visible and announces itself. You probably also noticed that the control lines were replaced with spectra at about 700 jumps, (wouldn't have been my first choice because of shrinkage, but it was a quick field repair when Jeff did not have any HMA.)

We can provide lower control lines in any material you desire... my choices would be HMA or Dacron.

People you must inspect your equipment on a regular basis and repair/replace as required. These aren't bicycles were flying through the air.

Symposium was great, long week, just got home... oh i'm tired!

Chris

Precision Aerodynamics

[cobaltdan 0]

when precision began using hma, we rasied serious concerns. we knew about the material for several years from the paragliding industry.

to refresh: a single fiber of hma will loose 60% of its strength after 4 hours of sunlight. it is uv and blue light sensitive. uv coatings do not work well and are not even being used. bartacking weakens the braded lines, special attention must be taken. many paraglider companies simply overlap and glue the lines with to make attachments. you see alot of hma on competition wings (competition wings are trashed after about 50 hours btw). the material had isues on standard wings as about a year after hma was introduced there were a rash of fatalities and injuries due to lines breaking. at the time it was even banned from use in germany.


it has been pointed out that skydiving canopies are perhaps different as they are not exposed to sunlight for long periods. i do not agree. jumps add up, and canopies are still exposed to uv and blue light when left out on packing mats. white tarp roofs do not filter blue light or black light uv. slider and deployment wear are also imposed on skydiving wings.

do i think that hma has a place in skydiving wings: yes. with careful manufacturing, user maintenece, and short product life cycles, it is suitable and has some advantages for specialized wings.

will we manufacture canopies with hma: no.

why not: it is my perception that preventative maintence does not exist in skydiving. the percentage of skydivers that always pack their own canopies, do preventative maintence and change their lines religously as per the canopy manufacturer's instructions are non existant to too small to cater any product for.

besides the entire reasoning to switch to hma is mislead imo anyway. spectra does change dimensions. yes. but it does so predictably. if you do your homework you can design canopies that, are not very sensative to changes in outer line length, and go into better not worse trim as the spectra shrinks. additionally the shrink of spectra is only several percentage. most manufacturers have trouble holding overal dimensions to similar specs on other aspects of the canopy.

with softer opening canopies you are far more likely to snap a hma line on a hook turn than opening. this will likely be below your hard deck. spectra is not prone to snaping.

i have yet to see any postings from titanium club members saying: yea damn spectra went out of trim causing my crash and broke my femurs.

you will never see me or anyone from atair speaking negatively about a competitors product. i believe it is quite poor form. i make exception when i see something that i believe will lead to serious injury.

sincerely,

dan<><>
atair aerodynamics
www.extremefly.com

Daniel Preston <><>
atairaerodynamics.com (sport)
atairaerospace.com (military)

[hookitt 0]

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i have yet to see any postings from titanium club members saying: yea damn spectra went out of trim causing my crash and broke my femurs.

How can one possibly argue with that?

My grammar sometimes resembles that of magnetic refrigerator poetry... Ghetto

[crazy 0]

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They are an outstanding line material. I wouldn't jump a canopy without it.

I completely agree with you. I want suspension lines, not rahat loukoum.
HMA can significantly improve both the fun, the comfort and the safety. Loss of trim has a significant effect on the flight characteristics, sometimes with unpredictable results and serious consequences (for instance slaming openings or collapsing). With HMA, no loss of trim, period.

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I've seen them worn. They wear visibly. Not like spectra, but if you keep track of jumps and are prepared to change them they aren't likely to suddenly snap on you. But that means not throwing your canopy to the packers and walking away for 400 straight jumps. You have to actually look at your gear to see what's going on with it.

Right, normal wear is visible. Premature wear (for instance, abrasion from the grommets, or sand) is obvious. In addition, as these lines have no cascade, there is no excuse for not replacing them when they wear out; it takes less than 5mn per line and you don't need any tool.
Proper inspection and maintenance is an important part of skydiving. Relying blindly on supposedly idiot proof technology is dangerous. Spectra won't save anybody from carelesness either.
About the horror stories of snapping without warning, ban from germany and other rumors, some of them have already been discussed in that thread.

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Come
Skydive Asia