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Carabiner Failure

Guest francis777

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reports yet another carabiner failure in use, the third to my knowledge - (though fortunately not whilst airbourne).

In 2005 the DHV issued a safety bulletin concerning these carabiners yet people are still flying with them.


It doesnt matter what make and each carabiner of the same make differes in "gate tollerance" so....

The advice is:-

Simple rule of thumb ........If your carabiner gate can be opened in

flight (under normal load) then it is probably subject to "oscillation

fatigue fractures" at the lower back corner and could fail without

warning. Check if it can be opened under load (hang your harnes and sit in it) and also look for tiny

fractures. If you decide to buy new ones then buy "pin lock" types.

If you go for "gated" ones again, check them in the shop on the

harness-sling to see if they open under load.

More complex approach.......read the report in link 1 . follow the

instructions and find the "actuation load" of each of your carabiners

then look in the table for your carabiner. look to see if its oscillation strength (-20%) is less than the figure you just measured. If it is..... bin the 'biners.

1). report into fatigue failure of carabiners

http://www.finsterwalder-charly.de/down ... er_eng.pdf

2). fatigue tables of various carabiners in common use

http://www.finsterwalder-charly.de/down ... 05_eng.pdf

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From that 2005 report it looks like if you are using Supair twistlock steel karabiners you should replace them however manufacturing may have been changed since then, obviously if yours are a few years old then it's highly likely they are of that era. Mine are Austrialpin Powerfly steel karabiners but I still want to try the hang test just for my own peace of mind.

Maybe worth posting what karabiners you use on here for reference, also could be worth doing a club "group buy" as they do wear out.

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of the three actual failures that I know have been reported, 2 have definitely been australpin parafly aluminium crabs.

whether steel or ally the same applies, if the gate can be opened or the twist lock untwisted whilst the crab is loaded then it will flex in use and get fatigued at the bottom corner.

I changed to steel twist locks when I dumped my ally australpins in early 2006 after i first heard about this problem but have dumped these for charly pin lock types now as these dont have that issue at all. also delta mailons are locked solid but are not fail safe as you must remember to screw them shut, they dont close automatically.

i think i saw that 500 hours is a sensible replacement cycle assuming the carabiner locks tight under load

Does anyone know if you can get a dye to put on the metal to show minute cracks? like they do with cylinder heads...

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See http://www.lasaero.com/article/a-ardrox

The Ardrox crack detection kit is a quick and easy way to make inspections of airframe, landing gear and components using highly sensitive dye penetrants which will show defects as bright red lines.

A set of 3 Aerosols:-

Red Dye 996PA

Developer 9D1B

Cleaner 9PR50A

The cleaner is handy for other uses as well.

approx £7 each


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  • 3 weeks later...

Very useful advice here guys, thanks.

The crack detection kit link I will use for sue.

Dan, you asked what crabs I use... I replaced all the carabiners on school harnesses (formerly ally astralpins) and my own kit with steel astalpin or steel twist locks, in 2005 . Except the tandem for which I purchased charly quick outs (these have zero actuation load) For my own kit in the coming season I intend to buy the pin-locks that Bendme kindly posted a picture of. These also have zero actuation load.

On my PPG harness I have used SupAir aluminium twist locks and these were fine in the hang test, but, as with all gated crabs, its not the type but the ones you actually bought that have to be individually tested. Glad to hear you are testing yours. Point to note... I am not a metalurgist but wonder if, over time, the steel gated crabs might lose a bit of bendiness and so need regular testing, say once or twice a year? Current adviice, as I understand it, is to replace crabs of whatever type after 500 hours.


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Hi Francis.

I'm thinking of changing my clips to either the pin lock or easy outs, both for the paramotor and free flying kit. any preference to either type. I like the pin locks, but do you have any thoughts on which would be best ?

with regards to the Stainless clips. The only problem you have with stainless is that it tends to age harden and then fail in a brittle fashion. i.e you do not get any precracking. they will just fail without warning. But this is dependent upon the type of stainless used, which is unclear. My experience is from Stainless chain used to suspend submersible pumps. we stopped using them because of the sudden catastrophic failure, and all failed in a predominantly brittle fashion, with little or no surface cracking.

Rigging wire on Yachts also tends to behave in a very similar fashion. My preference only, but I would not use stainless clips.

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All very good points Pete.

I changed to steel as this was the simplest option at the time, and bought a boxfull for all the kit. I intend to change my own to pinlocks on the solo this year both on the PPG and the PG harnesses for exactly the reasons you put forward. My own kit's steel crabs have had about 200 hrs on the PG and only 5ish on the PPG.

It is the Unknown element of all this that is the problem, and why I never attach my reserve to my crabs.

I definitely prefer quickouts on the tandem; not prefer but insist on. My SOP for cliff tandems requires it as I have assessed the risk of getting "blown back" on landing (when try to you get the wing down) and quick outs are the only way to "mitigate the risk" to passengers. An HSE necessity in this day and age, but one I agree with. :evil::D:D We land in winds of up to 26mph and letting one side of the wing go as we touch down is the safest way to kill the wing.

Quickouts are expensive and, if you feel getting blown back is not a major issue for you, I don't see the advantage of using them on a solo wing. Disadvantages are that they are matched pairs so are not interchangeable. Ie you would have to take them off if you used a different wing/motor combo. Changing them is a bit of a faff as they are allen keyed in and loctited both to the risers and to the harness.

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Having looked further into the reports I would note the following:

1: It is not necessary for the carabiner to open under flight loads for it to be a problem. If there is any "free play" of the gate under flight loads then it will be like flying with an open carabiner. Absolutely rubbish for its fatigue life.

2: The flight loads whilst performing a spiral can vary from 20Kg to 120Kg so test each carabiner at 20Kg to see if the "free play" exists. If it does don't do spirals.

3: The best carabiners are the ones with little or no "free play" which effectively become solid under a low load i.e. the "free play" is zero. This is what the DHV mean by "activation by gravity".

As Francis rightly points out the Finsterwalder Charley pin lock carabiners overcome this issue, but were subject to their own safety notice about two years ago due to a manufacturing fault. This will have been fixed now. They must be checked for security of the pin before each flight. Wear of the pins will also show up as either "free play" or a bent pin (which will be almost impossible to get out of the carabiner). We can get a bulk order together if people wish to order them as we have a supply deal with the manufacturer.



Hope this helps.


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