Carabiner failures in Powered Paragliding are not very common.
Their load ratingsare usually well beyond the achievable ones, even in the most radical maneuvers.
However, a few months ago, the world paraglider community learned about an accident in Germany where a certain type of carabiner broke during the flight. Luckily, the pilot deployed his reserve parachute and landed safely.
Some of us, mostly those who do not fly at high altitudes, do not employ a rescue system at all. In such a case, a carabiner failure may prove to have very sad consequences.
Being concerned about such accidents, a few pilots started a debate on the web and the results are different carabiner back-up systems presented in this article.
All authors are convinced that carabiner failures are very rare and isolated. However, we considered that even if they happen one in a million, this issue is well worth to be taken into consideration.
Below we will present the four systems:
1) The "Gary Shoaff" system
I just finished installing my new hookup for the Walkerjet. It employs the same reduntant safety that I utilized with my Xplorer paramotor. You will see that the wing is actually attached twice. If the D-shackle fails, there is a backup. If the biner fails, there is a backup. If the riser fails...I will not send any more e-mail.....
2) The "John Phillips" system:
Attached is a large photo that shows clearly how I am using mountain climbing "quickdraws" as mini risers to eliminate the metal to metal contact between the carabiner and the d-shackle. Note that the second quickdraw attaches to the red backup strap and is independent of the d-shackle. There is no load on the safety strap as the length of the safety strap is a bit longer then needed.
The connector for the safety strap and quickdraw is a mini "quick link" used for parachutes and available at ParaGear. It is rated with a working load well in excess of anything you could ever encounter with PPG.
The quick draws are rated at 22KN while the carabiner is rated at 18KN. The small rubber hoods on each end of the quick draw help hold things securely and prevent them from sliding about. Best part is that the quick draws can be bought in any length from about three inches up to several feet and cost less than $3.00 each.
One other small note: Notice how I used a ty-wrap to lock of the pin on the d-shackle. There is no way that the pin can come loose as the ty-wrap prevents the small ring from being able to turn.
3) The "Steve Tustison" system:
My mod is successfully used on my La Mouette paramotor with the ZR 250 engine.
The smaller loops are 5"x1" climbing spec runners I have got from MoJo's Gear. The slightly larger one is a 6"x9/16" which I purchased at REI. Both are rated 22kn. The shackle now only keeps things in position the bar.
The carabiner now allows a quick hookup to the glider. The rest
is standard La Mouette safety strap that attaches to the glider with a second (slightly thinner) carabiner. It works great.
4) The Alex Varv System:
The mod I built has a slightly different approach. The wing that I fly has very small riser loops. They do not allow installing two carabiners. I also tried to avoid two carabiners rubbing against each other. My first project utilized a Spectra line of 17 KN which was inserted in the riser loop, next to the carabiner. The main difficulty was to tie a reliable but small enough knot at the end of this very stiff cord.
The second project is based on a triangular carabiner (shown below) that I inserted above the riser loop (see picture below)
The next picture represents a closeup of the upper part.
Here is a close-up of the lower part of the system:
This system is very good and does not affect the geometry of the wing by pulling on any of the risers. However, compared to the other systems presented above it has the following shortfall:
Although the safety webbing is rated 17 KN (1 KN= 250Lb) and the mountain climbing carabiner is catalogued for 20 KN, the triangular biner is rated only a little over 300 Kg which is approximately only 660 Lb. A thicker triangular biner could be used but I considered it safe enough. With my weight all up below 300Lb, if the main carabiner failed, the back-up system would have to resist about half, considering that the failure happened at a load of 1G.
It means that the triangular biner could still resist 4,4 G.
I also considered that a carabiner failure would not happen in an instant and put a very high load on the safety system. The carabiner would likely crack, break and bend out while the load would gradually be taken over by the back-up system.
As seen in the pictures below, my safety system has also some slack and in normal flight conditions it will not bear any load.
However, I would like to point out that the weakest link in my system is the triangular carabiner. I am already looking into replacing it with a slightly different one, for a higher rate of load and most likely, I will use a mini "quick link" similar to the one presented by John Phillipsin his system.
The following picture is another general view of my mod: