Expected life of a canopy?

[davjohns 1]

I'm reasonably sure there is no tool such as I have in mind. Just thought I would ask.

It seems the engineers who design canopies might be able to give and estimated service life. Perhaps a chart where you could have years on one side and number of openings on another. Cross reference the two and you get a percentage that tells you how much life a canopy would be expected to have. Obviously, this would be subject to the actual inspection of the subject canopy.

I came across a study from 1984 that examined the service life of military nylon 66 materials. It said the canopies mostly deteriorate in storage; lines deteriorate due to storage and use.

I was just curious if any manufacturer had a chart in the back of a user's manual for a canopy that gave something along these lines. I know there are many variables that change everything, but there are some constants and averages as well.

David

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.

[peek 20]

davjohns

It seems the engineers who design canopies might be able to give and estimated service life.

I think that there are too many variables in how a parachute is used to predict wear. Mainly, is it used in desert conditions where dirt and sand become embedded in the fabric and lines, or is is used where the jumper lands on grass that looks like a sod farm?

Quote

I came across a study from 1984 that examined the service life of military nylon 66 materials.

Can you point us to that study?

[pchapman 261]

Yeah you're right, there's no easy way of knowing the life.

Some odds and ends thoughts on the issue:

And you'll need sensors on the canopy to check the UV exposure that depends on where you jump and pack, check how much you kneel on the back of the center top panel, whether that area has salt stains from sweat, check whether opening forces become rougher and on heading performance worse due to out of trim conditions including from shrinking spectra brake lines, etc. And then how does one put a value judgement on those things like opening performance? And as others have said, you'd need to take dust, sand, and grit levels into account.

You'll get people who'll tell you of canopies that lasted a very long time - like an acquaintance's Stiletto that went 3200 jumps with regular line changes, although the colours were getting pretty faded, until it tore on a jump but was landed.

One can do things like doing a tensile test on the top back center panel that takes a lot of abuse. On the other hand, if it rips at 25 lbs, does that mean it was a crap canopy, or could it have been jumped a couple seasons more?

In paragliding sometimes, one takes a line and does a destructive test on it, testing it to failure the check the remaining strength. But in skydiving we don't normally do tests like that, and just replace lines when we think they look bad. Our system is simplistic in that way.

As for the slow deterioration of nylon over time, the literature suggests there is some but it is pretty hard to quantify and in the skydiving world we admittedly don't have a good handle on that. It would be nice to learn more.

Still, I've had a 40 year old military round reserve pass tensile tests for supposedly acceptable strength. One really only knows strengths if one starts doing destructive tests. And if one finds an early 1980s square main that isn't all faded and baffed out, one wouldn't have any hesitation to jump it just because of the age of the nylon. As for reserves, things get trickier because one is down to one's last parachute. It used to be that a 20 year old reserve was often a bad thing, because it was some design that few wanted to jump in the modern era -- like a round or a Swift or an X-210. But nowadays we have plenty of PD reserves that are starting to be 20 years old so the design itself is really solid and nice landing. So I'm curious what people will start doing.

You do get a few companies putting arbitrary lives on canopies. We don't see that in skydiving, but pilot emergency rigs and some of their canopies are now lifed at 15 or 20 years, which to a skydiver seems like a cover your ass move or a money grab. (While riggers don't generally want to disobey a manufacturer's requirement, it has been argued that if the life was not in the original TSO paperwork, then it is not legally mandatory. But that's a whole other argument.) There are a few countries that place mandatory lives on skydiving gear, but that's pretty foreign to US thinking, and considered pretty arbitrary and unnecessary here.

We do of course have the few companies that want their reserves back for porosity testing, like PD with their 40 boxes on the canopy. Aerodyne wants a porosity check after 20 pack jobs, which pretty much would have to be done at the factory as riggers don't normally have a porosimeter. But that requirement is at the back of the manual and I bet few people send them in.

For our purposes, number of jumps (and environmental conditions) has a much greater influence than simple age.

[Boogers 0]

pchapman

As for the slow deterioration of nylon over time, the literature suggests there is some but it is pretty hard to quantify and in the skydiving world we admittedly don't have a good handle on that. It would be nice to learn more.

I remember reading a study many years ago, done by the guy that made F-111 parachute fabric. His name was George Harris I think. He put a bunch of swatches of parachute nylon on the roof of his building exposed to sunlight for a long time, and then brought them inside and tested them for strength degradation at various time intervals. It gave a good measure of how UV light weakens nylon fabric. I have no idea how to find that study now, or if ZP fabric would be different from F-111...

[davjohns 1]

See if this works. Australian DoD study of retired canopies and lines. Then, extrapolating from that evidence.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=5&cad=rja&ved=0CDoQFjAE&url=http%3A%2F%2Fwww.dtic.mil%2Fcgi-bin%2FGetTRDoc%3FAD%3DADA147698&ei=oV8PU56OPOjjywPFzIKwDQ&usg=AFQjCNGjZLj4AS2uLyZWa4xeG2WRHOEgcA&bvm=bv.61965928,d.bGQ

OK. It works. PDF file of the study results.

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.

[pchapman 261]

davjohns

See if this works. Australian DoD study of retired canopies and lines. Then, extrapolating from that evidence.

Nice find; I had only seen the abstract before.

To summarize the more useful parts of the results:

=============================

The paper was written in 1984, about military rounds. So this isn't the most up to date, although still useful.

The explanation for strength loss due to time alone (such as in storage) is that nylon oxidizes over time, and as with many chemical reactions, it happens faster as the temperature increases.

While they did do some tear tests on canopies of different ages, they weren't doing a longitudinal study, that is, they weren't testing the same canopy for 20years.

What they could do was to do accelerated aging tests: heat the fabric samples (say to 70-120 C), see how fast they degraded at different temperatures over 3 months, and mathematically come up with extrapolations for aging at lower, 'normal' temperatures for storage.

One parachute type they checked was an old design using taffeta that had a titanium dioxide coating. Warning bells will go off in the head of any old time rigger -- TiO2 was later found to degrade nylon strength. So those canopies degraded about about 10 times faster in strength than the others, so those tests are not very relevant to modern jumping.

The other canopy type tested was the ripstop on T-10 mains, which is military Type I fabric, about the same weight as F-111, but a lot more porous. So it somewhat resembles F-111 in strength.

The extrapolated strength loss of the canopy fabric -- i.e. calculated not measured -- would be about 1.75% when stored at 25 C over 20 years. Or about 1.5% if stored at 20 C for the same time.

This is really quite low! While useful, I'd like to see more data, even if I am a fan of jumping older canopies.

Strength loss tests when sitting out in the Australian sun were done with samples under window glass -- which I think kind of defeats the purpose, as window glass stops some UV, although certainly not all. Still, after 2 months only under 10% of strenth was lost, but by 111 days 25% strength was lost, and it kept increasing, such as to 75% after 180 days total.

As for dirt getting into lines:

Quote

Previous studies in these Laboratories have shown strength losses in suspension lines of up to 25% due to abrasive salt particles trapped in the structure of the line after salt water immersion and incomplete washing. Siliceous matter would be expected to have a similar effect.

Nylon strength actually increases at low temperatures, so tests of nylon parachute lines (as on the old military rounds) showed slightly better strength at -40 C and -20 C than at +22 C.

For reference, the document is:

AGE LIFE PREDICTION OF NYLON 66 PARACHUTE MATERIALS.
PART-I. MECHANICAL PROPERTIES
G.T. Egglestone and G.A. George
(Australian) DEPARTMENT OF DEFENCE
MATERIALS RESEARCH LABORATORIES
REPORT MRL-R-930
1984

[davjohns 1]

So, it sounds like the age is fairly marginal in terms of effect. Deployments generally = UV exposure, so would be more indicative of wear. It sounds like a chart would be pretty straight forward in average circumstances.

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.

[katzas 0]

Not sure this will help because it's about a reserve--but--I contacted the manufacturer of Raven canopies about this very issue. I received a prompt reply from the president of the company stating that he, as a master rigger, would not agree to sign off on any canopy that was about 15 years old or older--and he also said that many other riggers would not pack or sign off on a reserve of similar age. So--a reserve sees comparitively little use compared to a main. I suspect the service life of a main would be much less than the reserve life.

[riggerrob 558]

katzas

... I contacted the manufacturer of Raven canopies about this very issue. I received a prompt reply from the president of the company stating that he ... would not agree to sign off on any canopy that was about 15 years old or older-- ...

..................................................................................

Some manufacturers publish short service lives to limit their liability, while others publish short service lives as a sly way of saying that their earliest products were not nearly as good as current production.

For example, Raven reserves debuted about 30 years ago, circa 1984. Back then nobody loaded mains at 1 pound per square foot, so no body was loading Raven reserves at 1 pound per square foot.
I only did one jump on an early Raven 2 (215 square feet). I loaded it less than 1:1 and thought that it flew as well as its competitors.
Since not all of the first-generation Raven reserves opened fast enough to satisfy FAA TSO C23C, Precision soon offered free bikini sliders to speed up openings. First-generation Ravens should have their orange warning labels marked "-B" to indicate the new slider.
A few years later (late 1980s) they did a major redesign (V-tapes, new airfoil, etc.) to produce the Super Raven-D series. ... that basic design continued in production until the early 2000s. They went all the way up to the Raven Dash-M series. By then, skydivers routinely loaded ZP mains far heavier than 1:1. The Raven Dash-M developed a bad reputation after a California skydiver tore a Raven Dash-M 282 when he was over-weight (more 1:1), over-speed, and unstable when he scared his Cypres. Sometime during the free-fall, he also dis-located his right shoulder. Even though he survived, he ruined the reputation of Raven reserves.
It took a second accident (in British Columbia) before local skydivers started to take seriously my sarcastic comments about "stupid, fat white men jumping tiny Ravens." After a B.C. jumper broke multiple bones, while panic-turning and stalling his tiny Raven to avoid wires, as he landed off-DZ after scaring his Cypres ... The price of second-hand Micro Ravens dived to near zero after that incident.
By that time, Precision was already working on their next generation of reserves, the "R Max." I have only done one jump on an R Max 118 reserve. Even though I loaded it at the top edge of its envelope (almost 2:1), it still landed me softly.
The moral of the story is that Precision would like everybody to trade in their old Ravens for newer R Max reserves, because R Maxes vastly increase your chances of walking after landing.

[riggerrob 558]

"... the manufacturer of Raven canopies ... would not ... sign off on any canopy that was about 15 years old or older ..."

............................................................................

Several other manufacturers (GQ Security and National come to mind) - of round reserves - have published 15 or 20 year service limits to encourage owners to replace canopies that suffered from acid mesh. Acid mesh was a quality control problem back during the 1980s, that grounded thousands of round reserves and pilot-chutes. Many were re-certified, but the incident convinced most skydivers to convert to square reserves. By the mid-1990s, many major parachute dealers (e.g. Square One) refused to sell round canopies.

[davjohns 1]

katzas

Not sure this will help because it's about a reserve--but--I contacted the manufacturer of Raven canopies about this very issue. I received a prompt reply from the president of the company stating that he, as a master rigger, would not agree to sign off on any canopy that was about 15 years old or older--and he also said that many other riggers would not pack or sign off on a reserve of similar age. So--a reserve sees comparitively little use compared to a main. I suspect the service life of a main would be much less than the reserve life.

Because studies show a substantial decrease in strength over time?

Because he wants you to buy a new canopy so his business will prosper?

Because he is afraid of being sued?

Because design changes have made canopies so much safer that older designs are comparatively unsafe regardless of their age?

Opinions are nice. Facts are better. IMO

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.

[katzas 0]

I presume these are rhetorical questions--at least if they are aimed at me. If you really want answers to the questions you posed I suggest getting in touch with the author of the letter I received--his name is George Galloway. He's president of the company that makes Ravens and a master rigger with about 30+ years of experience in the sport. I'm sure he would welcome your questions and welcome the opportunity to answer them.

[gowlerk 1,912]

I fail to see what vague claims about a letter from Mr Galloway have to do with the expected lifetime of any canopy. Even those made by Precision. I will continue to follow their recommendations and the industry standard regarding canopy life. Namely that it is undetermined.

If you are going to claim he would not pack a 15 year old reserve you could at least quote exactly what he said. Otherwise you are merely paraphrasing and your claim is even more meaningless.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[Krip 2]

Until about 3 to 4 yrs ago when I quit for the last time I was still jumping my 5 cell swift reserve. I bought the reserve in 85.

Of course some riggers would absolutely refuse to pack the canopy.
(Stowing the brakes was a challenge, a lot of the riggers would have to get out the instructions.) Easier to decline for safety reasons

Getting the 25 yo reserve repacked wasn't that hard to do if you knew the right rigger that really knew what he was doing. The canopy was older but It hadn't been repacked that many times due to the smart pencil.

I had to land the 5 cell swift a few or couple of times it worked. The worst part about the canopy was I ordered a traditional white reserve, and I ended up with a sissie blue color.

Thanks to Ralph.

One Jump Wonder

[gowlerk 1,912]

I have two customers with 5 cell Swifts that I pack for. I tell them every time that they should upgrade to something with more modern landing characteristics. But I have no concern that they will open and function as designed.

I have 3 landings on them myself. I've seen blue ones and yellow ones, but no white ones. Maybe they all came through Ralph.

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[likestojump 3]

[Quagmirian 40]

I was just about to post that exact picture.

[likestojump 3]

Quagmirian

I was just about to post that exact picture.

How do you have a picture from my personal archives ?

[gowlerk 1,912]

No doubt about it Paul. You have all the good stuff!

Always remember the brave children who died defending your right to bear arms. Freedom is not free.

[likestojump 3]

gowlerk

No doubt about it Paul. You have all the good stuff!

I love the oddball things. Anything 5 cell is cool.
I too have only seen Swifts in white, baby (lite) blue, navy blue and yellow.

[Quagmirian 40]

likestojump

***I was just about to post that exact picture.

How do you have a picture from my personal archives ?That picture was used on Ebay I think. I download pictures to keep as reference, for, you know... reasons.

[Krip 2]

Ralph had my white swift but sold it to a walk in customer who wanted white.

Any color reserve is a good thing when you need to use one

Whine, Whine, Whine, anyone have cheese

One Jump Wonder

[Quagmirian 40]

Krip

Whine, Whine, Whine, anyone have cheese

Yes, but apparently the doctor says it not a good thing...

[davjohns 1]

katzas

I presume these are rhetorical questions--at least if they are aimed at me. If you really want answers to the questions you posed I suggest getting in touch with the author of the letter I received--his name is George Galloway. He's president of the company that makes Ravens and a master rigger with about 30+ years of experience in the sport. I'm sure he would welcome your questions and welcome the opportunity to answer them.

You are correct. They were not directed at you. I was just pointing out that he gave you his opinion without stating why. Of course, refusing to sign off is entirely his choice. I just think it would have been very helpful to explain why.

I know it just wouldnt be right to kill all the stupid people that we meet..

But do you think it would be appropriate to just remove all of the warning labels and let nature take its course.